Journal archives for May 2023

May 05, 2023

The dangerous dentition of the dromedary consists of extremely modified incisors, not canine teeth

@tonyrebelo @jeremygilmore @maxallen @paradoxornithidae @beartracker @matthewinabinett @simontonge @michalsloviak @botswanabugs @grinnin @saber_animal @zarek @jwidness @tandala @davidbygott @dejong

The dromedary (https://www.inaturalist.org/taxa/81542-Camelus-dromedarius) is unusual among domestic ungulates, in its ability to inflict mutilating bites on humans (https://www.sciencedirect.com/science/article/abs/pii/S0278239197903037).

Furthermore, the injuries are surprisingly complex (https://www.cureus.com/articles/76751-camel-bite-injury-to-the-face-in-an-adult-patient-skin-closure-controversy#!/ and https://pubmed.ncbi.nlm.nih.gov/22186231/ and https://www.omicsonline.org/open-access/camel-bites-a-unique-experience-2329-6879.1000192.php?aid=39310 and https://www.sciencedirect.com/science/article/abs/pii/S0020138311005328 and https://journals.lww.com/njms/Fulltext/2015/06020/Camel_bite_An_uncommon_mode_of_maxillofacial.7.aspx and https://journals.lww.com/njms/Fulltext/2015/06020/Camel_biteAn_uncommon_mode_of_maxillofacial.7.aspx and https://www.researchgate.net/publication/276389211_Camel_Bites-A_Unique_Experience and https://www.researchgate.net/publication/51879246_Camel_bite_injuries_in_United_Arab_Emirates_A_6_year_prospective_study and https://journals.lww.com/njms/Fulltext/2015/06020/Camel_bite_An_uncommon_mode_of_maxillofacial.7.aspx).

For example, according to https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4922227/:

"Due to large jaws size camel engulfs the head of the victim and crushes it like a 'nutcracker' resulting severe soft tissue and skeletal injuries to face...Typical of camel bite is that whole face is crushed between two strong jaws resulted into compression and crushing type of injury, which is surprising and different from any other animal bite."

The purpose of this Post is to show that it is the incisors, not the canines, of the dromedary that are unusually specialised for aggressive/defensive biting.

The anterior dentition of Camelidae can be bewilder zoologists (https://www.researchgate.net/publication/303857725_History_of_dentition_in_camels). In both sexes of adults of the dromedary, the four lower incisors are heterogeneous in form and function.

DIFFERENTIATING INCISORS FROM CANINES

I can explain the dentition of the dromedary with reference to the clearest photos available on the Web, as follows.

In each case I proceed from anterior to posterior on a given side (right or left), first for the upper jaw, and second for the lower jaw. I consider only the adult (permanent) dentition, not the milk (deciduous) dentition.

I begin with the following of an adult male individual (https://upload.wikimedia.org/wikipedia/commons/b/b1/Camelus_dromedarius_skull.jpg):

The anterior-most upper jaw is seen to be toothless. Incisors 1 and 2 have been lost evolutionarily, and replaced by a horny, bare pad (https://www.gettyimages.co.uk/detail/news-photo/pakistani-man-checks-the-teeth-of-a-camel-at-an-animal-news-photo/456193758?adppopup=true and https://www.gettyimages.co.uk/detail/news-photo/trader-shows-his-camels-teeth-at-a-livestock-market-set-up-news-photo/601774900?adppopup=true), similar to that of true ruminants. Most food is 'bitten' off by closing the three (6 if both left and right are considered) anterior-most lower incisors (which are spatulate rather than caniniform) against this toothless pad.

What this means is that, in the case of incisors 1 and 2 on the upper jaw, and incisors 1, 2, and 3 on the lower jaw, the dromedary is unremarkable, and similar to true ruminants. Even if this dental apparatus were used to bite an enemy, it would hardly be injurious, because there is no possible dental occlusion.

Continuing with the adult male (https://upload.wikimedia.org/wikipedia/commons/b/b1/Camelus_dromedarius_skull.jpg ):

The anterior-most teeth on the upper jaw are incisors 3 and 4. Both are stoutly caniniform, with 4 being larger than 3. Both show potential for aggressive/defensive biting, along the lines of Carnivora such as Panthera. However, they do not look particularly sharp/pointed.

Proceeding on the upper jaw, the next tooth, after a wide diastema (https://www.google.com.au/search?sxsrf=APwXEdeCq5b5stsY8L6E0t3QUC5oTC1mYA:1683328695130&q=diastema&si=AMnBZoFvNU0WynupgJGHQVzk85f5SygBC8IFGoglJKEiaBoxIykLSU9KM8YbOwoBJO_C8sThA8nPUYqirRxSgPA447CRFUPq9PavS3Hu-tQ-Jxkz86-zMWs%3D&expnd=1&sa=X&ved=2ahUKEwirjaeHqN_-AhXj6zgGHSGWAKcQ2v4IegQICBAT&biw=1013&bih=552&dpr=2.7), is the upper canine.

The upper canine is similar to the canines of Carnivora, but the points to note are that

  • it is smaller than the caniniform incisors, and
  • it is located so far back in the jaw that it its potential for injurious biting is limited.

Now, turning to the lower jaw in the same photo, viz. https://upload.wikimedia.org/wikipedia/commons/b/b1/Camelus_dromedarius_skull.jpg :

The first tooth located posterior to (with no diastema) the three spatulate incisors is incisor 4. What is surprising is that this incisor is somewhat caniniform.

Please note that lower incisor 4 fits between two upper teeth with similar caniniform shape, viz. upper incisors 3 and 4. This implies a capacity for not only piercing but also clamping.

The next tooth on the lower jaw, after a large diastema, is the lower canine. This mirrors its upper counterpart, and once again shows limited capacity for injurious biting, owing to its size and position. In particular, please note that the upper and lower canines are too short to reach each other, even when the mouth is fully closed.

Posterior to the canine teeth on both the lower and the upper jaw, there is a wide diastema before the molariform teeth are reached.

Because of the extreme flexibility of the gape, the molariform teeth could, in principle, be used to inflict a crushing bite on an enemy, in a way impossible in tight-mouthed ruminants such as giraffes. Also, please bear in mind that the normal bite of Diceros bicornis (https://www.alamy.com/stock-photo-diceros-bicornis-black-rhinoceros-skull-gallery-of-paleontology-and-59339980.html?imageid=9535B17E-6405-4E00-9794-559A1DABBC39&p=258772&pn=1&searchId=d43c3c58c0d9e1b13d43bc96739a3a84&searchtype=0), in which it routinely clips woody stems about 1 cm in diameter, is by means of the molariform teeth.

However, it is unlikely that the dromedary would resort to biting aggressively/defensively by means of the molariform teeth, because there are so many caniniform teeth far closer to the front of the mouth.

Now, turning to an adult female individual (https://commons.wikimedia.org/wiki/File:Camel_skull_02.jpg).

This differs from adult males in that

  • all the caniniform teeth are relatively small,
  • two of the upper caniniform teeth, including the canine itself, have been lost with wear/age,
  • the lower canine is so small, and slanted, that it seems to have lost any capacity for injurious biting, and
  • the remaining relevant teeth are upper incisor 4 and lower incisor 4, which deeply occlude in a way suggesting
  • sharpening of the lower, more blade-like incisor on the upper, longer and more pointed, incisor.

The important point about adult females is that, despite the reduction of the caniniform dentition relative to males, there is an upper/lower pair of caniniform incisors with an obvious capacity for injurious biting, by means of piercing and cutting/pincing/slashing.

Let us now refine this description, by examining another adult male individual (https://fineartamerica.com/featured/1-dromedary-camel-skull-millard-h-sharp.html).

Once again, the anterior-most toothlessness (upper) and spatulately incisiform teeth (lower), which are used in foraging, are clearly shown.

When it comes to the caniniform (but fairly blunt-looking) incisors, please note that lower incisor 4 occludes with upper incisor 4 in such a way that there seems to be a honing mechanism. In this sense, these canine-like teeth differ from those of Carnivora and somewhat resemble those of Suidae (https://a-z-animals.com/blog/wild-boar-teeth/) and Papio (https://twitter.com/AnaCarolina_Art/status/1349410432877006864).

These incisors seem adapted as much for slicing/pincing as for piercing.

In the case of the canines, please note that the lower is larger than the upper, and that the tips meet when the mouth is closed. However, once again there is so little scope for occlusion that the canines have limited capacity for injurious biting. They can provide extra grip on a large object such as a human head, rather than doing most of the mutilation.

My final illustrations, for adult males, are as follows (https://www.mediastorehouse.com.au/ardea-wildlife-pets-environment/kel-1213-5274232.html and https://www.sciencephoto.com/media/1009953/view/dromedary-camel-skull).

In these cases, please note that even upper incisor 3 has a honing mechanism, on lower incisor 3. This, once again, suggests that the use of the caniniform incisors is for slicing/pincing, as much as for piercing.

DISCUSSION

The dromedary possesses upper caniniform teeth, superficially resembling the canines of Carnivora. The fourth upper incisor is visible in the following expression, reminiscent of the 'fang-bearing' expression of felids (https://www.alamy.com/closeup-of-a-camels-head-and-open-mouth-image60186624.html?imageid=BD728EB3-A595-4542-9F76-AE7D81168649&p=191433&pn=1&searchId=e70747166a9108431a14954f9ac91060&searchtype=0 and https://www.gettyimages.co.uk/detail/photo/camel-with-open-mouth-royalty-free-image/478539813?phrase=camel+teeth&adppopup=true).

However, the most hazardous tooth seems to be the relatively inconspicuous fourth lower incisor, which is present in both sexes albeit small in females.

It is this tooth, I suspect, that enables the dromedary, in extreme cases, to decapitate a human victim over a period of several minutes (https://www.dailymail.co.uk/news/article-3604619/Camel-bites-owner-s-HEAD-left-tied-sweltering-heat-day.html).

In this sense, it seems that the incisor armament of the dromedary is somewhat analogous with the carnassial dentition of Carnivora (https://en.wikipedia.org/wiki/Carnassial).

The fourth lower incisor fits - like an inverse triangle - between two upper teeth, viz. the third and fourth incisors, allowing the side-to-side movements of rumination (https://mixkit.co/free-stock-video/camel-chewing-his-food-6870/ and https://www.youtube.com/watch?v=3yYgdrmC7xY and https://www.youtube.com/watch?v=VRWzdKzqdxI and https://www.youtube.com/watch?v=8J5cDMrsiQ8 and https://www.youtube.com/watch?v=k5-O8qTQYmM and https://www.youtube.com/watch?v=sC7SDGzwUjQ and https://www.youtube.com/watch?v=OsoJ2MtbwW0).

However, at other times, with slight adjustment of the jaws, it can also be honed. This is against the fourth upper incisor in particular.

The dromedary thus has the ability to cut objects by means of the fourth lower incisor. However, it probably never uses this while foraging.

Furthermore, when the dromedary takes a human head into its mouth in anger,

  • the lower jaw of the human victim seems particularly vulnerable, owing to the upwards action of this tooth, and
  • on a smaller scale, and with a narrower bite, the skin and flesh of the victim can probably be mangled and sliced, by working the fourth lower incisor against the third and fourth upper incisors.

What is odd about injurious biting by the dromedary is its combination of

  • piercing by caniniform incisors (analogous but not homologous with Carnivora),
  • slicing/shearing by incisors that are not used to slice or shear food, and
  • application of great bite-force even with the mouth wide open (to the degree of fracturing a human cranium).

The following show how widely the dromedary can open its mouth (https://www.dreamstime.com/royalty-free-stock-photos-camel-mouth-open-wide-image22659368 and https://www.alamy.com/stock-photo-camel-yawning-39032884.html?imageid=2AED7279-910E-435C-B34A-2A3686228BBD&p=67088&pn=1&searchId=e70747166a9108431a14954f9ac91060&searchtype=0).

In this way, the dromedary is extremely different from giraffes, which can open the mouth to a remarkably limited extent (https://www.istockphoto.com/photo/yawning-giraffe-gm145192923-5374061?phrase=giraffe+yawning and https://www.saczoo.org/wp-content/uploads/2007/08/8-15-07004-1.jpg and https://www.istockphoto.com/photo/giraffe-yawning-gm122995554-16661938?phrase=giraffe+yawning).

(Also see https://www.youtube.com/watch?v=A8CUBOH1zTs, which is probably misconceived)

The configuration of dentition and jaw musculature seen in the dromedary is, as far as I know, unique among mammals.

I have yet to investigate

  • whether South American camelids have dentition similar to that in Camelus, and
  • how the jaw muscles are adapted to apply force with the mouth wide open, which is impossible in true ruminants.

FURTHER ILLUSTRATIONS

https://www.alamy.com/stock-photo-a-camel-shows-its-teeth-while-bellowing-at-tourists-near-the-ruins-25666900.html?imageid=48063F49-FD6A-4D45-BFDF-9CB671E1D103&p=69169&pn=1&searchId=e70747166a9108431a14954f9ac91060&searchtype=0

https://www.shutterstock.com/it/image-photo/camel-teeth-head-761596021

https://www.alamy.com/stock-photo-camel-teeth-16258655.html?imageid=8E35C3E5-AFA5-445B-8D16-C7C0C6E63842&p=288835&pn=1&searchId=e70747166a9108431a14954f9ac91060&searchtype=0

https://www.alamy.com/an-angry-camel-opens-his-mouth-to-show-his-yellow-teeth-and-bad-breath-in-the-northern-territory-australia-image333783903.html?imageid=97E30379-306C-4140-A558-F965904842FF&p=340903&pn=1&searchId=e70747166a9108431a14954f9ac91060&searchtype=0

Posted on May 05, 2023 09:08 PM by milewski milewski | 4 comments | Leave a comment

May 07, 2023

The puzzle of head-nodding displays in Damaliscus

@matthewinabinett @davidbygott @gigilaidler

Members of the alcelaphin genus Damaliscus (https://www.inaturalist.org/observations?place_id=any&taxon_id=42273&view=species) have a peculiar habit of nodding their heads.

This is done to varying extent, in the various species/subspecies, in the approximate order phillipsi > pygargus > lunatus > jimela.

Estes (1991), on pages 135-136, states: "Exaggerated head-nodding is characteristic of Alcelaphus and especially Damaliscus...the catalogue of alcelaphine displays is heavily weighted toward visual signals...Alcelaphines also nod and shake their heads...Head-nodding is typically performed from the normal standing position and often while animals are filing and otherwise peaceful; in this context it may simply say to the animal ahead, 'Come on, get moving'".

For pygargus (the bontebok), the same author, on page 149, states: "Head-nodding is a low-intensity threat when directed at another animal (e.g., a territorial male approaching a bachelor), but is also closely linked with locomotion, common even in young calves, and contagious (David 1973)."

Joubert states: "Though head nodding 'is fairly conspicuous and of frequent occurrence' in the bontebok it is rather associated with the movements of the animals than forming an integral part of the challenge ritual (David, 1970)."

For phillipsi (the blesbok), Estes (1993, page 118) describes challenge rituals between territorial males as follows: "Looking away during approach (head-flagging); standing parallel head-to-tail, sniffing rumps - prompting tail-swishing and head-shaking; head-dipping".

The following video-clips show that phillipsi head-nods while walking, under some circumstances but not others. This is accompanied by holding the ear pinnae forward. At times the head is held low, rather than being nodded.

https://www.pond5.com/stock-footage/item/95033530-herd-blesbok-antelopes-grazing-grassland-south-africa

https://www.pond5.com/stock-footage/item/221684678-blesbok-antelope-walking-and-nodding-heads-grass-summer-sava

https://www.pond5.com/stock-footage/item/24637923-grazing-blesbok-antelopes

https://www.pond5.com/stock-footage/item/26282742-blesbok-antelopes-walking

https://www.pond5.com/stock-footage/item/88460484-blesbok-antelopes-standing-and-walking-grassland-south-afric

https://www.pond5.com/stock-footage/item/221684566-drone-aerial-blesbok-antelope-small-herd-walking-spring-gras

https://www.pond5.com/stock-footage/item/127174195-herd-blesbok-antelopes-damaliscus-pygargus-grazing-grassland

https://www.pond5.com/stock-footage/item/224602599-herd-blesbok-walks-through-tall-grasses-savannah-south

https://www.shutterstock.com/it/video/clip-1061460394-herd-blesbok-blesbuck-damaliscus-pygargus-phillipsi-zimbabwe

With respect to lunatus lunatus (the tsessebe):

Estes (1993, page 115), states that exaggerated nodding occurs when territorial males challenge each other by standing parallel, head-to-tail, in erect posture.

According to Joubert (https://journals.co.za/doi/abs/10.10520/AJA00445096_270):

"As the territory proprietor meets his rival he commences with head nodding, i.e. he repeatedly throws his head up into the air in up and down movements. If the rival accepts the challenge he will reciprocate in a similar fashion and the two animals assume a reverse/parallel stance the two also tend to whirl around in a tight circle. If the two animals sre well matched the head nodding becomes more intense and one or both at times even rear up on their hind legs while nodding. Nodding also takes place from the lateral presentation stance in which the displaying animal assumes a broadside position in front of the other...Even while giving chase at speed the challenger keeps nodding his head and once he has succeeded in passing the retreating male he will jump up into the air...and throw his head up. If this stops the fleeing animal, head nodding between the two is again resumed as described above. Head nodding in tsessebe may be interpreted ad threat behaviour...The more intensive the nodding becomes the higher the animal attempts to lift his head until the demonstrator eventually rears up on his hindlegs.

The following video-clips show that lunatus lunatus does not head-nod during walking under normal circumstances.

https://www.facebook.com/watch/?v=943095713099242

https://www.pond5.com/stock-footage/item/37723989-tsessebe-antelopes

https://www.storyblocks.com/video/stock/herd-of-common-tsessebe-running-on-the-savanna-of-moremi-game-reserve-in-botswana-bapnynkrpkjsgfjtm

With respect to jimela (the topi):

Estes (1993, page 114) states: "Standing and dozing with eyes closed, while nodding...Seen regularly in groups during rest periods (especially males); significance unknown."

The same author, on page 115, states that head-nodding occurs when territorial males challenge each other by standing parallel, head-to-tail, in erect posture.

https://www.pond5.com/stock-footage/item/127996328-herd-topi-antelopes-who-love-grasslands-are-playing

https://www.pond5.com/stock-footage/item/145569423-rare-tsessebe-antelope-walks-meadow

DISCUSSION

Head-nodding in alcelaphins shows no clear relationship with the size or shape of the horns, in the various genera, species, and subspecies.

Head-nodding seems to be a form of display, used intraspecifically. It does not seem to be used in reaction to potential predators, even as a 'displacement activity', i.e. a nervous reaction.

However, even the social/sexual functions of head-nodding are puzzling, from the viewpoint of evolution and adaptation.

In particular, the following questions arise.

Is it true that, of all of the approximately 200 species of ruminants on Earth, the blesbok (https://www.alamy.com/stock-photo-blesbok-antelope-showing-off-with-head-bobbing-movements-during-the-103493204.html) is the 'record-beater' in terms of head-nodding?

Why do the various forms of Damaliscus vary so much in the incidence of head-nodding?

What is it about the society and ecology of phillipsi that makes it adaptive for even females and juveniles to head-nod during walking?

How does head-nodding relate to facial colouration and the incidence of an auricular flag?

It is true that the extreme incidence of head-nodding in phillipsi is correlated with its possession of a facial bleeze plus an auricular flag. However, the relationship between head-nodding and a facial bleeze is inconsistent, because

  • the facial bleeze is most clear-cut in pygargus (the bontebok), in which head-nodding has a lesser incidence than in phillipsi, and
  • facial colouration is most poorly-developed in lunatus lunatus (the tsessebe), which shows the most pronounced head-nodding in masculine rivalry.
Posted on May 07, 2023 07:41 AM by milewski milewski | 7 comments | Leave a comment

Do all of the largest-bodied ungulates have disproportionate mouthparts?

Ungulates (https://en.wikipedia.org/wiki/Ungulate) range in body size from 1.5 kilograms (https://en.wikipedia.org/wiki/Java_mouse-deer) to perhaps 15 tonnes (https://en.wikipedia.org/wiki/Paraceratherium).

This is an astonishing range of ten thousand-fold, for mammals sharing unguligrade locomotion, in which the animals have

Please consider the allometry of the mouthparts of herbivores (https://research.wur.nl/en/publications/why-elephant-have-trunks-and-giraffe-long-tongues-how-plants-shap and https://www.researchgate.net/publication/272239184_Why_elephant_have_trunks_and_giraffe_long_tongues_How_plants_shape_large_herbivore_mouth_morphology and https://www.wur.nl/en/Publication-details.htm?publicationId=publication-way-343836393733 and https://www.semanticscholar.org/paper/Why-elephant-have-trunks-and-giraffe-long-tongues%3A-PretoriusBoer/bccd09c31c16d355369bff0aeb4911aaa8c7237a).

Also please see https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1749-4877.2012.00315.x and https://www.researchgate.net/publication/236183185_Structural_and_functional_comparison_of_the_proboscis_between_tapirs_and_other_extant_and_extinct_vertebrates.

Allometry is basically the study of variable proportionality (https://en.wikipedia.org/wiki/Allometry). As animals evolve from small to large, their proportions must change, in order to remain biologically viable.

This is because of the laws of physics - beginning with the principle that, as objects get bigger, their volume rapidly outpaces their surface-area (https://en.wikipedia.org/wiki/Surface-area-to-volume_ratio#:~:text=The%20surface%2Darea%2Dto%2D,object%20or%20collection%20of%20objects.).

In this Post, I explore the idea that, as the body size of ungulates increases evolutionarily, a threshold is reached at a body mass of about 500 kg in adult females.

Beyond this body mass, herbivores may become subject to a profound disadvantage in foraging. This is theoretically compensated for by means of various modifications, combining

  • extension of the mouthparts or neck, and
  • anatomical 'baffles' that discriminate against fibrous items.

The basic problem is that large items in the vegetation - which are a natural fit for large mouths - tend to be indigestible and nutrient-poor. An elephant-size ungulate, if 'normal' in shape, would tend to be relegated to a diet of wood and straw, which are not fit to eat in the first place.

As ungulates are scaled up, the mouth is, by default, correspondingly scaled up. The trouble with this is that large items in the vegetation tend to be too fibrous, nutrient-poor, and poor in digestible energy to sustain any ungulate.

If a megaherbivore was merely 'a small herbivore writ large', it would have a mouth too gross, clumsy, and slow-moving to select, at a sufficient rate, the palatable items in the vegetation, which tend to be small items.

Therefore, the foraging anatomy must theoretically be 'boggled', to maintain the rate at which suitably small and rich items can be procured.

This allometric principle leads to the predictions that

  • most ungulates weighing more than 500 kg will have mouthparts modified in ways not seen in small to medium-size ungulates, and
  • those small ungulates possessing aberrant mouthparts will prove to use these mainly for purposes other than foraging.

THE RELEVANCE OF ELEPHANTS

Proboscideans, the largest extant herbivores, are not ungulates.

However, they set an extreme in anatomical modification for foraging rapidly and selectively for relatively rich items such as shoots.

The proboscidean proboscis is derived from a seamless union of nose and upper lip. This proboscis combines extreme extension, flexibility, and dexterity, partly substituting for shortness of the neck in elephants.

The tip of the proboscis is, effectively, a pair of lips, mounted on a 'neck' so mobile that there is a virtually 'chimaeric' effect: a gross animal has a fine mechanism for the procurement of food, attached to its face.

The incisors and canine teeth of elephants are unrecognisably modified, or lost altogether.

Extant elephants are also surprisingly capable of bipedal standing (https://www.treehugger.com/worlds-tallest-land-animals-4869723), allowing them to reach even higher into the crowns of trees than their extended proboscides would suggest.

No ungulate, extant or extinct, rivals proboscideans in the extent and degree of modification of the anatomy relevant to foraging. However, I attempt, as follows, to assess the various allometric modifications that the largest-bodied ungulates do exhibit.

RHINOCEROTIDAE (https://en.wikipedia.org/wiki/Rhinoceros)

Ceratotherium: broadened lips and loss of incisors and canine teeth
Diceros: prehensile upper lip and loss of incisors and canine teeth
Rhinoceros: less modified than the above, in association with...

TAPIRIDAE

Tapirus indicus is marginal to this topic, because females average less than 500 kg. However, it possesses a small proboscis, of a type different from that of proboscideans. The anterior dentition is hardly reduced (https://upload.wikimedia.org/wikipedia/commons/f/fb/Tapirus_indicus_02_MWNH_374.jpg and https://upload.wikimedia.org/wikipedia/commons/0/05/Skulls_of_a_Malayan_tapir_%28Tapirus_indicus%29_and_a_Sumatran_rhinoceros_%28Dicerorhinus_sumatrensis%29%2C_Lee_Kong_Chian_Natural_History_Museum%2C_Singapore_-_20150808.jpg and https://www.skullsunlimited.com/products/replica-malayan-tapir-skull-tq-96).

HIPPOPOTAMIDAE

Hippopotamus: broadened lips and extreme modification of incisors and canine teeth in ways that make these teeth superfluous in foraging

https://www.dreamstime.com/royalty-free-stock-photo-river-hippo-grazing-image11517905
https://www.dreamstime.com/stock-photo-hippo-grazing-banks-chobe-river-botswana-image56118556
https://www.dreamstime.com/royalty-free-stock-image-hippopotamus-hippopotamus-amphibius-single-mammal-grass-tanzania-image35434556
https://www.dreamstime.com/common-hippopotamus-hippopotamus-amphibius-hippo-grazing-river-water-lily-leaf-nose-comic-shot-image206474792
https://www.dreamstime.com/royalty-free-stock-photo-grazing-hippo-adult-hippopotamus-green-grass-day-time-s-mouth-open-image36763505
https://www.dreamstime.com/common-hippopotamus-hippopotamus-amphibius-hippo-grazing-river-water-lily-leaf-nose-common-image174637948
https://www.dreamstime.com/stock-photo-hippo-hippopotamus-amphibius-close-up-image88289695
https://www.dreamstime.com/hippo-grazing-river-bank-chobe-national-park-image192796753
https://www.dreamstime.com/hippo-grazing-river-bank-chobe-national-park-image192796666
https://www.dreamstime.com/royalty-free-stock-photos-hippopotamus-grazing-image12071018
https://www.dreamstime.com/royalty-free-stock-images-hippopotamus-grazing-image5964319
https://www.dreamstime.com/hippopotamus-grazing-image274223993
https://www.dreamstime.com/hippopotamus-close-up-grazing-amphibius-amboseli-kenya-image272453131
https://www.dreamstime.com/hippopotamus-grazing-amphibius-waterhole-amboseli-kenya-image272453138
https://www.dreamstime.com/hippopotamus-grazing-pond-water-hyacinth-close-up-hipppotamus-hippopotamus-amphibius-grazing-image155571081

https://www.sciencedirect.com/science/article/abs/pii/S0304380003003053

https://onlinelibrary.wiley.com/doi/10.1111/mam.12056

https://www.semanticscholar.org/paper/Aquatic-foraging-by-Hippopotamus-in-Za%C3%AFre%3A-Response-Mugangu-M.-HUNTER/65e1b4ae82296e5600e513f646cbd7f8d8e4689c and https://www.degruyter.com/document/doi/10.1515/mamm.1992.56.3.345/html?lang=en

GIRAFFIDAE

Extant species of Giraffa qualify, because body mass of adult females about 800 kg

Giraffa:

  • extremely long neck,
  • extremely extensile, semi-prehensile tongue, and
  • extremely tight mouth

CAMELIDAE

Camelus: body mass of adult females approaches 500 kg.

The mouthparts are somewhat modified for foraging, mainly in the form of

The neck is also unusually long for ungulates, allowing wide scope from side to side and from ground-level to ?4 m high (https://www.researchgate.net/figure/Browse-line-at-camel-height-observed-on-Santalum-acuminatum-in-the-survey-area-in-2003_fig4_272493512 and https://www.researchgate.net/figure/Browse-line-at-camel-height-observed-on-Brachychiton-gregorii-along-the-Anne-Beadell_fig3_272493512).

BOVIDAE

Bovini (https://www.inaturalist.org/observations?place_id=any&taxon_id=846321&view=species):

The only extant forms of bovin bovids that, on average, surpass 500 kg in adult females are Bubalus arnee (https://www.inaturalist.org/taxa/74125-Bubalus-arnee) and Bos gaurus (https://www.inaturalist.org/taxa/74111-Bos-gaurus), both of which live on the Indian subcontinent.

In the case of Bison, no extant species qualifies. The closest is Bison bison athabascae, in which the average body mass for adult females approaches 500 kg.

However, several extinct species of Bison were more massive than the extant species, and thus qualify.

The situation is similar in the case of genus Syncerus. The extant species, Syncerus caffer, fails to qualify, because the mean body mass for adult females is somewhat less than 500 kg. However, the extinct Syncerus antiquus qualified (https://en.wikipedia.org/wiki/Syncerus_antiquus).

The lips and teeth of the largest-bodied bovins seem unremarkable, relative to less massive bovids.

The lips are noticeably broader in Bubalus than in Bison or Bos gaurus. However, this is not extreme.

It is possible that, in Bubalus, the tongue is as important as in Bos taurus, or more so, in being extensile and raspy, thus routinely sweeping grass into the mouth (https://www.shutterstock.com/it/video/clip-1098214151-thai-buffalo-grazing-green-grass).

If so, it may be the case that the tongue is extreme relative to all other bovids, as well as cervids.

The foraging methods of B. gaurus do not seem to have been documented.

The mouth of B. gaurus seems unremarkable (https://www.pond5.com/stock-footage/item/111939767-gaur-faces-camera-tadoba-andhari-tiger and https://www.pond5.com/stock-footage/item/145383265-close-face-indian-bison-gaur-gimbal-shot and https://www.pond5.com/stock-footage/item/74671091-close-portrait-indian-gaur-bison and https://www.pond5.com/stock-footage/item/73798916-close-female-indian-gaur-bison-standing-and-chewing-food and https://www.pond5.com/stock-footage/item/72928780-close-portrait-indian-gaur-bison-male and https://www.shutterstock.com/it/video/clip-26765767-indian-gaur-bison-female-jawing-bright-painted).

However, the following show that, even when B. taurus grazes short, green grass, the tongue is used (https://www.shutterstock.com/it/video/clip-1054995428-many-gaur-on-hill-natural-forest-khao and https://www.shutterstock.com/it/video/clip-1055819996-gaurs-eating-grass-on-mountains-khao-yai and https://www.shutterstock.com/it/video/clip-1054995176-gaur-herd-on-hill-natural-forest-khao).

Bison is remarkable for the extreme elevation of the withers (https://www.gettyimages.in/detail/news-photo/photo-shows-a-reproduction-of-a-seven-feet-tall-bison-who-news-photo/51660123?adppopup=true
), plus an outsize head. This may be crucial for foraging in snow, when the large head acts as a sweep for snow, efficiently uncovering the grass below.

However, this disproportionality of the head is a feature of males, more than females.

In summary, if there is something extraordinary about the foraging anatomy of the largest-bodied bovins, it is probably the extensile, raspy tongue, which van be used for grazing 'bulk-and-roughage' as well as fairly short grass.

CERVIDAE

Alces:

falls short of the criterion, because the greatest body mass recorded for females is 490 kg (https://en.wikipedia.org/wiki/Moose)

However, deserves consideration because it is the largest extant member of a major family of artiodactyls

The only species of deer in which adult females certainly weighed more, in average, than 500 kg is Cervalces latifrons (https://en.wikipedia.org/wiki/Cervalces_latifrons).

Would it be far-fetched to suggest that perhaps the females lf Cervalces possessed antlers, and that these were used to break branches while foraging?

Madoqua:

Saiga:

Litocranius:

Posted on May 07, 2023 01:33 PM by milewski milewski | 22 comments | Leave a comment

May 09, 2023

What is the most basic agenda of all living organisms?

A fundamental question in Biology is:

What do all organisms seek to maximise, in competition/cooperation with each other?

What ultimately determines whether

  • a given area of land will be occupied by forest or by grassland, and by large or small herbivores/carnivores?
  • a given volume of water will be occupied by plankton or kelp forests, and by fishes, jellyfishes, aquatic mammals, or aquatic birds?

What does the 'scoreboard' of all Life enumerate, whereby a given organism is a winner or a loser in the quest to occupy space?

This question has seldom been tackled head-on.

So, most Biologists, if put on the spot, would probably scratch their heads rather than answer immediately.

However, in all cases where I have received an answer, it has seemed unsatisfactory.

This is because the commonly-expressed answer is 'reproduction/replication'.

Most Biologists seem to think that the most basic agenda of living organisms is to reproduce.

That is to say, that all of evolution and adaptation is ultimately geared to the maximisation of reproduction/replication, before anything else.

How much explanatory value does this answer really have?

Is it not the case that reproduction is really a means rather than an end, and a mechanism rather than a purpose?

Is it not tautological (https://www.britannica.com/topic/tautology) to assume that organisms ultimately 'reproduce in order to reproduce'?

And, even if reproduction is the ultimate criterion for the competitive/cooperative success of organisms, how could we measure it comparatively? What is the relevant parameter (https://www.merriam-webster.com/dictionary/parameter), and which is the unit of measurement, for the 'scoreboard' of this hypothetical commonality of reproduction across all organisms?

If the answer is simply the rate of reproduction of individuals, then it should be the case that microbes dominate all ecosystems. This is because the smaller the individual body, the more rapid the turnover from one individual/generation to another.

Microbes will, everywhere and always, tend to outreproduce macrobes.

What this would look like is bacterial plaques covering the land to the exclusion of vegetation, and plankton occupying the seas to the exclusion of even fishes.

If life were resolved to a reproductive contest, large trees - let alone whole forests - would surely not exist? And, most particularly, the human species - which reproduces exceptionally slowly even among primates - would be uncompetitive?

It is difficult to theorise on cause and effect in Biology without knowing the ultimate effect that life is after.

So, what could this ultimate effect be?

Posted on May 09, 2023 10:01 PM by milewski milewski | 4 comments | Leave a comment

May 11, 2023

In the adaptive colouration of genus Damaliscus, is there a caudal flag?

@tonyrebelo @jeremygilmore @tandala @oviscanadensis_connerties @capracornelius @davidbygott @paradoxornithidae

A caudal flag is a conspicuous pattern of colouration on (and, additionally in some cases, adjacent to) the tail, which is activated by movement.

This is exemplified by

Whether a given species/subspecies qualifies as possessing a caudal flag depends, in part, on how conspicuous the colouration is on the rest of the figure. A given tail might qualify as a caudal flag on a plain-coloured animal. However, it might not qualify on an animal with overall colouration so conspicuous as to 'eclipse' even the moving tail.

The latter is perhaps exemplified by Antidorcas marsupialis (https://www.alamy.com/namibia-etosha-national-park-springbok-defecating-image457491377.html and https://www.inaturalist.org/journal/milewski/75660-the-springbok-antidorcas-marsupialis-seems-to-qualify-as-possessing-a-facial-flag-but-not-a-caudal-flag#).

GENUS DAMALISCUS IN GENERAL

All species/subspecies of Damaliscus have tails of moderate size, with the tail-tassel mainly blackish in tone.

The tail differs considerably in structure in the two clades within the genus, namely

  • pygargus/phillipsi, and
  • lunatus/korrigum/topi/jimela.

In the former, the tail-tassel is relatively large and bushy, whereas in the latter the tail-tassel is relatively small and two-dimensional (laterally flattened), leaving the tail-stalk relatively long.

The following are illustrative:

phillipsi:
https://willdlife.fandom.com/wiki/Blesbuck?file=Blesbok.jpg

lunatus lunatus:
https://stock.adobe.com/search?k=%22common+tsessebe%22&asset_id=284355340
https://www.dreamstime.com/royalty-free-stock-images-tsessebe-antelope-rare-damaliscus-lunatus-south-africa-image32399699
https://www.shutterstock.com/it/image-photo/common-tsessebe-bush-landscape-botswana-2144729843
https://www.shutterstock.com/it/image-photo/common-tsessebe-standing-meadow-sunlight-2144106859

topi:
https://www.pond5.com/stock-footage/item/171141159-pissing-coastal-topi-damaliscus-lunatus-highly-social-antelo

jimela
https://www.shutterstock.com/it/image-photo/african-male-topi-standing-alone-on-1480887302
https://www.dreamstime.com/topi-antelope-standing-hillocks-to-attract-his-mate-image189824089
https://www.dreamstime.com/male-topi-displays-himself-dirt-mound-image176022832
https://www.shutterstock.com/it/image-photo/topi-on-termite-mound-mara-national-1511326487
https://www.shutterstock.com/it/image-photo/topi-newborn-calf-masai-mara-1652939539
https://www.shutterstock.com/it/image-photo/urinating-topi-masai-mara-kenya-east-1191665062

This difference is visible already in infants, when the dark tone has yet to develop fully:

DAMALISCUS PYGARGUS PYGARGUS

The tail of the bontebok is large enough to be conspicuous, particularly because the white tail-stalk contrasts with the black tail-tassel (https://www.agefotostock.com/age/en/details-photo/bontebok-antelope/ESY-008277294/1). However, in terms of adaptive colouration, the tail is subsidiary to the ischiopygal bleeze, which is the more conspicuous feature (https://www.inaturalist.org/journal/milewski/76311-adaptive-colouration-in-the-bontebok-damaliscus-pygargus-pygargus-part-1-adults#).

The bontebok displays its tail in several social contexts (e.g. courtship, https://www.alamy.com/stock-photo-bontebok-blesbok-antelope-damaliscus-damaliscus-dorcas-bovidae-male-36820913.html?imageid=D177A04E-5BB2-42A8-8538-B839CCC540E6&p=26096&pn=5&searchId=78e3c36a9917c21e07efdd82f4c4fbc0&searchtype=0).

However, it has not been recorded to display the tail but in alarm or while fleeing.

It is difficult to assess the displaying of the tail in the context of predation, because the bontebok has never been observed reacting to non-human predators. Furthermore, it has seldom been observed to stot, although capable of doing so.

Estes (1993, page 118) mentions the following displays of the tail, in Damaliscus pygargus (including phillipsi):

"Territorial Advertising: Lowstretch, with tail curled up at high intensity (see Fig. 11.3). Herding and displaying to females"

"Submission: Head-low posture with tail curled up. Approaching with tail curled is response of intimidated blesbok to displaying male"

"Courtship: Lowstretch +/- tail curled up (see Fig. 11.3). Posture of territorial male approaching female. Male sniffs female's vulva. Female stands with tail out and ears back, then moves quickly away, wagging tail. Olfactory check of female's reproductive status"

The bontebok wags/swishes its tail only in reaction to insects, except for the social wagging described above.

The bontebok also raises its tail during defecation (https://www.alamy.com/stock-photo-africa-south-africa-west-coast-national-park-bontebok-antelope-damaliscus-56090059.html?imageid=7A7DA0E1-EDD1-47FE-9168-012DC072ABCE&p=183410&pn=1&searchId=abde0ec3b06a08943ffb523ff66f0db0&searchtype=0).

In view of the above, does the bontebok qualify for a caudal flag?

This is ambivalent.

An argument can be made for a caudal flag in the bontebok in a social/sexual context. However, it cannot in the context of anti-predator displays.

DAMALISCUS PYGARGUS PHILLIPSI

The tail-tassel of the blesbok is

The darkness of the tail-tassel extends on to the dorsal (upper) surface of the tail-stalk (https://www.shutterstock.com/it/image-photo/herd-blesbok-on-grassy-plain-one-378605818).

The tail of the blesbok differs from that of the bontebok in that

In extreme individuals, the whole of the tail-tassel is pale (https://animalia-bio.us-east-1.linodeobjects.com/animals/photos/full/original/blesbok-damaliscus-pygargus-phillipsi.webp).

In the blesbok, the tail is raised at times (https://www.inaturalist.org/observations/116855609). As mentioned above, this includes adult males in the courtship display:
see from about 15 seconds in https://www.youtube.com/watch?v=VWM5FJCLLfs
https://www.istockphoto.com/photo/blesbuck-and-plain-zebras-in-mlilwane-wildlife-sanctuary-swaziland-gm1182437620-332029147?phrase=pics%20of%20a%20blesbok
https://www.inaturalist.org/observations/10063549

As in the bontebok, this arguably qualifies the colouration of the tail as a caudal flag, in a social/sexual context.

However, the tail of the blesbok seems undemonstrative in the context of anti-predator reactions.

Like the bontebok, the blesbok wags/swishes its tail only in reaction to insects (https://www.istockphoto.com/photo/african-blesbok-in-the-african-bush-veld-gm1091176214-292722242?phrase=pics%20of%20a%20blesbok), except for the social wagging described above.

The only relevant instance is when the blesbok stands in mild alarm at the approach of a potential predator, then simultaneously performs the three following actions:

  • snorting once,
  • vigorously swishing the tail once, and
  • moving the legs as walking is initiated.

DAMALISCUS LUNATUS/KORRIGUM/TOPI/JIMELA

Estes (1993, page 115) mentions the following displays of the tail, in Damaliscus lunatus/korrigum/topi/jimela:

"Territorial Advertising: High-stepping in erect posture, with ears lowered and tail out. Herding and courtship display"

https://www.youtube.com/watch?v=-8R2Lp_S9Es
https://www.flickr.com/photos/90785747@N02/25779599611
https://www.shutterstock.com/it/image-photo/topi-massai-mara-1266686257
https://www.shutterstock.com/it/image-photo/topi-massai-mara-1266686242
https://www.alamy.com/stock-photo-topi-running-masai-marakenya-57612950.html?imageid=D3BA60CD-B021-42FE-BD27-B0BF39ADEB89&p=50837&pn=1&searchId=1acbb4918a3fb248f068c8228e9df229&searchtype=0

"Courtship: Standing stiffly behind female in erect posture with tail raised. Prelude to mounting"

The following, of jimela, show stotting (other than proud-trotting) in lunatus/korrigum/topi/jimela (https://www.shutterstock.com/it/image-photo/on-sunny-day-find-some-topis-2172550751 and https://www.dreamstime.com/royalty-free-stock-photos-beautiful-topi-antelope-mara-grassland-antelopes-resembles-hartebeest-differs-dark-purple-patchings-their-upper-image38932518 and https://www.dreamstime.com/royalty-free-stock-photos-topi-antelope-running-grassland-masai-mara-antelopes-resembles-hartebeest-differs-dark-purple-patchings-their-upper-image39073078). They show that, during this antipredator display, the tail - far from being raised - is actually tucked in.

In the case of D. lunatus lunatus, according to Joubert (https://journals.co.za/doi/abs/10.10520/AJA00445096_270):

"Severe or high intensity fighting...During the pushing duel the two males - still on their knees - interlock their horns and with tails either drawn in between the legs or switching from side to side try to push one another off the mark...When displaying to the females...in the low intensity form of this display the...bull retains his normal walking gait while the tail hangs loosely down or is withdrawn between the hind legs. In the high intensity form the legs and tail also enter into the display...movements are slow and delicate while the front legs are lifted high...with each stride forward and placed down carefully and gently, the movements slow but deliberate. The tail is lifted in accordance with the intensity of the display and in extreme cases is lifted above the horizontal plane. By means of this display the bull asserts his dominance over the cows...The high intensity form of the display is almost invariably assumed when the bull returns to his cows after a dispute with a rival male. Also at waterholes - where there is occasionally contact between adjoining herds - the display is conspicuous...If a male approaches a youngster it displays the submissive posture...Submissiveness is signified when an immature lifts his head up high, pulling its chin in tightly...Simultaneously the tail is held rigidly and horizontally away from the body. If being chased by the bull the immature retains this posture while giving long, stiff-legged bounds (stotting action). If the chase is severe this pace is too slow and the calf reverts to the normal manner in which the animals run at high speed. This applies to both male and female calves".

DISCUSSION

The following mislabelled photo, of Alcelaphus caama, may help to put the genus Damaliscus into perspective, in terms of conspicuous colouration of the tail (https://www.markeisingbirding.com/index/tsessebe). Please also scroll to the accompanying photo that includes an infant individual, in which the tail is already conspicuously dark.

In no species/subspecies of Damaliscus is the tail as conspicuous in colouration, or as obviously activated while fleeing, as in A. caama.

In Damaliscus, a caudal flag is plausible in a social/sexual context, activated mainly in mature males. The tail-tassel is large and dark enough, and contrasts enough with pale pelage on the buttocks and rump, for there to be a considerable display, particularly in courtship and masculine territoriality.

This applies even to

However, a caudal flag in Damaliscus seems unlikely in an anti-predator context. This is because there seems to be no significant display of the tail in stationary alarm or fleeing.

However, observations are needed of juveniles stotting in reaction to the arrival of predators - which has not been described in the literature, let alone photographed. If the activation of the tail described for the tsessebe by Joubert applies not only intraspecifically (in appeasement of masculine aggression) but also interspecifically (in display of individual fitness to cursorial carnivores), then this possibly occurs also in the bontebok, the blesbok, the topi, and the korrigum.

I repeat the following (https://www.youtube.com/watch?v=gnRO9HlPgo4), in the interests of giving Readers an engaging search-image.

For an index to my many Posts about the genus Damaliscus, please see https://www.inaturalist.org/journal/milewski/78238-an-index-to-my-posts-on-genus-damaliscus#.

Posted on May 11, 2023 12:26 AM by milewski milewski | 17 comments | Leave a comment

May 19, 2023

The tsessebe (Damaliscus lunatus lunatus) as a mudbuck

@tonyrebelo @jeremygilmore @tandala @paradoxornithidae @botswanabugs @jwidness @zarek @simontonge @michalsloviak @variani18

For most naturalists familiar with the tsessebe (Damaliscus lunatus lunatus), the image of this alcelaphin (https://en.wikipedia.org/wiki/Alcelaphinae) is far from a 'stick-in-the-mud'.

Here we have a lean antelope as fleet as a racehorse and even lighter on its feet, associated with firm ground where the only limitation is stamina.

Furthermore, the small fecal pellets of the tsessebe (https://www.naturefootage.com/video-clips/JLM170303_0359/tsessebe-standing-defecting and https://www.inaturalist.org/observations/112131138) indicate a species adapted to dry conditions.

So, it is surprising to find, on closer examination, that the tsessebe is peculiarly 'muddy'.

Had the tsessebe not already been named after the Setswana vernacular (https://en.wikipedia.org/wiki/Tswana_language), it might aptly-enough be called the 'mudbuck' (or, in Afrikaans, 'modderbok').

The association of the tsessebe with mud includes

The following additional photos show the tsessebe with its pelage bedecked with mud:

https://www.alamy.com/stock-photo-tsessebe-antelope-in-southern-african-savanna-141669385.html?imageid=B1CD8529-1B3C-4E1C-9D23-49BCE9234784&p=291902&pn=2&searchId=60e559f776350f3aa551632b23562389&searchtype=0

https://www.inaturalist.org/observations/150099139

https://www.inaturalist.org/observations/14220603

https://www.inaturalist.org/observations/8180095

https://www.alamy.com/rare-tsessebe-antelope-damaliscus-lunatus-at-a-waterhole-south-africa-image180857620.html

https://www.alamy.com/stock-photo-rare-tsessebe-antelope-damaliscus-lunatus-south-africa-58368578.html

I have yet to see similar mud-bedecking in the topi (Damaliscus korrigum jimela), despite the two taxa being widely regarded as belonging to the same species.

Adult males of both the topi and the tsessebe adorn the horns with mud (https://www.alamy.com/stock-photo-topi-masai-mara-getting-ready-to-fight-for-his-harem-92999365.html?imageid=738ECA19-2EFC-4B03-B124-D2668ECB02DD&p=284001&pn=1&searchId=bf1e71fcf2ea53c3266b9674b4a7c2d8&searchtype=0).

However, the tsessebe uses mud also to bedeck its pelage, to an extent unknown in the topi.

Furthermore, in the tsessebe,

Please compare:

Tsessebe

https://www.dreamstime.com/stock-photo-muddy-tsessebe-portrait-antelope-has-had-red-mudbath-image74100059 and https://www.alamy.com/stock-photo-portrait-of-a-tsessebe-antelope-that-has-had-a-red-mudbath-170259076.html?imageid=02E0BADE-66C9-4F06-BB26-192E662C72C2&p=291902&pn=7&searchId=b5919b63c16a90d70b8f3874012c89a6&searchtype=0 and https://www.alamy.com/stock-photo-a-group-of-tsessebe-antelope-that-have-had-a-red-mudbath-170259062.html?imageid=86B99247-BF43-4482-8CA2-06910CC95A80&p=291902&pn=6&searchId=c7d97a4328b8ff32aa812bc4af94c292&searchtype=0 and https://www.shutterstock.com/it/image-photo/tsessebe-antelope-having-mud-bath-southern-782490406 and https://www.flickr.com/photos/richardlewisjones/2318608064

Topi

https://www.gettyimages.co.uk/detail/photo/topi-antelope-damaliscus-lunatus-masai-mara-royalty-free-image/1172247501?phrase=topi%20antelope&adppopup=true and https://www.gettyimages.co.uk/detail/photo/topi-with-grass-and-mud-on-horns-royalty-free-image/522615612?phrase=topi%20antelope&adppopup=true and https://www.jkwildimages.co.uk/kenya/20w70v2f4407vwqb1d4vf6ar1cos4f and https://www.projectnoah.org/spottings/7405328

DISCUSSION

Alcelaphins are surprisingly diverse in their habits w.r.t. dust, mud, and dirt.

No alcelaphin wallows.

However,

Within Damaliscus, there is a correlation between the use of mud and the colouration.

The pigmentation/depigmentation of the bontebok (Damaliscus pygargus pygargus) is exceptionally clear and graphic, and always looks clean, with no role played by mud or dust (https://www.facebook.com/100903643309358/photos/bontebok-and-blesbok-are-two-similar-but-distinct-antelope-species-that-came-clo/1327874950612215/?locale=hi_IN). One does not even see the horns of males of the bontebok adorned with mud/earth.

At the other extreme is the tsessebe.

The pelage of the tsessebe retains the complex pattern of colouration typical of the genus. However, the pigmentation is so indistinctly differentiated that the patterns seem to have been 'muddied' in the first place, by a complex combination of brindling, sheen, and ambivalent pigmentation.

The inference is that, in some sense, the colouration of the tsessebe has evolved to be such that little is lost when the pelage is bedecked by mud. This may be the closest thing to the development of 'clothing' among ungulates that retain a full cover of hair.

Is there any other non-wallowing ruminant in which the colouration has evolved to be conferred partly by mud?

And does the above evidence not support the separation of D. lunatus from D. korrigum, as a species rather than a mere subspecies?

For an index to my many Posts about the genus Damaliscus, please see https://www.inaturalist.org/journal/milewski/78238-an-index-to-my-posts-on-genus-damaliscus#.

Posted on May 19, 2023 12:25 AM by milewski milewski | 31 comments | Leave a comment

May 20, 2023

Thought-provoking observations from a brief visit to the Karoo Desert National Botanical Garden and Paarl Mountain Botanic Garden, October 2001

@tonyrebelo @jeremygilmore @hamishrobertson

On 20 October 2001, I visited the Karoo Desert Botanical Garden (https://en.wikipedia.org/wiki/Karoo_Desert_National_Botanical_Garden) and Paarl Mountain Botanic Garden (https://www.youtube.com/watch?v=h5rTCSop3-g), and also stopped at the head of Bainskloof Pass (https://en.wikipedia.org/wiki/Bainskloof_Pass) on the way. I had three companions.

The following are selected observations on plants and animals, which I still find noteworthy after two decades.

KAROO DESERT BOTANICAL GARDEN

I was struck with the sheer size of Albuca canadensis (https://www.inaturalist.org/taxa/522608-Albuca-canadensis and
https://www.pacificbulbsociety.org/pbswiki/index.php/Albuca_canadensis).

This was large-bodied for a geophyte, robust-looking, and common in karoid vegetation on stony slopes, and in transitional vegetation between karoo and renosterveld. The plants of A. canadensis were about 1 m high, the stalks and leaves still green, and the capsules ripe.

I found Septulina glauca (https://www.inaturalist.org/taxa/119511-Septulina-glauca) to be abundant on Euclea undulata, Searsia undulata (https://www.inaturalist.org/observations/18689587), and particularly Searsia incisa (https://www.inaturalist.org/observations/11049753). It was also present on Carissa haematocarpa (https://www.inaturalist.org/taxa/528768-Carissa-haematocarpa).

This mistletoe was conspicuous. Its foliage was green, except for 'autumn-yellow' leaves, and the stems were brittle.

What I found significant about this mistletoe was its large body-size and the greenness of its foliage, considering that it is a parasitic plant.

I observed a Viscum on Dodonaea and S. undulata. This mistletoe was leafless, and dark, dull green. It shared the host-plant, S. undulata, with S. glauca.

'Bushclumps' were present, about 2.5 m high and about 10 m in diameter. These consisted of intertwined Euclea undulata, Searsia undulata, Septulina glauca, Asparagus retrofractus? (https://www.inaturalist.org/taxa/495846-Asparagus-retrofractus), and others.

Searsia incisa formed 'hedge-hummocks', 2 m high and 5 m wide, each large and dense enough to hide a whole group of humans.

Searsia undulata was not spinescent. However, its rigid configuration of stems can obviously function to block the stripping of foliage by large folivores (https://www.inaturalist.org/observations/145088817 and https://www.inaturalist.org/observations/96698984 and https://www.inaturalist.org/observations/93584409).

I ate the fruits of S. incisa, which were abundant at the time. These fruits are technically fleshy, according to the syndrome of endozoochory. However, the surface of the fruits was brownish-felty (https://www.inaturalist.org/observations/140039365 and https://www.inaturalist.org/observations/141243223 and https://www.inaturalist.org/observations/140223421), and the taste was 'resinous'. I found the same puzzle as I have found with Searsia generally, which is that the fruits never seem to ripen in a conventional sense, and they are not necessarily conspicuous even when 'ripe'.

Small heuweltjies (https://en.wikipedia.org/wiki/Heuweltjie) were present in the slopes. These were so small that one might doubt that they qualify as heuweltjies. However, they were clearly marked by the associated plants. These were the grey-green Pteronja incana, plus clumps of the taller shrub Euclea undulata, different from the matrix of indifferently dull-green karoid shrublets.

Pteronia incana (https://www.inaturalist.org/taxa/524304-Pteronia-incana) is associated with heuweltjies, here.

At the picnic site, I observed a bumble/carpenter bee (black and yellow), attending flowers of Grewia occidentalis (https://www.inaturalist.org/taxa/334567-Grewia-occidentalis).

I observed Messor capensis (https://www.inaturalist.org/taxa/426213-Messor-capensis), as follows.

A hole in the ground had fruits of S. undulata littered at entrance, plus the burr-fruits of clover. The workers were carrying whitish nymphs (as large-bodied as the workers), and perching 20 cm above the ground on a mesemb plant. I formed the impression that this was to expose the nymphs to sunlight. These ants seemed oddly confident and fearless, because I and a companion approached them closely to examine their behaviour, kneeling at the hole and speaking at normal volume, and they did not react.

I observed an individual of Chersina angulata (https://www.inaturalist.org/taxa/40021-Chersina-angulata) at midday, on a mown and irrigated lawn of Pennisetum clandestinum. It was eating the leaflets of a clover, with prostrate growth-form. This indicated that this tortoise preferred a herbaceous legume over green grass-blades.

BAINSKLOOF PASS

I observed an individual of Duberria lutrix (https://www.inaturalist.org/taxa/30326-Duberria-lutrix), at 15h00 in sunny, calm weather. It was basking on a dirt road among the weekend-cottages at the head of Bainskoof Pass. I.e. the environment was anthropogenic, rather than natural.

Three individuals of Canis familiaris (small-bodied breeds) were present in full view nearby, on a verandah/porch. They seemed oblivious to the presence of this snake, either because they had not seen it, or because they had already investigated it but associated it with the well-known deterrent odour. A failure of the dogs to observe this snake seemed to be ruled out by the fact that we, several human individuals, attended the snake, in plain view nearby. I inferred that the dogs simply chose to ignore our flagging of the presence of the snake.

This individual of D. lutrix was so calm and confident that it allowed us to step right over it, without fleeing or reacting.

PAARL MOUNTAIN BOTANIC GARDEN

I observed Microhodotermes viator (https://www.inaturalist.org/taxa/568761-Microhodotermes-viator), active on the surface at 17h00 in warm, sunny, calm weather. The vegetation was fully mature fynbos (overdue for wildfire), with e.g. Protea and Watsonia, on granite-derived loam.

I observed a hive of M. viator, bisected by excavation for the construction of a footpath. In its intact state, this hive had been buried shallowly on this granite-derived loamy slope. I estimated the original volume if the intact hive to have been more than 20 litres.

I watched a mini-swarm at work, scurrying around and cutting material from green shrubs. I observed a hole on the footpath. The workers were collecting twigs about 2.5 cm long, green shoots, green fallen leaves, and dry (dry) fallen leaves. They were making little piles of this litter and freshly-cut material, including the shoot-tips, cut by the insects in the green state, of Aspalathus. Two small samples of the collected material, that I observed, comprised >50% and about 40% green material.

Present at the same site was Trinervitermes trinervoides (https://www.inaturalist.org/taxa/567385-Trinervitermes-trinervoides) and its mounds.

DISCUSSION

A companion on this excursion, Anne Gray (a contributor to 'Kite', the journal of the Tygerberg Bird Club, https://www.tygerbergbirdclub.org/), told me the following about what was identified as Microhodotermes viator.

The location was the coastal road near Yzerfontein/Darling Road intersection (https://en.wikipedia.org/wiki/R315_(South_Africa)), about 80 km north of Cape Town, in September 2001. The vegetation was strandveld (intact, as opposed to usurped by introduced Acacia).

Anne observed the swarming of termite alates. About 25 individuals of Milvus migrans (https://www.inaturalist.org/taxa/5268-Milvus-migrans) were swirling around on the wing, catching slates in their talons. They ate the insects while flying, by passing the items from foot to mouth.

The timing suggests that M. migrans had recently arrived from Europe.

Also present, higher in the air, were Apus melba (https://www.inaturalist.org/taxa/144634-Apus-melba), Apus caffer (https://www.inaturalist.org/taxa/6619-Apus-caffer), and Apus affinis (https://www.inaturalist.org/taxa/6612-Apus-affinis). These swifts were also presumably eating the slates.

Anne observed a rain of the insects' wings, descending to the ground.

What do all these observations, made on a day's excursion from Cape Town in spring, add up to?

The southwestern Cape of South Africa is generally regarded as nutrient-poor. This is true, but within the Fynbos Biome are enclaves of nutrient-richer ecosystems, in which there is remarkable evidence of biological productivity.

In the enclave of karoo vegetation that I visited, I formed the impression that herbivory by large mammals was a normal function in this ecosystem.

The abundance of mistletoes seemed to reflect the lack of herbivory by Taurotragus oryx (https://www.inaturalist.org/observations/157165364). Would Diceros bicornis, formerly present here, also have persecuted these mistletoes?

The slow-moving snake Duberria lutrix, which is widespread in the southwestern Cape, is remarkably specialised for a diet of molluscs (https://animalia.bio/duberria-lutrix), and for effective deterrence of carnivores.

Paarl Mountain is an example of fynbos on granite, slightly nutrient-richer than similar vegetation on the more widespread substrates, sandstone and quartzite. I find it remarkable that a partly herbivorous (as opposed to detritivorous) termite operates in this ecosystem.

In the case of strandveld on the sandy coastal plain to the west, it seems that this same termite is productive enough to attract congregations of Milvus migrans, a bird usually associated with productive ecosystems.

Posted on May 20, 2023 10:00 PM by milewski milewski | 0 comments | Leave a comment

May 21, 2023

An apparent case of fright-moult (autotomy of feathers) in the laughing dove (Spilopelia senegalensis)

@felix_riegel @tonyrebelo @jeremygilmore @baldcoot @aguilita @ldacosta @jimsinclair @lsueza @adamwelz @colin25 @karimhaddad @lukedowney @thebeachcomber @botswanabugs

Autotomy (https://en.wikipedia.org/wiki/Autotomy) is known in various animals. However, its incidence in birds is poorly-documented.

There are intriguing hints, on the Web, of autotomy of the feathers in small-bodied columbids, viz.

Please see:
https://www.birds-online.de/wp/en/birds-online-english/health-and-diseases/plumage-disorders-and-molt/moult/fright-moult/ and https://www.sarveywildlife.org/blog.aspx?post=3023&title=Mourning-Dove-attacked-by-cat and https://feederwatch.org/unusual-bird/mourning-dove-without-tail-feathers/

The term used has been 'fright moult' or 'fright molt'.

Also please see https://www.youtube.com/watch?v=mLJ0m5gEEf0 and https://www.facebook.com/watch/?v=600613034506485 and https://www.birdnote.org/listen/shows/having-your-tail-scared and https://wrenandsparrow.com/blog/f/fright-molt and https://folkwaysnotebook.blogspot.com/2015/08/fight-or-flight.html.

If certain species of birds, particularly Columbidae (https://www.inaturalist.org/observations?place_id=any&taxon_id=2715&view=species), use autotomy of feathers as a way of escaping from predators, this seems analogous to the shedding of tails by lizards when attacked.

I have, at various times in my life, found piles of the feathers of doves, in both the Perth metropolitan area of Western Australia, and in Cape Town, South Africa.

I did not record all these occasions, which may possibly total as many as 20 over my lifetime so far, in which feathers were present in quantity but there was no trace of other body-parts.

I paid too little attention at the start, because I was naive about the possibility of 'fright moult' in birds. I had simply presumed that the feathers were the refuse of a kill, not considering that the bird might instead have escaped.

Once I realised the possibilities, I recorded the following.

On 5 July 2006, in the suburbs of Fremantle, Western Australia, I encountered particular evidence of this kind of autotomy. This was during a spell of calm weather, when there was no wind to remove the feathers.

On the lawn of a wide road-verge, I found what looked like the results of a 'feather-explosion'. I am unsure of the identities involved, but I suspect that the bird was an individual of Spilopelia senegalensis (https://www.inaturalist.org/taxa/1455922-Spilopelia-senegalensis), and the attacker was an individual of Felis catus, pouncing in vain by day, on the ground.

The road-verge here was wide, and the feathers were far (at least 3 m) from the tarmac. This means that the dove was probably not hit by a motor vehicle.

I collected most of the feathers, which totalled about 370 of various types and sizes (from one individual bird). If these feathers were shed on 4 or 5 July 2006, I found them one day after the attack, or on the same day.

The smallest were merely down feathers. The largest, which were >5 cm long, were probably secondaries.

I do not know if the attacker (probably F. catus) caught this dove, but I suspect that it did not.

Were the feathers detached in reaction to pressure exerted by the predator, or shed spontaneously before contact was made? On this occasion, some of the secondaries seemed to be aggregated at their bases, suggesting that they were detached in the clutches of the attacker.

However, the sheer number of feathers indicates that many or most of them were shed without being pulled off in any way by the attacker.

Has any Reader observed any similar evidence of fright-moult, referring to S. senegalensis, G. cuneata, Z. macroura, any other species of columbid, or any other species of bird?

Also please see https://www.inaturalist.org/journal/milewski/68965-the-difference-between-commensalism-and-habituation-exemplified-by-spilopelia-chinensis-in-australian-suburbs#.

Posted on May 21, 2023 12:30 PM by milewski milewski | 23 comments | Leave a comment

May 22, 2023

Does the greater kudu (Strepsiceros) possess an anterior auricular flag?

@magdastlucia

Everyone knows that the overall colouration of the greater kudu (Strepsiceros, https://www.inaturalist.org/taxa/42339-Tragelaphus-strepsiceros) is adapted for inconspicuousness.

The stripes and other markings tend to disrupt of the figure, particularly against a background of thorn scrub (https://www.inaturalist.org/observations/153426937).

Even the ear pinnae, which are remarkably large (https://www.inaturalist.org/observations/130293311), have a pattern intricate enough to contribute to this disruptive (camouflage) colouration (https://www.alamy.com/plains-game-on-the-african-plains-the-rare-roan-antelopes-greater-kudu-impalas-all-fair-game-for-the-predators-of-africa-image462891192.html?imageid=5EE28E15-6E74-4F9F-8C56-9D54B1F0BC5F&p=298851&pn=1&searchId=f89a4d97c4f3cea31551e30e7eb84de2&searchtype=0
and https://www.inaturalist.org/observations/122202839 and https://www.inaturalist.org/observations/159543578).

(Dear Reader, please bear in mind that the blush in the latter photo would probably not be visible to either the greater kudu or Carnivora, which are effectively 'red-green colour-blind'. Instead, these animals would see the ears in dark, pale, and 'shades of grey'.)

However, it is equally true that, in many views, the ear pinnae are conspicuous enough to draw attention to the figure (https://www.shutterstock.com/image-photo/female-greater-kudu-kruger-national-park-1072876346 and https://www.inaturalist.org/observations/155867431 and https://www.inaturalist.org/observations/161363460 and https://www.inaturalist.org/observations/146211806 and https://www.inaturalist.org/observations/143955834 and https://www.inaturalist.org/observations/137962439 and https://www.inaturalist.org/observations/103146864 and https://www.inaturalist.org/observations/63566582 and https://www.inaturalist.org/observations/53711503 and https://www.inaturalist.org/observations/368626).

Furthermore, the greater kudu seems not to have been recorded folding its ear pinnae out of sight in mild alarm, in the way known for a coexisting bovid that also has large ears, viz. the steenbok (Raphicerus campestris, https://www.inaturalist.org/observations/196285829 and scroll in https://www.africancraftsmarket.com/products/animal-skins/animal-skins-2/Steenbok-hide.html).

The potential conspicuousness of the ears in the greater kudu results partly from the size of the pinnae (https://www.istockphoto.com/photo/bus-service-a-female-of-kudu-taking-around-a-group-of-10-oxpeckers-gm871792544-145536069?phrase=antelope+legs&searchscope=image%2Cfilm).

This evolutionary enlargement reflects some adaptive combination of

  • acute hearing (mainly for vigilance),
  • thermoregulation (the bare skin on the front-of-ear becomes flushed with blood by means of dilation of the capillaries, in order to shed body heat), and
  • display (for communication, both intra- and interspecific).

My interpretation is as follows:

There is a preponderance of photos in which the ear pinnae show boldly, because this is the more photogenic option. Most observers, seeking a satisfactory photo, would hesitate to 'click the shutter' while the figure and its ears are hard to discern among the vegetational clutter.

When the figure is furtively active in relatively dense vegetation, it can 'freeze' the moment it detects the approach of a potential predator. Under these conditions, the front-of-ear can function congruently with the striping on the torso, to camouflage the figure.

If this succeeds, the predator overlooks the prey animal, and after a suitable pause the latter can resume quietly foraging.

However, if the individual concerned sees the predator begin to stalk, it can forestall this attempt by announcing itself in a way that clearly informs the predator that it has lost any advantage of surprise. The greater kudu can communicate this by moving a few paces into the sunlight, and standing attentively with the ears directed towards the threat.

This may perhaps be accompanied by gruff-barking in mild alarm (https://www.google.com/search?q=Audio+of+kudu+barking&sca_esv=596393425&sxsrf=AM9HkKkVdm9zDPj1trONw5hNvZoeGPzbdA%3A1704651678462&source=hp&ei=nuuaZdKOGsuVg8UP3oyogAs&iflsig=AO6bgOgAAAAAZZr5riFNgOQC3ak96SSAri5f5ov8WILy&ved=0ahUKEwjS1Yiu8suDAxXLyqACHV4GCrAQ4dUDCAw&uact=5&oq=Audio+of+kudu+barking&gs_lp=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&sclient=gws-wiz#fpstate=ive&vld=cid:790d618c,vid:yc3yldMnuKU,st:0 and https://www.facebook.com/watch/?v=2957306921206396 and https://www.google.com/search?q=Audio+of+kudu+barking&sca_esv=596393425&sxsrf=AM9HkKkVdm9zDPj1trONw5hNvZoeGPzbdA%3A1704651678462&source=hp&ei=nuuaZdKOGsuVg8UP3oyogAs&iflsig=AO6bgOgAAAAAZZr5riFNgOQC3ak96SSAri5f5ov8WILy&ved=0ahUKEwjS1Yiu8suDAxXLyqACHV4GCrAQ4dUDCAw&uact=5&oq=Audio+of+kudu+barking&gs_lp=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&sclient=gws-wiz#fpstate=ive&vld=cid:295d9cce,vid:IgVh-eVwI30,st:0).

In other words, I hypothesise that the pattern of colouration on the anterior surface of the ear pinna in the greater kudu has been adaptively configured in an ambivalent (versatile) way. The same pattern of dark and pale can function to hide the figure when held still and in shade or dappled shadow, or to advertise the figure - and its alert attentiveness - once concealment has proven futile and the better tactic is to step into the light and tell the predator 'I've seen you!'

An alternative framing invokes the difference between night and day.

Even if the pattern on the front-of-ear is bold enough that it tends to undermine camouflage in daylight, it is possible that in dim light it tends to function disruptively. This might be as important as the distinction between stationary and divulged by motion, because the greater kudu - unlike most bovids of its body size and more than the steenbok - is partly nocturnal.

On this basis, I would argue that the greater kudu qualifies as possessing an anterior auricular flag, but that this flag has been designed not to be mutually exclusive with camouflage-colouration.

Since inconspicuous (cryptic or disruptive = camouflage) colouration is the default assumption among ungulates, it is the bold aspect of the auricular pattern that deserves particular recognition.

In summary:
The greater kudu shows how the pattern on the front-of-ear can function as part of inconspicuous (disruptive) colouration before a potential predator detects the figure, and then as part of conspicuous colouration (anterior auricular flag) once 'freezing' is abandoned and the figure moves attentively in mild alarm, signalling to the intruder that it has been spotted.

Also please see https://www.inaturalist.org/posts/72489-display-of-the-tail-in-the-greater-kudu-is-puzzlingly-subtle-and-inconsistent#

Posted on May 22, 2023 11:18 PM by milewski milewski | 4 comments | Leave a comment

May 23, 2023

The ecological significance of forested mounds of the termite Macrotermes in the Caprivi Strip

@tonyrebelo @jeremygilmore @hamishrobertson @joshua_tx @s_k_johnsgard @botswanabugs @bartwursten @troos

In May 2006, a colleague and I visited the eastern Caprivi Strip (http://www.eyesonafrica.net/african-safari-namibia/caprivi.htm and https://en.wikipedia.org/wiki/Caprivi_Strip) to do the fieldwork for https://agris.fao.org/agris-search/search.do?recordID=US201301621709 and https://zslpublications.onlinelibrary.wiley.com/doi/abs/10.1111/j.1469-7998.2008.00544.x.

On the early morning of 19 May 2006, I studied an example of a large mound built - and still occupied - by Macrotermes (https://en.wikipedia.org/wiki/Macrotermes). We had slept at this location the previous night.

The height of this mound was >3.5 m above general ground level, and probably as much as 4.5 m. Its width (diameter, including the broad apron of the mound) was 25 m, measured from the general level of the floodplain that formed the matrix for the scattered mounds.

The scene in https://www.inaturalist.org/observations/149034602 is indicative. However, the sheer area of the mound - nearly 500 square metres - makes the situation difficult to photograph.

The species of Macrotermes could not be identified at the time, and - surprisingly - this seems still to be true today. The most likely candidates are Macrotermes natalensis and Macrotermes falciger, both of which are greatly underrepresented in iNaturalist.

VEGETATION ON THE MOUND

The plant community on the mound contained a total of about 20 spp., visible at the time of my visit.

Eight individual trees occurred on this mound, consisting of

Peripheral plants of M. mochisia, 1.5 m high, had been so heavily browsed by large folivores that their growth-form was bonsai/topiary-like (https://www.inaturalist.org/observations/67387378 and https://www.inaturalist.org/observations/116415537).

This was reminiscent of Gardenia (please see https://www.inaturalist.org/journal/milewski/60060-explaining-the-extreme-growth-form-of-gardenia-in-the-serengeti#), but with the crown less rounded.

The understorey on the mound consisted mainly of Euclea divinorum (https://www.inaturalist.org/taxa/343032-Euclea-divinorum) and Ximenia americana (https://www.inaturalist.org/taxa/83832-Ximenia-americana), the latter superficially resembling Gymnosporia senegalensis (which may itself have been present as a scarce species).

Carissa spinarum (https://www.inaturalist.org/taxa/369502-Carissa-spinarum) was common on this mound, but Diospyros lycioides (https://www.inaturalist.org/taxa/469308-Diospyros-lycioides) seemed absent.

Salvadora persica (https://www.inaturalist.org/taxa/197082-Salvadora-persica) was present on this mound. Dichrostachys cinerea (https://www.inaturalist.org/taxa/129706-Dichrostachys-cinerea) occurred only where the mound joined the surrounding ground level.

The main liane on the mound was Capparis tomentosa (https://www.inaturalist.org/taxa/342724-Capparis-tomentosa), festooning not only the periphery of the mound, but also the trees. There were also two lines of Cucurbitaceae, one with small fleshy fruits (possibly https://www.inaturalist.org/taxa/165503-Momordica-balsamina), and the other bearing large, knobbly melons, lying on the ground and ripening at the time (possibly https://www.inaturalist.org/taxa/1245066-Citrullus-naudinianus). Asparagus africanus? (https://www.inaturalist.org/taxa/505798-Asparagus-africanus) was present only as small individuals.

Setaria verticillata (https://www.inaturalist.org/taxa/79069-Setaria-verticillata) was sparsely present on the mound, brown and collapsed at the time, with the burr-like seed-heads evident (https://www.minnesotawildflowers.info/grass-sedge-rush/bristly-foxtail#lboxg-10). A lawn-type grass occurred immediately adjacent to the mound, but did not encroach even on to the apron of the mound.

?Kalanchoe lanceolata? (a fragile-looking ?annual succulent) was present, and in flower at the time.

I estimated the contributions to the total vertically-projected cover of the vegetation on this mound, as follows:

Diospyros mespiliformis (tall trees): 55%
Manilkara mochisia (shorter trees): 25%
Capparis tomentosa (robust liane): 10%
Ximenia americana (common spinescent shrub): 5%
Euclea divinorum: 2%
Salvadora persica (partly liane-like): 1%
Cucurbitaceous liane (large fruits): trace
Cucurbitaceous liane (small fruits): trace
Unidentified shrub with dentate leaves: trace
Setaria verticillata: trace
?Phyllanthus reticulatus: trace
Acanthaceae, unidentified perennial: trace
Asparagus africanus?: trace
Malvaceae, unidentified: trace
Crassulaceae, unidentified: trace
Grewia sp. with no apparent fruits (different from the sp. in nearby woodland of T. sericea): trace
Sundry unidentified (five spp.): trace each

VEGETATION IN THE MATRIX

In this general environment, the matrix (the surrounding plain) was a floodplain, bearing open savanna with a main stratum of short, coarse (plastic-like) grass (dry and brown at the time).

On the clayey flats (with a grey sandy surface over most of the area) of the matrix, there was a sparse stratum of trees and shrubs.

This consisted of Combretum imberbe and congeners, Senegalia nigrescens, Piliostigma thonningii (https://www.inaturalist.org/taxa/592162-Piliostigma-thonningii), Dichrostachys cinerea, and Ziziphus mucronata (https://www.inaturalist.org/taxa/340228-Ziziphus-mucronata), with a few individuals of Gardenia.

In the case of C. imberbe, most of the individuals on the floodplain were about 1-1.5 m high.

All of these spp. were absent from the mound itself.

Patches of cracking clay in the matrix supported only sapling-size/stunted Combretum imberbe (https://www.inaturalist.org/observations/133825301), and shrubs of Dichrostachys cinerea (https://www.inaturalist.org/observations/133105517).

However, the large mounds were not the only situation in which trees were concentrated. Terminalia sericea (including large trees) dominated on a sandy patch about 75 m away, slightly elevated above the level of the matrix of short grassland. This sand was fine-grained and pale grey, and at most 0.5 m deep over a hard layer, as we discovered when our van became temporarily stuck.

Accompanying T. sericea on the sandy patch were Grewia sp. (in ripe fruit, the edible layer of which was naturally completely dry), Gymnosporia senegalensis (https://www.inaturalist.org/taxa/340106-Gymnosporia-senegalensis), Philenoptera violacea (https://www.inaturalist.org/taxa/340211-Philenoptera-violacea), and Vachellia erioloba (uncommon) - all of which were absent from the mound described above.

ASSOCIATED ANIMALS

The area was well-grazed, albeit only by Bos taurus X indicus. Despite this substitution of domestic livestock for the original wild grazers, the ecosystem looked natural and healthy. The nearest village or kraal was at least several km distant.

There was abundant evidence of current foraging by termites throughout this area. The faeces of B. taurus X indicus were being promptly consumed by Macrotermes.

There was much evidence (in the form of mud-runnels) that Macrotermes was foraging for litter on the mound itself. This included grass (also covered by mud-runnels) being consumed by Macrotermes on the apron of the mound. However, my impression was that only trampled grass was suitable for Macrotermes.

The mud-runnels made for foraging by Macrotermes were present on the surface in the matrix, even where the surface was cracking clay. This was often on the faeces of B. taurus X indicus.

Hodotermes mossambicus (https://www.inaturalist.org/taxa/558312-Hodotermes-mossambicus) was abundant hereabouts, particularly on the floodplain. However, I did not see it at this location, perhaps because of the time of day.

The soil-heaps of mole-rats were absent from this whole area, despite the occurrence elsewhere in the Caprivi Strip of Fukomys damarensis (https://www.inaturalist.org/taxa/446619-Fukomys-damarensis).

Birds heard on/near this mound:

Vanellus coronatus (https://www.inaturalist.org/taxa/4877-Vanellus-coronatus), common on the short grassland of the matrix
Ptilopsis granti (https://www.inaturalist.org/taxa/144592-Ptilopsis-granti), heard repeatedly the previous night
Corythaixoides concolor (https://www.inaturalist.org/taxa/7238-Corythaixoides-concolor)
Streptopelia semitorquata (https://www.inaturalist.org/taxa/2988-Streptopelia-semitorquata)
Streptopelia capicola (https://www.inaturalist.org/taxa/2959-Streptopelia-capicola)
Streptopelia decipiens (https://www.inaturalist.org/taxa/2951-Streptopelia-decipiens)
Oriolus auratus (https://www.inaturalist.org/taxa/7868-Oriolus-auratus)
Pycnonotus barbatus (https://www.inaturalist.org/taxa/14588-Pycnonotus-barbatus)

DISCUSSION

In Africa more broadly, it is well-known that mounds of Macrotermes tend to support plant spp. absent from the matrix.

However, what is remarkable in this case is that the plant communities on and off this particularly large mound (comparable in area to a typical suburban residential plot) shared virtually no species of plants.

The mound supported a considerable patch of forest, which was

  • exempt from wildfire,
  • composed of plants dispersed and sown by vertebrates, mostly via fleshy fruits and endozoochory, and
  • surrounded by open savanna, itself probably exempt from wildfire when heavily grazed.

The presence of S. persica indicates that the soils on this mound, even at its apex, were rich in cations, particularly sodium (https://scialert.net/fulltext/?doi=ajpp.2020.14.22#:~:text=Salvadora%20persica%20(Arak%20or%20Miswak,often%20mucronate%20at%20the%20apex.).

The complete lack of caesalpinioid legumes, and indeed legumes in general, on the mound is noteworthy.

All of the trees, and most of the shrubs and lianes, on this mound possess fleshy fruits - many of them edible to humans (https://www.inaturalist.org/observations/69198499 and https://www.inaturalist.org/observations/156933406 and https://www.inaturalist.org/observations/68367756).

The protection of the whole mound from wildfire was owing to

  • the lack of a flammable lower stratum on the mound itself, and
  • the shortness of the grass in the surrounding matrix, partly owing to grazing.

The presence of faeces indicated that the vegetation on the mound was probably attractive to B. taurus X indicus, despite the scarcity of grass on the mound.

My impression was that three main consumers of grass interact in an important way in the complex of vegetation. In the matrix and probably also on the mound, grass is eaten mainly by ungulates and Hodotermes; the faeces (derived mainly from grass) of the ungulates are consumed by Macrotermes, which also consumes woody material of various plants; and the faeces of Hodotermes fertilise the whole ecosystem, particularly in the matrix.

What makes this situation, in the Caprivi Strip, remarkable is the combination of Macrotermes and Hodotermes. Extensive, forested mounds of Macrotermes are mainly a feature of tropical African woodlands, beyond the distribution of Hodotermes. The Caprivi Strip is at, or near, the northern limit of the distribution of Hodotermes. This unusual overlap in distribution seems to have produced a regime of thorough consumption of grass and litter, tending to exclude wildfire, and promoting palatable plants - including fruits edible for humans.

Posted on May 23, 2023 08:33 AM by milewski milewski | 14 comments | Leave a comment