Back to milewski's journal

milewski's Journal

Journal archives for May 2022

May 01, 2022

Similarities/differences between the porcupines of different Hemispheres: Erethizon vs Hystrix, part 1

@kevinatbrakputs @karoopixie @alexanderr @maxallen @caraleigh @danavan @jwidness @ken_j_allison @edporopat @arborsphere @whutchins @swampy @jnstuart @e-aus-kanada @nsharp @alwoodhouse @saber_animal @jakob @ariel-shamir @gwark @alanmuchlinski @bartwursten @markusgmeiner @christiaan_viljoen @markuslilje @opisska @ockertvs @lovecamp @asio-otus @lynnharper @birderryan @astanyoung @fatroosterfarm @miscelaineous @pfau_tarleton @donaldmcleod @pinawapt @jerry_deboer @douglasriverside @nvpyromelana @colincroft @jasonheadley @alexlamoreaux @aterrigeol @zonotrick @cindychrisler @tmurray74 @mlodinow @ungerlord @michael_oldham @desmond_macneal @camerondeckert @scottranger @justinhawthorne @jujurenoult @er1kksen @davidrscott @katzyna @ksled @dan_macneal @md-in-ns15 @mnerrie @dlcoleman @arcticory @nn4ever @codystricker @baywren @bert_raccoon @mikehannisian @meganhanson @amzapp @janeyd @mc1991 @josh_vandermeulen @zaccota @creedo @howlin_jay @erwinsieben @nyoni-pete @dewald2 @marco_vicariotto @emilianomori @ryruther @benjamynweil @ivanovdg19 @vmoser @natemartineau @lucaboscain @felix_riegel @mhughes26 @mhairimcf

(Many thanks to Kim Cabrera @beartracker for information useful in this series of Posts.)

Among the various mammals that defend themselves by means of spines, 'porcupines'

However, the term 'porcupine' conflates two different lineages of rodents (https://animals.sandiegozoo.org/animals/porcupine). While these are similar enough to be confused in the public mind, they also differ significantly.

TAXONOMY

Any comparison is complicated by the fact that

However, I treat collectively the five species of Hystrix, namely

BODY SIZE and FORM

Erethizon and Hystrix overlap broadly in body mass, in the range 6-13 kg. However, the former is smaller-bodied than the latter.

Erethizon weighs as little as 3.5 kg when adult and lean, whereas Hystrix weighs as much as 25 kg. The heaviest, fattest specimens recorded for the two genera are 18 kg vs 27 kg.

In Erethizon, males outsize females; in Hystrix, the sexes have similar body size (https://www.tandfonline.com/doi/abs/10.1080/11250008709355592).

In https://www.youtube.com/watch?v=w4NfE9mqU64, the individual of Panthera pardus is an adult male, probably weighing more than 55 kg. By comparison, this individual of Hystrix africaeaustralis - as likely female as male - may weigh as much as 25 kg.

Both genera have small eyes (https://stock.adobe.com/sk/search/images?k=porcupine+face&asset_id=480402738 and https://stock.adobe.com/sk/search/images?k=porcupine+face&asset_id=175434829 and https://www.istockphoto.com/photo/crested-porcupine-gm90848177-2184836) and the same dental formula. However, the skulls differ surprisingly. That of Erethizon (https://animaldiversity.org/collections/contributors/skulls/erethizon/e._dorsatum/87345.lateral/) is unremarkable among rodents. By contrast, that of Hystrix (https://www.inaturalist.org/observations/36773744 and https://www.inaturalist.org/observations/17389159 and https://animaldiversity.org/collections/contributors/phil_myers/ADW_mammals/specimens/Rodentia/Hystricidae/Hystrix_indica/lateral6337/) has extremely inflated nasal and frontal bones.

The cranium also seem to differ in relative size. If Erethizon is brainier than Hystrix, this would be consistent with its play behaviour in adulthood (https://psycnet.apa.org/record/1944-03113-001) and its performance in memorising mazes (https://psycnet.apa.org/record/2005-14412-004).

The tail is proportionately larger in Erethizon (https://www.sciencephoto.com/media/1009962/view/north-american-porcupine-skeleton and https://fineartamerica.com/featured/1-north-american-porcupine-skeleton-millard-h-sharp.html and https://www.istockphoto.com/photo/north-american-porcupine-on-a-branch-gm519080646-90356241) than in Hystrix (https://paolov.files.wordpress.com/2015/03/20140227_143245.jpg and https://www.alamy.com/porcupine-skeleton-in-profile-view-after-antique-engraving-from-the-19th-century-image434355969.html).

POSTURES and LOCOMOTION

Both genera use the same gait in walking.

Erethizon:
https://www.inaturalist.org/observations/26949994 and https://www.shutterstock.com/nb/video/clip-2870482-north-american-porcupine-erethizon-dorsatum-walking-along and https://www.youtube.com/watch?v=cnos437-t18 and https://www.inaturalist.org/observations/95054372 and https://www.pond5.com/stock-footage/item/12263333-north-american-porcupine-walking-along-road-leaf-stuck-its-f.

Hystrix:
https://www.istockphoto.com/photo/porcupine-walking-gm177703348-24110328 and https://www.youtube.com/watch?v=5nbaSyg3Z1M.

Both genera prefer to commute along pathways, and Erethizon depends on creating its own pathways when commuting across deep snow.

The tracks of Erethizon (https://www.bear-tracker.com/porcpine.html) and Hystrix (https://twitter.com/bgsurvival/status/731435193278566400) are similar. In both genera, the feet are usually pointed somewhat inward in the walking gait.

However, the forefeet of the two genera differ. In Erethizon (https://natureidentification.com/how-to-identify-porcupine-erethizon-dorsatum-tracks/), the claws are long, the bare surface is rough, and the pollex is present, albeit only as a clawless pad. These features differ from Hystrix (https://www.natureinstock.com/search/preview/cape-porcupine-hystrix-africaeaustralis-adult-close-up-of-front-foot/0_11296644.html and https://www.inaturalist.org/observations/19891886).

Both Erethizon and Hystrix are able to swim (https://www.researchgate.net/publication/330451642_Behaviour_of_a_porcupine_Erethizon_dorsatum_swimming_across_a_small_boreal_stream and https://www.youtube.com/watch?v=wt1PMbVnB44). Neither genus seems capable of jumping.

However, postures and locomotion differ between the two genera in important ways.

Erethizon differs categorically from Hystrix in adopting the following postures/gaits, all of which use the muscular tail as a prop:

Erethizon is capable of hanging upside down from branches (https://natlands.org/porcupines/ and https://www.istockphoto.com/photo/north-american-porcupine-gm1285939555-382593958), but cannot locomote while doing so.

By contrast, Hystrix climbs so poorly that adults can reputedly be kept captive by walls only one metre high.

Neither Erethizon nor Hystrix has spines on the ventral surfaces. However, in Erethizon the bristly hairs here - particularly on the ventral surface of the tail - enhance friction during climbing, compensating partly for the poor development of the pollex (https://www.inaturalist.org/observations/112849002 and https://www.shutterstock.com/nb/image-photo/north-american-porcupine-erethizon-dorsatum-on-310015790 and https://www.adfg.alaska.gov/index.cfm?adfg=northamericanporcupine.main).

Erethizon seems hardly able to run (https://www.youtube.com/watch?v=4v-XGIi0O4s and https://www.shutterstock.com/nb/image-photo/porcupine-running-thru-winter-snow-colville-108288905 and https://www.alamy.com/adult-north-american-porcupine-erethizon-dorsatum-running-in-glacier-bay-national-park-alaska-united-states-of-america-north-america-image417695139.html).

Hystrix is slow-moving relative to ungulates, but is versatile in its terrestrial gaits, as follows:

to be continued...

Posted on May 01, 2022 10:15 PM by milewski milewski | 23 comments | Leave a comment

May 02, 2022

Similarities/differences between the porcupines of different Hemispheres: Erethizon vs Hystrix, part 2

continued from https://www.inaturalist.org/journal/milewski/65099-similarities-differences-between-the-porcupines-of-different-hemispheres-erethizon-vs-hystrix-part-1#

COLOURATION

The colouration of both Erethizon and Hystrix combines

Erethizon differs from Hystrix in that, in the winter coat, the pale surfaces of the spines themselves are generally invisible on the body of the relaxed or normally active figure, being covered by long non-spiny hairs (https://www.agefotostock.com/age/en/details-photo/north-american-porcupine-erethizon-dorsatum-in-a-creek-bed-canadian-porcupine-common-porcupine-donjek-route-kluane-national-park-st/IBK-990718 and https://www.zoobasel.ch/en/aktuelles/news/1324/neu-im-zoo-basel-zu-sehen-ursons/).

The colouration of Erethizon is more variable individually, seasonally, and regionally, than that of Hystrix.

However, in Erethizon

In Hystrix, the tail is conspicuously pale, but only in

ANTI-PREDATOR DEFENCES

Both Erethizon and Hystrix base their anti-predator defences on barbed spines, which are much-thickened, fortified hairs with pithy (spongy) interiors (https://animaldiversity.org/collections/spinesquills/ and https://books.google.com.au/books?id=A3HuW_DMglQC&pg=PA17&lpg=PA17&dq=Fluorescence+of+porcupine+quills&source=bl&ots=6LnVvz0tS4&sig=ACfU3U07ghTW_RF0PEOYmHq9jQ1Bo6_PgQ&hl=en&sa=X&ved=2ahUKEwjUqbj3nMf3AhWWzDgGHTQHAmQ4ChDoAXoECCcQAw#v=onepage&q=Fluorescence%20of%20porcupine%20quills&f=false).

The spines not only pierce the skin of attackers, but detach easily from the source.

This leaves the spines firmly embedded and able to work their way, by virtue of the automatic/passive ratchet-mechanism of the barbs, either

  • perpendicularly, deeper into the body with the risk of penetrating internal organs, and/or
  • laterally and subcutaneously, parallel to the surface of the body.

See https://www.lichenlabs.net/product/porcupine-quill-cholla-cactus-spines/ and https://www.researchgate.net/figure/SEM-images-of-the-structure-of-the-Erethizon-quill-a-entire-morphology-in-transverse_fig4_230863177 and https://www.discovermagazine.com/planet-earth/why-porcupine-quills-slide-in-with-ease-but-come-out-with-difficulty and https://www.science.org/content/article/porcupine-quills-reveal-their-prickly-secrets and https://www.sciencephoto.com/media/107817/view/porcupine-quill-sem and https://www.npr.org/sections/health-shots/2019/04/09/711050307/porcupine-barbs-for-better-wound-healing and https://www.nbcnews.com/tech/tech-news/point-porcupines-inspired-improved-surgical-tape-flna1c7529221 and https://www.nature.com/news/barbs-make-porcupine-quills-into-nasty-needles-1.11986 and https://repository.up.ac.za/handle/2263/15216?show=full.

The two genera differ in:

  • the length of the longest spines: up to 7.5 cm in Erethizon vs up to 30 cm in Hystrix, and
  • the extent of spininess in the pelage: covering much of the body plus the crown in Erethizon, vs restricted to the back and hindquarters in Hystrix.

The following show the shortness of the spines of Erethizon:
https://www.inaturalist.org/observations/116397549 and https://www.inaturalist.org/observations/69200459 and https://www.inaturalist.org/observations/19849435 andhttps://www.featheredphotography.com/blog/2018/09/12/why-a-snoot-full-of-porcupine-quills-can-be-a-serious-matter/ and https://lmtribune.com/outdoors/porcupine-pointer-pain/article_3c62ccb8-c8cf-5867-a747-e225e0539781.html and https://www.cbc.ca/news/canada/edmonton/porcupine-quills-dog-attack-1.4594566 and https://kdvr.com/news/dog-that-had-encounter-with-porcupine-continues-to-recover-after-three-hour-surgery/ and https://www.petful.com/pet-health/porcupine-attacks-on-dogs/.

The following show the lengths of the spines of several species of Hystrix:
https://www.wildcard.co.za/krugers-daring-leopards-match-porcupines/ and https://www.youtube.com/watch?v=9Qr1LVaEysk and https://www.mensjournal.com/adventure/leopard-attacked-by-porcupine-suffers-painful-hunting-lesson/ and https://www.wildcard.co.za/krugers-daring-leopards-match-porcupines/ and https://www.dailymail.co.uk/news/article-3323494/He-REALLY-didn-t-think-one-Red-faced-leopard-looks-ready-throw-furious-fight-porcupine-ends-face-quills.html and https://www.dailymail.co.uk/news/article-2945715/Don-t-pick-nose-Lion-cub-gets-porcupine-s-quill-stuck-nostril-trying-eat-s-worse-ending-porcupine-cat-s-dad-turns-up.html and https://www.inaturalist.org/observations/102469650 and https://www.alamy.com/stock-photo-lion-cub-investiging-porcupine-87078362.html and https://owenslaterphotography.com/2016/12/02/honey-badger-vs-crested-porcupine/ and https://www.nationalgeographic.com/animals/article/lions-hunt-porcupines-human-impact.

When predators eat Erethizon, they discard the whole skin (https://www.inaturalist.org/observations/74560373). In the case of Hystrix, only the pelage itself is discarded, the skin apparently being eaten.

In both genera, the defensive syndrome is accentuated by

However, Erethizon and Hystrix differ in several ways, as follows.

Erethizon seems not to strike until the pelage is touched, whereas Hystrix attempts to strike preemptively once the potential predator approaches closely. Erethizon thus tends to strike as retaliation, whereas Hystrix tends to strike as intimidation. This is consistent with

  • the visual display being starker in Hystrix than in Erethizon, and
  • the defensive display being in a sitting posture in Erethizon vs a standing posture in Hystrix.

Both Erethizon and Hystrix have a large patch of spines on the rump, lacking guard hairs, that is exposed by the erection of the surrounding long pelage. In this rump-patch the spines (which are short in both genera) have mixed orientations (https://www.alamy.com/a-young-north-america-porcupine-erethizon-dorsatum-raises-the-quills-on-its-back-in-a-threat-display-upper-clements-annapolis-royal-nova-scotia-image246934252.html and https://www.alamy.com/north-america-united-states-alaska-denali-national-park-wildlife-porcupine-erethizon-dorsatum-spring-defensive-quills-up-image384814685.html and https://www.inaturalist.org/observations/96103364 and https://www.inaturalist.org/observations/35185393 and https://www.inaturalist.org/observations/8397945 and https://www.inaturalist.org/observations/21385210 and https://www.inaturalist.org/observations/92557550 and https://www.inaturalist.org/observations/6183394 and https://www.inaturalist.org/observations/3779300).

Only Erethizon uses odour as part of the defensive repertoire, compensating for the limited conspicuousness of the relatively short spines (https://www.researchgate.net/publication/227058437_Warning_Odor_of_the_North_American_PorcupineErethizon_dorsatum).

This odour is secreted from the otherwise bare-skinned patch of dark spines on the back/rump, and is facilitated by a wick effect of these spines themselves (https://books.google.com.au/books?id=A3HuW_DMglQC&pg=PA17&lpg=PA17&dq=Fluorescence+of+porcupine+quills&source=bl&ots=6LnVvz0tS4&sig=ACfU3U07ghTW_RF0PEOYmHq9jQ1Bo6_PgQ&hl=en&sa=X&ved=2ahUKEwjUqbj3nMf3AhWWzDgGHTQHAmQ4ChDoAXoECCcQAw#v=onepage&q=Fluorescence%20of%20porcupine%20quills&f=false and https://www.dreamstime.com/stock-photo-close-up-prickly-porcupine-northern-british-columbia-wildlife-as-seen-hike-canadian-forest-image57706727 and https://www.dreamstime.com/porcupine-photo-stock-close-up-profile-view-walking-gravel-side-road-foliage-foreground-rock-background-image219969435).

The release of the defensive odour is accompanied by a second stage in the activation of the pelage of the rump. In the first stage, what is displayed is a patch of mainly whitish spines. In the second stage, the tone changes to dark, and the warning changes from visual to olfactory.

Only Hystrix uses pilo-erection of long hairs other than guard hairs or spines to exaggerate its body size as part of the defensive display. This produces a 'nuchal crest' (https://www.robertharding.com/preview/743-880/porcupine-hystrix-africaeaustralis-limpopo-south-africa-africa/ and https://www.youtube.com/watch?v=EeZW3UcW1Yc and https://www.shutterstock.com/nb/image-photo/cape-porcupine-south-african-hystrix-africaeaustralis-1304830168 and https://wellcomecollection.org/works/dj2bhb4u/items and https://wildkratts.fandom.com/wiki/African_Crested_Porcupine?file=African+Crested+Porcupine.PNG and https://www.istockphoto.com/photo/porcupine-is-eating-in-namibia-africa-gm619090370-107922591).

In Erethizon, the guard hairs on the crown and nape can be long (https://www.inaturalist.org/observations/111701471 and https://www.alamy.com/north-american-porcupine-alberta-canada-image66233270.html), but there seems to be no particular display of these as part of the anti-predator reactions. Furthermore, the crown and nape - like the rest of the forequarters - are spiny in Erethizon (https://www.inaturalist.org/observations/40158394 and https://www.inaturalist.org/observations/45858048 and https://www.inaturalist.org/observations/45193401) while lacking spines in Hystrix.

In both genera, the tail bears erectile spines and can have warning colouration:

However, in Erethizon the tail is proportionately large and muscular enough to be wielded as a flexible, fast-moving, spine-embedding organ, and its colouration tends to contrast dark on the upper and lower surfaces with pale on the sides (https://www.robertharding.com/preview/764-609/porcupine-erethizon-dorsatum-mother-baby-captivity-sandstone-minnesota/). In Hystrix the whole tail tends to be conspicuously pale in two of the species (see above). This is fully exposed to view once the long pelage around the rump-patch is erected in the warning reaction (https://www.shutterstock.com/nb/image-photo/crested-porcupine-hystrix-cristata-adult-1646445481).

In Hystrix a main function of the tail (but restricted to certain species) is production of a warning sound - namely a hiss-like rattling - by means of specialised caudal quills. These are broad, hollow, and whitish, but blunt and harmless; in their full development they may have narrow, flexible stalks.

Both genera thus use percussion as part of their defensive repertoire.

However,

  • Erethizon clacks the incisors (https://www.inaturalist.org/observations/75603980) and chatters the cheek-teeth (mainly in males), and slaps the tail on the ground, whereas
  • Hystrix rattles the pelage (particularly the specialised caudal quills), grunts, and stamps the feet.

to be continued...

Posted on May 02, 2022 01:34 PM by milewski milewski | 20 comments | Leave a comment

May 05, 2022

Similarities/differences between the porcupines of different Hemispheres: Erethizon vs Hystrix, part 3

continued from https://www.inaturalist.org/journal/milewski/65187-similarities-differences-between-the-porcupines-of-different-hemispheres-erethizon-vs-hystrix-part-2#

HABITAT

The latitudinal ranges of the two genera overlap at 28-41 degrees N.

This means that the southern part of the distribution of Erethizon, in northern Mexico and many states of the USA, is at similar latitudes to

  • the northern part of the distribution of Hystrix indica in e.g. Turkey, Iran, Afghanistan, Azerbaijan, Turkmenistan, and Kyrgyzstan, and
  • the southern part of the distribution of Hystrix africaeaustralis in most of South Africa.

Furthermore, both genera occur in a wide range of ecosystems from semi-desert (e.g. Erethizon in Nevada, https://www.birdandhike.com/Wildlife/Mamm/06Rod/09_Ereth/Erethi_dor/_Ere_dor.htm and https://www.fs.fed.us/psw/publications/zielinski/psw_2017_zielinski002_appel.pdf) to forest (e.g. Hystrix in Borneo, https://www.alamy.com/malayan-porcupine-hystrix-brachyura-acanthion-brachyura-walking-indonesia-image8113983.html and https://www.inaturalist.org/guide_taxa/178762).

However, the habitat of Erethizon is partly subarctic, whereas that of Hystrix is mainly tropical and subtropical.

In their zone of latitudinal overlap, Erethizon depends on woody vegetation (https://www.inaturalist.org/observations/13334310 and https://www.alamy.com/stock-photo-a-north-american-porcupine-walks-up-a-sand-dune-in-the-desert-177548000.html), whereas Hystrix does not (e.g. https://www.inaturalist.org/observations/104564486 and https://www.inaturalist.org/observations/103038302).

REPRODUCTION

Both Erethizon and Hystrix are long-lived in captivity (maximum lifespan 30 vs 28 years). However, the natural lifespan of Erethizon is effectively limited by the wear of its cheek-teeth to less than 10 years.

Both genera reproduce slowly, with usually one offspring per birth and per year. In both Erethizon and Hystrix, the newborns are precocial, with open eyes and some spines already formed.

However, Hystrix is more fecund than Erethizon. The former bears up to four offspring per birth and can breed twice per year (https://www.nature.com/articles/s41598-021-99819-3). Gestation is far shorter in Hystrix (90-112 days) than in Erethizon (205-217 days).

The extreme gestation of Erethizon
(https://www.degruyter.com/document/doi/10.1515/mamm.2001.65.1.73/html and https://www.jstor.org/stable/1375243) seems related to the extreme seasonality in the quality of its diet.

It is consistent with the extended gestation in Erethizon that the weight of the newborn relative to the mother (about 7%) exceeds that in Hystrix - even if the single neonate of the former is compared with a collective litter of two in the latter.

Unlike Erethizon and most other mammals, Hystrix tends to be monogamous (https://www.tandfonline.com/doi/pdf/10.1080/11250009709356189 and https://www.researchgate.net/publication/355180627_Reproductive_behaviour_in_free-ranging_crested_porcupine_Hystrix_cristata_L_1758 and https://www.degruyter.com/document/doi/10.1515/mamm.1991.55.2.187/html and https://www.sciencedirect.com/science/article/abs/pii/0018506X85900376), with paternal as well as maternal care.

FORAGING AND DIGESTION

Both Erethizon and Hystrix are basically terrestrial, which is unsurprising for such large-bodied rodents. However, they deviate from this in opposite ways. Erethizon is partly arboreal (https://www.dreamstime.com/porcupine-tree-close-up-portrait-deag-branch-image186080332) and seldom digs for food, whereas Hystrix cannot climb and is partly fossorial (https://en.wikipedia.org/wiki/Fossorial).

Both genera eat a wide variety of mainly plant matter, from cambium to fruits and roots. However, Erethizon depends mainly on woody plants and (particularly in winter, https://academic.oup.com/jmammal/article/92/3/601/867307?login=false and https://pubmed.ncbi.nlm.nih.gov/20306197/) foliage for its staples, whereas Hystrix depends mainly on herbaceous plants (particularly tubers such as bulbs and corms) and does not eat fibrous foliage.

Both genera have an enlarged caecum in which fermentation occurs (http://www.jafs.com.pl/Digestive-physiology-resting-metabolism-and-methane-production-of-captive-Indian,102741,0,2.html), and neither is caecotrophic or coprophagous. Their feces are similar (Erethizon https://www.inaturalist.org/observations/113658290 and Hystrix https://www.inaturalist.org/observations/93737688).

Digestion is extremely efficient in Erethizon despite:

Both genera supplement their mineral nutrients by gnawing bones (https://www.istockphoto.com/photo/north-american-porcupine-erethizon-dorsatum-in-the-snow-near-haines-alaska-gm1266698735-371403945 and https://www.istockphoto.com/photo/porcupine-on-snow-with-moose-antler-and-birch-tree-in-winter-gm682855252-125266463 and https://www.yumpu.com/en/document/read/28237877/nutrition-of-the-north-american-porcupine-erethizon- and https://www.nature.com/articles/s41598-020-69252-z). Erethizon is well-known to seek out inorganic sources of sodium, which seems necessary owing to a seasonal excess of potassium to which Hystrix is not subject.

Both Erethizon and Hystrix hold food with their fore feet while eating.

However, a difference is that Erethizon, like most rodents, sits while doing so (https://www.istockphoto.com/photo/porcupine-gm490640318-75310819 and https://www.istockphoto.com/photo/north-american-porcupine-also-known-as-canadian-porcupine-or-common-porcupine-is-a-gm1391478903-448081294), whereas Hystrix keeps the forelegs on the ground (https://www.youtube.com/watch?v=8Q3TiLfH504 and https://www.alamy.com/porcupine-the-prickliest-of-rodents-though-its-latin-name-means-quill-pig-image179580322.html).

The lack of a sitting or squatting posture in Hystrix is possibly owing to the obstruction by long spines on the rump.

SOCIAL BEHAVIOUR

Erethizon shows minimal social behaviour. By contrast, Hystrix is not only monogamous but also somewhat gregarious in its underground refuges (https://animaldiversity.org/accounts/Hystrix_cristata/ and https://rep.bioscientifica.com/configurable/content/journals$002frep$002f92$002f1$002fjrf_92_1_004.xml?t:ac=journals%24002frep%24002f92%24002f1%24002fjrf_92_1_004.xml).

Both genera tend to be noisy in normal activity. Erethizon is by far the more vocal (e.g. https://www.inaturalist.org/observations/16521684 and https://www.inaturalist.org/observations/48843732 and https://www.inaturalist.org/observations/42157159). However, Hystrix snuffles loudly, and sometimes grunts, during foraging.

In most species of mammals, male offspring are more likely than female offspring to move far from the parental location. Erethizon is unusual in that it is the females that leave (https://sites.warnercnr.colostate.edu/wp-content/uploads/sites/30/2017/11/1998-Sweitzer-Berger-evidence_for_femalebiased_dispersal_in_north_american_porcupines_erethizon_dorsatum.pdf and https://www.jstor.org/stable/41717257).

to be continued...

Posted on May 05, 2022 04:40 AM by milewski milewski | 13 comments | Leave a comment

May 08, 2022

Similarities/differences between the porcupines of different Hemispheres: Erethizon vs Hystrix, part 4

@ludwig_muller

continued from https://www.inaturalist.org/journal/milewski/65447-similarities-differences-between-the-porcupines-of-different-hemispheres-erethizon-vs-hystrix-part-3#

DISCUSSION

Hystrix is one of the few genera of plant-eating mammals on Earth that qualify as possibly possessing warning colouration at the scale of the whole body. Another, Lophiomys (https://en.wikipedia.org/wiki/Maned_rat), is toxic instead of spiny. In none of these genera is the overall pattern stark enough to qualify as warning colouration without the pelage being activated.

Erethizon qualifies for warning colouration only tenuously, because the pattern

  • is only conspicuous once activated,
  • is restricted to a smaller proportion of the body than in Hystrix, and
  • is poorly-developed in certain individuals/regions/seasons.

The tail differs between Erethizon and Hystrix in various ways.

In Erethizon, the tail is large and used in posture and locomotion. On this basis it is unsurprising that it is also particularly important in anti-predator warning (conspicuous colouration https://www.inaturalist.org/observations/115828268, plus the sound of slapping) and defence (retaliatory striking to deploy caudal spines).

In Hystrix, the tail seems to play a negligible role in posture or locomotion. It may play an important role in deploying spines in H. brachyura and H. javanica.

However, in the other three species of Hystrix, the tail

Overall, Erethizon emerges as the lineage with the greater emphasis on the adaptive value of the tail.

If we disregard the tail, 'porcupines' can perhaps be compared in various ways with the koala, sloths, and mole-rats.

Erethizon somewhat resembles the koala (https://en.wikipedia.org/wiki/Koala) in being able to survive on nutrient-poor, toxic leaves for months at a time (see http://www.adfg.alaska.gov/index.cfm?adfg=wildlifenews.view_article&articles_id=491 and https://news.uaf.edu/the-alaska-porcupines-winter-in-slow-motion/). However, the analogy is limited because Erethizon

  • does so only after laying down large deposits of fat in autumn, and
  • eats bark and cambium in winter, as an extremely fibrous nutrient-supplement.

Alternatively, Erethizon somewhat resembles sloths (https://en.wikipedia.org/wiki/Sloth), all the North American species of which were larger-bodied and have recently become extinct.

Erethizon differs from both the koala and sloths in the development of its incisors (https://www.naturshowroom.com/wp-content/uploads/2020/04/IMG_2105-rotated.jpg and https://www.inaturalist.org/observations/43961088).

Hystrix instead somewhat resembles mole-rats, despite the differences in body size.

Across its distribution in Africa and Eurasia, Hystrix coexists with many genera and species of mole-rats belonging to three families (https://en.wikipedia.org/wiki/Mole-rat). The North American counterparts are gophers (Geomyidae, https://en.wikipedia.org/wiki/Gopher).

Portrayal of Erethizon as an undersize ground-sloth and Hystrix as an oversize gopher is

  • admittedly just caricature, and
  • counter to the observation that it is Erethizon that, in most ways, looks more like a gopher.

However, this portrayal conveys some of the actual adaptive differences between these versions of 'porcupine'.

Approaching this discussion from a different perspective:

If a given species possesses extreme armour/weaponry, is this in addition to normal anti-predator adaptations, or instead of them?

To the degree that tortoises are typical of armoured animals, their slow-movement suggests that the answer may usually be 'instead of'.

How do Erethizon and Hystrix fit into this conceptual framework?

Erethizon seems below-par in the following normal adaptations:

This suggests that Erethizon relies largely on its spines - and the associated syndrome of warnings (including odour), body-orientation, and tail-wielding - for protection from predators. Such specialisation is noteworthy given that the unexcited animal looks fairly defenceless until it spreads the pelage around the particularly spiny rump.

In the case of Hystrix, the only adaptations that seem below-par are eyesight and braininess. The armour/weaponry is obvious even when the animal is unexcited, but the animals retain locomotory speed and, in their capacity to bear up to four offspring per year, considerable fecundity.

In explanation of this, there are differences in the predatory regimes (excluding Homo sapiens, https://natureconservation.pensoft.net/article/62750/).

Erethizon is vulnerable mainly to Pekania pennanti (https://en.wikipedia.org/wiki/Fisher_(animal) and https://www.arcticphoto.com/supergal/wl/wl01/wl0140-00.htm) and Puma concolor (https://en.wikipedia.org/wiki/Cougar).

By contrast, three of the species of Hystrix are vulnerable to a guild consisting of several coexisting species:

Inasmuch as the predatory regime is particularly intense and diverse in the case of the African species, this may help to explain why Hystrix has retained relatively rapid locomotion and reproduction, in addition to its extreme armour/weaponry.

Several remarkable videos show Hystrix africaeaustralis defending itself against Panthera pardus. (Note that both the felid and the rodent possess whitish caudal flags.)

https://www.youtube.com/watch?v=gEYZl6gdDIE and https://www.dailymail.co.uk/embed/video/1272138.html and https://www.youtube.com/watch?v=dDtBYsSoMvU and https://www.youtube.com/watch?v=kmWs1FCkCxY and https://www.dailymail.co.uk/news/article-3481967/Ouch-did-Lioness-licks-wounds-getting-porcupine-quills-rear.html and https://www.dailymail.co.uk/news/article-9925091/A-prickly-customer-Leopard-left-quills-sticking-paws-hunting-porcupine.html and https://www.youtube.com/watch?v=kDFACDPDRqg and https://www.dailymail.co.uk/news/article-1248144/Young-leopard-gets-prickly-reception-tries-eat-porcupine.html and https://www.dailymail.co.uk/news/article-7430633/Leopard-bizarre-standoff-porcupine.html and https://www.dailymail.co.uk/news/article-2285373/Hell-feeling-prickly-Hungry-leopard-gets-spot-bother-trying-eat-porcupine.html and https://www.dailymail.co.uk/video/news/video-2488577/Video-Hungry-leopard-defeated-fearless-prickly-porcupine.html and https://www.youtube.com/watch?v=bBcnEhMfSho and https://www.huffpost.com/entry/leopard-porcupine-video_n_61f13217e4b0061af2586ab5 and https://www.facebook.com/watch/?v=2568431563219276 and https://www.mirror.co.uk/news/world-news/leopard-gets-prickly-reception-porcupine-5967709 and https://metro.co.uk/2010/02/03/leopard-has-a-prickly-moment-with-a-porcupine-73566/ and https://nypost.com/2015/03/23/hungry-leopard-takes-on-tough-porcupine-guess-who-won/ and https://www.earthtouchnews.com/natural-world/predator-vs-prey/claws-vs-quills-young-leopard-tries-its-luck-at-hunting-a-porcupine-video/ and https://www.independent.co.uk/news/world/africa/video-porcupine-takes-on-a-pride-of-17-lions-and-wins-9843974.html

The above include enough evidence from Kruger National Park, in particular, to suggest that nimble manoeuverability is essential to the anti-predator reactions of Hystrix.

Panthera pardus seems to find it relatively easy to kill H. africaeaustralis in culverts (cylindrical drains, made of concrete or metal, for stormwater, running under the road from one side to the other, https://www.gettyimages.ca/detail/news-photo/juvenile-spotted-hyena-cub-posing-in-front-of-den-entrance-news-photo/539279300?adppopup=true and https://somethingovertea.files.wordpress.com/2018/05/erosion6.jpg).

By contrast, when the encounter takes place on the surface of the road, the rodent seems relatively secure as long as it does not move off the open space.

I infer that H. africaeaustralis prefers the exposure of the road because it can keep orienting its body without obstruction. When in the culvert it is relatively constrained. It can fill the tunnel with the erect pelage while keeping its back to the predator. However, the felid can presumably snag the hindfeet by reaching forward at ground-level, thus knocking the rodent off its feet, in a way that would be impossible were the refuge a relatively narrow, natural burrow.

Posted on May 08, 2022 03:02 AM by milewski milewski | 15 comments | Leave a comment

May 10, 2022

Does the North American porcupine have eye-mask colouration?

In this Post, I define 'eye-mask' (https://en.wikipedia.org/wiki/Disruptive_eye_mask) as a dark feature of animal colouration that disguises the eyes, on a figure and head that are not dark overall.

This topic has recently started to appear in the scientific literature. See:

I note that mammals possessing eye-masks tend to fall into two categories, viz.

It makes sense that the eyes are particularly inconspicuous in animals that have overall colouration designed for hiding from prey, or from larger-bodied predators. However, any functional relationship between eye-masks and warning colouration remains to be explained.

As can be seen from the examples above, eye-masks in mammals occur mainly in predatory species. They are rare in plant-eating species.

However, a possible example is Erethizon dorsatum.

Is this plant-eater one of the few rodents to possess an eye-mask? And, if so, is this related to warning colouration in this 'porcupine'?

As far as I know, these possibilities have not previously been mooted in the literature.

Warning colouration in E. dorsatum is weaker and less consistent (see https://www.inaturalist.org/journal/milewski/65187-similarities-differences-between-the-porcupines-of-different-hemispheres-erethizon-vs-hystrix-part-2#) than those in either African-Eurasian 'porcupines' (Hystrix) or the various genera of skunks (https://en.wikipedia.org/wiki/Skunk). The subtle dark/pale contrasts depend on posture and muscular movements of the skin in E. dorsatum. They are absent in some individuals, partly owing to seasonal and regional variation.

EVIDENCE OF EYE-MASK IN ERETHIZON DORSATUM

The following individuals of E. dorsatum seem to possess an eye-mask:

https://www.inaturalist.org/observations/8175871
https://www.inaturalist.org/observations/11274273
https://www.inaturalist.org/observations/10788818
https://www.inaturalist.org/observations/28411661
https://www.inaturalist.org/observations/37898442
https://www.inaturalist.org/observations/44542308
https://www.inaturalist.org/observations/33855151
https://www.inaturalist.org/observations/45805001
https://www.inaturalist.org/observations/80415227
https://www.inaturalist.org/observations/79231635
https://www.inaturalist.org/observations/78933797
https://www.inaturalist.org/observations/78111758
https://www.inaturalist.org/observations/77306649
https://www.inaturalist.org/observations/76953405
https://www.inaturalist.org/observations/69636688
https://www.inaturalist.org/observations/64210546
https://www.inaturalist.org/observations/27843255
https://www.inaturalist.org/observations/49303934
https://www.inaturalist.org/observations/47206486
https://www.agefotostock.com/age/en/details-photo/adult-male-north-american-porcupine-erethizon-dorsatum-minnesota-usa/YY4-1640900

However, the pattern is not clear-cut because, in some individuals in some seasons/regions,

Juveniles tend to be dark overall, lacking mask-colouration (https://www.istockphoto.com/photo/porcupines-gm180723145-24209220 and https://www.istockphoto.com/photo/baby-porcupine-gm157719814-22029118 and https://www.istockphoto.com/photo/baby-porcupine-gm504918032-83421755 and https://www.masterfile.com/image/en/841-03506138/a-captive-baby-porcupine-erethizon-dorsatum-animals-of and https://www.istockphoto.com/photo/baby-porcupine-gm174802022-22029114).

Some individuals are pale overall, for unknown reasons, e.g. https://www.researchgate.net/figure/An-isabelline-colored-North-American-Porcupine-Erethizon-dorsatum-from-Yukon-Canada_fig1_270904496 and https://www.inaturalist.org/observations/49305543 and https://www.istockphoto.com/photo/the-north-american-porcupine-also-known-as-the-canadian-porcupine-or-common-gm1272502547-374755167.

DISCUSSION

The anti-predator defences of Erethizon dorsatum are centred on its hindquarters, leaving the face relatively unprotected.

The carnivore most adept at killing E. dorsatum is Pekania pennanti (https://www.adfg.alaska.gov/index.cfm?adfg=fisher.printerfriendly#:~:text=Hunting%20Method,to%20descend%20trees%20head%20first). The relatively small body and elongated, weasel-like shape of this mustelid allow it to bypass the posterior spines and reach the front, whether the rodent is on the ground or climbing a tree. The carnivore thus manages to bite the face repeatedly until E. dorsatum is incapacitated.

Given that the face is, as it were, the Achilles' heel of E. dorsatum, and that most attacks occur by night, it may make sense that the rodent would benefit from its eyes being hidden. Furthermore, the inconsistency of the pattern may help to deny would-be predators - other than M. pennanti - a clear search-image in the first place.

A result of this obfuscation is that E. dorsatum is peculiarly non-photogenic even by day.

As any scrolling of the thousands of observations in iNaturalist soon shows (https://www.inaturalist.org/observations?taxon_id=44026), the photographed figure often looks almost faceless (e.g. https://www.alamy.com/close-up-portrait-of-a-porcupine-image439051825.html) unless the illumination is particularly clear.

Posted on May 10, 2022 03:34 PM by milewski milewski | 6 comments | Leave a comment

May 17, 2022

Caudal flags in porcupines

Various mammals possess a caudal flag. This is defined as a pattern of dark and/or pale on the tail, in some cases extending to the adjacent rump or haunches, that is inconspicuous when the figure is stationary or at rest, but conspicuous when activated by movement.

Typical examples of caudal flags occur in

'Porcupines' (https://en.wikipedia.org/wiki/Porcupine) are two families of rodents, namely Erethizontidae and Hystricidae, in which certain species have evolved extreme defences in the form of spines (https://www.inaturalist.org/journal/milewski/65187-similarities-differences-between-the-porcupines-of-different-hemispheres-erethizon-vs-hystrix-part-2#).

In this Post I ask 'which of the 28 species of porcupines possess a caudal flag'?

The answer seems to be: three species, namely Atherurus africanus and two of the eight species of Hystrix. However, all of these are odd compared with other mammals.

The caudal flag in Atherurus, which is pale (https://ainawgsd.tumblr.com/post/181842995325/embed and https://www.agefotostock.com/age/en/details-photo/african-porcupine/FTF-R10000143/1), is odd in that

  • it functions as much audially as visually,
  • it is easily lost, during the lifetime of the individual, by means of autotomy, and
  • it may be conspicuous only in ultraviolet.

The two species of Atherurus share the same design of the tail, in which the hairs of the tassel produce a rattling sound when shaken (https://animaldiversity.org/accounts/Atherurus_africanus/). However, it is only in A. africanus that the paleness of the tassel qualifies as conspicuous, at least in terms of the spectrum visible to the human eye.

The caudal flag in Hystrix africaeaustralis and H. indica (https://www.alamy.com/stock-photo-indian-crested-porcupine-hystrix-indica-also-known-as-the-indian-porcupine-124427947.html and https://www.alamy.com/stock-photo-indian-crested-porcupine-hystrix-indica-also-known-as-the-indian-porcupine-124427951.html), which is likewise pale and produces rattling sounds, is odd in that

  • it functions as much audially as visually,
  • it becomes visible only when the pelage of the body is erected, and
  • it is less conspicuous than the dark/pale pattern of the pelage of the posterior part of the body.

Although some photos of Trichys (e.g. https://www.ecologyasia.com/verts/mammals/long-tailed-porcupine.htm) show the tail tassel to be pale, this probably does not qualify as a caudal flag.

Posted on May 17, 2022 10:54 AM by milewski milewski | 1 comment | Leave a comment

May 23, 2022

Do hares ever stot?

I thank @lefebvremax and @beartracker for helpful discussion of this topic.

Various species of ruminants stot (https://whyevolutionistrue.com/2013/01/03/antelope-pronking/ and https://en.wikipedia.org/wiki/Stotting).

This behaviour occurs also in a large-bodied, hare-like rodent, namely Dolichotis (https://www.alamy.com/stock-photo-patagonian-mara-cavy-dolichotis-patagonum-stotting-valdes-peninsula-86749556.html and https://www.youtube.com/watch?v=bHU2RAa_-Vo and https://www.youtube.com/watch?v=e0zSyhkyycA and https://www.alamy.com/patagonian-mara-cavy-dolichotis-patagonum-stotting-valdes-peninsula-chubut-patagonia-argentina-image263028463.html and https://en.wikipedia.org/wiki/Mara_(mammal)).

The nature of stotting is basically as follows. The animal:

  • moves exuberantly, expending energy in a conspicuous and inefficient way, and
  • handicaps itself in its locomotion, as if to show off its individual fitness.

Stotting is clearly a form of self-advertisement. However, questions remain of:

  • whether the demonstration is directed towards members of the same species on one hand, or potential predators on the other, and
  • what message is being sent.

As far as I know, no naturalist has previously claimed that any lagomorph stots, at least in the quadrupedal way. The words 'hare' and 'stot' do not seem to appear in the same sentence, anywhere in the biological literature.

What have been frequently mentioned are 'observation leaps' (https://academic.oup.com/mspecies/article/doi/10.2307/3504151/2600727?login=false and https://www.researchgate.net/publication/348464180_Lagomorpha_Locomotion), in which hares in the act of fleeing intersperse their normal gallop with occasional, particularly high bounds.

Nearly all authors seem to have assumed that 'observation leaps' function not as a form of self-advertisement, but rather as a way of maintaining a clear view of the potential predator.

Therefore, in view of the above:
Establishing that Lepus stots in evolutionary convergence with ruminants and Dolichotis would be something new to science.

At present, the evidence for stotting in hares falls into three categories (besides 'observation leaping', part of the function of which remains questionable), as follows:

  • sundry photos and videos suggesting aberrations from the normal gaits of running, often in uncertain circumstances,
  • clear evidence, in a few large-bodied, ecologically extreme species, of bipedal gaits unknown in other mammals but plausibly interpreted as a form of stotting, and
  • fairly unambivalent self-advertisement in one species, which probably constitutes stotting but has not been labelled as such.

HINTS OF STOTTING IN SUNDRY SPECIES

The following photos and videos suggest subtle forms of stotting. The contexts are unclear, and in some cases may be courtship and rivalry rather than reactions to the approach of potential predators. It is also possible that hares differ from ruminants and Dolichotis in that the bouncing gait occurs not as the animal initially runs but instead as it slows down from a bout of running.

Lepus californicus: https://inaturalist.nz/observations/101996083 and https://inaturalist.nz/observations/64044230

Lepus townsendii: https://www.inaturalist.org/observations/35863227 and https://www.researchgate.net/figure/Startled-white-tailed-jackrabbit-Lepus-townsendii-in-full-flight-in-native-grass-cover-at_fig2_339086542

Lepus timidus: https://www.shutterstock.com/nb/image-photo/mountain-hare-lepus-timidus-known-blue-396645550

Lepus europaeus:
Two gaits suggestive of stotting can be seen from about 4 minutes 30 seconds in https://www.youtube.com/watch?v=ylqBH7iOXl4 and from about 1 min 45 sec in https://www.youtube.com/watch?v=q3JM0hhNOOU.
The following show possible stotting: https://www.inaturalist.org/observations/106614136 and https://upload.wikimedia.org/wikipedia/commons/1/13/Feldhase%2C_Lepus_europaeus_2a.JPG and https://www.agefotostock.com/age/en/details-photo/european-hare-lepus-europaeus-adult-male-running-stotting-back-to-female-in-grass-field-suffolk-england-march/FHR-10512-00774-842 and https://www.alamy.com/european-hare-lepus-europaeus-adult-male-running-stotting-back-to-image61827919.html and https://www.inaturalist.org/observations/73530651 and https://www.inaturalist.org/observations/73202777 and https://www.alamy.com/european-hare-lepus-europeaus-adult-male-running-with-a-bouching-gait-known-as-stotting-over-grassland-suffolk-england-february-image462643335.html.

Lepus does not normally erect its tail in flight. I suspect that stotting in e.g. Lepus europaeus sometimes features both a bouncing action and the swinging of the tail higher than usual (as seen in the first photos in each of https://www.inaturalist.org/observations/106614136 and https://www.inaturalist.org/observations/73202777). This exposes not just the white underside of the tail (which is only partly exposed https://www.istockphoto.com/photo/running-hare-gm467394605-33962244 in normal fleeing gaits in Lepus) but also a white patch of pelage on the buttocks, which is hardly noticeable in the normal action of fleeing.

BIPEDAL LOCOMOTION IN LARGE-BODIED SPECIES, possibly qualifying as stotting

See:

Only a few species of hares use bipedal gaits when fleeing from potential predators (https://www.youtube.com/watch?v=xJoB5gk8riY). It seems reasonable to interpret this as a form of stotting. Lepus arcticus and L. alleni are both unusual for hares by virtue of their large body size and their gregariousness.

In L. arcticus, both hind legs move in synchrony in the bipedal gait. However, the action is different from that in wallabies because the strides are short and rapid, and the body is held upright.

In L. arcticus, there is an additional gait in which only three legs touch the ground (https://animaldiversity.org/accounts/Lepus_arcticus/), in what amounts to a self-imposed, running limp.

APPARENT QUADRUPEDAL STOTTING IN LEPUS CALLOTIS

See Lepus callotis in https://www.inaturalist.org/posts/64011-interspecific-variation-in-flags-as-features-of-adaptive-colouration-in-hares-part-2-other-species-of-semi-arid-north-america#.

This species seems to qualify for stotting in a quadrupedal gait resembling that in ruminants..

Best and Henry (1993) state: "When flushed, L. callotis alternately flashes its white sides while running away from the intruder...Another escape behavior is that of leaping straight upward while extending the hind legs and flashing the white sides. This behavior is seen when the white-sided jackrabbit is startled or alarmed by a predator."

Seemingly relevant is the fact that L. callotis is unusual in its social structure. This species is the only hare known to occur in pairs, with an obvious pair-bond.

DISCUSSION

Much remains to be documented and interpreted with respect to possible stotting in hares.

For example, a detailed review of Lepus timidus (https://www.jstor.org/stable/3504302 and https://www.researchgate.net/publication/275737416_Lepus_timidus) makes no mention of any gaits, despite the wide distribution of this species and its close relationship to L. arcticus.

Not only 'observation leaping' but also bipedal standing at the approach of potential predators (https://www.tandfonline.com/doi/pdf/10.1080/03014220709510074 and https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1439-0310.1993.tb00544.x), when conducted in the open (https://www.gettyimages.com.au/detail/photo/jump-royalty-free-image/89348401?adppopup=true), may make more sense as demonstrations of individual fitness than as ways of keeping a potential pursuer in sight.

Regardless of the poor coverage in the past, what is already clear is the diversity of gaits (plus postures such as demonstrative, bipedal standing) listed above as candidates for stotting.

No species of Lepus stots as frequently/predictably as do certain gazelles, deer, and Dolichotis. However, where hares seem to excel is in the variety of gaits that are candidates for stotting within a single genus. I know of no genus of hoofed mammal or rodent in which such a diversity of potentially self-advertising forms of locomotion occurs.

Posted on May 23, 2022 12:46 AM by milewski milewski | 5 comments | Leave a comment

May 24, 2022

Patterns of body size in hares

@sanjoaquinserpents @jorgejuanrueda @chewitt1 @tandala @tfrench @sammyboy2059 @capracornelius @saber_animal @ldacosta @aguilita @maxallen @marcelo_aranda @mr_fab @pelagicgraf @grinnin @jacob12_ @oviscanadensis_connerties @calebcam @galewski @dinofelis

The genus Lepus (https://en.wikipedia.org/wiki/Hare) contains about 32 species. These vary in average body mass by nearly five-fold, from about 1 kg in the smallest species to about 5 kg in the largest species.

Furthermore, this variation in body size does not generally conform to Bergmann's rule (https://en.wikipedia.org/wiki/Bergmann%27s_rule and https://www.tau.ac.il/lifesci/zoology/members/yom-tov/articles/Geographic_variation.pdf).

In this Post, I

  • list all the species of Lepus in decreasing order of body mass,
  • point out the biggest anomalies relative to Bergmann's rule,
  • seek general correlations between adaptive colouration and body size, and
  • suggest that stotting is restricted to large-bodied species plus a medium-size species characterised by pair-bonds.

The following list of the species of Lepus, in descending order of average adult body mass, is based mainly on Chapman and Flux (1990, https://portals.iucn.org/library/node/6047).

othus 4.8 kg
arcticus 4.5 kg
europaeus 3.8 kg
alleni 3.6 kg
saxatilis 3.5 kg
tibetanus (https://en.wikipedia.org/wiki/Desert_hare)/tolai (https://en.wikipedia.org/wiki/Tolai_hare) 3.5 kg
townsendii 3.25 kg
timidus 3 kg
flavigularis ?3 kg
castroviejoi 2.9 kg (https://animaldiversity.org/accounts/Lepus_castroviejoi/)
starckii 2.75 kg
callotis 2.7 kg
granatensis ?2.5 kg (https://animaldiversity.org/accounts/Lepus_granatensis/)
insularis 2.5 kg
oiostolus 2.5 kg
nigricollis 2.5 kg
brachyurus 2.5 kg
californicus 2.5 kg
capensis most subspecies ?2 kg
peguensis 2.25 kg
victoriae 2 kg
habessinicus 2 kg
comus 2 kg
fagani ?2 kg
melainus 1.84 kg
mandshuricus 1.8 kg
coreanus ?1.8 kg
sinensis 1.6 kg
hainanus 1.5 kg
yarkandensis 1.4 kg
americanus 1.3 kg
capensis subspecies omanensis and cheesmani 1 kg

The main support for Bergmann's rule lies in the fact that the largest-bodied species, namely Lepus othus, is restricted to Alaska (https://upload.wikimedia.org/wikipedia/commons/4/49/Lepus_othus_range_in_ak.png). However, this is undermined by the fact that also occurring in Alaska is the smallest-bodied species, namely Lepus americanus (https://en.wikipedia.org/wiki/Snowshoe_hare#/media/File:Lepus_americanus_map.svg).

The following photos, all taken in Alaska, show that the above two species look similar without any scale to show the nearly five-fold difference in body mass:

Furthermore, a single species, namely L. capensis, varies greatly among its subspecies within a limited range of latitudes in the Middle East (https://www.inaturalist.org/journal/milewski/42001-the-mystery-of-the-arabian-miniatures#). This is nicely illustrated by Figure 302, on page 213 of Harrison and Bates (1991).

The very smallest-bodied form of Lepus, namely L. capensis jefferyi, occurs on a coastal island in Arabia, namely Masirah Island (https://en.wikipedia.org/wiki/Masirah_Island). However, this does not detract from the fact that the subspecies of the nearby mainland in the mountains of Oman, namely L. capensis omanensis, is nearly as small-bodied. Furthermore, the subspecies of the vast sandy deserts (http://saudi-archaeology.com/background/geography-arabian-peninsula/) of the Rub al Khali (https://en.wikipedia.org/wiki/Rub%27_al_Khali), Dahana (https://www.britannica.com/place/Al-Dahna), and Nafud (https://www.britannica.com/place/al-Nafud), namely L. c. cheesemani, is also surprisingly diminutive despite occurring at medium latitudes straddling the Tropic of Cancer.

Defying any simple pattern, the smallest-bodied species and subspecies of Lepus fall into disparate ecological categories, namely

  • species adapted to forests (americanus in the subarctic and hainanus in the tropics), vs
  • species adapted to deserts (yarkandensis in northwestern China and certain subspecies of capensis in Arabia).

The general relationship between body size and adaptive colouration is as follows:

The relationship between body size and ostensible stotting in Lepus, although poorly-documented (see https://www.inaturalist.org/journal/milewski/66356-do-hares-ever-stot#), is as follows:

  • in large-bodied species (more than 3.5 kg), stotting tends to be bipedal,
  • quadrupedal stotting seems to occur only in several species (e.g. europaeus, townsendii, callotis) of body mass 2.7 kg or more, the smallest-bodied species of which (callotis) being unusual in its pair-bonded social structure, and
  • stotting of any kind has yet to be seen in any species of body mass less than 2.7 kg.
Posted on May 24, 2022 10:27 PM by milewski milewski | 6 comments | Leave a comment

May 26, 2022

Ecological notes on Syzygium (Myrtaceae) in southern Africa, part 1

@fynbos @troos @botaneek @mark_smale @fynbosphil @vandalsen @aavankampen @andrew_hankey @graham_g @sedgesrock @geoffnichols @ricky_taylor @richardgill @magdastlucia @reubenheydenrych @adriaan_grobler @dustaway @craig-r @terra_australis @julian70

One of the obvious biotic differences between southern Africa and Australia is in the incidence of Myrtaceae (https://en.wikipedia.org/wiki/Myrtaceae).

Myrtaceous trees and shrubs cover much of Australia across a wide range of climates and soils. By contrast, they tend to be few and far-between - and therefore easily overlooked - in southern Africa.

A main ecological difference between these continents is the extreme nutrient-poverty of Australia, together with a limited incidence of herbivores and an extreme incidence of wildfires.

This raises the question:
How do the indigenous Myrtaceae of southern Africa relate to poor soils, herbivores, and wildfire?

The following notes may begin to shed some light on this topic, focussing on syzygiums (https://en.wikipedia.org/wiki/Syzygium), a genus indigenous to both continents.

KWAZULU-NATAL (eastern South Africa, see https://upload.wikimedia.org/wikipedia/commons/a/ad/St_Lucia_Estuary_OSM.png)

The relevant myrtaceous tree species here are Syzygium cordatum (https://www.inaturalist.org/taxa/338719-Syzygium-cordatum) and Syzygium guineense (https://www.inaturalist.org/observations?taxon_id=132507).

These have succulent fruits and are dispersed and sown by birds and other frugivores, as well as (in the case of S. guineense) by flotation. In these ways they differ from wildfire-adapted Myrtaceae in Australia, as well as most woody plants adapted to poorly-drained substrates worldwide. The native people tend to spare S. cordatum owing to its edible fruits. The particular ecological relevance of S. cordatum is as one of the few indigenous members of its family to occur in savanna/grassland (as opposed to forest/woodland) in Africa.
 
The reference is: Tinley K L (1976) The ecology of Tongaland. Published by the Natal branch of the Wildlife Society, Durban. The fieldwork for this report was done in 1958.
 
In Kwazulu-Natal, my coverage starts near Kosi Bay (https://en.wikipedia.org/wiki/Kosi_Bay) in the far northeast of Kwazulu-Natal, moving southwards through the area of Lake Sibhayi to the Mkuze area.

Kosi Bay area:

Syzygium cordatum is a predominant tree in the tallest forest, found on permanently inundated substrates, in this area.

Swamp forest is about 10m high, reaching 18 m, occurring where the inundation consists of running rather than stagnant water. It reaches only 7.5 m high along minor streams.

Syzygium cordatum is the most frequent tree in swamp forest, where it is typically 15 m high. Associated trees include Ficus hippopotami, F. capensis, Ilex mitis, Schefflera umbellifera, Bridelia macrantha, Voacanga thouarsii, Morella serrata, Rapanea melanophloeos, Erythrina caffra, Sapium ellipticum, Barringtonia racemosa, Halleria lucida, Afrocarpus falcatus, and Rauwolfia caffra, and the palm Raphia australis is present. An abundant epiphyte is the fern Stenochlaena tenuifolia, which virtually clothes the tree trunks from ground level to the crowns. Lianes include Canthium gueinzii, Lygodium kerstenii, Smilax kraussiana, Ipomoea digitata, and Cissampelos torulosa.
 
Now let us account for the lowest vegetation in the Kosi Bay area, and work our way through the various intermediates between grassland and forest, including savannas and woodlands, and the seral stages of these.
 
Grassland in this area also features S. cordatum, this time as a stunted plant only knee-high. Other woody species occurring in grassland are Diospyros lycioides, Parinari mobola (< 0.75m), Dalbergia obovata (< 0.2m!), Ochna arborea (< 0.3m), Strychnos innocua (< 1.2m) and S. spinosa (< 1.2m).

Where the palms Phoenix and Hyphaene are conspicuous, leading the re-conversion of grassland to forest on what I take to be rather poorly-drained substrates, S. cordatum persists through the succession. It takes the form of e.g. a short tree, 2 m high, in patches of scrub in the grassland. Here it is associated with e.g. Vachellia kosiensis, Sclerocarya caffra, Canthium ventosum, Trichilia emetica, and Strychnos madagascariensis.

Syzygium cordatum remains common in woodlands 4-10 m high, containing also Terminalia sericea, Antidesma venosum, Peltophorum africanum, Strychnos spinosa, Vachellia kosiensis, Combretum molle, Alizia adianthifolia, Vachellia nilotica, Ficus stuhlmannii, S. caffra, T. emetica, S. madagascariensis, Albizia versicolor, Apodytes dimidiata, Manilkara discolor, and many others.

These woodlands have various heights and densities and are, at least partly, successional to dense forest other than swamp forest or dune forest (see https://en.wikipedia.org/wiki/Forests_of_KwaZulu-Natal).

Syzygium cordatum is absent from these 'climax' forests inland of the littoral belt, whether short or tall, in which it is replaced by e.g. Scolopia, Mimusops, Sideroxylon, Ekebergia, Hymenocardia, Apodytes, Manilkara, Diospyros, and many others. One species of Myrtaceae is present: an uncommon tall shrub or low tree in the mid-stratum, namely Eugenia natalitia (https://www.inaturalist.org/taxa/585523-Eugenia-natalitia).

These dense, wildfire-free forests have many species of lianes of at least 20 genera, and correspond at least partly to what in Australia would be called ‘vine thicket’. Epiphytes including Usnea are present. Where the dense forest is tallest, the predominant tree is Manilkara discolor. An example is Mabibi Forest, in which the emergent trees reach 15 m high. I find this dominance interesting in view of the recent revelation that Manilkara may be the only ectomycorrhizal genus in the study area.

The large snail Metachatina kraussi (https://www.inaturalist.org/taxa/675199-Metachatina-kraussi) is common in these forests.

Dune forest, which occurs in places in the littoral belt, also lacks S. cordatum. Its main trees are: Ptaeroxylon obliquum, Ziziphus mucronata, Celtis africana, Inhambanella henriquesii, Ficus quibeba, Mimusops caffra, Canthium obovatum, Ficus natalensis, Euclea sp., Warburgia salutaris, Croton zambesicus, Vachellia kosiensis, Diospyros sp., Sideroxylon inerme, Cassipourea gerrardii, Teclea gerrardii, and Cassine aethiopica.
 
To summarise so far:
 
Syzygium cordatum is common in the inland part of the Kosi Bay area, being generally associated with a combination of poor drainage and anthropogenic disturbance. It probably tolerates some wildfire as well, although Tinley (1976) does not mention this aspect. This syzygium occurs as plants ranging in heights from grass-high to > 15 m, depending partly on the successional stage, and seems capable of persisting in low, recovering vegetation provided that the subsoil is (seasonally?) waterlogged. Tinley (1976) describes this low vegetation as grassland, but it contains woody plants and is possibly more precisely described as open low savanna of anthropogenic origin.

In the narrow swamps along watercourses, S. cordatum not only grows into a medium-size tree (about 15 m high), but becomes a major component of the forest, just short of dominant.

Other, better-drained forests in the Kosi Bay area, whether inland or on the coastal dunes, lack this syzygium.
 
Lake Sibhayi area:

Syzygium cordatum occurs in stunted form in the area of Lake Sibhayi (https://en.wikipedia.org/wiki/Lake_Sibhayi). This a nutrient-poor part of Amatongaland (https://en.wikipedia.org/wiki/Amatongaland and https://www.researchgate.net/figure/The-Mkuze-Wetland-System-showing-the-extent-of-the-floodplain-and-the-location-of_fig1_7139313).
 
According to Tinley (1976), a main habitat of S. cordatum in this area is the level just above that of the lake edges, where the upper soil is not waterlogged although the subsoil probably is. In such situations S. cordatum is the only tree, growing with the grasses and sedges Urelytrum squarrosum, Bulbostylis contexta, Monocymbium ceresiiforme, Eragrostis sp., Imperata cylindrica, Mariscus sp., Andropogon sp., Ischaemum arcuatum, Eragrostis capensis and E. chapelieri, Perotis patens, and Dactyloctenium geminatum.
 
Another main habitat of S. cordatum is woodland/savanna. One variant is ‘umdoni veld’, in which S. cordatum shares the tree stratum with many other taxa, e.g. Strychnos spinosa and S. madagascariensis, Dichrostachys cinerea, Albizia adianthifolia, Mundulea sericea, Hyphaene natalensis, Brachylaena discolor, Sclerocarya caffra, Ziziphus mucronata, Trichilia emetica, Apodytes dimidiata, Ficus stuhlmannii, and Vachellia nilotica ssp. kraussiana. “In the eastern section [of the Lake Sibhayi area] Syzygium cordatum is the dominant woodland species changing to Terminalia sericea in the west, where the latter is dominant. The central part of Sibayi has an overlap of both types of vegetation.”

Tinley (1976) notes that “This country is commonly used by hippos for grazing purposes”. Although nobody expects S. cordatum to be eaten by the hippopotamus (https://www.inaturalist.org/taxa/42149-Hippopotamus-amphibius), the habitat is surely affected by this megaherbivore in Amatongaland. This defies resemblance to Australia, where megaherbivores are absent.
 
Swamp forest occurs in the Sibhayi area as in other parts of Amatongaland. The tallest trees are Ficus hippopotami, Macaranga capensis, Voacanga thouarsii, Morella serrata, and Halleria lucida, and the main plant near ground level is the scandent fern Stenochlaena tenuifolia. Syzygium cordatum occurs only at the edges, in this area.
 
Syzygium cordatum also occurs at the edges of two other types of forest, namely coastal forest and dune forest, in the Sibhayi area (see https://en.wikipedia.org/wiki/Forests_of_KwaZulu-Natal; bushpig, bushbuck, cane rat, red duiker, and suni occur in both types, but the nyala is absent from dune forest.)

Syzygium cordatum in the Sibhayi area is thus absent from vegetation that is free of wildfires (coastal and dune forest as well as swamp forest), or subjected to permanent inundation at the surface (swamp forest). On the other hand, it also seems to be excluded from considerable areas of grassland owing to wildfire and/or good drainage. Where the intermediate conditions suit it, it can be the most prominent species of tree in savanna.

to be continued in https://www.inaturalist.org/journal/milewski/66595-ecological-notes-on-syzygium-myrtaceae-in-southern-africa-part-2# ...

Posted on May 26, 2022 09:23 PM by milewski milewski | 6 comments | Leave a comment

May 27, 2022

The peniform clitoris of the spotted hyena, reconsidered

(writing in progress)

Everyone knows that the spotted hyena (Crocuta crocuta, https://en.wikipedia.org/wiki/Spotted_hyena) is odd in having a peniform clitoris.

The usual interpretation is that this allows females to emulate masculinity in a society that is matriarchal to an unusual degree among mammals. Or, more particularly, that females have converged with males by having extremely modified genitalia. In various publications the view is taken that the spotted hyena shows ‘sexual monomorphism’ (https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1439-0310.1986.tb00570.x#:~:text=Abstract,clitoris%20closely%20resembling%20a%20penis and https://www.researchgate.net/publication/230213058_Sexual_Monomorphism_in_Spotted_Hyenas_Crocuta_crocuta) and that the peniform clitoris of the female ‘mimics’ the penis.

However, let us rethink the whole conceptual framework.

The conventional view - which I question in this Post - can be elaborated as follows:

  • The female genitalia are similar to those of the male, including a peniform clitoris which looks so similar to a penis that the sexes are hard to distinguish.
  • Clitoral greetings are particularly important for maintaining a strict hierarchy, in which females tend to dominate males.
  • The erect peniform clitoris is used in greetings between individuals, during which olfactory signals are exchanged.
  • The size and scent of the peniform clitoris provide an honest form of communication between individuals.
  • The need for females to dominate males in competition for food arises from the unique strategy of the spotted hyena in travelling for up to five days away from the den on foraging excursions, to generate and then bring back milk to the young.
  • 'Sexual mimicry' (https://dash.harvard.edu/bitstream/handle/1/41467428/113481%20muller.pdf;jsessionid=3AA952CD2804CE17C8AAD0C7CC130F3D?sequence=1 and https://sciencetrio.wordpress.com/2009/11/09/genital-mimicry-social-erections-and-spotted-hyenas/) in the spotted hyena is thus partly explained by the idea that successful breeding depends - more than in any other mammal - on full dominance of females over all males, and maintenance of the female hierarchy across a clan which can be extensively dispersed.

However, this account throws up several incongruities. 

Females display the peniform clitoris not to males (which have their own separate hierarchy) but to females. It is the subordinate, not the dominant, individual that tends to show an erection in greeting rituals. In juveniles of the spotted hyenas, the clitoris is larger (relative to body size) than in adults. Only in the spotted hyena does the clitoris double as a birth canal; this species actually gives birth through its clitoris. (An enlarged clitoris per se is not unique to the spotted hyena, occurring also in e.g. true moles (Talpidae, https://en.wikipedia.org/wiki/Talpidae) and the fossa (Cryptoprocta ferox, https://en.wikipedia.org/wiki/Fossa_(animal)). And in other ways as well, the peniform clitoris is not actually analogous to the penis.

These incongruities suggest that a central question about this species is not why the clitoris is so penis-like, but why the birth-canal has been relocated to pass through an organ as narrow as a penis. Please note that the clitoris could theoretically have been just as penis-like but separate from the vagina, with only the urethra running through the clitoris.

What I have not seen pointed out previously is that it has - in evolutionary terms - always been possible for the peniform clitoris of the spotted hyena to contain the urethra (and thus to be the route for micturition, just like the penis) without also serving as a birth-canal. After all, in most mammals the urethra and the vagina are separate in the first place. So the spotted hyena has chosen, evolutionarily, not only to fuse the the urethra with the clitoris, but also to fuse the vagina with the clitoris. These are two different changes, and the more puzzling one is the fusion of the birth canal with a penis-like tube because this makes birth so difficult. The risks are potentially lethal.
  
The penis is mainly an organ of masculine intromission, but the peniform clitoris is - I hypothesise - mainly an organ of demotion.

Please consider that, In the spotted hyena, there are two ‘bottlenecks’ of life-and-death importance in the groin of the female.

Firstly and most importantly, there is a metaphorical bottleneck of the milk supply to offspring. The whole life-history strategy of the species depends on milk flowing at a certain rate and timing for reproduction to succeed. Let us assume for now that a crucial aspect of the spotted hyena is how odd the lactational bottleneck is in breeding females.

The second bottleneck is that of the birth canal, which has been converted into the narrowest form conceivable. This more literal bottleneck means that both birth and growth have been so configured as bottlenecks.

These bottlenecks may ensure that  the most proficient individual females reproduce successfully with the resources acquired by the whole clan. Crucial here is that the milk supplied by the dominant females exceeds what it would be if the spotted hyena foraged as a solitary animal. The collective procures much of the food (by gregarious hunting and by gregariously overpowering the lion) but a few individuals channel much of this food through their bodies.

The security of the milk in the female's udder is of paramount importance. Production of milk over five days of exertion, by virtue of access to food in an extremely competitive species, is likely to be vital for survival of young. The peniform organ is an instrument whereby inferior/lower-ranking females reaffirm their place unequivocally. This increases the security of the milk because it largely removes the risk of a milk-bearing female being challenged and injured, or prevented from eating, by other females of the clan. This rationale also invokes larger predatory species; the spotted hyena needs to have unquestioned access to the kill but it also needs conspecific help in its contests with the lion (Panthera leo). This is why the collective of the clan is so important and it is crucial that all members know their place in it.
  
We can accept that the peniform clitoris is an honest organ in the spotted hyena, preventing any miscommunication or political pretences that could put the most valuable members of the clan, namely the dominant milk-bearing females, at risk. There is a premium on olfactory truthfulness in this species, revealing the true political alliances, because the complex alliances cannot be observed in real time, and must be observed virtually instead. The peniform clitoris hypothetically ensures that there is minimal deception given that a given individual of the spotted hyena is unable to see most of the interactions among other individuals in the way possible in e.g. baboons (Papio). Honesty is crucial because the spotted hyena has a ‘virtual’ clan rather than one in which political machinations can be observed in real time.
 
What, then, is the true main function of the peniform clitoris of the spotted hyena? My goal here is to label this ‘an organ of ....’ along the lines of calling the penis ‘an organ of sexual intromission’. I suggest that the answer is 'social demotion' (as opposed to promotion).
 
The reason why this is worth careful consideration is that no other animal seems to possess an organ of demotion, and demotion is something different from submission in the sense of surrender. Besides, submission already has a particular social meaning in Biology.
 
Submission needs no special organ because all the animal has to do is lower its head or its ears, put its tail between its legs, whimper, or lie with its belly exposed. Submission means ‘giving up’ in the context of a particular agonistic event. What happens in the spotted hyena is different: it is indeed submission in the sense that the individual submits to a process in which it is usually 'humiliated' (the process being the detailed olfactory examination of its peniform clitoris). However, submission describes this poorly because surrender takes only a moment whereas what really happens in the greeting ceremony of the spotted hyena is more like an interrogation.
 
'Sexual monomorphism’ is misleading in the spotted hyena because the peniform clitoris and the normal mammalian penis are functional opposites, in the following sense. The penis is always erected and displayed in a context of promotion, i.e. the male individual promotes himself socially and/or sexually. No male animal except the spotted hyena, as far as I know, erects its penis to ‘submit’ to any other individual, or to be 'humiliated'. The penis is mainly a sex organ but in its social use it is promotive, implying superiority where there is rivalry among males.
 
A crucial aspect of the spotted hyena, not reflected in the conventional view, is that the relationship has been inverted. The peniform organ is now erected demotively rather than promotively. Female in erection affirm their demotion, and this has perhaps extended partly to males, which may experience erection not merely in sexual excitement or self-assertion vs other males, but also as a way of affirming ‘I remain demoted’ to a courted female.
 
It is by this rationale that I suggest that we regard the peniform clitoris of the spotted hyena as ‘an organ of demotion’.
 
Come to think of it: does the spotted hyena erect its peniform organ while micturating?
 
Given that in both male and female of this species the peniform organ serves as a spout for urine, and given that in flaccid mode the peniform organ is little more than a bump on the surface of the body, it is easy to assume that the act of micturition – even if only for reasons of hygiene – would involve the partial erection of the peniform organ. And this may indeed be a reasonable assumption in the male.

However, we know that, in the case of female, there is no ceremonial micturition; urine is passed urine without ritual, often while lying down, soiling the fur of the flanks. This leads me to doubt that females bother to erect the clitoris, even partially. This, if true, would be important because it shows that the peniform clitoris hardly qualifies as a functional spout for urine. It is not really convergent with the penis in this function, if the female does not actually convert her flaccid clitoris into a spout while micturating.
  
The problem with the terms 'sexual mimicry' and 'sexual monomorphism':

Mimicry is essentially functional, i.e. the object concerned gets an advantage from resembling the object that it resembles. By mimicking a toxic butterfly, a harmless butterfly implies a functional similarity, in this case toxicity (which is untrue). This correct use of ‘mimicry’ surely does not apply to the spotted hyena. If it were a case of mimicry, then we would expect that the peniform clitoris would behave like a penis.

The only functional similarity is that the clitoris produces scent, much as the penis does - which is not enough evidence of overall mimicry. Besides, it seems tenuous to claim that the organ needs to resemble a penis physically to produce the scents in question. The vulva of the normal female mammal is perfectly capable of giving off scents. So even here the case for mimicry seems weak.

'Monomorphism' is too easily misinterpreted (the more insidiously for the fact that this is usually implicit rather than explicit) to mean that the genitalia of the female are like those of the male. I think the truer interpretation of the same facts is that what is most remarkable is how functionally different these female genitalia are from normal mammalian male genitalia.

If the peniform clitoris were really to resemble the penis functionally, the following would apply.
 
Firstly, the clitoris would be used for penetration. This is conceivable if one imagines that in the spotted hyena there might have been a matriarchal system in which a female ritual of dominance consisted of rape-like actions. It is interesting that there seems to be no recorded instance of female-on-female rape in the animal world, but if such a thing was possible it would surely be in a species with a peniform clitoris. Even anal rape is conceivable in the spotted hyena given that this species lacks a vagina in the conventional sense.
 
Because nothing of the sort occurs in the spotted hyena, the concept of mimicry does not seem apt. As far as I know, females do not even mount subordinate individuals ritually, as happens in e.g. certain ruminants.
 
Secondly, the clitoris would be used as a spout for urine, particularly in scent-marking (as seen in the domestic dog). As far as I know, there is no mimicry of the penis w.r.t. micturition, other than the fact that the urine exits from the peniform organ (I suspect usually in its most flaccid state).
 
Thirdly, the clitoris would be used in the body language of self-assertion or the display of confidence/libido. This is seen in primates including humans, signified by the slang word ‘cock’ and ‘cocky’. In fact there is nothing ‘cocky’ about erection of the peniform clitoris. Instead its erection being a particularly clear signal of self-demotion rather than self-promotion.
 
So, could it be that this puzzle, i.e. that the clitoris of females superficially resembles the penis of males while not mimicking it functionally, that is central in our understanding of the species as a whole?
  
And is the fact that the spotted hyena gives birth through its clitoris not, in a sense, proof of a lack of mimicry?

No sexual mimicry in the spotted hyena

The spotted hyena shows sexual mimicry with a clitoris as prominent as the penis (see above photographs). This is part of an extremely matriarchal social system in which females have a ‘cocky’ attitude and bully males.

Although the genitalia look identical between the sexes in the spotted hyena, the peniform clitoris cannot be said to mimic the penis because the main functions of the two organs are more disparate than in most mammals. Unlike the penis, the peniform clitoris does not function as a focus of sexual pleasure. Its erection signifies neither libido nor confidence. It is not used as an urinary spout in scent-marking, and micturition is unaccompanied by leg-cocking. It is not used assertively; females perform neither rape nor token mounting to enforce the hierarchy. And it is less conspicuous than the adjacent udder3 for much of the life of the female. Furthermore, for the female to mimic the male spotted hyena would be pointless because in this species the male is no stronger than the female in the first place.

Crocuta crocuta adult female:
http://scientopia.org/img-archive/scicurious/img_498.jpg

 
Crocuta crocuta adult female:
http://ak-hdl.buzzfed.com/static/2014-03/enhanced/webdr05/29/13/anigif_enhanced-10290-1396114410-13.gif

1 Crocuta crocuta adult female:
http://scientopia.org/img-archive/scicurious/img_498.jpg

2 Crocuta crocuta adult female:
http://ak-hdl.buzzfed.com/static/2014-03/enhanced/webdr05/29/13/anigif_enhanced-10290-1396114410-13.gif

3 which is likely to be equally important in emitting scents and imparting information on social status

(writing in progress)

Posted on May 27, 2022 06:28 AM by milewski milewski | 12 comments | Leave a comment
Member of the iNaturalist Network   |   Powered by iNaturalist open source software |   Documentation for developers