Plants eaten by the savannah elephant in the Cape Floristic Region, part 4

@dianastuder @botaneek @troos @ehbidault @craigpeter @alastairpotts @adriaan_grobler @dhoare @outramps-tanniedi @petrabroddle @vynbos @richardadcock @steve_cousins @chris_whitehouse @graham_g @cpvoget @sedgesrock @magdastlucia @lucstrydom @strandloper @abdullateefismail @drmckenzie @sp_bester @wynandc @yvettevanwijk1941 @rcswart @felix_riegel @wolfachim @annsymons @sandraf @lindaloffler @outrampsjenny @zaniekk @ludwig_muller @tonyrebelo @jeremygilmore @emmspaul @venturefoth @robertarcher397 @jan_hendrik @douglaseustonbrown @pieterwinter @benjamin_walton @andrew_hankey @francoisdurandt @warrenmcc @richardgill @tania_morkel @lukegallant @karooicus @s_k_johnsgard @joshua_tx @lanechaffin @jayhorn @frank_arroyo @aavankampen @qgroom @entwisle @nyoni-pete @jimmy_finsbury @rudivs @dereksilberblatt @gromit

...continued from https://www.inaturalist.org/journal/milewski/61212-plants-eaten-by-the-savannah-elephant-in-the-cape-floristic-region-part-3#.

Loxodonta africana has been recorded eating such a wide variety of plants in the Knysna area (see parts 1-3) that it may be more meaningful to focus on the species rejected than on those accepted.

So, in afromontane forest and fynbos in the Cape Floristic Region, which foliage is rejected as food by L. africana?

I have arranged the rejected species by categories as follows.

Dominant trees, the foliage of which is rejected by ruminants as well: Podocarpaceae, namely Afrocarpus falcatus and Podocarpus latifolius. Olea capensis shows a similar pattern although trees are occasionally damaged by, and Koen (1983) found a single seedling germinating in feces of, L. africana.

Other common trees in afromontane forest, the foliage of which is largely rejected by L. africana despite being accepted by ruminants: Nuxia floribunda, Ocotea bullata and Elaeodendron croceum.

Tall shrubs/small trees of forest edges: Diospyros whyteana and Diospyros dichrophylla.

Shrubs of forest edges/understorey, the foliage of which is rejected by L. africana despite being accepted by ruminants: Halleria lucida.

Legumes in fynbos and at forest edges: Aspalathus and most other species in most genera.

All geophytes and Iridaceae (although rhizomes, corms and non-green bases are accepted).

DISCUSSION

The rejection of podocarp conifers (and Olea) is unsurprising, because these constitute the tallest indigenous trees in the Cape Floristic Region. The foliage of geophytes tends to be toxic to folivores generally.

It is noteworthy that L. africana, when foraging in fynbos, accepts the foliage of nutrient-poor Ericaceae, Bruniaceae and certain Proteaceae.

The rejection of Nuxia and Fabaceae may be owing to certain toxins that are harmful to L. africana despite being neutralised by the digestive system of certain ruminants. Toxicity is particularly likely for Elaeodendron croceum, based on its tropical congener Elaeodendron buchananii (https://pdf.sciencedirectassets.com/273500/1-s2.0-S0254629998X42006/1-s2.0-S0254629915308425/main.pdf?X-Amz-Security-Token=IQoJb3JpZ2luX2VjEDIaCXVzLWVhc3QtMSJGMEQCIGmu3pJb%2FisBLfJOCeLoBzuZ0WhxOjzFTa9mujcqKbQBAiBJhGTK4IbC4bn9CTS3Lto5%2FyCfINJYtsCQTb%2FUIp6TmSr6AwhaEAQaDDA1OTAwMzU0Njg2NSIMvW2GYuQFIM%2BVMJcsKtcD4%2FxCvZIskYstV0%2BwgKUP63rmHW%2FXfz87UIAkTE5ExydeBOKT0Cc18C8CEy802yaSqmdt0IEENSnIMskod%2BUXIcxvdWGEXEFqIxUfWXyAIusNwCmKjxD%2FYcQAeKx7i819PGy9YkUqU34Pbl7OYkgrBt4PXszkVY3xfkVEk%2BZlQjmuyaV9qx4QT1vynO1n1vry7Ee0mkF16kdsg29viUOAxVMaul5rZR9rlZ3yM1P2%2BDduQ%2BaRsLH6e31iGDyjnRsfPEXVXX%2F0kSWBsZi2yJndXbrwC6d66OQvdB%2BaG8ZbEg%2BlAJIAXnMW%2BswuHSEkWe3JE2SVl9jxaSBxO6y6x7mhKkaIo7rra8nzLBnJ88%2Bjjl49JQrT%2FCr8n1ro8SBnexASEQZcOFclxe0CbyuVvVe0XpDhnEy1lcBfBT0V%2FwiVEVQ8lM26ZpwRL8VeJX8t%2FbSWFy2WfFj3F8mUBic%2BFiuaPCpqUs%2FJ4ZabamnsE0GqwdJ%2Bc8puSpNcvlhYzQLXyC8snBtVUNfZ%2BUNfgW%2B8CvW4lMZmkiPHe2xquiAmp852hwZdzOttPiF9Xa6bl7LyE5HssThavScxCQprZ6tqj8XHuTwMM%2BpJo9kbXnvob9DcmGjE3c8vDn%2F4MI22tI8GOqYBedHuwTWS5EEQUnCA1G8%2FQKqZVdiferCgpTcnilJ0ncv1rZcKI8omAIs%2BhHxP3lTssacUfhpS1hLdoM296992RXSRPFdhuCiMuJfAQtokf4darLMVnMKX6cjlHRIyYcFNJLxiz8j1e2yWrcs9EIWCRKp1USYgmw536zKD%2Bw0mf18pVJx3eRYoShYV%2FxWOZdbNqZo%2BflyS8riy3otz9RAyQTOywZ190w%3D%3D&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Date=20220123T104503Z&X-Amz-SignedHeaders=host&X-Amz-Expires=300&X-Amz-Credential=ASIAQ3PHCVTYTRW2CXMO%2F20220123%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Signature=99148af27ce9251fbde27126587fed3436a729abb4d0f39f71a4ab2f8f099e18&hash=c2234326fde0e78bcc28cfafa3e8fd0b8c7fc4e6bce74e779320310dc945325f&host=68042c943591013ac2b2430a89b270f6af2c76d8dfd086a07176afe7c76c2c61&pii=S0254629915308425&tid=spdf-64759978-abcd-4fb1-8f34-8cad4cf285ef&sid=7ba1a56014d1844b70786665b7b44e4f12e6gxrqa&type=client).

The general rejection of Fabaceae is surprising in view of:

  • the relative richness in protein of these nitrogen-fixing plants,
  • the acceptance of non-indigenous, nitrogen-fixing legumes in the form of Australian species of Mimosaceae, and
  • the acceptance of both phyllodes (Acacia melanoxylon) and bipinnately compound leaves (Acacia mearnsi) in the latter cases.

It is particularly noteworthy that the indigenous Virgilia tends to be rejected by L. africana whereas the non-indigenous A. melanoxylon is a favourite. Acacia melanoxylon was deliberately planted for its valuable wood, but has been so persecuted by L. africana that foresters have abandoned the project in the Knysna area. Furthermore, the bark of the Australian spp. of Acacia seems palatable to L. africana despite being so astringent that these plants have commercial value as a source of tannins.

The rejection of Diospyros is surprising given that Diospyros mespiliformis is damaged by L. africana in tropical Africa (https://www.walshmedicalmedia.com/open-access/is-elephant-damage-to-woody-vegetation-selective-of-species-plant-parts-and-what-could-be-plausible-factors-influencing-.pdf).

It is noteworthy that Rhodocoma gigantea is eaten by L. africana. This is an exceptionally tall member of the Restionaceae, a family characteristic of fynbos.

Until Gareth Patterson recorded this species and other restios in 20% of his fecal samples of L. africana in the Knysna area, it had been assumed by scientists and naturalists that restios are too fibrous and nutrient-poor to qualify as food for megaherbivores. This had long been at odds with the simultaneous assumption that restios are a staple food of the vole-like rodent Otomys irroratus (https://en.wikipedia.org/wiki/Southern_African_vlei_rat#Diet_and_Feeding_strategies).

We now realise that L. africana does indeed eat restios. Furthermore, vernacular names for R. gigantea and species in at least four other genera (thanks to @tonyrebelo for pointing this out) hint that the consumption of restios by L. africana was known to the indigenous pastoralists of the southwestern Cape centuries ago. All these species are called 'olifantsriet'.

Finally, returning to the topic of spinescence:

In general, spinescence occurs in plants palatable, not unpalatable, to folivores. This principle seems largely to hold good for L. africana in the Knysna area, because the most spinescent species in the flora (e.g. Scolopia spp,, Gymnosporia buxifolia and Zanthoxylum davyi) are part of the diet. The principle extends to Aloe spp., which are leaf-spinescent but in a way configured to protect the pithy stems to some degree. However, it seems not to hold for Diospyros dichrophylla, which grows deterrent-looking struts on the boles (see comment in https://www.inaturalist.org/journal/milewski/61009-dwarf-ebonies-part-1-white-milkwood-as-symbolically-but-not-biogeographically-south-african#new_comment) but seems to be ignored by L. africana.

Reviewing these findings overall, which are the biggest surprises?

For me, the answer is:

  • the routine acceptance by L. africana of the foliage of 'ericoid' (small-leafed, heath-like) shrubs in fynbos, despite the nutrient-poverty of these plants and their tendency to be consumed by wildfires rather than animals, and
  • the targeting of Australian spp. in both afromontane forest (Acacia melanoxylon) and fynbos (Acacia mearnsi and Hakea sericea) despite the general avoidance of other legumes and despite the failure of these acacias to support folivores in their natural habitats in Australia.
Posted on January 15, 2022 10:03 PM by milewski milewski

Comments

If you read Gareth's publications on the Knysna Elepghants you will see that the elephants definitely do eat the fruiting stems of some Restios. He would also be able to list other plants they eat or do not eat?

Posted by yvettevanwijk1941 about 2 years ago

@yvettevanwijk1941 Hi Yvette, Many thanks for this interesting information. Do you have access to a copy of Gareth's book?

Posted by milewski about 2 years ago

Gareth has written two books and a couple of papers. My son made a movie with him callesd "The Secret Elephants" . I will find the papers and post them links here, and yes, I have both books. I think they are still available from places like Loot or Amazon. His email is gpatterson@wispernet.co.za/. He probably knows more about teh elephants than anyone else, although recently other researchers have set lots of camera traps to see if they show more than one elephant, apparently not, But they should also have info about what the elephant is eatign in the pics? I think I also have the paper they published about it, will look for it.

Posted by yvettevanwijk1941 about 2 years ago

@yvettevanwijk1941 Many thanks, your help with this would be much appreciated. It would be good to make this review of the diet as complete as possible. I think that, to this day, many naturalists in the southwestern Cape would doubt that restios are palatable to elephants in any circumstances. The truth seems to be one of those paradoxes that arise from everything being relative. On one hand, it is true that fynbos is poor in large mammals compared to various other biomes. On the other hand, it is also true that fynbos remains uniquely rich in large mammals compared to all other 'heathlands' on nutrient-poor soils worldwide and all other shrublands under winter-rainfall and adjacent climates worldwide. Even if L. africana was scarce and nomadic in fynbos, its presence is significant in an ecosystem so full of adaptations to fire at the expense of herbivory. Furthermore, not only is Taurotragus oryx - which everyone acknowledges to be at home in fynbos - an exceptionally large ungulate, but Papio ursinus ursinus is one of the largest-bodied of monkeys (see https://a-z-animals.com/blog/the-worlds-10-largest-monkeys/). The local form of porcupine (https://en.wikipedia.org/wiki/Cape_porcupine) is also noteworthy in body size, and the aardvark Orycteropus afer - which occurs to this day in fynbos as far south as Cape Agulhas - is the most massive myrmecophage on Earth.

Posted by milewski about 2 years ago

You would also need to look back in history.
We walk at Cape Point ... at Olifantsbos.

We used to live in Porterville among wheat fields, where we had a river and mountains both named for Once Were Elephants.

Porcupines eat bulbs, of which fynbos has a huge variety. For example Babiana - named for the fact that baboons eat them.

Posted by dianastuder about 2 years ago

But:

Porcupines have livers that detoxify poisons most animals will drop dead from.
Babiana is unusual in having edible bulbs, but contractile roots that pull down the corms as the baboons try to dig them up.
These are not "usual"

Posted by tonyrebelo about 2 years ago
Posted by ludwig_muller about 2 years ago

The Knysna Elephant: A Brief Note on their History and Habits - Philips 1925

Posted by rcswart over 1 year ago

Perhaps the podocarps grew to tall trees, because the elephants don't eat them?

Posted by dianastuder over 1 year ago

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