Plants eaten by the savannah elephant in the Cape Floristic Region, part 3

continued from part 2:

Phillips (1925) found evidence of the following species, particularly their fruits: Trichocladus crinitus, Secamone alpini, Scutia myrtina, Maytenus acuminata, Maytenus peduncularis, Clematis brachyata, Physalis sp. (non-indigenous), and Quercus sp. (non-indigenous; recorded also by Carter 1970).

The following is my commentary on a study (von Gadow 1973) done a quarter of a century before my own, from a forester's viewpoint: https://www.researchgate.net/publication/269396526_Observations_on_the_utilization_of_indigenous_trees_by_the_Knysna_Elephants.

Before von Gadow began his study, it had already been noted that "observations within the whole Knysna forest area confirmed the high utilisation rate of Ilex mitis, Canthium ventosum (now Canthium inerme), Cassine peragua, Maytenus acuminata and Rhus macowanii (now Searsia rehmanniana)...High preference for Scolopia mundii and Kiggelaria africana".

(Here is information for the species, among the above, not already covered in parts 1 and 2 of this series of Posts: https://www.inaturalist.org/taxa/527633-Cassine-peragua and https://www.inaturalist.org/taxa/593914-Searsia-rehmanniana and https://www.inaturalist.org/taxa/593861-Scolopia-mundii).

Von Gadow found the following indigenous species of trees to be broken by L. africana in afromontane forest. The list is in decreasing order of preference by L. africana.

Non-indigenous species of trees:

  • Acacia melanoxylon (saplings were victimised by L. africana)

My commentary:

Zanthoxylum davyi (https://www.inaturalist.org/taxa/469304-Zanthoxylum-davyi) and Ilex mitis were much preferred, the trees being avidly pushed over by L. africana.

Kiggelaria africana was eaten by L. africana despite being cyanogenic (and possibly goitrogenic), which may help to explain its ability to regenerate vegetatively from the base. Searsia and Pterocelastrus likewise regenerate from the base.

Canthium spp. were somewhat preferred by both L. africana and Philantomba monticola (https://en.wikipedia.org/wiki/Blue_duiker).

Maytenus spp. were preferred by both L. africana (M. acuminata) and Tragelaphus sylvaticus (M. peduncularis)(https://en.wikipedia.org/wiki/Cape_bushbuck)

The following were not pushed over, or their branches damaged; L. africana seems to exclude them from its diet:

Von Gadow stated:
"Maytenus peduncularis, Nuxia floribunda, Halleria lucida and especially Ocotea bullata are major feeding plants of other forest herbivores. It therefore seems remarkable that these species have not been taken by elephant."

Halleria lucida was not preferred by L. africana, although it seems preferred by Tragelaphus sylvaticus.

The foliage of Ocotea bullata was eaten by Tragelaphus sylvaticus but not L. africana.

Diospyros spp. (which occur in the understorey) were apparently ignored by L. africana.

The foliage of Afrocarpus falcatus and Podocarpus latifolius was apparently largely ignored by both L. africana and Tragelaphus sylvaticus.

The following show spinescence in Zanthoxylum davyi:

https://www.inaturalist.org/observations/69304408
https://www.inaturalist.org/observations/20105235
https://www.inaturalist.org/observations/45476289
https://www.inaturalist.org/observations/79375054
https://www.inaturalist.org/observations/100298267
https://www.inaturalist.org/observations/100226115
https://www.inaturalist.org/observations/98091939
https://www.inaturalist.org/observations/92581999
https://www.inaturalist.org/observations/78961485
https://www.inaturalist.org/observations/77064580

Spinescence in Zanthoxylum is difficult to interpret. Members of this genus have extremely spinescent boles, which look particularly adaptive as a defence against L. africana. However, this genus of about 250 species is remarkably widespread on Earth in the tropical and subtropical zones, and the spines occur on the boles of most species regardless of the megafauna - including Australia where the marsupial fauna has never contained any animal resembling elephants.

to be continued...

Posted by milewski milewski, January 15, 2022 10:47 AM

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