Giraffes as tree-shunners

https://www.naturepl.com/stock-photo-reticulated-giraffes-giraffa-camelopardalis-desert-dwelling-giraffes-image01531311.html

https://www.youtube.com/watch?v=rWO2E0fVEXA

https://www.pnas.org/content/pnas/112/42/12992.full.pdf

@botswanabugs Hi Tony, Here are some answers to the questions you posed.

There is a general neglect of adult females in the photography of large animals, which is a pity because females are in some sense central to the species (males varying greatly relative to females depending on sexual dimorphism).

Geophagy by giraffes has been under-studied, and as far as I know has not been recorded at termite mounds. The most familiar case is in Nairobi National Park, where the animals have been photographed eating earth on a bare patch that I assume to be natural. What has been more frequently recorded in giraffes is osteophagy (bone-nibbling).

Any correlation between the incidence of giraffes and that of large mounds of Macrotermes is more likely to be negative than positive. This is because large mounds are generally associated with the relatively poor substrates (short of deep sand). Miombo typically has large mounds of Macrotermes and typically lacks giraffes. One exception to this trend is in southern Kruger National Park, where there are large mounds in the habitat of giraffes (vegetation containing Combretum apiculatum). Combretum tends to be commonest on substrates poor enough for large mounds of Macrotermes but rich enough for giraffes.

As far as I know, all Vachellia spp. show a pattern in which spines are restricted to the zone above ground that is accessible to ungulates. As far as I know, no species of Vachellia spontaneously produces any spines to speak of unless the stems are damaged. What this means is that if you look carefully at the crown of e.g. V. tortilis above 6 m (in the habitat of giraffes) or 3 m (in the habitat of eland/greater kudu), you will find a virtual lack of spines even if the lower branches of the same individual plants are conspicuously spinescent. In Senegalia, the pattern may be different and warrants investigation. Balanites is different because its (green) spinescence is more fundamental/intrinsic, i.e. apparently not induced by damage. In some spp., the length of the spines may indeed vary with height above ground.

Giraffes eat the shoots, leaves, flowers and fruits of Vachellia and Senegalia in interesting ways. During the hot dry period before the rains break, flowers appear in anticipation, and at this time giraffes concentrate on them. Vachellia tortilis is effectively evergreen, and its flowers seem unimportant to giraffes, at least in a relative sense. Several spp. of Vachellia have pulpy pods specially designed to attract ungulates as dispersers and sowers, and obvious examples include V. erioloba, V. tortilis and V. nilotica. However, these fall to the ground when ripe, and would not in any case be dispersed and sown by giraffes because these ruminants tend to grind their food finely (unlike eland). Giraffes do eat the fruits but mainly when they are still green.

So, whereas the eland can disperse and sow various plants including Vachellia, giraffes tend to destroy the seeds. In partial compensation, it has been suggested that Giraffa giraffa pollinates Senegalia nigrescens.

Thank you for posting your observations - not only in referencing the incidence of giraffe in the landscape and the defensive mechanism of their foodstuff, but also in sharing this insightful information through a comment to my posting of the animal. I appreciate you and the work you do to enrich the experience of participation at iNaturalist.

@ajott Many thanks for pointing out that I was not clear enough. It is this sort of criticism that helps authors to improve their writing. In response to your questions I have completely rewritten the Post. Is it any clearer now?

@milewski you are certainly enriching inat with your journal posts !

https://62e528761d0685343e1c-f3d1b99a743ffa4142d9d7f1978d9686.ssl.cf2.rackcdn.com/files/149774/area14mp/image-20161213-25487-1831ktb.jpg

Also, the map you posted in your last comment shows the recent distribution, which is heavily influenced by human presence and I would be very careful to take it in as an explanation for historical facts. ... but yes, also the historcial range spares dense tropical forest or the driest desert regions for understandable causes: https://giraffeconservation.org/wp-content/uploads/2020/07/Map_Final_Light_Full_2020.png

https://www.researchgate.net/publication/227993229_Consequences_of_herbivory_by_native_ungulates_for_the_reproduction_of_a_savanna_tree

https://www.sciencephoto.com/media/477944/view/masai-giraffes

https://www.alamy.com/stock-photo-herd-wild-herbivorous-cloven-hoofed-animals-giraffes-african-savannah-136920644.html

@botswanabugs That is possible. However, I think one of the best clues is the sheer number of photos on the Web of infants in open vegetation. I have the impression that infants are photographed, relative to adults, more frequently in giraffes than in most other ungulates. If giraffes hide to a considerable extent in dense vegetation then surely this would apply particularly to infants, and photos of infants would be scarce? Instead the photographic record suggests that infants of giraffes actually prefer open vegetation, which also seems consistent with their precocial gregariousness.

Estes (1991, page 206) states: "For the first week...the calf spends half the day and most of the night lying, preferably beside a bush or fallen tree. It lowers its head when alarmed...The mother often stays farther than 100 m from a concealed calf and may leave it alone for periods of up to 4.5 hours...From the second week through the second month calves spend most of the day just standing and looking...mothers allow their offspring to begin associating with other calves. Up to 9 young giraffes may associate in creches, over half the time at distances of under 10 m...Absent mothers usually return before dark, suckle their offspring and remain with them overnight, then suckle them again before going off to spend the day browsing".

This seems to confirm that the hiding period is brief (only about one week), and that the main danger to infants is at night, when they are closely guarded by their mothers. However, Estes does not mention any dependence on dense vegetation in birth or parenting.