Giraffes as tree-shunners

Giraffes are associated with trees.

These, the tallest of animals, eat the foliage of trees. Mature males habitually forage with the neck upright, reaching to nearly 6 meters above ground. And the colouration of giraffes camouflages them among trees.

Keeping this in mind, look at the trees in the following.

EDGE OF NAMIB DESERT (Namibia)

https://www.offset.com/photos/giraffe-in-in-habitat-damaraland-namibia-1047806
https://www.alamy.com/stock-photo-giraffe-family-group-in-the-namib-desert-on-the-skeleton-coast-31832519.html
https://www.mindenpictures.com/stock-photo/reticulated-giraffe-(giraffa-camelopardalis)-desert-dwelling-giraffe-in/search/detail-0_90726373.html
https://www.inaturalist.org/observations/72438564
https://www.offset.com/photos/a-giraffe-walks-in-an-arid-landscape-with-rocky-hills-940670
https://www.offset.com/photos/steenbok-at-etosha-national-park-namibia-africa-838947
https://www.offset.com/photos/desert-giraffe-giraffa-camelopardalis-capensis-with-her-young-namibia-68129
https://www.offset.com/photos/a-giraffe-on-a-rocky-slope-at-sunset-940691
https://www.nationalgeographic.org/media/desert-created-water/student/
https://giraffeconservation.org/programmes/nw-namibia/
https://wildark.org/journals/one-familys-journey-save-giraffe/

DRIEST PART OF KALAHARI, KGALAGADI TRANSFRONTIER PARK (South Africa/Botswana)

https://www.gettyimages.com.au/detail/video/herd-of-giraffes-running-in-the-kalahari-desert-stock-footage/1126573044?adppopup=true
https://www.dreamstime.com/stock-image-giraffe-sand-dune-kalahari-desert-image9092951
https://www.inaturalist.org/observations/69322385

SEMI-ARID KENYA

https://www.alamy.com/stock-photo-reticulated-giraffe-giraffa-camelopardalis-reticulata-adult-walking-90935956.html
https://focusedcollection.com/472519906/stock-photo-two-male-female-reticulated-giraffe.html
https://www.topafricasafaris.com/9-days-reticulated-giraffe-safari/

DEEP IN THE SAHARA (Niger, Libya and Algeria)

https://www.sciencephoto.com/media/173183/view/giraffe-petroglyph
https://www.flickr.com/photos/libyan_soup/442282617
https://www.agefotostock.com/age/en/Stock-Images/giraffe-engraving-algeria-sahara.html
https://www.dreamstime.com/stock-photography-ancient-rock-art-niger-depicting-giraffe-image20602042
https://www.bradshawfoundation.com/giraffe/
https://en.wikipedia.org/wiki/Dabous_Giraffes

TREELESS PLAINS OF EAST AFRICA (Kenya/Tanzania)

https://www.picfair.com/pics/06014572-giraffe-giraffa-camelopardalis-in-the-desert-rift-valley-province
https://fineartamerica.com/featured/giraffe-standing-in-the-grasslands-of-paul-banton.html?product=poster
https://dissolve.com/stock-photo/Giraffe-standing-grassy-field-against-sky-Maasai-Mara-royalty-free-image/101-D1301-86-010
https://www.gettyimages.com.au/detail/photo/herd-of-reticulated-giraffes-in-laikipia-landscape-royalty-free-image/1046940850?adppopup=true

SERENGETI PLAIN (Serengeti National Park/Ngorongoro Conservation Area, Tanzania)

https://es.123rf.com/photo_15758167_single-giraffe-walking-on-huge-savannah-plains-of-the-serengeti-national-park.html
https://www.earthmaho.com/2017/02/safari-serengeti-national-park-tanzania.html
https://fineartamerica.com/featured/wild-giraffe-in-the-unending-plains-of-volanthevist.html
https://www.shutterstock.com/nb/image-photo/zebras-giraffe-all-together-serengeti-national-762734845
https://www.safaribookings.com/serengeti/wildlife-photos#photo2

Do the above not clearly show that various species of giraffes occur far from trees?

Giraffa giraffa angolensis extends to the tropical margin of the Namib desert, and is often photographed in vistas that are bare of even shrubs.

Giraffa giraffa giraffa is at home in the southwestern Kalahari (https://en.wikipedia.org/wiki/Kgalagadi_Transfrontier_Park), where the mean annual rainfall of only 15 centimeters is in line with the driest parts of the Australian continent.

Giraffa reticulata is restricted to semi-deserts in northeastern Africa, where trees occur patchily.

Giraffa camelopardalis is thought to have occurred widely across the Sahara when this area was semi-arid, before about 5,000 years ago.

Even the equatorial Giraffa tippelskirchi tippelskirchi is often photographed in grassland. And this includes the treeless Serengeti Plain itself.

So - beyond reminding us that everything is relative - where does this leave our notion that giraffes are associated with trees?

Well, giraffes are paradoxical in a way: categorically dependent on trees but at the same time quantitatively avoidant of trees.

An explanation lies in the following:

  • giraffes depend on a nutrient regime that tends to be associated with semi-aridity,
  • a combination of nutrient-richness and drought tends to keep the vegetation low and open,
  • adult females of giraffes, which experience particular nutritional demands while producing milk, tend to forage with the neck horizontal, rather than upright, and
  • the most important food-plants tend to be tall shrubs, and saplings suppressed by hedging at 2-3 meters high.

Because nutrient-richness tends to correlate with drought, the trees actually attractive to giraffes tend to be sparsely distributed and hardly taller than large shrubs.

Now consider the other side of this picture.

Giraffes, in contrast to their success in 'scrubby' vegetation at the edges of deserts, have failed to penetrate the greener savannas. This means that they are naturally absent where most trees occur. Compare https://www.researchgate.net/figure/Distribution-range-of-giraffe-subspecies-A-Within-historic-times-after-Dagg-1962-B_fig1_343724052 with https://tropicalsavannaafrica.weebly.com/location.html.

Beyond the equatorial forests that nobody expects to be inhabited by giraffes, most of the trees in Africa form 'moist-dystrophic' woodlands and savannas, which are equally unsuitable. The most extensive savannas in Africa - naturally empty of giraffes - are miombo woodlands in the southern hemisphere (https://en.wikipedia.org/wiki/Miombo) and their equivalents in the northern hemisphere (e.g. https://en.wikipedia.org/wiki/West_Sudanian_savanna and https://en.wikipedia.org/wiki/East_Sudanian_savanna and https://en.wikipedia.org/wiki/Guinean_forest%E2%80%93savanna_mosaic and https://en.wikipedia.org/wiki/Northern_Congolian_forest%E2%80%93savanna_mosaic). Please see https://www.inaturalist.org/journal/milewski/59559-caesalps-on-southern-continents-part-3#.

All of these occur under rainfall conducive to leaching of nutrients, and on substrates (e.g. derived from granitic rocks) that are nutrient-poor in the first place. Giraffes are naturally absent from most of the woodlands and savannas because most trees - in Africa and on other continents alike - are malnutritious and/or too high-crowned for even the tallest ruminants to reach or suppress.

In order to understand why most trees are malnutritious for giraffes, it helps to realise that:

  • giraffes are ruminants (cud-chewers),
  • all ruminants depend on quality rather than quantity of food,
  • as the largest ruminants, giraffes have exceptionally rapid metabolism and growth for their body size, and thus
  • giraffes depend on a certain minimum concentration of nutrients - unmet by most trees - in their food.

The soils nutrient-rich enough to produce palatable trees for giraffes tend to be confined to dry climates because:

  • one of the most important ecological factors is leaching of nutrients by rain (https://en.wikipedia.org/wiki/Leaching_(agriculture)), and
  • this is so important that nutritious foliage is more likely to be available on deep sand under a dry climate than on ostensibly fertile loam under a rainy climate.

For a further understanding of the ecological principles, see:
https://www.cambridge.org/core/books/abs/an-african-savanna/rich-savanna-poor-savanna/250CE7D38625726AB335E2D5675AC01F
https://link.springer.com/chapter/10.1007/978-3-642-68786-0_10
https://onlinelibrary.wiley.com/doi/10.1111/j.1365-2028.1984.tb00700.x
https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2028.1984.tb00700.x
https://www.researchgate.net/publication/229892875_Rainfall_soil_nutrient_status_and_biomass_of_large_African_savanna_mammals
https://www.sciencedirect.com/science/article/pii/S2351989421003206
https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.1015.3682&rep=rep1&type=pdf
https://www.jstor.org/stable/3683266.

Does the following not emerge as a pattern more informative than any simplistic association with trees?

Giraffes depend not on the crowns of trees as much as on large shrubs, plus like-size saplings of drought-tolerant, relatively nutritious trees, suppressed and maintained at convenient height by repeated pruning (https://www.tripadvisor.com/LocationPhotoDirectLink-g673057-d1906680-i53400053-Kalahari_Red_Dunes_Lodge-Mariental_Hardap_Region.html and https://www.oregonlive.com/travel/2010/11/your_best_shot_giraffes_hiding.html and https://www.dreamstime.com/stock-photo-giraffes-feeding-tree-giraffa-camelopardalis-thorn-kalahari-desert-south-africa-image94555452).

Publicado por milewski milewski, 04 de diciembre de 2021

Comentarios

@milewski thanks so much for this very interesting article.

Perhaps us inaturaitsts can make an effort to get more pics showing
a) Lactating females with horizontal necks feeding on smaller trees and shrubs
b) Soil eating by giraffes- which soils and do they target termite mound soil ?
c) trees having more spines at the bottom than at the top and which species have this trend.
Does spine length vary with height.

Do giraffes favour leaves, flowers or fruit of vachellias and senegalias ? Which of these three are most nutritious ?
I, not a Biologist at all and am just curious. Though I live in central Botswana, being carless I dont have access to giraffes but could make more observations of thorn trees and their spines.( though being old I wont climb to the tops of trees).

Is there any correlation between giraffe distrbution and mound building termite distribution

lots of questions but I dont expect answers to all/

thanks

Tony Benn (aka Botswanabugs)

Publicado por botswanabugs hace 7 meses (Marca)

@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.

Publicado por milewski hace 7 meses (Marca)

Thanks so much again a lot to digest and think about.
i shall certainly take a look at the effects of goat brousing on my ,local vachellias and senegalias and their spine formations. Pleanty to record on inat. I just wondered if giraffes have a preference or dislike for eating tree parasites ( tapinanthus /viscum etc) on thorn trees or others. What a benefit to the trees if they do selectively prefer the parasites and a problem for trees if they dont.

I and others have noticed a massive decline in the number of large termite mounds in grazing lands of our corner of Central Botswana near Serowe over the last 40-50 years. Though this has nothing at all to do with giraffe feeding I wonder if this decline has been statistically/scientifically proven to be happening elsewhere in savannas in Africa. Perhaps its just an effect of electric lighting on a massive scale in nearby villages messing up and altering their flight patterns after heavy rains and attracting them to lit verandahs.

Tony.

Publicado por botswanabugs hace 7 meses (Marca)

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.

Publicado por dull2shinetoo hace 7 meses (Marca)

I am actually not completely sure what you want to say here? Giraffes not typically occuring where taller (as tall as the animal) trees are? No, I bet this is not it, as a not only my own observations but also a lot of observations on this platform dispute this. And even if so, what exactly do you want to say?
That trees typically eaten by giraffes only have defensemechanisms in place in reach of the giraffe neck? Ok, I can easily believe this... there are some incredible defenses by Acacia trees against giraffes. Would not be surprised. This has not been formally observed yet? Or is there something else you want to say here, that I am missing?

Publicado por ajott hace 7 meses (Marca)

@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?

Publicado por milewski hace 7 meses (Marca)

@dull2shinetoo Hi Marcia, I'm so glad that you find value in these Posts. It is indeed my intention to enrich iNaturalist by helping to broaden and deepen the experience for participants. With best wishes from Antoni.

Publicado por milewski hace 7 meses (Marca)

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

Publicado por botswanabugs hace 7 meses (Marca)

@botswanabugs You are most gracious.

Publicado por milewski hace 7 meses (Marca)

It is now more clear to me what you mean.
I am not sure I agree with the underlying suggestions about what is commonly assumed to be giraffe habitat. In your writing it sounds like it has always been assumed that giraffes are forest animals closely associated with trees. I am not sure if this has been true at some time, as I am not a giraffe specialist, but it surely is not true since a looooong time. E.g. Berthold Laufer writes in his "The giraffe in history and art" from 1928 " The steppe and open bush country are the proper home of the giraffe, but occasionally it seeks the forest". So it´s known that the forest and tree-rich regions are not the typical habitats of giraffes. It also makes sense, at least if you assume the long neck was an evolutionary advantage associated with the occacional tree in a barren landscape. In dense woods it seems to be much less of an advantage, as for example the abilty to climb seems much more usefull and competitive and food usually is anyways not the most pressing factor on survivla for plant eaters in the forest. For me it´s totally logical that the evolution of the giraffe happened where trees were not too common and giraffes (and actually also elephants) living in woody areas nowadays are descentands from those individuals that merely happened to also be able to cope more or less well in densly overgrown habitats. Why giraffes "decided" to live in those open landscapes with regular food shortages in the first place is a different story, but I guess a lot can be explained by basics in ecology (such as competition, predators...)

Publicado por ajott hace 7 meses (Marca)

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

Publicado por ajott hace 7 meses (Marca)

@ajott Many thanks for this detailed discussion, which I'm sure other readers will find interesting. Perhaps you could comment on some of the other Posts on the topic of giraffes, as well?

Publicado por milewski hace 7 meses (Marca)

Do photographers and their vehicles also shun dense forests and prefer open spaces where it is easier to see animals like giraffe ?

Publicado por botswanabugs hace 7 meses (Marca)

@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.

Publicado por milewski hace 7 meses (Marca)

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