Puzzles about the geographical distribution of the bush duiker

The bush duiker (Sylvicapra grimmia) is the most widespread and altitude-tolerant species of wild ungulate in Africa, but its distribution and habitat are inconsistent and unpredictable in certain ways. Here are the most important questions.

Firstly, why has the species not occurred in Mediterranean North Africa, and which species - if any - has replaced it ecologically, there? The nominate subspecies grimmia (see https://www.inaturalist.org/observations/64169127) is common in various vegetation types in the mediterranean-type climate of South Africa, suggesting that the species should also occur in the similar climate of rainy winters and dry summers in the other hemisphere. Yet the genus Sylvicapra seems absent even in the fossil record in North Africa.

Secondly, why does subspecies pallidior (see https://www.inaturalist.org/observations/42383809), adapted to the Sahel of the Sudan and Chad, not extend farther west? And why does the similar, but disjunct, subspecies coronata (see https://www.facebook.com/Niokolo.Koba.Expedition/photos/a.1520863891514532/1675677672699819/), occur only in extreme western West Africa? Put together, the puzzle is: why is the bush duiker absent from the Sahel all the way between Senegal and Chad?

Thirdly, why is the bush duiker absent from most of the Horn of Africa (from Eritrea through Djibouti and Somaliland to Somalia and eastern Kenya), given that it is widespread in similarly dry climates in southern Africa (subspecies steinhardti) and the eastern Sahel?

Fourthly, why is it that, to this day, not one photo of the bush duiker has been published from the whole Serengeti Ecosystem, including Ngorongoro Conservation Area and the Maasai Mara National Reserve? The subspecies here is nyansae, which is arguably synonymous with hindei, the subspecies of the Kenyan highlands east of the Great African Rift. And why are there so few photos of the bush duiker - apart from freshly-dead trophies posted on the websites of the hunting industry - from elsewhere in Tanzania, where the subspecies is orbicularis? In contrast to the extreme frequency of photos from e.g. Kruger National Park in South Africa (where the subspecies is caffra), I have yet to see any photo of this species from Manyara, Ruaha, Saadani, Mkomazi, Rukwa, Selous and other reserves in Tanzania. Indeed, there is a puzzling overall scarcity of photos of orbicularis (an exception is https://www.inaturalist.org/observations/4988736), despite its wide distribution from the lower Zambesi River across most of Mozambique and Tanzania to eastern Kenya (where there is also a lack of photos in the Tsavo national parks).

Publicado por milewski milewski, 23 de agosto de 2020

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If you are looking for photos from the serengeti the Serengeti Lion Project operates a grid of 225 trail cameras in the Serengeti National Park. In the 7.18M images captured between 2010 and 2016 volunteers on the Snapshot Serengeti project identified 114 animals as common duiker, however less than a quarter are clearly duiker most are other misidentified antelope. The similar (smaller?) camera trap grid in Grumeti ~50km NW has also capture duiker photos but unfortunately the data has not been made available.

More details: https://www.nature.com/articles/sdata201526

Publicado por lwnrngr hace casi 2 años (Marca)
Publicado por milewski hace 9 meses (Marca)

What seems to happen is that the niche of Sylvicapra is partly usurped, in the equatorial zone from Tanzania to the Horn of Africa, by Madoqua. This leaves Sylvicapra common only at altitudes too high for Madoqua (e.g. in Aberdares National Park) and, at lower altitudes, too close to human settlement for Madoqua.

Publicado por milewski hace 9 meses (Marca)

I have certainly never seen them in either Tsavo East or West. If I do, I'll certainly do my best to get a photo! Based on their habitat preference elsewhere in Kenya, I wouldn't expect them to be numerous or common in either Tsavo NP, but possibly present in low numbers in some of the forest patches in Tsavo West and maybe up on the Chyulu Hills

Publicado por zarek hace 9 meses (Marca)

@zarek Many thanks again for adding this valuable information.

Publicado por milewski hace 9 meses (Marca)

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