Surprising differences in displays of the tail between the blackbuck and other gazelles

All ruminants with visible tails can swish or flick the tail to shoo insects attracted to the anus and vulva. However, gazelles and their relatives (tribe Antilopini) are surprisingly variable in the other uses of their tails, along lines which I have not seen mentioned in the literature. Let me start with the genera Gazella, Eudorcas and Antilope.

Gazelles and their relatives display their tails mainly in reaction to the appearance of potential predators, and in social interactions within the group. These categories naturally tend to be blurred in playful behaviours that serve to rehearse reactions to danger.

Most species of Gazella and Eudorcas tend to wag the tail conspicuously as soon as they go from standing to walking and trotting, and then relax the tail again when galloping (e.g. see Gazella gazella in https://www.youtube.com/watch?v=mDXpdgATnBI). One way to interpret this is that the animals are signalling to the potential predator (including photographers) that the individual is energetic and alert, and thus not worth singling out for pursuit. However, Gazella subgutturosa and marica tend not to move the tail until running, when it is held more decidedly erect than in other gazelles (see https://www.istockphoto.com/video/goitered-gazelle-gm483199995-26191233). And Antilope leaves the tail inert throughout the locomotory sequence of reaction to potential predators (see https://www.youtube.com/watch?v=1I5jRQCI3VU), even sometimes when stotting (see https://www.gettyimages.com.au/detail/video/blackbuck-antelope-pronks-on-grassland-velavadar-stock-video-footage/918301414 and https://www.gettyimages.com.au/detail/video/blackbuck-antelope-pronk-on-grassland-velavadar-stock-video-footage/918308808).

The contrast can be illustrated by comparing Eudorcas thomsoni with Antilope cervicapra. Thomson's gazelle wags its black, long-tasselled tail with particular zeal when milling hesitantly in view of a safari vehicle (e.g. see https://www.shutterstock.com/da/video/clip-1021228609-herd-thomson-gazelles-drinking-waterhole-serengeti-tanzania), whereas no amount of nervousness will get the blackbuck to wag its nondescript tail - which lacks a noticeable tassel - in similar circumstances. Instead, the blackbuck tends to express its tension at a whole-body scale by leaping high into the air (see https://www.gettyimages.com.au/detail/video/pronking-blackbuck-females-run-and-leap-on-indian-stock-video-footage/1B02605_0001), in a way never seen in Thomson' gazelle.

Where the blackbuck - which is the most sexually dimorphic of antilopins - does display its tail is in masculine behaviour (rivalry and courtship, extending to lekking). Here, the adult male 'hypererects' the tail so that its tip touches the rump (see https://www.inaturalist.org/observations/66647799 and https://www.gettyimages.ca/detail/photo/indian-blackbuck-antelope-cervicapra-male-display-royalty-free-image/90065036?adppopup=true). This looks more like an olfactory than a visual display, because the tail tends to be rather redundant in the whole-body showiness of the black-and-white masculine figure as he walks in an unusual gait, which can be called a 'perfect amble'.

However, nobody seems to have found a scent-gland under the tail in the blackbuck. The displays, and lack thereof, of the tail thus remain an odd aspect of the blackbuck.

Posted by milewski milewski, March 08, 2021 11:33

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