Why does the gerenuk stot?

The gerenuk (Litocranius walleri) is unusual in hiding more than other gazelles. Its secretive mature makes sense in view of its relatively densely vegetated habitat and its limited gregariousness.

The gerenuk has inconspicuous colouration because it has lost the extensive, eye-catching pale and dark on the flanks and hindquarters which are typical of gazelles. It has been frequently photographed despite its skulking habits and arid, remote habitat, because its extreme ability to forage bipedally has particular appeal in the human mind.

Oddly, the gerenuk retains the ability, typical of gazelles, to stot in display of its individual fitness. This takes the form of style-trotting and stiff-legged bouncing, complete with the flaring of the white fur on the posterior haunches (which has yet to be captured photographically). Two peculiarities are: 1) the tail, although proportionately long among gazelles, is hardly raised during stotting, and 2) emphasis is instead added by the folding of the legs at the height of each bounce.

Stotting is generally associated with prey species capable of particular speed and stamina, because it demonstrates to the scanning predator the likelihood that pursuit of the individual in question would be futile. The gerenuk has been assumed to lack speed and stamina, relative to most gazelles. This is based on its extreme lankiness, the clutter of tall shrubs and short trees in its typical habitat (which make for an obstacle-course rather than an open field of flight), and the inability or reluctance of the gerenuk to leap over plants in the way tragelaphins (e.g. kudus) do.

So, what is the adaptive advantage of stotting in the gerenuk?

One possible explanation is as follows. All large predators tend to be scarce and transient in the habitat of the gerenuk because of a lack of drinking water and the sparsity of other prey. This means that, often, the predator will be relatively naive with respect to the specific nature of the gerenuk, while nonetheless being dissuaded in a mentally 'hard-wired' way by any stotting displays observed.

What the gerenuk might be doing, in stotting, is to convert what is in other gazelles an eminently honest display of fitness into a deceptive display suggesting borrowed identity and false context. In short, confusing rather than informing.

Do readers have a better explanation?

Posted by milewski milewski, March 31, 2021 02:25

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