Was the blue wildebeest a newly-clothed emperor in the eyes of the hunter-explorers?

How many iNaturalists can see any blue in the colouration of the blue wildebeest (Connochaetes taurinus taurinus)? For example, see https://www.inaturalist.org/observations/38573826 and https://www.inaturalist.org/observations/28361284 and https://www.inaturalist.org/observations/49703363.

This is what I think may be going on.

There is an element of adaptive conspicuousness in the colouration of wildebeests. It pays these gregarious, self-advertising animals to be easily visible to each other and predators by day, while remaining able to blend into the darkness of night (see my Journal Posts 'Adaptive colouration in wildebeests: parts 1 and 8', July 2021, in https://www.inaturalist.org/journal/milewski?page=2). So the conspicuous paleness of the rump in certain perspectives (e.g. see https://www.inaturalist.org/observations/29077207) is achieved not by depigmentation but by reflective qualities of the texture and microstructure of the hairs. These work at the brightest times of day to give a conspicuous sheen, but 'switch off' conveniently at night.

I go on to hypothesise as follows.

Both wildebeests and their predators are naturally 'colour-blind' in a similar way to red-green colour-blind men (see https://www.color-blindness.com/red-green-color-blindness/ and https://en.wikipedia.org/wiki/Dichromacy) and they tend to see in the blue-violet-ultraviolet range of wavelengths more than humans can (https://www.themeateater.com/wired-to-hunt/whitetail-hunting/deer-vision-how-whitetails-see-color-light-and-movement). What this would mean is that the sheen on the wildebeest's rump in the midday sun, modest in human eyes, looks glaring to the animals themselves. And then is invisible at night.

One of the oddities of red-green colour blindness in humans is that it is compensated by an increased sensitivity to ultraviolet. Perhaps this evolved to give ancestral hunters a spectrum of individual talents in which some men could read tracks and spot game or venomous snakes free of the distracting effects of full-colour vision.

I suspect that, among the first gun-toters who reached far enough north in South Africa to encounter Connochaetes taurinus taurinus for the first time, about one in twenty were ultraviolet-sensitive (= red-green colour-blind). These individuals saw the wildebeest as obviously bluish. And their fellows, although outnumbering them 20 to one, were reluctant to admit that they could not see the blue. At the same time, there was nothing else so obviously odd about this rather bovine animal that made for a competitively apt name. And so the name 'blouwildebees' stuck.

And it continues to stick today (https://en.wikipedia.org/wiki/Blue_wildebeest), because none of us, the silent majority mystified by the adjective, wants to be first in calling out the Emperor's New Clothes. We subconsciously assume that someone knows, or sees, better than us, so we go along with a harmless misnomer.

And the delightful irony is that, in the wildebeests' own eyes, they are indeed in a meaningful sense blue: cavorting mirrors under the African sky.

Posted on 19 de julho de 2021, 07:44 PM by milewski