Regional interspecies mimicry in conspicuous colouration of ruminants?

All three of the largest ruminant species in the Saharan region have extremely pallid colouration, unmatched by desert ungulates elsewhere. Why have the scimitar-horned oryx (Oryx dammah, http://www.mammalogy.org/oryx-dammah-2129), addax (Addax nasomaculatus, https://en.wikipedia.org/wiki/Addax#/media/File:Addax_nasomaculatus.jpg) and dama gazelle (Nanger dama, https://treshabarger.com/2018/05/15/dama-gazelle-2/) converged in this way?

Likewise, four sympatric species of ruminants in western North America resemble each other in pale patterns, in this case a bold whitish patch on the hindquarters. Why have the wapiti (Cervus canadensis, https://www.pestdetective.org.nz/image?Type=culprit&ID=142&Parent=170), Rocky Mountain mule deer (Odocoileus hemionus hemionus, https://www.canadiannaturephotographer.com/january2014.html and https://www.sagegrouseinitiative.com/how-do-mule-deer-use-sagebrush/), bighorn sheep (Ovis canadensis, https://www.featheredphotography.com/blog/2019/10/31/an-impressive-desert-bighorn-ram/) and pronghorn (Antilocapra americana, https://www.nps.gov/articles/pronghorn.htm) converged in this way?

In both cases, the regional convergences have arisen independently in unrelated clades, as if to suggest some sort of interspecies mimicry.

In Muellerian mimicry, various toxic or venomous species converge on a single pattern of warning colouration, apparently to reinforce a shared message to potential predators. In the case of the above ungulates, there is no question of warning colouration in this strict sense, because there is scant ability to harm predators in self-defence. Instead the relevant anti-predator tactic, in addition to gregarious vigilance and fleeing, is of self-advertisement of individual fitness and vigour. This show-off pattern, accentuated by stotting gaits, persuades the scanning predator that the individual has no debility that would make it vulnerable. Could something similar to Muellerian mimicry apply here?

The relevant message to the potential predator is 'before you attack me, here is some honest information suggesting that it may be too costly to you'. In the case of Muellerian mimicry as strictly defined, the information is about chemical harm that the prey animal could inflict on the predator. But if we broaden the concept, then information about fitness could be similarly useful inasmuch as a futile chase costs the predator energy and opportunity while at the same time risking accidental injury and the attracting of unwanted attention from the predator's own predators.

If this working hypothesis makes enough sense to deserve testing, which new name should we adopt for this type of interspecies resemblance?

פורסם על-ידי milewski milewski, יוני 01, 2021 01:55 לפנה"צ

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