Adaptive colouration in wildebeests, part 7: emerging questions
What is it about the structure of hairs in wildebeests? The name 'black wildebeest' is apt in view of the truly dark appearance of gnou at a distance, but in reality even mature males have medium pigmentation (e.g. see https://stockfresh.com/image/6151781/black-wildebeest and https://www.thetaxidermystore.com/black-wildebeest-taxidermy-hide-mount-for-sale-17442.html). How do 'coffee-coloured' figures come over as perennially black, particularly given that gnou - perhaps more than any other species of subSaharan African ruminant - has winter pelage? And the same puzzle applies to the alternative common name 'white-tailed gnu': how does a dust-coloured tail (https://stockfresh.com/image/589888/black-wildebeest) come over as white?
Why are albojubatus and mearnsi adaptively different, e.g. in the occurrence of a facial flag, despite both being 'white-bearded', migratory species? Why does the buccal semet in taurinus (e.g. see https://www.shutterstock.com/nb/image-photo/close-wildebeest-open-zoo-thailand-1328189888) disappear in maturity, and does it occur at all in mearnsi?
Why do infants and young juveniles lack brindling and have paler feet than in any adults? The fawn ground-colour of infants, complete with countershading, is consistent with inconspicuousness. However, they might be even more inconspicuous if brindling were present from birth, and if the feet were similar in tone to the rest of the figure. And why are facial flags, particularly in albojubatus and mearnsi, more precocial than caudal flags (for taurinus eastern form see photos 5-8in https://blog.londolozi.com/2011/12/07/impala-and-wildebeest-babies/#gallery)?
Why is there an odd combination of striping (i.e. brindling) with a lack of countershading on the torso of adults? This is particularly incongruous in johnstoni because the pale of countershading on the inner surfaces of the upper legs is the best-developed of any wildebeest (see https://www.shutterstock.com/image-photo/blue-wildebeest-selous-game-reserve-tanzania-1040741800). Under which circumstances could infant and/or adult wildebeests blend into their surroundings?
Why are manes and beards present in both sexes and visible already at birth (see taurinus eastern form https://www.dreamstime.com/royalty-free-stock-photo-black-wildebeest-young-image2971855)? This is particularly puzzling because manes and beards vary from lax to stiff (upright), and mane-bases vary from dark to pale, among forms of wildebeest.
How frequent is the incidence of the white rostral bar in johnstoni, relative to sex, age and individuality? Why is this marking so consistent in hunted trophies (e.g. see https://www.thetaxidermystore.com/nyasa-wildebeest-taxidermy-shoulder-mount-for-sale-14264.html) but so inconsistent in photos taken in the wild?
Comentarios
Agregar un comentario