Adaptive colouration in wildebeests, part 1: large-scale conspicuous features

Most species of ungulates have certain inconspicuous features and certain conspicuous features, depending on the range/scale. In the case of wildebeests (Connochaetes), what is the overall effect at a distance and how does this differ among the various species and subspecies?

Wildebeests certainly have features of colouration adaptively conspicuous to scanning predators by day (e.g. for mearnsi see https://www.tanzaniaodyssey.com/blog/wp-content/uploads/2019/04/Tz7.jpg), but let us examine the various species/subspecies (https://www.researchgate.net/figure/Map-showing-the-distribution-of-wildebeest-subspecies-in-Africa-including-some-important_fig2_305317918). What is particularly interesting about this genus is the diverse ways in which the dark/pale contrasts have been achieved.

In gnou, conspicuous overall darkness (https://videohive.net/item/black-wildebeest-herd-in-grassland/28616219 and https://www.alamy.com/black-wildebeest-standing-in-grass-in-profile-image402457280.html) is achieved mainly by a poorly-understood anti-sheen quality of the fur, which is based on the physical structure of the hairs as much as their pigmentation. A similar anti-sheen effect also occurs in other forms of wildebeest (particularly mearnsi) but has to be weighed against a sheen effect on the hindquarters and back.

In mearnsi, there is a combination of overall darkness and a pale-looking rump (produced by sheen rather than depigmentation, see https://www.inaturalist.org/observations/77947564 and https://www.inaturalist.org/observations/41187666 and https://www.inaturalist.org/observations/36223318 and fourth photo in https://www.tripspoint.com/1/kenya/nairobi/tour/multi-day-tours-cruises/masai-mara-wildebeest-migration-safari/846 and https://www.inaturalist.org/observations/69048380).

In the western form of taurinus, the dark mane is permanently erect, which in combination with the dark beard and front of the face gives the anterior of the figure in profile a conspicuously dark accentuation (see https://www.picfair.com/pics/011975278-wildebeest-antelope).

In johnstoni there is in some individuals a bold whitish (depigmented) bar on a dark-pigmented face (see https://fineart.ha.com/itm/zoology/taxidermy/nyasaland-wildebeest-shoulder-mount/a/5000-48128.s and https://www.africahunting.com/media/32-nyasaland-wildebeest-tanzania.3371/).

In cooksoni, the front of the face is conspicuously dark relative to the pale forequarters (e.g. see fourth photo in https://www.edwardselfephotosafaris.com/the-top-5-wildlife-attractions).

In albojubatus, the beard and cheeks are conspicuously pale relative to the dark front of the face (see https://safaritalk.s3.amazonaws.com/monthly_04_2015/post-49296-0-93207700-1428854993.jpg and https://endangeredandrareanimals.net/2020/01/09/white-tailed_wildebeest/ and https://www.dreamstime.com/eastern-white-bearded-wildebeest-backlit-grazing-amboseli-national-park-kajiado-county-kenya-connochaetes-taurinus-albojubatus-image194773653).

Returning to gnou, both the mane and the tail can be conspicuously pale. For the mane see https://videohive.net/item/black-wildebeest-in-open-grassland-south-africa/26491133 and https://www.robertharding.com/preview/764-5249/black-wildebeest-whitetailed-gnu-connochaetes-gnou-mountain-zebra/ and https://www.alamy.com/black-wildebeest-walks-across-track-in-profile-image402467544.html and https://rangerdiaries.com/diary/black-wildebeest-2/ and https://visitstothepark.files.wordpress.com/2013/02/rietvlei-28-10-2012-255.jpg and https://www.dreamstime.com/black-wildebeest-south-african-plains-green-landscape-photographed-africa-image164824270. For the tail see https://www.ispotnature.org/communities/southern-africa/view/observation/814193/black-wildebeest and https://www.inaturalist.org/observations/52750792 and https://www.inaturalist.org/observations/67127234 and https://www.inaturalist.org/observations/40749840.

Publicado por milewski milewski, 09 de julio de 2021

Comentarios

The following shows that the tail of gnou can be truly white:
https://www.zoochat.com/community/media/black-wildebeest-marwell-wildlife.81010/. However, this may be somewhat unnatural given that these horns are also unusually pale.

Publicado por milewski hace alrededor de 1 año (Marca)

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