Adaptive colouration in wildebeests, part 6: auricular and buccal semets

Certain forms and growth-stages of wildebeests possess auricular and buccal semets. These small-scale dark/pale patterns on ears and mouth hypothetically function as dynamic social signals, particularly when the group lies down to ruminate by day, with ears and jaws rotating. However, no form of wildebeest seems to retain a buccal semet in maturity.

In gnou there is only the faintest hint of an auricular semet (see https://www.shutterstock.com/nb/image-photo/black-wildebeest-whitetailed-gnu-connochaetes-gnou-413407261 and https://www.taxidermy.net/attachments/145341/ and https://www.taxidermy.net/attachments/145343/ and https://www.taxidermy.net/attachments/145344/). Instead, the ear is exceptionally plain for a ruminant.

By contrast, the following of adult albojubatus shows how the movements of the ears are accentuated by dark/pale markings: https://www.shutterstock.com/nb/video/clip-18837476-eastern-white-bearded-wildebeest-relaxing-zoo-small-group. A similar pattern on the back of the ear can be seen in taurinus (https://www.agefotostock.com/age/en/details-photo/blue-wildebeest-connochaetes-taurinus-lying-on-ground-face-covered-with-dry-mud-kgalagadi-transfrontier-park-northern-cape-south-africa-africa/ZI6-2631216) and in infant mearnsi (https://www.inaturalist.org/observations/72549813).

These views of juvenile taurinus show the graphic pattern on the front of the ears: https://www.dreamstime.com/closeup-young-blue-wildebeest-calf-looking-camera-its-mother-passing-background-kruger-national-p-park-image216239773 and (also showing a hint of the pattern at the mouth) https://www.dreamstime.com/group-young-blue-wildebeest-connochaetes-taurinus-staying-kalahari-desert-close-to-waterhole-red-sand-image172003983.

The following of taurinus shows a buccal semet in infants and juveniles: https://www.gettyimages.com.au/detail/photo/young-blue-wildebeest-royalty-free-image/986499878?adppopup=true and https://www.dreamstime.com/stock-photo-blue-wildebeest-calf-young-connochaetes-taurinus-south-africa-image42229647 and https://www.canstockphoto.com/blue-wildebeest-1577851.html. The buccal semet persists up to the adolescent stage: https://www.alamy.com/stock-photo-close-up-of-a-blue-wildebeest-connochaetes-taurinus-grazing-21318693.html and https://www.bookmundi.com/nairobi/six-days-masai-mara-amboseli-wildlife-safari-24782 and https://www.shutterstock.com/nb/image-photo/close-wildebeest-open-zoo-thailand-1328189888. However, it disappears in maturity: https://dissolve.com/video/Tight-shot-wildebeest-gnu-chewing-cud-short-grass-African-royalty-free-stock-video-footage/001-D58-40-034.

By comparison, the buccal semet seems faint even in infants of gnou (see https://www.shutterstock.com/nb/image-photo/very-young-black-wildebeest-calf-has-1671747409).

The following of taurinus shows that the auricular semet is already present at birth https://www.dreamstime.com/stock-photo-baby-wildebeest-young-blue-calf-connochaetes-taurinus-closeup-okavango-delta-botswana-image67079970.

Although more information is needed, it seems that the auricular semet occurs throughout life in all forms except gnou, and that the buccal semet is restricted to infants, juveniles and adolescents, disappearing in maturity.

Posted on 10 July, 2021 18:56 by milewski