Adaptive value of prominent orbits in Bison: sexual dimorphism instead of horizon-wide vigilance?

Various ruminants of open vegetation have the eyes placed laterally on the skull, so as to be able continually to scan a wide horizontal range behind as well as in front of the animal.

Dama dama

female https://www.horniman.ac.uk/object/NH.0.419/https://dept.dokkyomed.ac.jp/dep-m/macro/mammal/en/specimen/DKY_1577S.html

male
http://www.jakes-bones.com/2010/10/how-i-cleaned-up-my-fallow-deer-skull.html
https://bcgforums.com/threads/fallow-deer-portrait-with-the-600pf.29472/
https://www.jungledragon.com/specie/61/fallow_deer.html

Cervus canadensis

female

https://www.biokids.umich.edu/resources/contributors/skulls/cervus/c._elaphus/59189.dorsal/
https://pixabay.com/photos/wapiti-deer-head-female-deer-5778159/

male

https://www.birdandhike.com/Wildlife/Mamm/08Art/03_Cer/Cervis_can/_Cer_can.htm

Some of the ruminants referred to also have bony orbits so prominent (almost 'tubular') that the eyes are metaphorically on stalks.

Antilocapra americana

https://www.sciencephoto.com/media/857338/view/pronghorn-antelope-skull
https://vanat.ahc.umn.edu/museum/pages/PronhornSkull1.html
https://outlawskulls.com/antelope-skulls.html
https://www.chichesterinc.com/PronghornSkulls.htm
https://www.flickr.com/photos/nikonpaul/19732814289
https://www.onthewingphotography.com/wings/2011/10/30/antelope-island-pronghorn-buck-portrait/
https://www.natureplprints.com/2011-highlights/pronghorn-antelope-antilocapra-americana-15261491.html

Saiga tatarica
https://upload.wikimedia.org/wikipedia/commons/e/e4/Saiga_Antelope_Skull_and_Taxidermy.jpg

In some cases, this means that the eyeballs can be seen even when the head is viewed from directly behind.

https://www.researchgate.net/figure/Ventral-dorsal-and-lateral-views-of-skull-and-lateral-view-of-mandible-of-an-adult_fig3_228649156

Bison bison: Fig. 1 on page 2 in https://www.science.smith.edu/departments/Biology/VHAYSSEN/msi/pdf/i0076-3519-266-01-0001.pdf
Bison bonasus: Fig. 3 in https://journals.openedition.org/paleo/3237?lang=en

Publicado el 30 de julio de 2024 por milewski