Ungulate mouths are what they eat
If you’ve not been licked by a white-tailed deer and a bison, you might not have a reference point to know that their tongues are all that different. But, thanks to your friends at the Monteith Shop, all of your questions about ungulate tongues can be quelled.
Different species of ungulates tend to eat different vegetation, and their mouths are shaped to do this efficiently. Deer, for example, are picky in what parts of the plant they eat, so they need a mouth that lets them select particular parts of the plant. In addition to having soft tongues, deer have wider mouths and long lips, which let them maneuver and strip small leaves from twigs. In contrast, bison eat grass and other tough vegetation, so their tongues are rougher, the openings of their mouths are proportionately smaller, and their lips are shorter and stiffer. This all helps to prevent the grass they’re eating from falling out. And yes, even the uniquely shaped head and mouth parts of the moose are a function of their diet. The combination of individual anatomical features, such as the roughness of an ungulate’s tongue with the shape of their mouth, help ungulates to be successful in their habitats.
Reference: Hoffman, R. R. 1989. Evolutionary steps of ecophysiological adaptation and diversification of ruminants: a comparative view of their digestive system. Oecologia 78:443-457.