Deer are what biologists call “even-toed ungulates.” That means that they’re hoofed animals that bear weight equally between their third and fourth toes. Even-toed ungulates include deer, elk, and moose, as well as some more unusual creatures. Goats, cows, camels, giraffes, and pigs, are all even-toed ungulates too. Whales are also technically part of this group, since whales descended from hoofed creatures that lived on land.
Other hoofed animals are less closely related to deer. These animals are “odd-toed ungulates,” and they descend from animals that put their weight on their third toe. Horses, peccaries, and rhinoceroses are all examples of odd-toed ungulates. Who’d have thought that whales are more closely related to deer than horses are?
Photo by Bureau of Land Management