Before seeing rhinos at Ol Pejeta, I walked into a room with all kinds of antelope, zebra, and carnivore skulls and bones on display. Right at the entrance there was a bush elephant skull positioned next to another skull of almost the same size. I knew rhinos were large, but I hadn’t realized just how gigantic they were. For some reason I had always thought of them as in the same size tier as hippopotamus, an already enormous animal. Adult southern white rhinoceros (Ceratotherium simum) are actually on average 1,000 pounds heavier than hippos, a ~33% increase!— making them the second heaviest terrestrial animal.
Rhinos belong to the order Perissodactyla, a clade containing the jungle-inhabiting tapirs of the Americas and Southeast Asia, equids (horses, zebras, and asses), as well as extinct beasts such as the indricotheres. One feature that differentiates perissodactyls from artiodactyls, as sister groups of ungulates, is how weight is distributed across the digits of their feet. Artiodactyls (even-toed ungulates) bear two enlarged digits that support the weight of the body more or less equally, while perissodactyls (odd-toed ungulates) are characterized by an enlarged central digit. In horses the outer digits are reduced, and a single hoof masks a massive central digit, in contrast to extinct equids which indeed featured tridactyly as the ancestral state. Perissodactyls, being the less diverse extant group, more easily stand out as having the unusual and “odd” digit arrangement. Seeing rhinos and tapirs in the wild, I was immediately taken in by their bizarre skull shapes, but it turns out their feet are as equally interesting.
Photographed in situ [1]
