A reader writes, "If hippology is the study of horses, then what is the term for the study of hippopotamuses?" We hate to place the cart before the horse, but let’s get things straight: the hippopotamus is sometimes known as the "river horse;" the Greek hippo- means "horse;" while potamus means "river." The word hippopotamus has been around since the sixteenth century, while horse is as old as English itself. (来源：EnglishCN.com)

The hippopotamus is one of the largest living land mammals (after the elephant and the white rhinoceros); a nocturnal feeder, it spends most of its day resting or sleeping in or near water. The hippopotamus is a member of the order artiodactyla, ungulate (or hoofed) mammals whose functional toes of the hind feet and forefeet are even in number, and whose third and fourth digits of each foot are paired and symmetrical. (The word artiodactyla comes from the Latin word meaning "having an even number of toes.")

To take things one step further, the hippo falls in the division of artiodactyla called the bunodonta, a name that recognizes its tuberculated molar teeth. Now that we’ve talked so much about the hippopotamus and its various groupings, can we come up with an answer to our original question? In short: no. The best we can come up with is this: studying hippos falls into the category of mammology with a concentration in hippopotamuses or hippopotami.