The miniature hippopotamus, or “house hippo” (hippopotamus domesticus) is reclusive and nocturnal. It is one of only three extant species in the family Hippopotamidae, the others being its much larger relative, the common hippopotamus (Hippopotamus amphibius) or Nile hippopotamus, and the pygmy hippopotamus (hexaprotodon liberiensis). The house hippo displays many terrestrial adaptations, but like the hippo, it is semiaquatic and relies on water to keep its skin moist and its body temperature cool. Behaviors such as mating and giving birth may occur in water or on land. In the wild the house hippo is herbivorous, feeding on ferns, broad-leaved plants, and grasses, and are particularly fond of cassava leaves. Feral domestic house hippos have adapted to a broader diet similar to that of cockroaches or house mice.

Until the 19th century house hippos were unknown outside West Africa, where there is a long tradition of keeping them as semi-domestic pets. When zoo specimens were found to breed well, house hippos were introduced to pet stores in the early 20th century. Similar to parakeets, a significant number of these pet hippos escaped or were released and are now found throughout Canada. There is some debate about whether the North American hippos have become a separate species, with some scientists proposing the trinomial name hippopotamus domesticus canadensis.

In the wild, house hippos live in shallow lakes or rivers with slow-moving water and a soft bottom. Semi-domestic African house hippos live primarily in or near cassava fields. Although they do some harm to the leaves of the cassava plants, farmers encourage house hippos because they repel the much more damaging whitefly (bemisia tabaci).

Feral domestic house hippos live almost totally indoors except during mating season. They make dens in inaccessible parts of houses such as behind bookshelves or under kitchen counters. Though not expert nest-weavers, they do line their dens with foraged substances such as yarn or dryer lint.

Wild house hippos are found in West Africa, primarily in Liberia, with small populations in Sierra Leone, Guinea and Ivory Coast. A subspecies (hippopotamus domesticus heslopi) was once found in Nigeria.

Because of their popularity as pets in the early 20th century, feral North American house hippos are now found in almost all urban areas of Canada, with the largest populations thought to be in Toronto, Vancouver and Halifax. Importing house hippos as pets was illegal in the United States so there is not thought to be a feral population there, though there have been some sightings in eastern states such as New York and Vermont. There are also isolated populations in Louisiana and Colombia. Because these were imported separately it is not clear if they are the the same species.

It’s not clear how large Canada’s house hippo population is or whether they are endangered. There is some evidence that improved insulation and winterproofing are making it harder for them to make dens and to find other hippos during breeding season. With no influx of other hippos to counter the effects of cold, poor reproductive years or inbreeding, these isolated sub-populations are expected to disappear over time 

Because house hippos are currently considered an invasive species, there are no official conservation efforts. Our research is helping to show that Canada’s house hippo is a separate subspecies and worth protecting.

Some scientists believe that Canada’s house hippos are descended from the extinct Nigerian subspecies. There is also a possibility that they may be remnants of the European ice age hippos. If either of these are true, house hippos are a priceless remnant of our lost biodiversity.

We also promote house hippo awareness programs to let more Canadians know about this animal and to see them as companions instead of pests.

Everyone has a part to play to save the house hippo. Click here to find out what you can do.