Contact species seek out or tolerate close physical presence with conspecifics and sometimes with other species. (e.g. turtles, most primates, horses, elephants and goats). These animals have no individual distance. Hippos act like contact species when they are in the water by day but they are profoundly territorial at night on the feeding grounds. Within their enclosure they may defend the area and thus are potentially very dangerous to a keeper. Distance species neither solicit nor tolerate physical contact, aside from the period of reproduction and rearing the young. These animals maintain an individual distance (flamingos, penguins, many deer, giraffes, and tigers)

Hippos can be territorial at night and may pose a danger to
other animals or keepers at this time.