Although crocodiles occasionally prey on hippopotamus calves, even large adult crocodiles rarely attack them because of the aggressive defense by mother hippos and the close protection of the herd, which pose a serious threat. Hippopotamus calves have been observed to at times act brazenly around crocodiles, foraging without apparent concern and even bumping into the reptiles. However, some large crocodiles have been recorded as predators of subadult hippos; anecdotally, the infamous giant crocodile Gustave was reported to have been seen killing adult female hippos. A specimen from Zambia was found to have eaten a "half-grown hippo". At the no-longer-existent Ripon Falls in Uganda, one adult male hippopotamus was seen to be badly injured in a mating battle with a rival bull hippo, and was then subsequently attacked by several crocodiles, causing it to retreat to a reedbed. When the male hippo returned to the water, it was drowned and killed by the group of crocodiles amid "a truly terrifying commotion". However, other than rare instances, adults of megafauna species such as hippopotamuses, rhinoceroses, and elephants are not regular prey and are not typically attacked, with the exception of giraffes, since their anatomy makes them vulnerable to attack while taking a drink.