Particularly large adults, on occasion, take on even larger prey, such as giraffe ("Giraffa camelopardalis"), Cape buffalo ("Syncerus caffer"), and young African bush elephants ("Loxodonta africana"). Even heavier prey, such as black rhinoceros ("Diceros bicornis"), have been killed by crocodiles. In one case in the Tana River of Kenya, as observed by Max Fleishmann (communicated via letter to Theodore Roosevelt), a crocodile was able to bring down one of these huge herbivores by the help of muddy bank terrain, the adult female rhino's poor decision to enter deeper water rather than retreat to land and finally having been joined in drowning the animal by one to two other crocodiles. An additional case of predation on an adult black rhino was reportedly observed in northern Zambia. A bull giraffe that lost his footing on a river bank in Kruger National Park was seen to be killed by a large crocodile, while in another case there, a healthy bull buffalo was seen to be overpowered and killed by an average-sized adult male crocodile measuring after a massive struggle, an incident less commonly seen at this size. Since crocodiles are solitary hunters, the Nile crocodile is the only predator in Africa known to attack full-grown buffaloes alone, compared to the preferred pride attack method of lions.