One of their purposes in nature is to control the amount of catfish in the rivers and streams.
Without this control, rivers would soon be stripped of all vegetation without which, smaller fish, turtles etc. would not be able to survive.A distance of up to twenty kilometres will be walked by them at night in search of another water hole or stream if their current one dries up.
Their favourite food is medium sized antelope which they kill by holding it underwater until it drowns and then they will break off large portions by shaking it about and swallow it hooves and all. One impala, for example, take approximately twenty eight days to digest and so they will not feed again will during that time.