Separated family members have been seen contacting each other over distances of a 1-2 kilometers and play back experiments have shown that elephants are able to recognize the voices of other elephants from 1-1.5 km and occasionally from 2 kilometers apart. It has been shown that, under certain environmental conditions, very powerful calls can travel up to ten kilometers (over 300 km2), and while elephants might not be able to recognize individual voices at this distance, they may well be able to recognize calls of females versus males, large aggregations versus smaller groups, and an estrous female advertising for a mate.