A study in South Africa has found that human voices cause considerably more fear in wild mammals than the sound of lions.
Scientists played recordings of people speaking normally through speakers hidden at water holes in the Kruger national park.
About 95% of animals including antelopes, warthogs, giraffes and leopards were extremely frightened and rapidly ran away.
Recordings of snarling and growling lions caused considerably less alarm; some elephants responded by trying to threaten the source of the big cat calls.
It's thought the animals have learnt that contact with humans is extremely dangerous, due to hunting, gun use and using dogs to catch them.