From Bruce Mullinax, Great Falls, Virginia, US
You report that certain whales whisper to their calves to avoid alerting predators (27 July, p 17), and that mother orangutans instruct their offspring to move on with a loud scratch (20 July, p 19). I wonder how many other animals use similar anti-predator tactics.
I know the deer around my house produce a barely audible, low-frequency moo to “talk” to their fawns and to adults within their social group. I think they use it to rein in a hyperactive fawn that has wandered too far. A mother also uses it to call a fawn from its nesting area after she has returned from foraging and is ready to give milk. I need to be pretty close to hear the call. I assume the fawn’s ears have evolved to detect the sound from quite a distance.
