Humans are a funny lot. While we seem to be relentless voyeurs, we generally frown on eavesdropping as an invasion of privacy. But in the animal world, eavesdropping can be a matter of life or death. Animals rarely communicate in isolation. Often it pays for one species to monitor the dialogues of others, particularly when predator warnings are involved.
Small animals in particular do well to pay attention to the alarms of other species, as they are often preyed upon by the same larger hunters. Even very unrelated species can listen in and understand each other's signals. Vervet monkeys respond to the alarm calls of superb starlings, while mongooses are well-versed in hornbill calls.
Alarm calls aren't just a simple matter of shouting "Look out!", and many species have different calls for different predators. But one of the most sophisticated alarm systems so far discovered is used by a small, ...
