Squirrels eavesdrop on birds to check for predators

Grey squirrels eavesdrop on birds’ chattering to determine whether an area is safe to forage, US researchers have discovered.

Scientists have previously established that squirrels listen out for the calls of nearby predators, but researchers at Oberlin College in Ohio in the USA wanted to see if they also interpreted birds’ contented conversations as an indication of safety. When a predator such as a hawk calls from the skies, nearby songbirds respond with alarm calls. Once the threat has dissipated, the songbirds return to their normal chatter – something it appears grey squirrels take advantage of.

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To make the discovery, the researchers observed the behaviour of 54 wild Eastern grey squirrels in parks and residential areas across Oberlin, Ohio, and set up speakers nearby that played a recording of the call of a red-tailed hawk, a common predator of both squirrels and small birds. Upon hearing the call, the squirrels responded with typical vigilant behaviours seen when a suspected predator is near: standing up, freezing on the spot or fleeing from the perceived threat.

The team then followed this with a ‘post-hawk’ period of 30 seconds of silence, followed by a 3-minute recording of either bird chatter recorded from birds visiting a feeder one busy morning or general ambient background noise. The squirrel’s movements were then monitored again to find out how long they remained vigilant before returning to foraging.

The squirrels who were played the bird chatter resumed their activities more quickly than those who were played the ambient noise. “We were excited to find out that squirrels eavesdrop on non-alarm sounds that indicate the birds feel relatively safe,” the researchers said. “Perhaps in some circumstances, cues of safety could be as important as cues of danger.”

The researchers now intend to carry out further studies into the phenomenon.

“One of the next steps includes determining what exactly the squirrels were cuing in on – particular bird species or particular kinds of noises, versus a more general category of ‘chatter’,” said study leader Professor Keith Tarvin.

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