Vampire bats 'prefer to forage for blood with friends'

Female vampire bats may prefer foraging for blood with their friends, research suggests.

The animals that form bonds in captivity and continue those friendships in the wild also hunt together, meeting up over a meal after independent departures from the roost, the study found.

When roosting together in trees, the bats can be observed grooming each other and even sharing regurgitated blood meals.

Previous studies have shown this cooperative behaviour is directed towards close relatives and social partners.

Study co-author Gerald Carter, assistant professor of evolution, ecology and organismal biology at The Ohio State University, said: “We looked at the possibility of different scenarios, and we found that they leave the roost to forage independently of each other, but then the ones that have a relationship are somehow finding each other and associating out on the cattle pasture – and we think they’re coordinating,”

To investigate whether the social bonds of the animals also influence their foraging behaviour, researchers attached tiny sensors – backpack computers – to 50 female common vampire bats (Desmodus rotundus).

This included 27 wild bats and 23 that had been captive for nearly two years – before releasing them back into their wild roost on a cattle pasture in Tole in Panama.

While the tagged bats almost never left the roost together, closely bonded females often reunited far from the roost, the study found.

The animals that associated with more partners in the roost also met up with more partners during foraging trips.

Audio recordings of vampire bat calls in La Chorrera, Panama, revealed three distinct call types.

These were downward sweeping social calls, antagonistic buzz calls, and n-shaped feeding calls.

Researchers say the latter has not previously been observed in wild or captive vampire bats.

They hypothesise the bats may meet up with trusted partners during foraging trips to share information about hosts or access to an open wound.

It is suggested this collaboration might save on the time and effort involved in selecting and preparing a wound site on the cattle.

The bats may be able to identify friends and foes on the wing through the downward sweeping calls, which are similar to contact calls used to recognise partners in the roost.

The researchers said: “How far does ‘friendship’ go?

“We show that social bonds of vampire bats are not restricted to grooming and food sharing at the roost, but bonded individuals even hunt together, highlighting the complexity of their social relationships.”

The study is published in the Plos Biology journal.