Even vampire bats enjoy dinner with friends! Females who roost together tend to forage for blood together too, study finds

  • Researchers strapped backpack sensors to 50 female vampire bats in Panama
  • Just over half were wild bats and the rest had been in captivity for two years
  • The team found that females who roost together find each other when foraging 

It isn’t just humans who like to go out for dinner with friends, according to a new study, that found female vampire bats go out foraging for blood with their mates. 

Animals that form bonds in captivity and continue those friendships in the wild also hunt together, according to researchers from Ohio State University in Columbus.

The team attached tiny senors to 27 wild and 23 captive female vampire bats, before releasing them back into their wild roost on a cattle pasture in Tole, Panama.

They found that when roosting together in trees the bats have been seen grooming each other, sharing meals and meeting up to forage even after leaving the root.

It isn’t just humans who like to go out for dinner with friends, according to a new study, that found female vampire bats go out foraging for blood with their mates. Stock image

VAMPIRE BATS: BLOOD FEEDING MAMMALS

The leaf-nosed bats are commonly found in Central and South America. 

The food source of the flying mammals is blood, known as hematophagy. 

There are three living bat species that feed solely on blood: 

  • The common vampire bat (Desmodus rotundus) 
  • The hairy-legged vampire bat (Diphylla ecaudata)
  • The white-winged vampire bat (Diaemus youngi) 

The three species all seem more similar to one another than to any other species, experts say.

This suggests that feeding on blood only evolved once, and they have a common ancestor. 

Study co-author Gerald Carter and colleagues wanted to find out whether social bonds formed between bats also influenced foraging behaviour.

The professor of evolution, ecology and organismal biology said they looked at the possibility of different scenarios for their behaviour.

‘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,’ said Prof Carter.

The 50 female bats, Desmodus rotundus, wore backpack computers as they were released to their usual roosting site, or from captivity.

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.

They essentially found that bats with a large group of friends are more likely to continue to meet up with those friends when out finding food.  

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

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

Bats that spent more time near each other in the roost during the day also spent more time together outside at night and encountered each other while foraging more frequently than bats not showing signs of social bonds. 

Foraging encounters between bats that had close relationships were, on average, longer in duration as well.

‘If you think about it, a longer interaction is more likely to be cooperative or affiliative than a short encounter, which could be neutral or aggressive,’ Simon Ripperger, a former postdoctoral researcher in Carter’s lab, explained.

Audio recordings of vampire bat calls in La Chorrera, Panama, where this study took place, revealed three distinct call types made by the flying mammals.

Animals that form bonds in captivity and continue those friendships in the wild also hunt together, according to researchers from Ohio State University in Columbus. Stock image

These were: downward sweeping social calls, antagonistic buzz calls, and n-shaped feeding calls, with the last of them not previously observed in vampire bats. 

They may be able to identify friends and foes while flying using the downward sweeping calls, which are similar to contact calls used to recognise partners in the roost. 

The findings prompted the researchers to question ‘how far ‘friendship’ goes’.

‘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.

DO VAMPIRE BATS EVER FEED ON HUMANS?

It’s long been thought that a species of vampire bat known as the hairy-legged vampire bat only feeds on the blood of birds.

There are three species of vampire bats: Common vampire bat, Hairy-legged Vampire Bat, White-winged Vampire Bat

But, scientists have now discovered for the first time that they sometimes feed on humans too.

The worrying prospect could lead to the spread of disease, as vampire bats are known to be major transmitters of rabies.

Researchers from the Federal University of Pernambuco in Brazil set out to look at how the species would behave in a situation of scarcity of birds.

The team analysed 70 faeces samples from a colony of hairy-legged vampire bats, living in the Catimbau National Park in Brazil.

To their surprise, they found that three samples contained traces of human blood.

The researchers believe that human intrusion in the national park could be driving the vampire bats to try mammal blood.

In their paper, published in Acta Chiropterologica, the researchers wrote: ‘The record of humans as prey and the absence of blood from native species may reflect a low availability of wild birds in the study site, reinforcing the impact of human activities on local ecological processes.’

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