When Sick Vampire Bats Isolate Themselves From Their Community - Latest Study

Published October 28th, 2020 - 07:11 GMT
Vampire bats   (Shutterstock)
Vampire bats (Shutterstock)
The researchers captured 31 adult female vampire bats from a hollow tree in Lamanai, Belize in Central America. 

Wild vampire bats socially distance when they are sick by spending less time in their community, a new study suggests. 

In the wild, US researchers injected bats with endotoxins, which stimulate an immune response, fixed them with proximity sensors and recorded their movements. 

The sick creatures associated with fewer group mates, spent less time with others, and were less socially connected to healthy group mates, they found.   

The experts say sickness-induced social distancing in animals does not require cooperation from others and is probably common across species. 

'When animals are sick, they often encounter fewer individuals,' say the experts in their research paper, published in Behavioral Ecology.  

'We tracked this unintentional "social distancing" effect hour-by-hour in a wild colony of vampire bats.

'As tracking technology improves the capacity to create dynamic animal social networks from large, high-resolution datasets, we expect researchers to gain new insights into the patterns and processes underlying the spread of pathogens, information, or behavioral states.'         

The researchers captured 31 adult female vampire bats from a hollow tree in Lamanai, Belize in Central America. 

The team injected half the bats with an endotoxins, also known as lipopolysaccharides, an immune-challenging substance, to make them sick, while the other half received harmless saline injections.

The researchers then glued proximity sensors to the bats and released them back into their tree.

'The sensors gave us an amazing new window into how the social behaviour of these bats changed from hour to hour and even minute to minute during the course of the day and night, even while they are hidden in the darkness of a hollow tree,' said study lead author Simon Ripperger at the Ohio State University. 

'We've gone from collecting data every day to every few seconds.' 

The team tracked changes over time in the associations among the 16 sick bats that had received endotoxin injections and the 15 control bats.

In the six hours after injection, a sick bat associated on average with four fewer associates than a bat that had been injected with saline.

On average a control bat had a 49 per cent chance of associating with each control bat, but only a 35 per cent chance of associating with a sick bat.

During the treatment period, sick bats also spent 25 fewer minutes associating with another partner. 

These differences declined after the treatment period and when the bats were sleeping or foraging outside the roost. 

Scientists had previously seen social distancing behaviour in lab conditions, but wanted to find out if it occurred in the wild.

These studies had revealed that endotoxin-injected bats were physiologically immune-challenged, slept more, moved less, engaged in social grooming with fewer partners in a cage and even produced fewer vocal calls to their fellow mates.

'In this field experiment, we showed that these effects of sickness behavior extend to proximity-based association durations and social network connectivity in the natural environment,' the team say. 

'Sickness behavior can therefore slow the spread of a pathogen that is transmitted at higher probability with higher rates of physical contact (e.g., grooming) or closer proximity.'

In another study this week, researchers in Singapore claim that bats excel as carriers of viruses such as coronaviruses without getting as sick as humans do, by adopting multiple strategies to reduce pro-inflammatory responses.  

Bats act as reservoirs of numerous zoonotic viruses, including SARS-CoV, MERS CoV and the Ebola virus. 

It's been thought the SARS-CoV-2 virus, which causes Covid-19, originated from bats, although the exact origin of Covid-19 not yet been officially confirmed. 

It is likely to have its ancestral origins in a bat species but may have reached humans through an intermediary species, such as pangolins – a scaly mammal often confused for a reptile. 

This article has been adapted from its original source.

© Associated Newspapers Ltd.

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