Sick vampire bats isolate from friends but continue to care for family
'It's kind of similar to what we observe with self-isolation or social distancing'
Blood-sucking bats may have something to teach humans about self-isolation.
New research suggests vampire bats living in virus-plagued colonies cut back on interactions with sick acquaintances but they continued to care for their closest relatives.
"Interestingly, strong family bonds were less affected by the appearance of this simulated disease than weaker social relationships," said Sebastian Stockmaier, a PhD student at the University of Texas and the study's lead author.
"Sick moms kept taking care of their young and healthy moms kept taking care of their sick young, too.
"Whereas social interactions between unrelated individuals decreased, social interactions between related individuals were maintained."
Much like humans, bats are social creatures living in large, highly interconnected communities.
The nocturnal hunters live in colonies numbering in the hundreds to thousands, sleeping wing to wing on cave walls.
When illness strikes, it spreads quickly within the population.
While the study was conducted long before the pandemic hit, and didn't involve any strain of coronavirus, Stockmaier can't help drawing parallels between the behaviour of sick bats and the human effort to slow the spread of COVID-19.
"It's very interesting because it's kind of similar to what we observe with self-isolation or social distancing right now," Stockmaier said in an interview with CBC Radio's Edmonton AM.
"We're often still around close friends or family even if we social distance. And they would still take care of us if we fall ill and we would do the same."
Highly social blood sippers
Stockmaier, working with researchers from Texas and Panama, has been studying a small captive population of bats in Panama.
Bats are the perfect case study, he said. They develop bonds that many have compared to human friendships. Highly concerned with hygiene, bats groom each other, preening family members and unrelated neighbours.
More importantly, bats share food to prevent starvation in the colony. Bats returning from successful hunts regurgitate bites of their blood meals into the mouths of their hungry friends.
Their survival strategies are reciprocal and help create a social structure within the colony.
Lazy bats who continuously freeload off their friends and beg for meals by licking the mouths of successful hunters are eventually cut off from the free food. Grooming sessions also stop if not returned.
The behaviours ensure the survival of the colony but can also make them susceptible to communicable disease.
They're always eating blood and blood is not very nutritional.- Sebastian Stockmaier
To study these interactions, Stockmaier and his team at the Smithsonian Tropical Research Institute in Panama baited wild bats with cattle blood and captured them in nets.
The bats were injected with a bacterial extract that stimulated their immune systems and mimicked the symptoms of a virus without actually making them ill. The bats became too lethargic to hunt or clean themselves.
"This immuno-stimulant triggers this very common set of sickness behaviours," Stockmaier said.
"They're triggered by our own immune system and they make you lethargic and make you sleep more, they make you socially disconnected, all these feelings you have when you're sick."
To simulate a night of missed hunting and encourage food sharing, some bats were periodically removed from the colony for 24-hour stints and denied food.
Sick bats continued to socialize but their social interactions changed. Grooming time with bats outside the family circle declined, but sick bats begging for a meal would be fed. Familial structures remained intact.
Mothers continued to feed their young no matter who was sick.
"They would groom each other less, but food sharing didn't change and that's presumably because food sharing is a much more important social interaction for them in terms of survival," Stockmaier said.
"They're always eating blood and blood is not very nutritional. And so if they can't get this food shared from others, then they run the risk of starvation."
Their bonds are very similar to human friendship.- Sebastian Stockmaier
Not all diseases are created equal and further research is needed, Stockmaier said.
But he's hopeful the work can help conservationists better predict how pathogens move through bat populations, and shed light on the spread of disease among some equally social, albeit much larger mammals.
"It's important to focus on these species that have these social structures that have some similarities to ours," he said.
"Their bonds are very similar to human friendship. I think that's what makes them so so interesting."
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