Survival instinct
Humans could learn from animals on how to adapt when sickness abounds
The Caribbean spiny lobster can smell when another lobster is sick with a contagious virus, and it will leave to find a different den. Garden ants infected with a lethal fungus spend more time away from their colony. And house finches take social distancing actions based on the strength of their own immune systems.
These animals hunker down by themselves or steer clear of the sick among their groups. They have no vaccines.
And right now, humans are (mostly) trying to do the same as we battle to slow the spread of COVID-19.
“It just made me think of all the other animals in the natural world that I’ve read about and studied that do similar behaviors,” said Dana Hawley, a professor in the Department of Biological Sciences at Virginia Tech, of pandemic social distancing. “To some extent, it gave me a little comfort in knowing we’re not alone in having to do this behavior.”
Hawley and Julia Buck, an assistant professor at the University of North Carolina Wilmington, wrote an article for Scientific American on how animals use social distancing during outbreaks, giving examples from the work of several scientists.
Hawley, sheltering in her home in Blacksburg, Va., couldn’t help but think of garden ants. A colony’s forager ants are most likely to encounter lethal fungal spores while searching for food. If one of these ants gets infected, it will
Banded mongooses, clockwise from top left, mandrills, Caribbean spiny lobsters and ants practice some form of social distancing when virus or pathogens threaten their survival or reproductive health.
spend more time away from the colony, according to research led by Nathalie Stroeymeyt of the University of Bristol located in the United Kingdom.
Healthy ants in the colony also reduce their social interactions, and the nurse ants that care for the brood (eggs and larvae) move younglings farther inside the nest and away from foragers.
“When I started social distancing,” Hawley said, “the first thing that occurred to me is, ‘Hey, we’re basically like a giant ant colony right now.’”
And animals, just like humans, must weigh the costs of isolation.
Caribbean spiny lobsters use dens as shelters from predators. But a lobster will risk the open water — and being eaten — if it smells the urine of another lobster and detects a chemical associated with the Panulirus argus virus 1, which kills more than half of the juvenile lobsters it infects, according to researchers at the University of Florida and Old Dominion University in Norfolk, Va.
Mandrills will sometimes accept the risk if it’s a close family member. In general, these primates avoid grooming other mandrills that are heavily infected with intestinal parasites. But if certain close relatives are infected, the primates continue grooming them, according to studies led by Clémence Poirotte when he was at the French National Centre for Scientific Research. Primates can benefit from strong, unconditional alliances. For instance, female mandrills with the strongest social ties start breeding earlier and may have more offspring.
And other animals, such as banded mongooses, may prioritize cooperation in hunting and defense over the risk of getting sick. These animals maintain close interaction even if their troop members are visibly sick with tuberculosis, according to research led by former Virginia Tech graduate student Bonnie Fairbanks.
“There are really complicated tradeoffs between disease protection and other social benefits,” said Julia Saltz, an assistant professor who teaches animal behavior and population genetics at Rice University.
But ultimately, she noted that animals don’t practice social distancing to save their species. They’ve evolved to protect their specific lineage — themselves, relatives and future offspring. The reason ants leave the colony when sick is because they are highly related, all born from the queen.
Sebastian Stockmaier, who is working toward his doctorate in ecology evolution and behavior at the University of Texas at Austin, is studying how sickness affects the social interactions of vampire bats. These bats feed on blood, which isn’t very nutritious. Bats can die after missing one meal, so they’ll feed one another. They also groom each other to maintain social bonds with family and unrelated bats.
In his study, Stockmaier gave bats an injection that made them express common sickness behaviors, such as being lethargic, but didn’t actually infect the bats with a pathogen. He said “sick” moms continued grooming offspring (and healthy moms groomed “sick” offspring) but reduced their grooming of unrelated bats.
More broadly, he said animal experiments provide an opportunity to study how animals respond to pathogens – and then how pathogens respond to animals’ behavioral changes.
“We’re not the only ones that are getting infected with pathogens or parasites,” he said, “and so I think these behaviors have just evolved in a lot of animals to reduce transmission risks.”
Hawley emphasized natural selection. Nature has proven through monkeys, fish, insects and birds that animals are more likely to survive when they practice social distancing during an outbreak.
“The big takeaway for me is it’s worth the sacrifice,” she said. “We would not see this behavior so commonly in nature if it wasn’t so strongly favored by natural selection.”
But thankfully, humans are an animal capable of creating vaccines.