Verified by 
Social Distancing in Nature
What can we learn about disease prevention from animals?
Posted March 17, 2021 Reviewed by Gary Drevitch
- New research casts a light on how other species shift social interactions, and practice social distancing in the presence of a contagious pathogen.
- Animals from ants to bats to lobsters employ a variety of strategies to prevent the spread of infection, including avoidance, active and passive self-isolation, and exclusion.
- These evolved behaviors, which in some cases include caretaking, are generally quite effective.
It’s been about a year since the phrase “social distancing” entered our collective vocabulary. But it’s not a new concept. In a recent review in the journal Science, researchers examined various forms of social distancing practiced in the animal kingdom. It turns out that infection can change social behavior in a range of species. Understanding these social dynamics can shed light on processes like how diseases spread, as well as model ways to prevent disease transmission.
Sebastian Stockmaier, who studies sickness behaviors in vampire bats at the University of Texas at Austin, worked with a group of epidemiologists, evolutionary biologists, and other experts to write the review. The team identified six ways that the presence of a contagion can alter social interactions among animals from ants to humans.
One common strategy is avoidance. This is when you recognize that another individual is sick and maintain your distance to avoid getting sick, too.
“This is familiar to all of us right now,” Stockmaier says. “When we’re at the grocery store and someone sneezes, we’ll step away from that person.”
Pathogen avoidance is practiced by diverse species including termites, mandrills, Trinidadian guppies, and Caribbean spiny lobsters. Healthy spiny lobsters, for instance, may proactively abandon their den if they detect an infected group member in it. It’s not a decision they make lightly, as it results in the loss of protection of their group and den and potential exposure to predators. However, sometimes it is worth the risk to avoid a lethal virus.
The researchers also looked at different ways that individuals self-isolate and differentiated between two mechanisms. Active self-isolation, in which an individual actively removes themselves from others to protect the group, is known mostly in social insects such as ants and bees. For example, within hours of exposure to an infectious fungus, ants will spend more time outside the nest, limiting their encounters with susceptible nestmates.
Passive self-isolation, on the other hand, occurs inadvertently, when infected individuals feel lousy and so limit their everyday activities. We’ve all felt this way before, says Stockmaier, and he points to another example from his own research. To study how sickness affects social networks and interactions in vampire bats, Stockmaier injects individual bats with a small piece of gram-negative bacteria, a harmless substance that triggers an immune response and subsequent sickness behaviors, such as lethargy.
“We found that when vampire bats feel sick, they are less active, groom themselves less, and also interact with and groom others less,” he says. “As a result of being lethargic, they are less socially active.”
Honeybees and some other social insects don’t take chances when it comes to protecting their nests from sickness, engaging in a strategy termed exclusion. This happens when healthy bees aggressively drag sick ones from the hive, forcing them into isolation.
There is also a softer side to social insects: They, like humans, can also engage in caretaking behavior, helping infected nestmates even as they incur the risk of infection themselves. For example, ants and termites will physically remove or chemically deactivate infectious fungal spores on contaminated nestmates.
Finally, the team reviewed proactive social distancing, which we humans are all too familiar with at this point. This strategy involves everyone keeping their distance from one another, even when healthy, to reduce the risk of transmission. In response to the ongoing COVID-19 pandemic, most countries have implemented generalized social distancing. Black garden ants do something similar. If a fungus-contaminated ant is introduced to the nest, the other ants increase their social distance from one another, likely reducing transmission rates by limiting inadvertent spread by asymptomatic carriers.
Overall, the review highlights that self-isolation, avoidance, exclusion, and group-wide social distancing can reduce the spread of contagious pathogens, whether it’s among ants, bats, or people.
“We are not the only animals that are constantly exposed to infectious diseases,” says Stockmaier. “Other animals have evolved these strategies to deal with that threat and they seem to be very effective.”
References
Stockmaier S, Stroeymeyt N, Shattuck EC, Hawley DM, Meyers LA, and Bolnick DI. Infectious diseases and social distancing in nature. (2021). Science 371(6533): eabc8881. Doi: 10.1126/science.abc8881.
