Do Sick Animals Socially Distance?
According to a new review in the journal Science, when highly social animals — such as ants, mice and bats — get sick, their social interactions change, too.
A group of common vampire bats just hanging around. Credit: Josh Moore, Smithsonian Tropical Research Institute TRI
When we get sick, we change our social interactions—we keep away from others and we don't share food. It turns out, humans aren't the only species to do it.
According to a new review in the journal Science, when highly social animals — such as ants, mice and bats — get sick, their social interactions change, too. For example, sick vampire bats groom each other less, move less and call out less, and this may help reduce the spread of disease. It's not active social distancing, but rather more like the way we humans are less active when we're feeling lousy. Ants on the other hand are more proactive: when sick, they will actively self-isolate in a way that helps protect the rest of the colony.
By studying how social behavior changes in various animals, scientists are hoping to better understand the effectiveness of different strategies humans use, like social distancing, to combat the spread of diseases like COVID-19.
Today on the show we'll meet Sebastian Stockmaier, a recently minted PhD scientist at the University of Texas at Austin, who has spent seven years studying vampire bats and how their social behaviors change when they feel sick.
Read the new review paper in the journal Science: Infectious diseases and social distancing in nature
Music for today's show was produced by: Podington Bear - https://www.podingtonbear.com/
Photo credit: Josh Moore, Smithsonian Tropical Research Institute
Marc Airhart: This is Point of Discovery. I'm Marc Airhart. Over the last year, in an effort to slow the spread of the coronavirus, many of us have dramatically changed our social behaviors. We wear masks—we socially distance—we avoid crowds. If we feel sick, we stay home. But what about the rest of the animal kingdom? Do sick animals socially distance?
MA: I called up Sebastian Stockmaier, a biologist who just received his Ph.D. from the University of Texas at Austin. He studies a particular type of bat. Like us, they're incredibly social. This is how they talk to each other …
MA: Stockmaier studies how these bats' and other animals' social behaviors change when they get sick. By studying these effects, he and other scientists hope to learn which social behaviors do a better job of slowing the spread of infectious diseases. That's something that may have implications for our own battle with diseases like COVID-19. For the bats he studies, there are some important parallels.
Sebastian Stockmaier: They form these long-lasting relationships with each other that are based on food sharing and then they also groom each other. And so you have these really strong social bonds between kin, but also between non-kin.
MA: He says these bats are also a lot easier to work with than some animals.
SS: We can capture an entire roost, we can bring it into a flight cage. And we pretty much simulate the social environment they have in nature, because they forage for maybe four or five hours a night and the rest, they just spend in this roost together to interact with each other. So we can simulate their social environment in this fairly small space. And so I think they're a great study system for these kinds of questions.
MA: His field site is in the Central American rainforest of Gamboa.
SS: For the last, you know, seven field seasons, I live directly next to the Panama Canal. And then you can take these field vehicles and you can drive into the jungle. It's a beautiful place.
MA: Hm. I wonder if he needs a field assistant. He told me that -- to capture bats flying through the rainforest at high speed -- in the dark – isn't as hard as you might think. You just have to know where they go for dinner.
SS: The easiest way to catch vampire bats is to find cattle, any kind of livestock, and then just set up nets, and you'll catch vampire bats.
MA: Wait, did he say VAMPIRE bats?
SS: And one word I had a lot of trouble with initially was the word vampire, because you know in German, the V and the W are kind of like, it's almost reversed. So I would call it "wampire" a lot. Now, over the years, I've gotten used to say the word vampire correctly.
MA: In scary movies, vampire bats attack people. But in real life, they favor farm animals.
SS: With the introduction of livestock in those areas, the vampire bat populations have exploded because it's like such an easy food source for them. Imagine you're a vampire bat in the jungle, and you have to fly around every night and find some kind of animal. Now, all of a sudden, somebody just put 200 cows in the same place every night. It's just very easy to exploit compared to finding an animal in the jungle.
MA: If they're lucky, soon the scientists have captured a whole group of bats in their nets and brought them back to the field station where they're put into large flight cages.
SS: And they're actually fairly easy to work with in captivity if you're willing to handle big amounts of blood.
MA: On second thought, I don't think I want to be a field assistant.
SS: So that is one of the challenges. We go to the local slaughterhouse and get our blood there. Because it's very warm and very, very humid there, we have to keep it on ice. It's usually like a two-hour drive. We get to bring it back, we have to immediately freeze it, it can't go bad because if it goes bad, they'll drink it and they'll die, so that it's kind of like high pressure there. But then once you have the blood, we provide it in little bird feeders. And so they'll just fly down to the bottom of the cage and then they'll just lap it up from the bird feeders.
MA: Okay, so catch the bats. Check. Feed the bats. Check. Now it's time to do some science.
SS: I'm injecting them with an immune-stimulant. So it's not an actual pathogen. So we're not using something that is infectious. We're using something that is a molecular part of a pathogen that triggers these symptoms, so it mimics like an infection. And then we can observe their social behaviors with each other using these infrared cameras.
MA: Stockmaier was really careful to point out that this injection doesn't hurt the bats. It doesn't actually give them an infection. It just tricks their immune systems into thinking they're sick.
SS: It's something we experience too, right? When we're sick, we're like lethargic. We're less interested in social interactions, we usually eat less.
MA: Which brings us to the big question: Do vampire bats who FEEL sick socially distance like humans? Stockmaier says their social behavior definitely changes.
SS: And so what we see for these immune-challenged bats is that they're a lot less likely to groom other bats.
MA: While this may help slow down the spread of disease, Stockmaier doesn't think sick bats are consciously trying to protect their roost mates. It's more that they don't feel well, so they're conserving their energy. He calls it passive isolation. In fact, bats that feel healthy continue to groom the ones that act sick and share their food with them.
SS: Which is even weirder, because that's something that's like, very close contact. The sick individual sticks its tongue into the mouth of the healthy individual, which is not something, you know, that's very intuitive to do between a healthy and a sick individual.
MA: OK, maybe we humans don't do THAT. But we do take care of close family, even when they're sick. And Stockmaier says vampire bats do too. The bond between a mother and daughter vampire bat starts with a long gestation period -- seven months.
SS: Which is incredibly long for an animal that size, very long weaning periods. And usually mothers and their daughters stay together for the rest of their life. They become each other's main food-sharing donors. So those maternal bonds are very strong. And so what we find is that the effects of sickness are less pronounced in these bonds. Sick mothers will keep grooming their offspring. Healthy mothers will also keep grooming their sick offspring. What we see is that these vampire bats are socially less active, but it depends on the relationship between two individuals.
MA: See, I think now, for the next Mother's Day, I'm going to make a card for my mother and I'm going to say you know, you are a great mother. You were just like a vampire bat. Think she would appreciate the reference?
SS: Yeah, vampire mothers are amazing.
MA: So we started out by asking whether vampire bats socially distance the way we do. And the bottom line is no, they don't. To find something more like what WE do with social distancing to prevent the spread of disease, you have to look a little farther away on the tree of life.
SS: Now, if you look in ants for instance, ants will actually, if they sense that they're infectious, they'll leave the nest. So they'll isolate themselves from the others. They're actually practicing a very similar form of social distancing that we're doing right now. So what will happen is that if fungal-exposed ants are introduced to colonies, they'll isolate themselves to some extent, but then individuals within the group that are healthy, will also step away from each other, as like this precautionary measure. So that is something that's very similar to what we're doing right now, we're self-isolating. We're having these gatherings where we like, sit apart from each other. Even though we know that the others may be not sick, but you know, they potentially are so it doesn't even have to be that there's a infected or infectious individual around.
MA: The ants live in complex communities, just as we do, where the actions of one party can affect many others.
SS: This is an altruistic act that's driven by the fact that all the ants are very related to their sisters, they work towards this common goal of protecting the queen. And so for them, it makes sense for this behavior to have evolved to protect the colony as a whole.
MA: Scientists say it is one more example of lessons from the animal world that humans can relate to -- and learn from.
SS: You know, we're not alone in doing this, right? So animals have evolved these behaviors, animals are practicing these behaviors, animals are threatened by pathogens as well. And so we're starting to find more and more overlaps.
MA: Point of Discovery is a production of The University of Texas at Austin's College of Natural Sciences and is a part of the Texas Podcast Network. The opinions expressed in this podcast represent the views of the hosts, and not of The University of Texas at Austin. Music for today's show is by Podington Bear. Our website is at pointofdiscovery.org.There you'll find a transcript of this show, studies about social distancing in animals, and videos of vampire bats. If you like what you heard, be sure and tell your friends. We're available wherever you get your podcasts, including Apple Podcasts, Google Podcasts, Stitcher and Spotify. Our senior producer is Christine Sinatra. I'm your host and producer Marc Airhart. Stay safe out there!