Animals do social distance! Several species of animals like lobsters, bullfrogs, and even tiny ants stay away from sick individuals and isolate them. This prevents the disease from spreading to other individuals.
Social distancing is the act of maintaining a safe distance from others to slow the spread of a contagious disease. Before the coronavirus pandemic, most of us had never heard of ‘social distancing’ before, but in a matter of months, this term has become ubiquitously known across the globe.
Now, after reading this, one might think that social distancing applies only to humans, but lo and behold! The animal kingdom was social distancing long before humans gave it a name!
For most of us, social distancing feels unnatural and strange, but in the animal kingdom, it’s quite common, and in some cases, it is actually the norm. Just like humans, when an animal contracts a disease in the wild, other individuals (or conspecifics in ecology terms) stay away from the infected individual to protect themselves and limit the disease’s spread.
For many years it was unclear how animals could identify diseased individuals. More importantly, the exact mechanisms that animals used were ambiguous. However, over the last few decades, scientists have learned more and more about animal social distancing.
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Social Distancing — The Lobster Way
During the early 2000s, scientists tested how Caribbean spiny lobsters (Panulirus argus) responded to individuals infected by the Panulirus argus virus 1. This pathogenic virus is highly infectious (and lethal), infecting juvenile spiny lobsters via physical contact. This is especially worrisome, since spiny lobsters are highly social. They live together, often sharing dens. Therefore, without mechanisms to limit the pathogen’s spread, the lobsters would be in real trouble.
Through their experiments, the scientists found that those lobsters infected with the virus avoided sheltering with healthy conspecifics, though some preferred to cohabitate with another infected individual. They found that among the infected lobsters, 93% of them were solitary while the rest continued to share dens.
Going one step further, scientists tested this mechanism in their laboratories. In their experiment, diseased and healthy lobsters had to choose between an empty den or one with either a diseased lobster or a healthy one. Interestingly, they found that healthy lobsters avoided entering dens with diseased individuals, but shared dens with those who were healthy.
A follow-up study by the same research group in 2010 revealed that healthy spiny lobsters used chemical cues to identify infected individuals and avoid sheltering with them. In contrast, the diseased lobsters showed no bias towards dens and entered normally, regardless of the individual inside being healthy or diseased.
Social Distancing — The Bullfrog Way
During the late 1990s, scientists discovered that bullfrogs (Rana catesbeiana) social distanced when conspecifics contracted Candida humicola, a yeast infection that affects the intestines of many anuran species. Bull frogs are especially susceptible to C. humicola. It spreads when tadpoles ingest water that contains feces or the pathogen’s cells. This infection is known to severely reduce the growth rates of bullfrogs, while also causing mortalities.
Here, scientists found that uninfected individuals spent over 75% of their time avoiding infected bullfrogs. Similar to the spiny lobsters, bullfrogs also relied on chemical cues sent out by the infected individuals to protect themselves. On the other hand, infected individuals showed no bias in cohabitating with either infected or non-infected individuals.
Social Distancing — The Ant Way
Who would have ever thought that even the tiniest of creatures practice social distancing!
Ants are extremely social, boasting intricate social networks that still hold many secrets. They live in colonies that may range from a handful of individuals to a highly organized nest comprising millions of individuals. Communication is therefore absolutely vital for them, whether it is to get resources or prevent the spread of disease in their nests. Therefore, it was natural for scientists to wonder how ants respond to diseases in their midst.
A few years ago, a group of scientists investigated how ants (Lasius niger) altered their behavior in the presence of pathogens. They discovered that forager ants were more likely to be infected than indoor workers, as they spent more time outside the nest. They also found a clear segregation between those who were at higher risk of being infected (the foragers) and those considered high-value individuals, such as the nurse ants and the queen. This segregation means that whenever a nest is faced with a disease outbreak, the queen and the nurses isolate themselves from the foragers to reduce transmission of the disease.
Unfortunately, there are only a handful of studies that document social distancing among wild animals. However, from the few studies that have been conducted, one thing is very clear—animals have practiced social distancing long before humans learned about, and they do it a lot better than us too!