When a person is sick, he usually prefers to stay home in bed, have chicken soup or a cup of tea and warm himself with a blanket instead of going to work. 

Now it appears that bats also maintain social distancing that could help prevent the spread of contagious diseases in their colonies, according to researchers at Tel Aviv University (TAU) who have just published a new study published in Annals of the New York Academy of Science under the title “Sick bats stay home alone: fruit bats practice social distancing when faced with an immunological challenge.” 

The Covid-19 pandemic has introduced us to expressions like lockdown, isolation and social distancing, which became part of social conduct all over the world. TAU researchers showed that sick bats, just like people with acute conditions, prefer to stay away from their communities –probably as a means for recovery and possibly also as a measure for protecting others. 

The study was conducted by postdoctoral researcher Dr. Kelsey Moreno and doctoral candidate Maya Weinberg at the laboratory of Prof. Yossi Yovel, head of the Sagol School of Neuroscience and a researcher at School of Zoology at the Wise Faculty of Life Sciences.

The study monitored two colonies of Egyptian fruit bats – one living in an enclosure and the other in its natural environment. To study the behavior of bats when they get sick, the researchers injected several bats in each group with a bacteria-like protein, thereby stimulating their immune response without generating any real danger to the bats. Tests revealed symptoms such as a high fever, fatigue and weight loss, and the ‘ill’ bats’ behavior was tracked with GPS.

Along with its many advantages, they wrote, social roosting imposes a major risk of pathogen transmission. How social animals reduce this risk is poorly documented.

The researchers discovered that the “sick” bats chose to keep away from the colony. In the first group, they left the bat cluster of their own accord and kept their distance. In the second group, the “ill” bats also moved away from the other bats in the colony and also stayed in the colony and didn’t go out in search of food for two successive nights.

Weinberg explained that this social distancing behavior is probably caused by the need to conserve energy – by avoiding the energy-consuming social interactions in the group. She stressed, however, that this behavior can also protect the group and prevent the pathogen from spreading within the colony. 

“Sick-like (immune-challenged) bats exhibited an increased immune response, as well as classic illness symptoms, including fever, weight loss, anorexia, and lethargy. Notably, the bats also exhibited behaviors that would reduce pathogen transfer. They perched alone and appeared to voluntarily isolate themselves from the group by leaving the social cluster,” they wrote.

In addition, the fact that sick bats don’t leave the cave prevents the disease from spreading to other colonies. “The bats’ choice to stay away from the group is highly unusual for these animals. Normally, these bats are extremely social creatures, living in caves in very crowded conditions,” Weinberg continued. “In fact, the “sick” bats’ behavior is very reminiscent of our own during recovery from an illness. Just as we prefer to stay home quietly when we are ill, sick bats, living in very crowded caves also seek solitude and peace as they recuperate.”

Yovel added that the study’s findings suggest that the likelihood of bats passing pathogens to humans under regular conditions is very low because sick bats tend to isolate themselves and stay in the cave. “We observed that during illness bats choose to stay away from the colony and don’t leave the cave, thus avoid mixing with other bats. This suggests that in order to encounter a sick bat, people must actually invade the bats’ natural environment or eliminate their habitats. In other words, if we protect them, they will also protect us.”