Are there people in your life that maybe if the circumstances were different you wouldn’t be as close to them as you are? Perhaps a randomly selected partner for a school project or a family friend that otherwise you wouldn’t connect with, but since you’ve spent so much time with them you get to know them very well? This type of bonding through proximity, or nearness, is common in humans and many animal species. Recently, researchers found that vampire bats will form stronger bonds with other bats they’ve been housed with, compared to unknown bats.
In the wild, vampire bats live in large groups of over a hundred bats – that’s a lot of bats to keep track of! Within these large groups, bats will spend more time with some bats than others. These bats will sleep in the same place, share food, and groom each other. Think of it like spending time with your family or a close friend! In captivity, bats living together will show a preference for each other’s company even after more bats are introduced to them. However, none of the experiments done on this topic have had proper controls to show that it is the proximity causing preference for certain relationships rather than other factors or simply chance. Therefore, Razik and their lab experimentally tested whether housing vampire bats close together leads to lasting relationships.
To test this theory, the researchers put the bats in the experiment through three different phases. In the first phase, all twenty-one bats collected from three different locations were housed together in a large cage and allowed to freely interact with each other. After six weeks, the researchers divided the bats into seven randomly assigned groups, containing one bat from each of the three collection locations. These groups of three were housed together for one week in smaller cages. After a week, all bats were once again housed together in the large cage for nine more weeks. The researchers then recorded the interactions between the bats, such as grooming. While this grooming serves the practical purpose of cleaning the animal it is also a social behavior like if you were to braid your friend’s hair during recess!
They found that grooming increased in bats that were isolated together compared to bats that were not housed together for one week. Additionally, the grooming of bats from different capture sites increased. However, the grooming of bats from the same capture site did not decrease as the grooming of other bats increased. This shows that the forced proximity led to relationships that lasted longer than the time they were forced to stay together. This kind of research is really exciting as it expands our knowledge of what kinds of factors can affect the social lives of animals!
References
Razik I, Brown BKG, Carter GG. 2022. Forced proximity promotes the formation of enduring cooperative relationships in vampire bats. Biology Letters 18, 20220056. (https://doi.org/10.1098/rsbl.2022.0056)
