In my seven-sibling family, “dibs” is the most frequently heard phrase at holiday meals. Everyone wants to lay claim to the turkey drumstick or the end piece on the ham or the last (several) beer(s) in the fridge. And it’s not just me and my brothers and sisters that warn each other to back off from our food: Scientists now think that bats do it, too.
Researchers at the University of Maryland were examining audio recordings of big brown bats (Eptesicus fuscus) when they noticed that some of the noises the animals made were a little weird. They were unlike the sounds that bats usually use for echolocation, and turned out to be social or communicative calls, the bat version of conversation.
One of the calls consisted of three or four long, low downward sweeps through a range of frequencies and then a few short, buzz-like calls. The “frequency-modulated bout” (FMB), as the researchers dubbed it, only seemed to be made when the bats were hunting for food.
To learn more about the FMBs, the researchers, led by biologist Genevieve Wright, dangled a mealworm in a lab enclosure and let some bats have at it, either individually or in pairs, while they recorded things with high-speed video and audio equipment.
The recordings revealed that only male bats emitted FMBs, and only when they were hunting with another bat. Once one bat produced an FMB, the other one quickly changed its behavior, breaking its flight path toward the food and increasing the distance between itself and the calling bat. The bat that made the noise then claimed the prey for itself. When both bats produced FMBs, the one that emitted more of the calls usually nabbed the mealworm.
All this suggests that the FMBs have a repellent effect on nearby bats, and are the animals’ way of calling dibs on a prey item and saying “hey, that one’s mine, back off!”
The researchers are left with a nagging question, though. Why do only male bats call dibs? It might be that females don’t need to because they usually hunt alongside related bats and roost-mates, while males often forage with other, unrelated males and there is stronger competition for prey. The researchers also say its possible that only males make the FMBs because they’re related to a male-specific mating call. Even though Wright’s team only examined the calls outside of mating season, other researchers have described calls similar to the FMB being used during mating to assert control over a contested mate.