Scientific study reveals softer side of world’s largest meat-eating bats

By Stephen Beech

The world’s largest carnivorous bats greet each other with "hugs" and share food, reveals new research.

Spectral bats have a "surprisingly rich" social life - displaying affectionate greetings and providing food to family group members, say scientists.

Researchers were "astonished" to discover how "gentle and cooperative" the apex predators - also known as false vampire bats - are in their natural habitat.

The nocturnal lifestyle of spectral bats has made it challenging to study their behavior in the wild.

But researchers installed a motion-sensitive infrared camera inside a hollow tree in a tropical forest in Guanacaste, Costa Rica, where a family group of four spectral bats was roosting.

The meat-eaters, which can have a wingspan of up to three feet (one metre), were previously thought to be solitary foragers.

But, after three months of filming, the research team identified that the bats were in fact far more sociable than was previously suspected.

The team categorized eight main types of behavior - including social interactions, food provision and play.

Within the roost, the researchers found that bats would often groom each other and make social vocalisations.

The videos also revealed a social greeting similar to a hug, where one bat would greet another by wrapping its wings around the returning bat’s body.

Study leader Marisa Tietge said: "Adult bats returning to the roost with prey were observed voluntarily transferring the food to a younger bat in the colony.

"This behavior may allow adult bats to gradually transition their offspring from milk to a carnivorous diet and help young bats to develop their prey-handling skills before they leave the roost."

Although spectral bats were previously thought to be solitary foragers, the researchers recorded bats leaving or returning to the roost together, and the transfer of prey from the adult male to the lactating female was also observed.

The study, published in the journal PLOS One, is the first to describe food provision and other complex social behaviors in a wild group of spectral bats.

The researchers say their findings suggest that both parents help to care for the young, a strategy that is relatively rare among mammals.

Tietge, a research associate at Leibniz Institute for Evolution and Biodiversity Science in Germany, said: "The presence of two young bats in the colony, which are likely to be the breeding pair’s pups born in different years, indicates that spectral bats remain in the roost for an extended period.

“Spectral bats exhibit a level of cooperative behavior and biparental care that is rarely documented in bats – a fascinating area for future research.

“We were astonished by how gentle and cooperative these apex predators are.

“The most endearing behavior was forming a tight cuddle-ball when falling asleep: each bat wrapping one wing around its nearest neighbour, all snouts touching.

“Rather than hunting and raising young in isolation, the study shows complex cooperation behavior, strong monogamous pair bonds, as well as extended parental investment and biparental care - traits highly unusual in carnivorous mammals, especially bats."

She added, "I was astonished to find that the bats seemed to recognize me after several consecutive weeks of visiting the roost.

"At first, I was greeted with threat-like calls, and the bats broke their roosting formation to hide in the corners.

"But over time, their response shifted to just a few curious looks - no vocalisations, and they remained in a relaxed roosting formation.

"Even after nine months away, they appeared to recognize me immediately when I returned the following season."