Bats that shine

Bats are sometimes called the “invisible mammals”. Their nocturnal lifestyle, combined with their silent hunting strategy and hidden lairs, makes them obscure except to the most dedicated chiropterologists. But new light is being shed on this typically dark mammal, and just in time for Bat Week.

Six species of North American bats recently managed to surprise researchers who learned that the flying mammals emit a strange green glow after being illuminated by ultraviolet light. Checking 60 separate museum specimens, scientists working at the Georgia Museum of Natural History found that they all glowed a shade of green under ultraviolet light. Although several insects, plants and mammal species, including flying squirrels and pocket gophers, have been shown to glow, this is the first time researchers have documented this phenomenon in North American bats. They published their findings in Ecology and evolution.

Interestingly, the bats all seemed to glow in the same places, particularly on their wings and hind limbs. Because they all glowed similarly with the same hue, the authors suggested that the function of this feature is not to differentiate between species or sexes. “It’s cool, but we don’t know why this happens,” Steven Castleberry, study co-author and biologist at the University of Georgia, said in a statement. “What is the evolutionary or adaptive function? Does it actually serve a function for bats?” Castleberry and his colleagues posit that the glow could be a remnant of an ancient adaptation retained by many bat species, but add that studying it in living bats could provide more information about its ecological function.

Mammals have other tricks up their sleeves. In a struggle for survival between bats and rats, researchers have revealed intelligent behavioral changes. Things can get rather tricky between Egyptian fruit bats and black rats where their ranges overlap. They fight over food and sometimes even attack each other. It turns out that fruit bats change the way they feed depending on the abundance of rats and their shared resources.

Researchers at Tel Aviv University studied hundreds of hours of video of a semi-natural colony of bats over seven months and noticed that the bats changed their feeding strategies in unexpected ways between winter and warmer months. In winter, when rats – which sometimes prey on bats – and food were scarce, the bats behaved nervously, landing less frequently and showing increased vigilance, which decreased their feeding efficiency. But when the weather warmed and the bats’ chances of encountering food and rats increased, they landed and fed more often. This time of year has also seen an increase in bat-rat interactions, with bats sometimes boldly attacking rodents.

The researchers published their results in BMC Biology. “We tend to describe relationships between different species in simplistic terms, either as competition or predation,” Yossi Yovel, study co-author and bat biologist at Tel Aviv University, said in a statement. “This study shows how complex such relationships can be and how animals are able to adapt their response strategies to changing circumstances.”

As new knowledge about bat physiology and behavior emerges, scientists are also discovering entirely new species. Researchers studying Philippine rainforest bats have officially named six new species. All bat species new to science are so-called tube-nosed bats, members of the genus Murine. Scientists from the Royal Ontario Museum, the Field Museum in Chicago and Lawrence University in Wisconsin used several methods, including morphological analyzes and genetic testing, to confirm the classification of the new species, all of which subsist on a steady diet of insects in their protected forest. “The discovery process has been long and slow, but these six previously unknown species clearly show how wonderfully extensive the Philippines’ biodiversity is,” Lawrence Heaney, curator emeritus of mammals at the Field Museum and co-author of the book. Zootaxa paper detailing the discovery, in a statement.

As you progress through Bat Week 2025, think about these oft-maligned wonders of nature. They may frighten some, but they are also a source of constant scientific surprises.

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Main image: Ecology and evolution

• Bob Grant

  Published on October 27, 2025

  Bob Grant is the associate editor of Nautilus.