Meet the bat that eats other bats

Scientists are learning more about the rarely seen spectral bat, Latin America’s “jaguar on the wing.”

By Jason Bittel
Published 16 Dec 2021, 19:37 GMT
More mysteries revealed about bat-eating bat
A spectral bat, the largest bat species in the Western Hemisphere, consumes a short-tailed fruit bat.
Photograph by Marco Tschapka

“It’s the Vampyrum!” Winifred Frick called out from the darkened trail ahead. The rainforest around us thrummed with katydids, while howler monkeys whooped into the clammy night. As I caught up with Frick at the mist net—a spool of black mesh scientists used to catch bats for study—I looked over her shoulder, and the sight made my heart flutter.

Frick, the chief scientist at the nonprofit Bat Conservation International and an ecologist at the University of California, Santa Cruz, was running point on the nets at this year’s bat survey in Belize. During the past week on this November expedition, I’d seen dozens of bats up close in Lamanai Archaeological Reserve: Wrinkle-faced bats with faces like bulldogs, proboscis bats with Pinocchio noses, and even common vampire bats with toothy grins.

None was bigger than a songbird. But the bat staring back at me now was the size of a crow—with the ears, snout, and bared teeth of the Big Bad Wolf. Vampyrum spectrum, more commonly known as the spectral bat, is the largest bat in the Western Hemisphere, with wings that can stretch more than three feet. 

Vampyrum spectrum is sometimes also called the great false vampire bat—false, because it doesn’t slurp blood like its vampire cousin; it eats flesh. These apex predators hunt rodents, large insects, birds, and other bats, sometimes attacking them in mid-flight.

With this in mind, Frick—who has handled thousands of bats in her 20-year career but never a spectral bat—reached into her pack for an even thicker pair of leather gloves. “If I’m not careful, it will bite the crap out of me,” Frick said.

The week before, a different net crew had caught a female spectral bat—the first of the species seen during 14 years of annual surveys here.

Disentangling the bat from the net to get a closer look, Frick was surprised to discover hole-punches in each wing—suggesting that this was the same female colleagues had caught earlier. (Hole punching is a quick and harmless research method for acquiring genetic samples. The skin repairs itself quickly and does not impede flight.)

“Bats are important parts of mammalian biodiversity, and Vampyrum in particular is a great example of a bat with serious wow factor,” Frick says. “They are the jaguars on the wing in the rainforests of Central and South America.”

‘A very special bat’

Melissa Ingala, a research associate at the American Museum of Natural History, in New York City, and colleagues placed a small PIT tag beneath the bat’s skin and took faecal samples to determine what she’d eaten recently. If the bat is caught again, the team can compare the faecal samples to see if her diet has changed—important information about the animal’s behaviour, Ingala said.

“It's so rare to catch these guys that we just don't know that much about them,” says Nancy Simmons, head curator of the Department of Mammalogy at the American Museum of Natural History. Simmons and Brock Fenton, professor emeritus at Western University in Canada, organise these annual bat surveys—an effort that’s yielded at least 60 scientific publications so far.

“I think the Vampyrum, in particular, are just cruising through the forest looking for small vertebrates, and when they hear something odd, they go in to investigate,” Simmons says. (Learn how vampire bats survive on blood.)

Bats generally are thought of as eaters of insects, fruit, or nectar, but a recent study shows that Vampyrum is just one of nine bat species that qualify as carnivores.

The research suggests that these species, which include the woolly false vampire bat (Chrotopterus auritus) and the frog-eating bat (Trachops cirrhosus), play an underappreciated role as top predators in their ecosystems, in part by helping to control prey populations.

From southern Mexico all the way to Brazil, the spectral bat soars through the night in search of birds, snatching them from tree branches or nests. The flying mammals also snag rodents scurrying among the leaf litter.

“They swoop down and envelop their prey, using their wings like a fan,” says Rodrigo A. Medellín, an ecologist at the University of Mexico who co-authored the recent study on carnivorous bats and was not part of the Belize expedition.

Then, just like a jaguar, “they administer the killing bite, usually biting the top of the head or back of the neck.”

Dramatic as that sounds, scientists have rarely witnessed it, likely because there are very low densities of spectral bats, as is the case with other apex predators. Further, because predators need room to hunt, habitat loss is a serious problem for them: The International Union for Conservation of Nature lists spectral bats as near threatened by extinction.

“This forest might have five—it's probably just this female, her mate, and their offspring,” Ingala said. By comparison, there might be hundreds or even thousands of various other bat species in the same woods.

“This is a very special bat,” said Ingala.

For these carnivores, family comes first

In an effort to learn more about spectral bats, Medellín has made a standing offer that if someone can show him a Vampyrum roost in his native Mexico, he’ll give them $1,000 (£700) on the spot. So far, the reward has yielded three roosts.

“Which is three more than anybody else knows in the world,” quips Medellín, who is also a National Geographic Explorer-at-Large. 

These few roosts already have revealed valuable information. For example, Medellín and his team have observed that when female spectral bats are stuck at home with a pup that can be almost half their size, the male will carry rodents and other prey back to her.

“This kind of supplemental feeding was not known from these bats,” Medellín says.

Similarly, Medellín’s experiments with captive spectral bats have shown that they stop echolocating when they approach prey—perhaps because ultrasound would tip off other bats and even some rodents. Instead, they seem to rely on sounds made by the prey themselves.

“There's also one hypothesis out there that I need to test, which is that the bats may be using smell as well,” he says. This is because many of the bird species Vampyrum has been known to eat, such as cuckoos and motmots, have strong body odours and nest communally. “These are big advertisements for a predator,” Medellín says.

Medellín says he’s intrigued that the bats will kill and eat large birds, such as Amazon parrots. They can be heavier than a spectral bat and “can easily decapitate [one] with their beaks,” he says. “And still, Vampyrum is eating them.”

It’s Vampyrum’s world

Medellín’s recent study notes that some meat-eating bat species live in overlapping territories, and their presence or absence seems to affect other bats’ behaviour. (Amidst the coronavirus pandemic, why bats need our backup – not our blame.)

He notes, for example, that both Vampyrum and Chrotopterus (woolly false vampire bats) like to roost in hollow trees. Yet in areas where both species occur, Chrotopterus tends to roost in caves, archaeological sites, and culverts.

“But when Vampyrum drops from the system, either because you’re going up in elevation or latitude, then Chrotopterus goes back into the hollow trees,” he says.

All of which suggests to Medellín that other bat species living in Vampyrum’s world adjust their behavior for their own security. And now that I’ve seen a spectral bat in the flesh, I can’t say I blame them.

The National Geographic Society, committed to illuminating and protecting the wonder of our world, funded Explorer Rodrigo A. Medellín’s work. Learn more about the Society’s support of Explorers highlighting and protecting critical species.

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