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Ancient Bees Burrowed Inside Bones, Fossils Reveal
Bones of now extinct species became a haven for bee babies thousands of years ago, scientists report in a first-of-its-kind discovery
Illustration by Jorge Machuky
Thousands of years ago in what is now the Dominican Republic, there was a cave full of bones. And those bones were full of bees.
In a paleontological first, researchers have discovered that bees used the jawbones of now extinct mammals as burrows. It’s not clear what species of bee was exploiting this grisly opportunity—only their smooth-walled nests were left behind, nestled in the tooth pockets of ancient rodents and sloths. But such behavior has never been documented before, says Lázaro Viñola López, a postdoctoral researcher at the Florida Museum of Natural History and one of the discoverers. “It was something completely unexpected,” he says.
When Viñola López and his colleagues climbed past the jagged entrance of the cave, called Cueva de Mono, they were on the hunt for fossilized lizards, which they found—in excess. They also found tens of thousands of bones of extinct rodents and sloths, leading them to conclude that they’d stumbled upon the killing field of an ancient family of owls that likely nested in the cave and regurgitated the bones on the cave floor. Though it’s difficult to precisely date the fossils, the species come from the late Quaternary period, which started 125,000 years ago, and include ones that went extinct more than 4,500 years ago, the researchers reported on Tuesday in Royal Society Open Science.
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From “Trace fossils within mammal remains reveal novel bee nesting behaviour” by Viñola López et al., in Royal Society Open Science 12; December 16, 2025 (CC BY 4.0)
Within the dirt filling the empty tooth sockets of both the rodent and sloth jawbones, Viñola López and his colleagues noticed strange, smooth cuplike structures they eventually realized they were made by bees. The hard, smooth walls were the result of a waterproof layer that solitary bees add to their brood cells, where the insects’ larvae develop.
More than 90 percent of bee species live solo, and most make their burrows in the ground. “Modern bees, as far as I know, aren’t known to nest in caves, nor are they known to nest in these sediment-filled cavities of bones,” says Anthony Martin, an Emory University paleontologist, who was not involved in the study but researches trace fossils, or burrows and tracks left behind by ancient animals. He called the finding “a two-for-one surprise.”
Viñola López and his colleagues suspect the bees were using the bones not long after the owls burped them up and may have done so because soils in the surrounding forests were thin.
Paleontologists working in a cave on the Caribbean island of Hispaniola have discovered the first-known instance of ancient bees nesting inside pre-existing fossil cavities.
Illustration by Jorge Machuky
The bee-nest-filled bones were found in three of four soil layers, suggesting the bees used the cave over long time periods. There are also single tooth cavities filled with up to six different nests. “It’s probably multiple bees coming and doing communal nesting,” Viñola López says.
The bones might have provided an extra bit of protection from predators such as parasitic wasps.
“It’s kind of like a thermos,” Martin says. “They had this outer protective layer that was provided by the bone, and then they had their brooding cell, which was in the sediment, so they had double protection.”
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