Thousands of years ago, bees came across scattered bones in a cave – and decided to use them as nests in an impressive feat of adaptability.
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The ancient bee nests were discovered on the Caribbean island Hispaniola, once a key territory for the pirates of the area, in a cave called Cueva de Mono, which used to be home to generations of giant barn owls around 20,000 years ago. These owls would routinely cough up pellets containing bones of their prey, including a rodent called a hutia, slowly turning the cave floor into a graveyard.
Cueva de Mono is especially rich in fossils, and was previously identified by Juan Almonte Milan, curator of paleobiology at the Dominican Republic’s Museo Nacional de Historia Natural.
This discovery is rare and marks the first known record of bees making their nests in a preexisting fossil structure without altering it. But the researchers weren’t looking for bees when they entered the cave – they were interested in studying the hutia. The bee nests would’ve been missed if it weren’t for the careful attention of Lazaro Viñola Lopez, a doctoral student at the Florida Museum of Natural History.
"Usually, when collecting fossils, you get all the sediment out of the alveoli while cleaning the specimen," he said.
But Viñola Lopez inspected the fossils closely before cleaning – and the smoothness of one cavity caught his eye. Initially, he thought it was wasp cocoons mixed in with the fossil material, something he’s already encountered in the past. But wasp nests commonly have rough walls made from chewed plant material and saliva. Bees are more meticulous – they coat their nests with a waxy substance, creating the smooth interior.
Digging deeper
Burrowing bees generally prefer to make their nests out in the open, with only one recorded instance of them nesting inside caves. So, why did these bees forego tradition and find shelter not only in a cave, but within its fossil graveyard? Simple – it was most likely their only option in a quite unforgiving landscape.
“The area we were collecting in is karst, so it’s made of sharp, edgy limestone, and it’s lost all of its natural soils. I actually fell on it at one point, so I can tell you all about it,” said Mitchell Riegler, also a doctoral student at the museum and co-author of the study.
Whatever soils do manage to build up over time are washed into the numerous caves dotted around the island, accumulating there and acting as the only fitting habitat for burrowing bees of the region.
The bees likely arrived in the cave long after the owl, when what was left of its prey had already been scattered and buried in the ground. The bee started digging, but before it got to its preferred depth, it came across the ancient leftovers – the hutia’s teeth, or rather the indentations in the jaw that once housed them. Turns out, they were almost the perfect size for the insect’s nest.
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Scientists are not sure how long swarms of these bees made their nests in the cave’s fossils – but they do know they were used repeatedly, with some cavities containing as many as six layers of nests stacked inside one another like Russian dolls. Instead of digging new tunnels, the bees reused existing empty ones.
With this rare discovery being such a remarkable example of the adaptability of different species, the researchers will carry on studying other fossils recovered from Cueva de Mono. Additional findings are expected to be published in the future.
Read the full findings here.
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Top image credit: Lazaro Viñola López et al.
