Bees often associated with large colonies serving the queen involving hundreds, if not thousands insects. In fact, this is usually not the case.
“Most bees are solitary. They lay eggs in small cavities and leave pollen for the larvae to feed.” explained paleontologist Lazasro Vignola Lopez. “Some species of bees dig burrows in wood or soil or use empty structures for nests.”
Vignola Lopez, a researcher at Chicago's Field Museum, added that some European and African species even build nests inside empty snail shells. However, a hive inside a bone is something new even to experienced researchers. This newly discovered example, estimated to be around 20,000 years old, is also the first known example of such a house, both past and present. The results are detailed in a study published Dec. 16 in the journal. Royal Society Open Science.
Researchers discovered a unique find while exploring numerous limestone caves scattered throughout the southern Dominican Republic. Sinkholes are common on the Caribbean island of Hispaniola and are often so well protected from the elements that they act like underground time capsules.
These windows into the past are largely thanks to the work of the island authorities. owls. Birds of prey often build their nests inside these caves, where they cough regularly. owl pellets filled with undigested bones of prey. Over thousands of years, these layers of bones fossilized on top of each other in carbonate layers formed during rainy periods. However, the opportunity to see these remains with your own eyes is not for the faint of heart.
“The initial descent into the cave is not very deep – we tied a rope to the side and then climbed down,” said Viñola Lopez. “If you go in there at night, you will see the eyes of the tarantulas that live inside.”
After passing large spiders through an underground tunnel about 33 feet long, paleontologists began to find various fossils. Many of them belonged to rodents, but there were also bones from birds, reptiles and even sloths, totaling more than 50 different species of animals.
“We think this was a cave where owls lived for many generations, maybe hundreds or thousands of years,” Vignola Lopez said. “The owls would go out hunting and then return to the cave and drop pellets. [found] fossils of the animals they ate, fossils of the owls themselves, and even some turtles and crocodiles that may have fallen into the cave.”
While cleaning up his findings, Vignola Lopez noticed a smooth, almost concave sediment inside one of the dental sockets of the mammal jaw fossil. Dirt doesn't usually accumulate in fossils this way, but then Viñola Lopez started finding more examples.
“I thought, 'Okay, there's something weird here,'” he recalled.
The mysterious fillings reminded Vignola Lopez of some fossilized wasp cocoons he examined during excavations in Montana. After CT scanning the samples, his team noticed that the sediment structures looked almost identical to the fossils preserved from his college days. Some even still contained pollen grains from the mother bees, probably enclosed in separate nests as food for their larvae.
Although there were no fossilized insects in the nests, this was to be expected. The caves, although protected from the outside world, are still extremely wet and warm – conditions not suitable for preserving fragile exoskeletons.
“Since we didn’t find any bee bodies, they may have belonged to a species that is still alive today—very little is known about the ecology of many bees on these islands,” Vignola Lopez said.
The fossilized bone nests are the first of their kind ever discovered, even in modern ecosystems. There may be other examples, but it is also possible that caves provided a unique environment for bees. Without much soil on top of the region's limestone, the insects may have resorted to nesting in caves. There, bones discarded by owls became a convenient alternative home for bee larvae.
“This discovery shows how strange bees can be—they can surprise you,” Vignola Lopez said. “But it also shows that when you look at fossils, you have to be very careful.”
PopSci Gift Guide for 2025
