Bees exhibit an extraordinary range of species and behavior, from solitary types that nest in burrows to social variants that construct intricate nests. This nesting diversity is partially captured in the fossil record, with trace fossils dating from the Cretaceous to the Holocene. In a recent study, Field Museum paleontologist Lázaro Vignola López and his colleagues unveil novel nesting behaviors based on trace fossils unearthed from Late Quaternary cave deposits on the Caribbean island of Hispaniola. Osnidam Almontei was discovered within the cavity of a vertebrate corpse.
A reenactment of the life of bees with evidence of them building their nests in caves and using the bone cavities as housing chambers for several egg-laying cells. Image credit: Jorge Mario Macho.
“The initial descent into the cave isn’t very deep. You secure a rope to the side and rappel down,” Dr. Vignola López explained.
“Entering at night, you can spot the eyes of tarantulas residing there. As you navigate through the 10-meter-long underground tunnel, fossils start to emerge.”
Fossil layers were separated by carbonate deposits formed during rainy periods in antiquity.
Although rodents made up most of the fossils, remains of sloths, birds, and reptiles—over 50 species in total—were also found. Together, these fossils narrate a compelling story.
“We hypothesize this cave served as a home for owls over generations, potentially for hundreds or even thousands of years,” Dr. Vignola López remarked.
“The owl would venture out to hunt and return to the cave to regurgitate pellets.”
“We’ve collected fossils of the prey the owl consumed, its own remains, and even bones of turtles and crocodiles that may have inadvertently fallen into the cave.”
Dr. Vignola López and his colleagues observed that the sediments in empty tooth sockets of mammalian jaws didn’t accumulate randomly.
“The surface was notably smooth and slightly concave, which is unusual for sediment burial. I noticed this pattern across multiple specimens and thought to myself, ‘There’s something peculiar here.’ It reminded me of a hornet’s nest,” he noted.
Many well-known nests constructed by bees and wasps belong to social species that coexist in large colonies, raising their young together—like the bees in honeycombs or paper wasp nests.
“However, the majority of bee species are solitary. They deposit eggs in small cavities and leave pollen for their larvae’s nourishment,” Dr. Vignola López continued.
“Some bee species create nests in tree hollows, in the ground, or utilize vacant spaces. Certain species in Europe and Africa even nest within discarded snail shells.”
To investigate the possible insect nests within the cave fossils, the researchers conducted CT scans and X-rays of the bones, capturing 3D images of the compacted soil in the tooth sockets without damaging the fossils.
The shape and composition of the deposits bore similarities to mud nests created by some contemporary bee species. Some of these nests contained ancient pollen grains that mother bees had sealed for their larvae.
The researchers propose that bees combined saliva and soil to construct small nests for their eggs, smaller than the eraser on a pencil.
Nesting within larger animal bones provided protection for bee eggs from potential predators such as wasps.
While the bees themselves were not preserved, the unique characteristics of the nests allowed for a taxonomic classification.
They named the nests Osnidam Almontei, in honor of the scientist Juan Almonte Milan, who first discovered this cave.
“Since no bee remains were found, they may have belonged to a currently existing species. Our knowledge on the ecology of various bee species in these islands is limited,” Dr. Vignola López stated.
Scientists speculate that this behavior arises from a combination of factors. With little soil covering the limestone terrain in this region, bees may have opted for caves as their nesting sites, rather than digging into the ground like many other species.
Additionally, this cave had been home to generations of owls, with numerous owl pellets accumulating over the years, providing the bees with ample use of the bones the owls left behind.
“This finding illustrates the peculiarities of bees. They can be surprising, and it emphasizes the importance of meticulous examination when studying fossils,” Dr. Vignola López remarked.
of paper published today in Proceedings of the Royal Society B Biological Sciences.
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Lazaro W. Vignola-Lopez and others. 2025. Fossil traces in mammal remains reveal a new nesting behavior for bees. R Soc Open Science 12(12):251748; doi: 10.1098/rsos.251748
Source: www.sci.news
