Why Vulture Bees Prefer Rotting Flesh Over Pollen

Like their namesake, vulture bees have a taste for animal carcasses. In Costa Rica's rainforests, these meat-eating stingless bees (Trigona) will slurp on sugar from fruit or sip nectar from stems and leaves like most of their buzzing cousins, too, but microbes in their gut microbiomes prefer carrion over pollen as a protein source, reports Philip Kiefer for Popular Science. 

Compared to vegetarian bees, these carrion-lovers had dramatically different microbiomes, according to a study published this month in the microbiology journal mBio. The guts of vegetarian stingless bees, honeybees and bumblebees all contained the same five microbes. However, vulture bee stomachs were riddled with specialized acid-loving bacteria that allow them to digest meat without getting sick from toxins that form on rotting flesh, reports Morgan McFall-Johnsen for Insider.

In 1902, entomologist Filippo Silvestri gave the species its scientific name,Trigona Hypogea, after studying pinned specimens, reports Jennifer Ouellette for Ars Technica. Two other recorded examples of bees feeding on rotting flesh date back to 1758 and 1827. However, the bee's carnivorous tendencies were first observed in 1982 by entomologist David Roubik while studying bees at the Smithsonian Tropical Research Institute in Panama. Currently, only three vulture bee species are known to exist.

Roubik's observations found that the bees do not have another source of protein, and their legs do not sport as many hairs to collect pollen as vegetarian bees have. When analyzing the stored honey in the carrion bees' hives, it did not contain pollen grains. Instead, the vulture bees partly digest the meat and then transport it to the nest where it is then regurgitated for other bees, the New York Times reported in 1982.

"These are the only bees in the world that have evolved to use food sources not produced by plants, which is a pretty remarkable change in dietary habits," study coauthor Doug Yanega, an entomologist at the University of California-Riverside (UCR), tells Ars Technica.

Most bees also have saddle bag–like structures on their legs for carrying pollen, but vulture bees have much smaller leg baskets, which they use for carrying meat back to their hives. To gather their hauls, vulture bees have a unique set of teeth they use to slice bits of meat. Once in the hive, the vulture bees store the meat chunks in small pods, leave them there for two weeks to cure, and then feed it to their larvae, Insider reports.

To identify what bacteria lives in the stomachs of vulture bees and how it compares to other bee species, researchers extracted DNA from bee abdonmens—but first they had to capture them. To do so, researchers set up 16 bait stations with roughly two ounces of raw chicken hung from branches 4.9 feet off the ground, CNN's Katie Hunt reports. The team collected a total of 159 bees, including vegetarian bees that feed exclusively on pollen and nectar as well as others that feed on both pollen and meat, per CNN.

Vulture bee guts had a specialized cocktail of the acid-producing bacteria Lactobacillus in their bellies. This type of bacteria may create a more acidic environment in their guts to fight off pathogens that grow on carrion, per Insider. Other species of meat-loving animals, like hyenas and vultures, also have acid-producing microbes in their stomachs. 

 "We hypothesize that the bees are using those acid-producing bacteria to acidify their gut," Jessica Maccaro, co-author of the study and graduate student at UCR, said to Popular Science. "They get these pathogens which infect them through their gut. So they have all these Lactobacillus in there that will acidify the gut—and that literally pickle the pathogen."

Elizabeth Gamillo | | READ MORE

Elizabeth Gamillo is a correspondent for Smithsonian and a science journalist based in Milwaukee, Wisconsin. She has written for Science magazine as their 2018 AAAS Diverse Voices in Science Journalism Intern.