The vast majority of bees feed on pollen and nectar, but certain species have evolved to feast on meat, substituting dead animal carcasses for flower meadows.
To better understand this extreme shift in diet, scientists at the University of California-Riverside, Columbia University and Cornell University studied the gut bacteria or microbiome of the so-called vulture bees in Costa Rica.
The researchers found the bees' guts are rich in acid-loving bacteria similar to those found in vultures, hyenas and other animals that feed on carrion.
Their study was released on Tuesday in the journal mBio, published by the American Society for Microbiology.
Only three species of bee in the world — all vulture bees — have evolved to get their protein exclusively from dead meat, and they live only in tropical rainforests.
However, there are other bee species that will consume fresh animal carcasses when available but also forage for pollen and nectar, according to the study.
Bees and gut bacteria
The guts of honeybees, bumblebees and stingless bees are colonised by the same five core microbes, and they have retained these bacteria for roughly 80 million years, the study noted.
The researchers wanted to find out how the guts of vulture bees differed.
The scientists set up 16 stations baited with 50 grams of raw chicken dangling from branches about 1.5 metres above the ground.
To deter ants, they coated the string with petroleum jelly.
They collected 159 bees in total, including, for comparison, bees that feed on pollen and meat and vegetarian bees that feed exclusively on pollen and nectar.
After studying the microbiomes of the bees by extracting DNA from their abdomens, the researchers found vulture bees had lost some of the core microbes most bees have and developed a more acidic gut.