Scientists perplexed by flesh-eating ‘vulture bees’ that have quit pollen to feed on dead bodies

Some bees have now evolved the ability to only eat flesh because of an “intense competition for nectar” and of an evolved gut that resembles vultures instead of other bees, revealed a new study.

These adaptations in a little-known species of tropical stingless bees or “vulture bees” are also complemented by changes in the kinds of bacteria that live in their guts, pointed out researchers of a study published in the journal mBio on Tuesday, which sheds light on how diet affects gut microbes.

While bees typically feed on nectar, the researchers, including those from the University of California (UC) Riverside, said that the “intense competition for nectar” has led to a species of stingless bee in the tropics evolving the ability to feed on flesh.

“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,” UC Riverside entomologist Doug Yanega said in a statement.

Usually, honeybees, bumblebees and stingless bees have guts that are colonised by the same five core microbes, most of which have been retained over roughly 80 million years of evolution.

In these tropical bees, however, many ancestral “core” microbes have been lost, while some have been retained, the researchers pointed out.

The bees have also entered into “novel associations” with some acid-loving microbes, which have similarly been found in vultures and other animals feeding on dead remains.

“This research expands our understanding of how diet interacts with microbiomes on both short and long timescales in one of the world’s biodiversity hot spots,” the scientists wrote in the study.

To capture these bees for the study, the researchers first set up baits made of fresh pieces of raw chicken suspended from branches and smeared with petroleum jelly to deter ants.

These traps attracted both vulture bees as well as related species that opportunistically feed on meat for their protein.

While usually stingless bees have baskets on their hind legs for collecting pollen, scientists observed that the vulture bees used those same structures to collect flesh bait.

They then compared gut bacteria found in vulture bees with those in other stingless bees that feed both on meat and flowers and in those that feed only on pollen. The most extreme changes were found in the exclusively meat-eating bees.

“The vulture bee microbiome is enriched in acid-loving bacteria, which are novel bacteria that their relatives don’t have,” study coauthor Quinn McFrederick said.

“These bacteria are similar to ones found in actual vultures, as well as hyenas and other carrion-feeders, presumably to help protect them from pathogens that show up on carrion,” Dr McFrederick added.

They found that the vulture bees had the gut bacteria Lactobacillus – found in fermented food, like sourdough – and also Carnobacterium, which is associated with flesh digestion.

The scientists, however, also suspect that these bees might be acquiring microbes, such as A. micheneri, from the rotting meat they consume.

They also called for further studies to determine whether the bees’ meat-eating lifestyle influenced the growth of these microbes, or if the bacteria were the ones to enable the diet.

“It is important to note that while a change in diet could have modified the microbiome, it is also possible that a shift in microbiome enabled a change in dietary lifestyle, or even that both the change in microbiome and the change in diet were linked to a different unmeasured phenomenon in the evolutionary history of these unique bees,” the study noted.

“It’s crazy to me that a bee can eat dead bodies. We could get sick from that because of all the microbes on meat competing with each other and releasing toxins that are very bad for us,” said Jessica Maccaro, a UCR entomology doctoral student.

While the bees feed on meat, they also store honey in separate chambers in their hives.

“They store the meat in special chambers that are sealed off for two weeks before they access it, and these chambers are separate from where the honey is stored,” Dr Maccaro said.

The scientists believe further studies of these vulture bees can offer “rich insights” into how diet interacts with gut microbiomes.