Scientists studying bee Colony Collapse Disorder that's decimating hives of the vital pollinating insects around the globe say environmental stressors on the hive's inhabitants may be to blame.
Those stressors can push honeybees to start foraging for pollen earlier in life, and when too many young bees leave the hive it can bring on a tipping point in the tightly regulated social dynamics of a hive, a team of British, Australian and U.S. researchers says.
Environmental stressors on bees including pesticides, parasites and poor food quality can kill of large number of mature forager bees, triggering a rapid maturation of the next generation and pushing them to leave the nest before they are ready, the researchers explain.
Bees that start foraging younger complete fewer flights and are more likely to die during their first flights, they say.
A resultant domino effect can lead to the collapse of a bee colony within weeks, they report in the journal PNAS.
"Young bees leaving the hive early is likely to be an adaptive behavior to a reduction in the number of older foraging bees," says Clint Perry from Queen Mary University of London.
Colonies will regularly respond to an unexpected high loss of foragers by sending bees out earlier in their life cycle, but they normally will return to stability rather rapidly.
"But if the increased death rate continues for too long or the hive isn't big enough to withstand it in the short term, this natural response could upset the societal balance of the colony and have catastrophic consequences."
Colony collapse disorder has affected about 30 percent of honeybee colonies in North America and Europe annually for the last 10 years.
Any disruption to the rigid social order of a hive can rapidly lead to problems and a collapse of the hive, says research leader Andrew Barron of Macquarie University in Australia.
"It's very rapid. Your colony goes from having lots of bees to no bees in a few weeks," he says. "There's no obvious pathogen and there's no corpses left in the hive."
The researchers' analysis closely fits what people in the field are reporting about colony collapse, he adds.
"The colony looks like it's doing OK. It looks like it's doing what normal colonies do -- it's got high feed, it's got foragers, it's got brood, but you come back about two weeks later and you've got an empty box."