Stressed bees die sooner, leading to abrupt collapse of colonies

 

An international team of scientists believe they may have worked out why bee colonies collapse rather than decline. Their findings appear in the Feb. 10 issue of PNAS.

Colony collapse disorder has raised concern that declining honey bee populations will harm successful crop pollination and lead to widespread hunger and malnutrition.

Søvik

The research was conducted in Australia by a team including Andrew Barron of Macquarie University in Sydney, Australia; Clint Perry of Queen Mary University of London; and Eirik Søvik, PhD, now a postdoctoral research associate in the Deparment of Biology in Arts & Sciences at Washington University in St. Louis.

Pathogens, pesticides and nutritional deficits have previously been identified as stressors linked to colony collapse disorder, but it was a mystery why bee colonies sometimes collapsed so rapidly, leaving bee keepers with an empty hive box.

The new study used radio tracking to follow thousands of bees throughout their entire lives to map their accelerated decline. The researchers found that bees reacted to stress by starting to forage when young, but the young precocious foragers did not cope well with having grown up too fast.

"Bees diplay a predictable pattern of behavioral development," Søvik explained. "They begin adult life performing in-hive tasks, shifting to foraging when they are two or three weeks old. Varied stressors, such as loss of foragers, starvation or disease, can cause bees to accelerate their behavioral development and forage precociously."

Precocious foragers completed fewer foraging trips in their lifetime and experienced a higher rate of early death, putting pressure on the colony's social structure. This disrupted the colonies’ finely balanced social dynamics, triggering a population collapse.

“Bee colonies contain a precise balance of bees specialized in the different roles the society needs. If that balance is upset by young bees starting to forage early, sometimes the colony cannot cope,” said senior author Andrew  Barron of Macquarie University’s Department of Biological Sciences.

“There is a breakdown in division of labor, and loss of the adult population, leaving only brood, food and few adults in the hive.”

With their greater understanding of the collapse process, the authors are now exploring possible strategies to improve colony resilience including rescue packages for sick colonies, and new sensors to detect colonies at risk of failure.

“Other factors previously implicated in colony collapse, all have different treatments," Søvik said. "Our study suggests that it might be better to pursue more general preventative measures.”