The mystery of the disappearing bees revealed?

It’s no secret that honey bee populations have been rapidly declining of late, with the phenomenon of colony collapse disorder (CCD) causing concern around the globe. An international group of scientists, including Australians, thinks the cause of this collapse lies in young bees who are growing up too fast.

Writing in the journal Proceedings of the National Academy of Sciences, the researchers explained that many factors have been identified as stressors linked to CCD, including pathogens, pesticides and nutritional deficits. However, it remains unclear “why colonies frequently react to stressors by losing almost their entire adult bee population in a short time, resulting in a colony population collapse”, they said.

The scientists used radio tracking to follow thousands of bees throughout their entire lives to map their accelerated decline. They found that bees reacted to stress by starting to forage when young - but did not cope well with having grown up too fast.

“Precocious foragers completed far fewer foraging trips in their life and had a higher risk of death in their first flights,” the authors said. This put pressure on the colony social structure and disrupted the colonies’ finely balanced social dynamics, triggering a population collapse.

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

The researchers constructed a demographic model where forager death rates were chronically elevated and found that “an increasingly younger forager force caused a positive feedback that dramatically accelerated terminal population decline in the colony”, they said. This resulted in a breakdown in division of labour and loss of the adult population.

By understanding the process of colony failure, the authors hope to identify effective strategies to improve colony resistance. These include rescue packages for sick colonies and new sensors to detect colonies at risk of failure.

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