Honey bee colony death rates are unsustainably high. High failure rates are a continuing concern. In North America, annual colony losses averaged 29.6% between 2006 and 2013. In some cases, colony failure has been so rapid that outwardly healthy colonies lost most of their adult bees in a matter of weeks. This has been described as colony collapse disorder. Is the stress one of the main factors?
Many stressors are contributing to bee colony failure, most with a strong anthropogenic component. These include parasites and pathogens, pesticides, and nutritional stresses. The parasitic mite Varroa destructor and its associated viruses and the gut parasite Nosema have both been linked to high colony failure rates. There is increasing concern about the role of pesticides and agrochemicals in honey bee colony losses, and nutritional deficits arising from limited floral diversity and abundance have also been linked to elevated rates of colony failure.
An international team of scientists, including Macquarie University’s Dr Andrew Barron and Queen Mary University of London’s Dr Clint Perry, believe they may have worked out why bee colonies globally have been collapsing.
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.
Precocious foragers completed fewer foraging trips in their lifetime, and experienced a higher rate of early death, putting pressure on the colony social structure. This 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. If that balance is upset by young bees starting to forage early, sometimes the colony cannot cope,” said Dr 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.
Since 2007. Dr Barron and his team have been studying how animals with small brains are capable of solving complex problems. In particular, their exploration of the neurobiology of major behavioural systems in bees is becoming foundational work for understanding and developing more complex neurological systems, such as a bionic human brain. In 2015. Dr Barron was awarded an ARC Future Fellowship to develop a computational model of the honey bee brain.