Honeybees Get Stressed and Live Less When They Are Transported For Pollination, According To Study

26 Aug 2016 --- Migratory beekeeping is stressful and cuts the lifespan of bees which are transported around the US to pollinate a variety of crops.

According to new research, the stress could be eased if the honeybees, among the world’s most important pollinators, had better access to food. 

Honeybees are regularly transported around the US by being trucked long distances to pollinate crops like apples, almonds and berries. 

Hongmei Li-Byarlay, a National Research Council senior research associate in North Carolina State's Department of Entomology and Plant Pathology is the co-first author of a paper describing the research, which aimed to be the first to directly measure stress in these types of colonies.

It shows that in general traveling bees live shorter lives than stationary bees and have much higher oxidative stress levels which exacerbates ageing and could weaken disease resistance and ability to fight off parasites. 

"We found that migratory beekeeping influences the lifespan of bees, but how this impacts health and honey bee aging is more complicated and often more influenced by the environment these colonies are in," says Michael Simone-Finstrom, an NC State postdoctoral researcher and co-first author of the study.

Commercial colonies that had traveled to pollinate almonds in California and then in Maine were compared against bees from colonies that remained stationary in the North Carolina State apiary. Traveling colony bees died one day before the stationery bees. 

"One day may seem trivial, but when a normal forager bee lifespan is only around 20 days, one day is significant," adds Simone-Finstrom.

During the second experience, the lifespan and colony health of migratory bees that traveled short distances of between 35 to 60 miles, in North Carolina, were compared to stationary bees. Both of the colonies were controlled by the research team. 
"We saw the same lifespan differences as in the first experiment, plus we saw more oxidative stress in traveling bees when compared to stationary bees," Li-Byarlay adds.

Although the increase in stress levels was only apparent early in the season between May and June, a time when the had plenty of access to food. As the flowers dried up in the North Carolina heat, stationary bees had to work harder to find food while the traveling bees were moved into new fields blooming with plants and therefore did better. 

In the third and last experiment, the oxidative stress levels of stationary bees were compared against the levels of bees transported across North Carolina for three hours each day for six consecutive days. The results shed light on how the bee-rearing environment, where bees were raised as larvae, can impact the oxidative stress levels when bees become adults. In this experiment, foraging bees raised in migratory bee colonies had higher oxidative stress levels than foraging bees raised in stationary hives.

The next steps could be to look at longer-term effects of bee migration and the interaction with nutrition, according to Li-Byarlay who wants another study to examine bees over a four month period in late spring and early summer. As honey bee colonies nationwide currently experience higher annual mortality, understanding effects through overwintering and mitigation of these effects would be particularly insightful.