Honey bee lifespans are 50% shorter today than 50 years ago

Entomologists have found that honey bee lifespans are 50% shorter than in the 1970s, which corresponds with colony loss and reduced honey production

Entomologists from the University of Manitoba have found that for individual honey bees kept in a controlled laboratory environment, honey bee lifespans are 50% shorter than in the 1970s. When scientists modelled the effect of today’s shorter lifespans, the results corresponded with concerning factors, including increased colony loss and reduced honey production.

Scientists explain that colony loss is not unusual in beekeeping because bee colonies naturally age and die off. However, in the past few decades, U.S. beekeepers have become increasingly concerned following reports of high colony loss.

To understand colony loss and reduced honey bee lifespans, researchers have focused on the following factors:

• Environmental stressors
• Diseases
• Parasites
• Pesticide exposure
• Nutrition

This is the first study to show an overall decline in honey bee lifespan independent of environmental stressors, hinting that genetics may influence the broader trends in the beekeeping industry.

Understanding reduced honey bee lifespans

“We’re isolating bees from the colony life just before they emerge as adults, so whatever is reducing their lifespan is happening before that point,” said Anthony Nearman, a Ph.D. student in the Department of Entomology and lead author of the study.

‘If we can isolate some genetic factors, then maybe we can breed for longer-lived honey bees’

“This introduces the idea of a genetic component. If this hypothesis is right, it also points to a possible solution. If we can isolate some genetic factors, then maybe we can breed for longer-lived honey bees,” Nearman concludes.

“When I plotted the lifespans over time, I realized, wow, there’s actually this huge time effect going on,” Nearman explained.

“Standardized protocols for rearing honey bees in the lab weren’t really formalized until the 2000s, so you would think that lifespans would be longer or unchanged because we’re getting better at this, right? Instead, we saw a doubling of mortality rate.”

Historically, lab-kept bees have had a similar lifespan to colony bees

Historical records of lab-kept bees suggest a similar lifespan to colony bees. Scientists generally assume that isolated factors that reduce the lifespan in one environment will also reduce it in another.

Previous studies have also demonstrated that shorter honey bee lifespans corresponded to less foraging time and lower honey production in the real world. However, this is the first study to connect those factors to colony turnover rates.

When the team modelled the effect of a 50% reduction in lifespan on a beekeeping operation, where lost colonies are replaced annually, the resulting loss rates were around 33%. This is very similar to the average overwinter and annual loss rates of 30% and 40% that have been reported by beekeepers over the past 14 years.

It’s possible that their lab-kept bees could be experiencing some sort of low-level viral contamination or pesticide exposure during their larval stage when brooding in the hive and that worker bees are feeding them. Having said that, the bees have not shown overt symptoms of those exposures, and a genetic component to longevity has been shown in other insects, such as fruit flies.

Next for the researchers is comparing trends in honey bee lifespans across the U.S. and globally. If they find differences in longevity, they will be able to isolate and compare potential contributing factors such as genetics, pesticide use and the presence of viruses in the local bee stocks.