Bees living in isolation have half the lifespan they did 50 years ago: study

The lifespan of lab-reared honey bees today is half of what it was fifty years ago, according to a new study, which researchers suggest could be a sign that environmental stress isn't the only factor affecting the global bee population.

Insects aren’t exactly known for lengthy lifespans, but beekeepers have been noting disproportionate declines and high colony turnover rates for years now, researchers note, with beekeepers in Canada seeing average losses of nearly 45 per cent of their bees last winter and some reporting losses of up to 90 per cent of their bees.

Factors such as climate change and parasitic mites that target bees have been noted as contributors to the problem, but this new research shows that even with those confounders removed, there’s still a concerning pattern unfolding.

The study, published early November in the peer-reviewed journal Scientific Reports, looked at the lifespans of bees that were kept in a controlled laboratory environment and found that their lifespans were 50 per cent shorter than they were in the 1970s.

Researchers say it is the first study to display a clear decline in bee lifespan independent of environmental stressors.

"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," Anthony Nearman, a Ph.D. student in the University of Maryland Department of Entomology and lead author of the study, said in a press release. "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."

In order to isolate the bees from external factors, researchers collected bee pupae from honey bee hives within 24 hours of the bees emerging from the individual honeycomb cells they slowly developed from eggs to larvae to pupae.

The bees were placed in an incubator until they were finished developing, and then were placed in special cages to keep them isolated.

Part of the study was originally to look at diet — whether supplementing the bees diet of sugar water with plain water would create a diet closer to their natural conditions and a longer lifespan — but then Nearman realized that the lifespan of his bees was significantly shorter than those in similar lab experiments conducted decades ago, regardless of diet.

Caged honey bees that were offered water in addition to the sugar water lived longer than those who were only given sugar water, from two to five times longer.

But still, Nearman’s bees were only living for around 17.7 days, compared to 34.3 days in the 1970s.

When he investigated further into other lab studies over the past 50 years, an unexpected trend emerged.

"When I plotted the lifespans over time, I realized, wow, there's actually this huge time effect going on," Nearman said. "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."

Researchers acknowledge that this is a laboratory study, so the results aren’t directly applicable to bees raised by beekeepers or in wild colonies, but previous studies have shown that there is a similar lifespan seen between beekeeper colonies and the lifespan of laboratory bees.

And shorter lifespans has an impact on the bees' ability to produce honey. According to the release, other studies have found that there is lower honey productions and less foraging time among bees with shorter lifespans.

So taking this into account, what would it look like if this drop in lifespans seen in this lab study was true for the broader bee population? Researchers estimated that this would mean a bee colony loss rate of around 33 per cent, similar to the average loss rates that beekeepers have been reporting over the last 14 years.

If the bees are having shorter lifespans regardless of other factors, this means there could be a genetic component, researchers say, something that could help beekeepers in the future to selectively breed more resilient bees with longer lifespans.

Researchers added that more research needs to be done to determine the full scope of these trends to see if they exist across the wider U.S. and other countries in order to pinpoint the contributing factors and improve the lifespan of bees.

The study also noted that their data on caged bees living longer when offered water along with sugar water should inform best practices on how bees in laboratory studies are raised. This change, researchers say, would ensure not only less stress for the bees, but better study results, as studies looking into the health of bees won’t be confounded by a poor diet leaving them malnourished.