As bee colonies mature and die off naturally, colony turnover is an acknowledged issue in the beekeeping industry. However, American beekeepers have seen high loss rates during the previous ten years, necessitating the replacement of more colonies in order to maintain operations. To figure out why, scientists have looked into environmental factors, infections, parasites, pesticide exposure, and nutrition.

Entomologists at the University of Maryland have found that the average life span of a honey bee kept in a lab is 50% shorter than it was in the 1970s. Scientists’ simulations of the impact of today’s shorter lifespans matched the trends in decreased honey production and higher colony loss observed by American beekeepers in recent decades.

As bee colonies mature and die off naturally, colony turnover is an acknowledged issue in the beekeeping industry. However, American beekeepers have seen high loss rates during the previous ten years, necessitating the replacement of more colonies in order to maintain operations. To figure out why, scientists have looked into environmental factors, infections, parasites, pesticide exposure, and nutrition.

The fact that this study is the first to document a general loss in honey bee longevity that may be unrelated to environmental stressors suggests that genetics may be playing a role in the general trends observed in the beekeeping sector.

The report was released in the journal Scientific Reports today.

Anthony Nearman, a Ph.D. student in the Department of Entomology and the study’s primary author, explained that bees are isolated from colony life just before they become adults, and “whatever is reducing their lifespan is happening before that point”.

And this brings up the idea that genes play a role.

“If this hypothesis is right,” according to the author, “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 first noticed the decrease in lifespan when he was working with associate professor of entomology Dennis van Engelsdorp on a study about how to raise adult bees in the lab in a consistent way.

Researchers took honey bee pupae from hives when they were about 24 hours away from emerging from their wax cells, confirming the results of previous investigations. The gathered bees were raised to adulthood in an incubator and housed in special cages.

When comparing the median lifespan of his caged bees to caged bees in similar experiments conducted in the 1970s, Nearman found that the median lifespan of his caged bees was half that of caged bees regardless of diet. This led him to evaluate the effect of supplementing the caged bees’ sugar water diet with plain water to better mimic natural conditions.
(34.3 days in the 1970s vs. 17.7 days now.)

This led to a closer look at all of the published lab studies from the past 50 years.

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

“Standardized protocols for rearing honey bees in the lab,” according to the researcher, “weren’t really formalised 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.”

Despite the fact that a colony and a laboratory are very different environments, historical records of lab-kept bees suggest that they have a similar lifespan to colony bees. Additionally, scientists typically assume that isolated factors that shorten lifespan in one environment will also shorten it in another. Shorter honey bee lifespans in the actual world were also linked to less time spent foraging and reduced honey production, according to earlier studies. This research is the first to link such variables to colony turnover rates.

When the team simulated the impact of a 50% decrease in longevity on a beekeeping business in which lost colonies are replaced annually, the resulting loss rates were approximately 33%.

This is quite similar to the 30% and 40% average yearly and overwinter loss rates recorded by beekeepers over the previous 14 years.

Nearman and vanEngelsdorp highlighted that the larval period, when the bees are brooding in the hive and being fed by worker bees, may be when the lab-kept bees are exposed to some form of low-level viral contamination or pesticide exposure.

However, the bees have not manifested overt signs of such exposures, while fruit flies and other insects have demonstrated evidence of a genetic component to lifespan.

The researchers’ next steps will be to compare patterns in honey bee lifespans across the United States and in other nations.

They can evaluate and isolate potential contributing factors including genetics, pesticide use, and the presence of viruses in the local bee stocks if they discover disparities in longevity.

Source: 10.1038/s41598-022-21401-2

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