COLLEGE PARK, Md. — In another blow to bee pollinators, a new study has found that honey bees are living significantly shorter lives compared to 50 years ago. Several bee species are at risk of extinction from a loss of habitats and human activities, and this new finding suggests genetics may also be driving bees to die faster. Understanding which genes are shortening the lives of bees may help with the future breeding of honey bees which live longer.
Beekeepers know colony turnover is common as bees naturally age and die. Over the past decade, however, beekeepers have been reporting unusually high bee mortality rates and requiring more money and time to replace the colonies. According to the study authors from the University of Maryland, this is the first study to show a decline in honey bee lifespan regardless of environmental stressors. Instead, it’s possible their genes may be the culprit for their shorter lifespans.
The idea to study the honey bee life cycle came from a previous investigation where scientists were raising adult bees in a laboratory. The team collected bee pupae from honey bee hives when the pupae were within 24 hours of emerging from the wax cells they are reared in. The collected bees finished growing in an incubator and then placed in special cages when reaching adulthood. In that study, the team was looking at the effects of swapping caged bees’ sugar water with plain water, mimicking the natural conditions of the wild. Study authors realized that no matter what food or water they gave the honey bees, the caged bees died sooner than expected (17.7 days versus 34.3 days in the 1970s).
“When I plotted the lifespans over time, I realized, wow, there’s actually this huge time effect going on,” says lead study author Anthony Nearman, a PhD student in the department of entomology, in a university release. “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.”
What’s killing off honey bees so fast?
In the current study, the team reviewed the literature on honey bees over the past 50 years. Historical records of lab-kept bees showed similar lifespans to colony bees, though scientists had assumed that isolating bees would reduce their lifespan. Another reason to pursue this study is that past research has shown a link between shorter lives, foraging time, and lower honey production.
Modeling results showed the present-day lifespan of honey bees is 50 percent shorter than in the 1970s, which corresponds with a 33-percent disruption in honey production over the next few decades. This is similar to the average honey loss of 30 to 40 percent reported by beekeepers in the last 14 years.
An alternative explanation is that lab-kept bees could be experiencing low-level viral contamination or pesticide exposure during the larval stage. However, bees have shown symptoms related to these exposures and there have been other insect research linking certain genes to longevity in fruit flies.
The next step researchers are taking is to compare trends in honey bee lifespans across multiple countries. If others besides the U.S. are reporting longevity differences, the team can then isolate and compare potential factors such as genetics, pesticide use, and viruses in the local bee stocks.
The study is published in Scientific Reports.