As bee colonies age and die off naturally, colony turnover is an accepted factor in the beekeeping industry. However, over the last decade, beekeepers in the United States have reported high loss rates, necessitating the replacement of more colonies to keep operations viable. To figure out why, scientists have looked into environmental stressors, diseases, parasites, pesticide exposure, and nutrition.
This is the first study to show an overall decline in honey bee lifespan that is not caused by environmental stressors, implying that genetics may be influencing broader trends in the beekeeping industry. The study was published in the journal Scientific Reports on November 14, 2022.
Nearman first noticed the decline in lifespan while working on standardized protocols for rearing adult bees in the laboratory with entomology associate professor Dennis van Engelsdorp. To replicate previous research, the researchers collected bee pupae from honey bee hives when the pupae were within 24 hours of emerging from the wax cells in which they are reared. The collected bees were grown in an incubator before being housed as adults in special cages.
Near man was testing the effect of replacing the caged bees' sugar water diet with plain water to better mimic natural conditions when he discovered that, regardless of diet, the median lifespan of his caged bees was half that of caged bees in similar experiments in the 1970s. This prompted a more thorough examination of published laboratory studies from the previous 50 years.
Despite the fact that a laboratory environment is very different from a colony, historical records of lab-kept bees suggest that they have a similar lifespan to colony bees, and scientists generally assume that isolated factors that reduce the lifespan in one environment will also reduce it in another. Previous research had also shown that shorter honey bee lifespans corresponded to less foraging time and lower honey production in the real world. This is the first study to establish a link between those variables and colony turnover rates.
When the researchers simulated the impact of a 50% decrease 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 reported by beekeepers over the last 14 years of 30% and 40%, respectively.
Near man and Van Engelsdorp speculated that their lab-kept bees may have been exposed to low-level viral contamination or pesticides during their larval stage when they are brooding in the hive and being fed by worker bees. However, no overt symptoms of those exposures have been observed in bees, and a genetic component to longevity has been observed in other insects such as fruit flies.
The researchers' next step will be to compare trends in honey bee lifespans across the United States and other countries. If they discover differences in longevity, they can isolate and compare potential contributing factors such as genetics, pesticide use, and virus presence in local bee stocks.
Honey bee life spans are now 50% shorter than they were 50 years ago.
Another study conducted by College of Maryland entomologists discovered that the life expectancy of individual bumblebees kept in a controlled lab environment is half that of the 1970s. When researchers demonstrated the impact of today's shorter life expectancy, the outcomes related to the expanded state misfortune and diminished honey creation patterns seen by US beekeepers in ongoing many years were revealed.
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