American scientists have shown that the average lifespan of bees has been reduced by 50% compared to the 1970s. Possible causes.
European common bees (Apis mellifera) have a 50% shorter lifespan than half a century ago. The dramatic data, detected in the laboratory, can explain both the collapse of honey production – also caused by climate change – and the increase in the loss of hives, a phenomenon catalysed starting in 2006, when the mysterious “depopulation syndrome” emerged. . Urticaria”. According to scientists’ calculations, if in the 1970s laboratory-reared bees lived an average of 34.3 days, today the survival is only 17.7 days. According to the authors of the study, this sharp decrease could be caused by genetic factors, the use of pesticides and viruses.
The two scientists Anthony Nearman and Dennis van Engelsdorp, both of the entomology department of the University of Maryland (United States of America), have shown that today’s bees have half the longevity of bees from the 70s of the last century. . . The two researchers came to their conclusions after raising the bees with different types of water (deionized, with 1% sodium chloride in deionized or tap water) and comparing the data with historical experiments. Determining the average lifespan of a bee is not easy because several factors contribute to it. Queens, for example, as detailed in the study “Honeybee lifespan: the critical role of pre-foraging stage” published in the scientific journal Royal Society Open Science, can live up to 5 years, while workers live two six weeks in the summer and one twenty weeks in winter. On average, it is estimated that a worker can live from 30 to 60 days.
Under controlled laboratory conditions, with bees raised from the nymphal stage in special incubators and cages, the two scientists observed that the pollinating insects had half the longevity of 50 years ago, kept under conditions similar to the experimental data (17.7 days against 34.3 days). These data emerged regardless of the type of diet administered to the bees. “When I assessed lifespan over time, I realized, wow, there is this huge effect of time going on,” Dr. Nearman said in a press release. “Standardized protocols for keeping honey bees in the lab weren’t formalized until the 2000s, so you’d think lifespan would be longer or the same, because we’re improving in that area, aren’t we? Instead, we’ve seen a doubling of the death rate “, commented the scientist.
Several previous investigations have shown that the reduced longevity of bees corresponds to a shorter foraging time by the colonies and consequently to a lower honey production. Based on this data and using a standardized model used by researchers to track honey bee populations (called BEEHAVE), the two scientists showed that the halving of longevity detected in the laboratory could be associated with the loss of hives and reduced production of honey observed in recent decades. In a simulation, it was shown that with the half-life of bees, the hive loss rates were around 33%. The data, the researchers explain, are very similar “to the average winter and annual loss rates of 30% and 40% reported by beekeepers over the past 14 years”.
As mentioned, the reasons for this collapse in bee longevity are unclear, but the use of pesticides – particularly neonicotinoids, considered the main culprits of hive depopulation syndrome – could contribute to the spread of viruses in hives that affect the bees. of the larval stage and potential genetic factors that emerge. Research details “Water supply increases lifespan of caged worker bees and caged worker bees live half 50 years ago” were published in Scientific Reports.