Just when you thought things couldn’t get worse for bees, a new study suggests we've been inadvertently feeding them birth control. Previous research has shown the world's most widely used pesticides, neonicotinoids, have hurt the lifespan and reproduction of honeybee queens and reduced the number of bumblebee queens, reports the Guardian. But new research out of the University of Bern in Switzerland finds two neonicotinoids, thiamethoxam and clothianidin, also cut live sperm in males by 39%. Sperm viability was also 8% to 11% lower than in bees not exposed to the pesticides, reports National Geographic. Here's why that's a big problem: A queen bee collects sperm from up to 20 males to ensure genetic diversity when she reproduces. If that sperm is of poor quality, worker bees will kill the queen to protect the colony, reports Deutsche Welle.
"As the primary egg layer and an important source of colony cohesion, the queen is intimately connected to colony performance," researchers say. There's more bad news: In addition to reducing live sperm, scientists found exposure to thiamethoxam and clothianidin also cut bee lifespans by a third, from 22 days on average for unexposed bees to 15 days. In fact, only 68% of male bees exposed to neonicotinoids lived to reach sexual maturity at 14 days, compared to 83% of unexposed bees. These "important lethal and sub-lethal effects" could have "severe consequences for colony fitness, as well as reduce overall genetic variation within honeybee populations," scientists say, though they acknowledge that disease, habitat loss, and parasites are also responsible for recent colony losses. (See how one pesticide-maker is trying to help.)