Beekeepers experienced fewer losses this winter than they have the past few years, according to an annual survey by the U.S. Department of Agriculture, the Bee Informed Partnership and the Apiary Inspectors of America.
Total losses to managed honey bee colonies from all causes were 21.9 nationwide for the 2011-12 winter, according to a news release.
That compares with about 30 percent reported during the 2010-11 winter, 34 percent in 2009-10, 29 percent in 2008-09, 36 percent in 2007-08 and 32 percent in 2006-07.
The unusually warm winter could be one reason for the lower mortality rate this winter, according to the release.
But there's been no scientific study to back that hunch.
Nevertheless, January ranks as the fourth warmest in U.S. history.
"A warm winter means less stress on bee colonies and may help them be more resistant to pathogens, parasites and other problems," Jeff Pettis, co-leader of the survey and research leader at the Agricultural Research Service Bee Research Laboratory in Beltsville, Md., said in the release.
Among beekeepers reporting losses, 37 percent said they lost at least some colonies without finding any dead bees.
The absense of dead bees is one of the classic symptoms of colony collapse disorder.
Because the survey was conducted purely with interviews, scientists didn't have opportunities to verify the exact cause of bee mortality.
At least half of responding beekeepers reported losses greater than 13.6 percent, a level that most beekeepers say they consider acceptable.
Preliminary results of the survey can be viewed at Bee Informed.
Full survey results will be available later this year, according to the release.