For our native bees, one of the most compelling hypothesis for rapid population decline is the transfer of pathogens from managed to wild bumblebees. The actual pathogens implicated are the protozoans crithidia bombi and nosema bombi. However, other pathogens may be effecting populations as well.
Field documentation of pathogen transfer shows the spread emanating from infested commercial hives. Also, the timing of decline onset in native bee species corresponds with the acceleration of transportation of managed colonies during the 1990s. Declines in bombus occidentalis, b. affinis, b. terricola and b. pensylvanicus have all been attributed to this disease.
Case Study: White Nose Syndrome and Bats
For our native bats, disease has had a large effect on population numbers. It has become the largest threat to native populations.
White Nose Syndrome, first observed in New York cave populations in 2009, has since killed approximately 5.7-6.7 million bats. Click here and scroll to the bottom of the page to read more about how this fungus is devastating native bat populations.