Question a da week

[Lee Borgersen]

                                     Question of the week


Q: What causes ruffed grouse numbers to rise and fall?

A: Grouse populations are known to fluctuate in a 10-year cycle in prime grouse range. Numerous studies have been conducted to determine the cause of these cycles. Possible mechanisms that have been considered include predation, spring and winter weather, tent caterpillar effects on cover and forage quality, and parasites, to name a few.

Some studies have found support for a relationship between raptor populations and grouse cycles. Northern goshawks switch between targeting snowshoe hares and grouse as populations of each of these prey species rise and fall. However, a 2008 study by researchers from University of Minnesota and the Ruffed Grouse Society reported that the most supported explanation for grouse cycles included winter precipitation and temperature. Grouse counts were highest during cold winters with lots of snow for roosting and during warm dry winters. Conversely, grouse counts were lowest during warm snowy or cold dry winters. However, neither predators nor winter weather can entirely explain grouse cycles, so the phenomenon requires further study.

Charlotte Roy, DNR grouse project leader