SYNCHRONOUS AND NONSYNCHRONOUS POPULATION FLUCTUATIONS OF SOME PREDATORS AND THEIR PREY IN CENTRAL SWEDEN

To test the alternative prey hypothesis (APH), we examined 29-yr time series of bank voles (indexed by snap-trapping) and 6 game species (indexed by bag records) from Gavleborg county, central Sweden, for the occurrence of synchronous population fluctuations. Only voles and the 3 grouse species exhibited cyclic fluctuations; grouse fluctuations were highly synchronous, and positively correlated with vole fluctuations. Although hares were positively correlated with grouse, they were negatively correlated with voles. Fox were positively correlated with voles and grouse; however, a strong negative relationship was observed between fox and hares. During a sharp decline in fox numbers during the early 1980's due to sarcoptic mange, both grouse and hares exhibited a strong positive numerical response, but, not in synchrony. In addition, grouse exhibited large fluctuations during the fox decrease whereas hares did not. Due to the contradictory predator-prey interactions observed, these results provide only partial support for APH.