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 (in dexed by bag records) from Gavleborg county, central Sweden, for the o ccurrence of synchronous population fluctuations. Only voles and the 3 grouse species exhibited cyclic fluctuations; grouse fluctuations wer e highly synchronous, and positively correlated with vole fluctuations . Although hares were positively correlated with grouse, they were neg atively correlated with voles. Fox were positively correlated with vol es and grouse; however, a strong negative relationship was observed be tween 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 additio n, grouse exhibited large fluctuations during the fox decrease whereas hares did not. Due to the contradictory predator-prey interactions ob served, these results provide only partial support for APH.