Rainfall, ambient temperature, and Clethrionomys californicus capture frequency

Abstract

Sixty Western Red-backed Voles Clethrionomys californicus inhabiting an old-growth mixed conifer forest in north-western California (USA) were studied over 2 years to assess relationships among vole capture frequency, rainfall, and ambient temperature. Red-backed Voles were encountered more often and recapture rates per vole doubled with the tripling of yearly rainfall. In addition, more voles were captured during wet months than dry months. Analysed over weekly intervals, captures were positively correlated with the amount of weekly rainfall, a greater proportion of the known vole population was encountered during wet weeks than dry weeks, and increased weekly rainfall resulted in an increased proportion of the vole population captured. Significant relationships were not found between daily rainfall and vole captures, but both minimum and maximum daily ambient temperatures were lower when voles were trapped. Vole captures increased with decreases in daily and weekly minimum and maximum ambient temperatures. Weekly rainfall in combination with minimum weekly temperatures accounted for the greatest explanation of variability in vole capture frequencies. These results document that rainfall and ambient temperature have an impact on Western Red-backed Vole capture frequency; thus these weather variables should be addressed as covariates in analyses focused on capture data for this species.