Influences of weather and moonlight on activity patterns of small mammals: a biogeographical perspective

We analyzed 15 years of trapping data on prairie voles (Microtus ochrogaster) and cotton rats (Sigmodon hispidus) to elucidate behavioural responses to weather by season and time of day. Use of such a long-term data set is rare and ameliorates many of the problems with short-term data sets typically used for such analysis. The trapping was conducted in the east-central part of Kansas (U.S.A.), near the southern edge of the distribution of prairie voles and the northern edge of the distribution of cotton rats. These distributions provide the framework for differing hypotheses as to responsiveness of individuals of the two species to weather phenomena as indicated by the probability of capture. Probability of capture was statistically significantly affected by weather, most frequently by precipitation and temperature. Effects varied with season and between species, and were generally consistent with hypotheses based on the northern (boreal and temperate) history of prairie voles and southern (subtropical and temperate) history of cotton rats and with predation-avoidance hypotheses. Variation in the probabilities of capture of cotton rats was more associated with weather, especially in the colder seasons, than was variation in the probabilities of capture of prairie voles. In summer, capture rates of prairie voles were more susceptible to weather than were those of cotton rats.