Response by coypus to catastrophic events of cold and flooding

Abstract

Population dynamics of the coypu, Myocastor coypus, were studied in central‐West France. This species has recently colonized temperate regions despite physiological sensitivity to cold weather. Live‐trapping over three years demonstrated that increasing population densities from summer into autumn were associated with a faster population turn‐over, homogeneous dispersion, and reduced rates of weight gain. Densities fell by 71% over a cold winter in which canals froze for 20 consecutive days, and by 69% over a mild winter with a flood of 5 weeks duration. Mortality was high in the coldest weather, and 45% of those surviving had frost lesions. A scarcity of males after the cold winter (up to 1♂: 3.3♀) was matched in a nearby population at artificially low density, where dispersing males predominated after the flood. The effect of the cold winter on reproductive output was to synchronize littering in summer, at a time of rich food supply. It was concluded that a flexible response to winter conditions enabled coypus to minimize the effects of extreme events and maximize their colonizing potential.