Annual cycle of a coypu <i>(myocastor coypus)</i> population: male and female strategies

Abstract

Male and female strategies were compared for wild–living populations of coypu (Myocastor coypus Molina) censused during two years in marshlands of central–west France. In a habitat composed of a canal network bisecting pasture fields typically 0–5 ha in size, coypu movements were largely restricted to stretches of open water, though males explored further from water than females. Adults occupied home ranges with a mean size of 3–82 ha or 1. 19 km of canal, males on average moving faster over a larger area and using a greater length of canal than females. Movements within partially shared ranges were most positively coordinated between male–female pairs, while male–male interactions were less frequent. Juvenile coypus were largely absent from the late winter population. Synchronization of litters in March–April resulted in a peak of juveniles in early summer. The sex ratio of juveniles and sub–adults reversed from a male bias in summer to a female bias in autumn. Population densities peaked in November at 4 ha, with a significant female bias (1M: 1–6F). In the same month, a neighbouring population at lower density (1 ha ‐l after treatment with rodenticide) was significantly male biased (2–7M:lF) and may therefore have been acting as a sink for males dispersing from the high density population. Transients comprised 63% of the population. Females were resident longer than males, 22% of females remaining at least 5 months against 6% of males. Dispersal was recorded only for males aged 6 months or older. The general result, of exploratory behaviour amongst males contrasting with the establishment of longer term home ranges by females, is discussed in terms of male reproductive success and the capacity for females to influence nutrient supply to their litters.