Structural changes in an apparently stable chamois population in Basin Creek, Canterbury, New Zealand

Abstract

Numbers of chamois (Rupicapra rupicapra) observed annually in Basin Creek, Canterbury, New Zealand, remained at between 42 and 72 from 1974 to 1977, despite movements of large numbers of migrants. Numbers changed seasonally, with a female peak in summer and a male peak in the breeding season (May to June) each year. The proportion of adult females increased over the study period; those of adult males, kids, and yearlings fluctuated. The number of social groups containing adult females also increased. Chamois in Basin Creek were predominantly solitary animals and group size rarely exceeded four. Groups of two or more formed mainly during the breeding and birth seasons. Group size declined during the study. Average monthly inflow of the marked population was 17.6%, and average monthly outflow was 23.4%. Migrants contributed most to both inflow and outflow in all seasons. Depending upon weather conditions, productivity varied between 89 and 100%, which is high for chamois populations. Kid mortality was significantly higher in 1976 than in other years; this was related to poor summer-autumn weather and subsequent outbreaks of disease. Population numbers appear to be regulated by a combination of social and spatial factors and food availability, and not productivity and kid mortality.

Keywords:

• Chamois
• Rupicapra rupicapra
• Avoca River
• population dynamics
• migration
• productivity
• mortality