Capurro, A. F., Gatto, M., and Tosi, G. (1997). Delayed and inverse density dependence in a chamois population of the Italian Alps. Ecography 20: 37-47.

Keywords: 8IT/Alps/density/density dependent/intraspecific competition/Malme/population dynamics/Rupicapra rupicapra/snow cover/weather

Abstract: Both density dependent and density independent factors have been considered important determinants of the dynamics of ungulate populations. Intraspecific competition for food and the amount of snow cover were suggested in the past as factors that influence the demographic parameters of the chamois Rupicapra rupicapra. We present a 10 yr study on a closed population of the Italian Alps. Animals, divided by sex and age class (kid, yearling, subadult, adult, old), were counted over the period 1981-1990. The number of chamois hunted and the number of carcasses found each year and the daily snow height were also available. We investigated possible correlations between several demographic parameters and both snow cover and chamois density, accounting for sex- and age-differential mortality and a possible delay in density dependence. Results are as follows: a) there is no statistically significant correlation between snow cover and demographic rates; b) there is no detectable compensation between natural and hunting-related mortality; c) birth rate is density independent for any time delay; d) when calculated from carcasses, total mortality, mortality of 1-yr-old and older males and females significantly depend on total density with 2 years'lag, while kid mortality is not related to density for any time delay; e) when calculated from censuses, all mortality rates significantly depend on total density with 2 years'lag, although the variance explained by delayed density is definitely smaller for kids; f) nonlinear regression of kid mortality from censuses against density of kids in the same year yields a much higher coefficient of determination and inverse density dependence is evidenced. However, discrimination between delayed and inverse density dependence in kid mortality is impossible, given our dataset. In general, results support the hypothesis that intraspecific competition, epidemics and predation, rather than weather, play a role in the dynamics of this ungulate population.