Abstract
We analyzed the effects of population density and climatic variables on the rate of population growth in the guanaco ( Lama guanicoe), a wild camelid species in South America. We used a time series of 36 years (1977-2012) of population sampling in Tierra del Fuego, Chile. Individuals were grouped in three age-classes: newborns, juveniles, and adults; for each year a population transition matrix was constructed, and the population growth rate (λ) was estimated for each year as the matrix highest positive eigenvalue. We applied a stepwise regression analysis with population growth rate (λ) as dependent variable, and total guanaco population (in natural logs), annual mean precipitation, and winter mean temperature as independent variables, with and without time lags. The effect of population size was statistically significant, but the effect of the climatic variables on guanaco population growth rate was not significant.
Highlights
In order to understand population dynamics and optimize the management of wildlife populations it is important to identify how groups are affected by environmental factors and their own density, in species living in extreme environments
Density-dependent processes are affected by environmental conditions, and many wildlife population dynamic and management models include the effects of climatic covariates (e.g., Dennis & Otten, 2000; Colchero et al, 2009)[3,4]
Environmental covariates In addition to the direct density-dependence, we evaluated the possible impact of two environmental covariates on guanaco population dynamics: average annual precipitation and winter temperature
Summary
In order to understand population dynamics and optimize the management of wildlife populations it is important to identify how groups are affected by environmental factors and their own density, in species living in extreme environments. Stabilization results from density-dependence, with a regulatory effect that varies in intensity with the size or density of the population itself. Density-dependent processes are affected by environmental conditions, and many wildlife population dynamic and management models include the effects of climatic covariates (e.g., Dennis & Otten, 2000; Colchero et al, 2009)[3,4]. In the case of the Ricker model (one of the most simple and most used population models), Corani and Gatto (2007)[5] proposed an original way of incorporating climatic covariates: they were included as affecting the population growth rate
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