Estimating population trends using population viability analyses for the conservation ofCapra pyrenaica

Abstract

2008. Estimating population trends using population viability analyses for the conservation of Capra pyrenaica. Acta Theriologica 53: 275-286.Large herbivore populations can suffer important oscillations with considerable effects on ecosystem functions and services, yet our capacity to predict population fate is limited and conditional upon the availability of data. This study investigated the interannual variation in the growth rate of populations of Capra pyrenaica Schinz, 1838, and its extinction risk by comparing the dynamics of populations that were stable for more than two decades (Gredos and Tortosa-Beceite), populations that had increased recently (Tejeda-Almijara), and populations that were in decline (Cazorla-Segura) or extinct (the Pyrenees population; hereafter, bucardo). To estimate quasi-extinction threshold assessments (50% of population extinct in this study), which have implications for the conservation of the species, we used empirical data and the predictions derived from several theoretical models. The results indicate that when variance of log population growth rate reaches a specific threshold, the probability of quasi-extinction increased drastically. For C. pyrenaica, we recommend keeping population variance < 0.05, which will reduce the likelihood that the irruptive oscillations caused by environmental and demographic stochasticity will put the population at risk. Models to predict the dynamics of C. pyrenaica populations should incorporate temporal stochasticity because, in this study, it strongly increased the likelihood that a population declined.

Evaluación del estado de la población de cabra montés de los montes de Toledo: relaciones con el ciervo

“…En general, los encuestados perciben que esta población en la actualidad se encuentra en aumento, si bien es cierto que no es un crecimiento especialmente acusado a tenor de las densidades observadas. Esta tendencia poblacional es congruente con la descrita para otras poblaciones de cabra montés de CLM (Acevedo et al, 2007a) y otras poblaciones peninsulares de esta subespecie (Escós et al, 2008).…”

“…Escós et al (2008) analizando la evolución temporal de varias poblaciones de cabra montés, mostraron que todas las poblaciones de C. p. hispanica están en notoria expansión numérica, pero la población de C. p. victoriae monitorizada, la de Gredos, se mantiene estable en los últimos años. Esto indica que podrían existir razones ecológicas diferentes a la competencia que explicaran que las poblaciones de esta subespecie no tuvieran la misma potencialidad que la C. p. hispanica para expandirse.…”