APPLICATION OF THE STAGE-PROJECTION MODEL WITH DENSITY-DEPENDENT FECUNDITY TO THE POPULATION-DYNAMICS OF SPANISH IBEX

A stage-class population model with density-feedback term included was used to identify the most critical parameters determining the populat ion dynamics of female Spanish ibex (Capra pyrenaica) in southern Spai n. A population in the Cazorla and Segura mountains is rapidly declini ng, but the eastern Sierra Nevada population is growing. The stable po pulation density obtained using estimated values of kid and adult surv ival (0.49 and 0.87, respectively) and with fecundity equal to 0.367 i n the absence of density feedback is 12.7 or 16.82 individuals/km(2), based on a non-time-lagged and a time-lagged model, respectively. Give n the maximum estimate of fecundity and an adult survival rate of 0.87 , a kid survival rate of at least 0.41 is required to avoid extinction . At the minimum fecundity estimate, kid survival would have to exceed 0.52. Elasticities were used to estimate the influence of variation i n life-cycle parameters on the intrinsic rate of increase. Adult survi val is the most critical parameter, while fecundity and juvenile survi val are less important. An increase in adult survival from 0.87 to 0.9 1 in the Cazorla and Segura mountains population would almost stabiliz e the population in the absence of stochastic variation, while the sam e increase in the Sierra Nevada population would yield population grow th of 4-5% per annum. A reduction in adult survival to 0.83 results in population decline in both cases.