Estimates of Population Size and Changes of the Walia Ibex

Abstract

Methods of assessing population size and changes have to consider the particular environmental situation in Simen, which can be summarized as extremely heterogenous and partly inaccessible but small and overlookable. Among several attempts aimed at gauging the absolute population size, there is none that does not imply a high degree of uncertainty. Three which are believed to have some measure of reliability and to be sufficiently valid to serve as rough estimates are presented in the first part of this chapter. But in fact, in order to plan adequate measures for protection and management it is not necessary to tally the exact number of living animals. Indeed, it is only vital to judge as precisely as possible whether the population remains stable, or whether it is decreasing or increasing. A statistically valid method was proposed in 1971 and subsequently carried out by the Park Warden and the Game Guards in charge (Nievergelt 1971). This method and some results are summarized in the last section of this chapter.