Cambios de largo plazo en el paisaje y los ensambles de micromamíferos y rapaces en Chile central

Abstract

San Carlos de Apoquindo, a piedemont area to the east of Santiago city, is a site with 30 years of data on vertebrates. Using LANDSAT satellite imagery for the years 1975, 1989 and 2003, we studied the spatiotemporal trajectory of land use and its putative effects on vegetation, small mammals and raptors. On the basis of a landscape-level analysis, we interpreted long-term trends in the abundance of small mammals and in the diet of raptors. Satellite imagery reveals an accelerated expansion of the urban area in detriment of agricultural land and native scrubland. Native mammal species of small and medium size do not display large variation of abundance during the 30 years study period, but larger-sized native mammals show reduced population numbers. The European rabbit (Oryctolagus cuniculus) currently is among the most abundant mammal species in the area, and seems to be favored by the temporal transition from dense to sparse scrubland. In the diets of Chilean Eagle (Geranoaetus melanoleucus) and of native Harris' Hawk (Parabuteo unicinctus) there is a marked decrease of the native rodent prey Octodon degus and a concomitant increase of the exotic prey Oryctolagus cuniculus. In addition, there is a decreasing trend in richness and abundance of raptors throughout the study period, which is associated to both urban expansion and scrubland fragmentation and reduction. We propose that urban encroachment, together with areal reduction and fragmentation of native scrubland, has resulted in a decrease of the Octodon degus population, and in its subsequent decrease in the diet of both native eagles and hawks, which in turn has determined increased predation on exotic rabbits. © Sociedad de Biología de Chile.