Tree cavities and cavity users in two caldén forests of Argentina managed as a protected area or for cattle ranching

Abstract

Animal populations that require tree cavities can be either limited or structured depending on the quality andavailability of tree cavities in their ecosystems. Over the last century, the Cald´en forest of Argentina has experiencedsevere habitat degradation due to anthropogenic activities. Here, we report the density and characteristicsof cavities and their vertebrate users in areas of the Cald´en forest with two different types of management: aprotected area and an area with cattle ranching. The average density of cavities was 16.1 cavities/ha. However,the reserve’s cavity density was four times higher than the ranch’s (19.5 vs. 5.8 cavities/ha). The characteristicsof the cavities and their support trees showed significant variations, but they were generally similar betweensites. Forty-four vertebrate species use or may use tree cavities. The proportion of recorded species using cavitiesin the reserve was higher (30/41 vs. 6/32; p < 0.01). While most cavity users in the semi-arid forest are notthreatened, this ecosystem has been dramatically fragmented, with only 11% of its original area remaining. Ifanthropogenic activities continue to alter this fragile ecosystem, it is possible that in the future, many species,including tree cavity nesters, will suffer a decline in their populations.