Capture-recapture study of monito del monte (Dromiciops gliroides Thomas 1894): estimating population density from hierarchical models

RIVAROLA, MD; AMICO, GC; CARLO, T; MORALES, JM

Bariloche, Argentina

Congreso; VI Southern connection congress; 2010

Dromiciops gliroides is an arboreal and nocturnal marsupial endemic to the northern portion of the temperate forests in southern South America associated with Nothofagus forest. We studied the population density and home range of D. gliroides in Llao-Llao Municipal Park, Bariloche, Argentina. The study was conducted during the summer of 2009. Two square grids were established 150 m apart. Each grid consisted of 25 live-traps spaced at 10 m intervals. Traps were run over four consecutive nights each month. Captured marsupials were fitted whit PIT-tags before release at the point of capture. A total of 72 individuals were caught out of 152 captures. Bayesian Analysis was implemented using data augmentation method in WinBUGS and MCMC were used to estimate posterior probabilities. We estimated that capture probability was three times larger for juveniles than adults even though the ratio of juveniles to adults was estimated as 41/59. Capture increased with weight but did not vary with sex. Finally, a spatially explicit capture model estimated population density as 21 Ind/ha, and the average home range was 1,44 ha. These estimates are based on assuming fixed activity centers and exposure to traps as a function of animal movements within their home ranges rather than ad-hock guesses about sampled area. Home range sizes are similar to those obtained through telemetry studies both in the study area and in Chile. Thus, this rare and endangered marsupial can be locally abundant.