Influence of habitat attributes on density of Virginia opossums (Didelphis virginiana) in agricultural ecosystems

Abstract

In agriculturally fragmented ecosystems, mesopredators play dominant roles in food webs through scavenging. We examined the influence of habitat attributes associated with carrion on local Virginia opossum (Didelphis virginiana Kerr, 1792) density in an agricultural landscape. We conducted opossum mark–recapture in 25 forest patches from 2005 to 2010, which represented the most extensive sampling of opossums to date. We analyzed mark–recapture data with a closed robust design and evaluated effects of landscape features linked to carrion on opossum density and female opossum density with generalized linear mixed-effects models. We included landscape-level (1481.6 m buffer) and patch-level covariates linked to carrion in addition to other covariates associated with high opossum densities. We developed a set of 19 candidate models and examined model fit with Akaike’s information criterion. The top model for opossum density included the density of adjoining roads, whereas the top model for female density included patch size, although the statistical null was a competing model in both cases. The long-distance dispersal capability and generalist diet of the opossum likely precluded us from detecting a definitive relationship between covariates and opossum density. The scale of effect for opossum density in agriculturally fragmented landscapes is likely larger than the spatial scales examined here.