The use of stratified traps in estimating density: Peromyscus and Blarina

Abstract

Snap traps were set on the surface of the leaf litter, across excavated burrows, and in circular ditches in a mesic hardwood forest in Maryland. Over a thirty-day period, the overall rate of capture for Blarina brevicauda and Peromyscus leucopus was very similar -50% of the total catch of each was taken on day-6. However, 19/28 shrews and only 1/16 mice were taken in burrows. Apparently trap position can influence the rate of capture and, to reduce behavioral bias in achieving rapid estimates of density, it is suggested that traps be vertically stratified. Stratifying traps horizontaly to include more restricted portions of the micro-habitat should be tested experimentally with standard methods.

Factors affecting distribution and removal rates of small mammals in a lowland swamp forest

“…At least four hypotheses have been proposed for differential trap responses in small mammals: dominant species effects due to social interaction (Calhoun, 1964), vertical stratification of habitats resulting in reduced exposure to traps (Barbehenn, 1973), »strange object reactions« or trap neophobia or neophilia (Faust et al, 1971) and differential activity due to weather changes . Examination of distribution of animals around the octagon shows that golden mice and cotton mice were almost completely segregated from each other even though both species were relatively abundant in this habitat (Fig.…”

“…Gentry et al (1968) found a significantly greater capture rate of golden mice in traps placed at about eye level on wooden platforms on trees. The third species, shorttailed shrews, are most frequently captured in snap traps emerging from the leaf litter or underground burrows (Barbehenn, 1973). The distribution of these three species in the lowland swamp forest could be superficially viewed as a classic case of niche diversification.…”