U.S. Geological Survey Home Page USGS Patuxent Wildlife Research Center Science Meetings; dedicated to Chandler S. Robbins USGS Patuxent Wildlife Research Center; Science Meetings dedicated to Chandler S. Robbins Dedicated to Chan Robbins USGS Patuxent Wildlife Research Center; Science Meetings dedicated to Chandler S. Robbins Poster Abstracts from USGS Patuxent Wildlife Research Science Meetings, October, 2006
Patuxent Science Meeting 2006 Poster Abstract

Effects of habitat fragmentation and landscape context on mammalian

predators in Northeastern National Parks

Talancy NW (URI), Husband T (URI), O'Connell AF, Gilbert AT, Annand E (IAP)

Human disturbance is a significant source of land use change around the world, specifically in

the northeastern United States, where expanding human populations are causing increased

landscape development, habitat fragmentation, and pressure on wildlife populations. The effects

of fragmentation on a number of wildlife species have been well-documented, but for species

like medium-sized mammalian predators that are often cryptic and elusive, these effects are

difficult to evaluate and not well understood. Medium-sized mammalian predators occupy an

important niche in most ecosystems and because they are wide ranging may be more sensitive

than other taxa to landscape scale influences. In 2004, we used remote cameras, track

plates, and hair traps to collect presence/absence data on medium-sized mammalian predators

in 8 National Park Service (NPS) sites in the northeastern United States. We collected data

on environmental variables at multiple spatial scales and modeled the responses of 10

mammalian species to these variables using site occupancy models that incorporate the

probability of detection for each species. Detection probabilities for medium-sized mammalian

predators varied among time, space, and species, were all <1 and most frequently <0.4.

Cumulative detection probabilities showed that the number of days of sampling will range

between 18 and 174 to detect the target species with a 95% level of confidence. Using site

occupancy models to account for this variation in detection, we determined that landscape

scale variables were good at describing differences in the occurrence of predators. Variables

that focused on the amount of human disturbance, such as the amount of landscape

development, fragmentation, and distance to the nearest occupied building, were the most

important in describing the probability of site occupancy. At the local scale, habitat variables

such as canopy closure, coarse woody debris, and habitat edge were more important to the

target species than the proportion of non-native vegetation or vegetation diversity. Overall,

models that included variables from multiple spatial scales increased the accuracy of site

occupancy estimates, but no single spatial scale was consistently better than others. This

research suggests that landscapes surrounding NPS sites should be considered as important

sources of variation in species presence and patterns of distribution. Detection is an important

parameter to incorporate when sampling wildlife populations because detectability varies over

time and space, and non-detection of a species does not imply absence. This study provides

statistically valid occupancy estimates for 10 medium-sized mammalian predators that will

Friday, September 22, 2006



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