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Pilot Project for Mammal Survey Along Appalachian Trail: Influence of landscape structure on mammal occupancy

A grey fox is photographed by a trail camera on the A.T.
A grey fox is photographed by a trail camera on the A.T..Smithsonian photo.

Overview

Habitat loss and fragmentation cause a variety of ecological impacts that trigger different responses in different mammal species. Many large mammals have experienced dramatic range contractions, while others have expanded following natural reforestation. Recent studies have shown that mammalian carnivore species richness, persistence, and abundance are best predicted by forest fragment size and isolation. Although fragmentation is frequently detrimental to large carnivore populations, ungulates and some mesopredators thrive on conditions that accompany habitat disturbance.

Broad scale studies are often limited by financial and human resources, but these limitations can be overcome using new cost-effective and non-invasive techniques such as remote camera trapping and volunteer-based citizen science.  With a dense human population serving as both a driver of landscape fragmentation and as a volunteer base, the forests of the Appalachian Mountains in the Eastern United States are an ideal testing ground for these techniques. 

Objective

Data from this program we be used to develop models for predicting the occurrence of mammal species. We have several goals for this proposed research:

1. To determine if landscape fragmentation and human land use, rather than habitat and terrain variables, are the best predictors for mammal occupancy along the AT corridor.

2. To understand the changes in animals populations on lands associated with the trail.

3. To create an effective volunteer system to collect reliable mammal survey data over a large scale using remote camera technologies.

Methods

During 2009, 50 heat and motion triggered cameras were used to sample 447 sites along a 1024 km section of the A.T. to assess the effects of available habitat, hunting, recreation, and roads on eight mammal species (white-tailed deer, raccoons, American black bears, Virginia opossum, coyotes, bobcats and red and gray foxes). The sites were surveyed either by volunteers from the established A.T. volunteer network, or by a wildlife technician.  All surveyors followed the protocol from the 2007-2008 years.

Significance & Findings

bobcat on trail cam
Bobcat 'photo trapped' during the study.Smithsonian photo.

Occupancy modeling revealed the importance of available forest to all eight species except opossums (Didelphis virginiana) and coyotes (Canis latrans). Hunting on adjoining lands was the second strongest predictor of occupancy for three mammal species, negatively influencing black bears and bobcats, while positively influencing raccoons. Modeling also indicated an avoidance of high trail use areas by bears and natural inclination towards high use areas by red fox. Roads had the lowest predictive power on species occupancy within the corridor and were only significant for deer. The occupancy models stress the importance of compounding direct and indirect anthropogenic (human) influences operating at the regional level. Scientists and managers should consider these human impacts and their potential combined influence on wildlife persistence when assessing optimal habitat or considering management actions.

Large-scale studies looking at eastern mammal communities are uncommon, but are important in understanding the ecology of this region and the interplay between mammals with large home ranges and human development.  Although secondary forests have reclaimed parts of the Appalachian region, many of these forests have been fragmented by roads and development. Being able to model this fragmentation and its effects on mammal distributions is a critical need for federal and state agencies. Developing a predictive GIS model that effectively incorporates human impacts in its designation of suitable habitat could be an effective tool for wildlife managers.  This study also contributes to the knowledge of remote camera technology and its effectiveness in conducting accurate wildlife surveys. Camera-traps can provide information on otherwise elusive and data-deficient species. 

 

Key Contacts


Dr. William McShea

Wildlife Ecologist
Conservation Ecology Center
National Zoological Park
McsheaW@si.edu
540-635-6563 (office)


Fred Dieffenbach

Environmental Monitoring Coordinator
Northeast Temperate Network / Appalachian NST
Fred_Dieffenbach@nps.gov
802-457-3368 ext. 36
802-457-3405 (fax)

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