Carolyn G. Mahan

Effects of Forest Fragmentation on Burrow-site Selection by the Eastern Chipmunk (Tamias striatus)

-We compared habitat variables associated with burrow sites of eastern chipmunks (Tamias striatus) and random sites in a reference (uncut) and a managed, fragmented (by even-aged clearcutting) forest sector in central Pennsylvania. Burrow sites typically were characterized by steeper slope, higher number of logs, and higher numbers of stumps in both forest sectors. Our findings suggest that despite differences in extent of forest fragmentation and availability of habitat variables, chipmunks select burrow sites associated with similar physical and vegetative characteristics.

The Trill of the Chase: Eastern Chipmunks Call to Warn Kin

Abstract The trill vocalization is given by eastern chipmunks (Tamias striatus) when being pursued by a predator. To examine the adaptive significance of this vocalization, we assessed the effects of sex, age, and distance from the burrow on the occurrence of the call. Chipmunks were released either 10 or 100 m from their burrow and chased by an experimenter to simulate a terrestrial predator. We found that adult females trill more often when released 10 m from their burrow (67% of 24 chases) than when released 100 m from their burrow (14% of 21 chases). Adult males, on the other hand, showed no significant difference in their probability of trilling based on the distance from their burrows (45% of 20 chases at 10 m and 55% of 20 chases at 100 m). Adult females trilled more than adult males when released 10 m from their burrow (67% compared with 45%) but less than males when released 100 m from their burrow (14% compared with 55%). Juvenile females only trilled when released 10 m from their burrows (45% of 11 chases), and juvenile males did not trill at all. We attributed sex, age, and location differences in giving the trill vocalization to the effects of kin selection on antipredator behavior.

Overstory Tree Composition of Eastern Hemlock Stands Threatened by the Hemlock Woolly Adelgid at Delaware Water Gap National Recreation Area

Abstract We described overstory tree age and composition among hemlock stands that varied in physiographic structure at Delaware Water Gap National Recreation Area located in northeastern Pennsylvania and northwestern New Jersey. Hemlock stands were comprised primarily of eastern hemlock (Tsuga canadensis), chestnut oak (Quercus prinus), black birch (Betula lenta), Eastern white pine (Pinus strobus), and white oak (Quercus alba). Forest stands characterized by steep slopes and high gradients supported the highest basal area of hemlock. Trees within hemlock stands ranged in age from 68.0–148.0 years. These data are valuable because as eastern hemlocks decline throughout the mid-Atlantic region of the United States due to infestation of the exotic insect pest, the hemlock woolly adelgid (Adelges tsugae), hardwood species will likely become more prominent in these stands in the future. The documentation and description of tree composition of a threatened ecosystem prior to its decline is important for future restoration efforts and potential tree replacement in forest stands.

THE POTENTIAL ROLE OF STRONGYLOIDES ROBUSTUS ON PARASITE-MEDIATED COMPETITION BETWEEN TWO SPECIES OF FLYING SQUIRRELS (GLAUCOMYS)

There is growing evidence that populations of the northern flying squirrel (Glaucomys sabrinus) are declining in the eastern United States, perhaps due to competition with the southern flying squirrel (Glaucomys volans). Potential causes include parasite-mediated or apparent competition from the shared intestinal nematode, Strongyloides robustus, which has been shown to detrimentally affect the northern flying squirrel but not the southern flying squirrel. To investigate this hypothesis, we conducted a preliminary study on the parasite community of both flying squirrel species from sites in Pennsylvania where the two species occur sympatrically and where G. sabrinus is now considered endangered at the state level. We compared these parasite communities with those from northern flying squirrels from northern New York where the southern flying squirrel is absent. We found eight species of gastrointestinal parasites (Pterygodermatites peromysci, Lemuricola sciuri, Syphacia thompsoni, Syphacia spp., Capillaria spp., Citellinema bifurcatum, Strogyloides robustus, and an unidentifiable cestode species) in both species of flying squirrels examined for our study. The parasite-mediated competition hypothesis was partially supported. For example, in Pennsylvania, S. robustus was overdispersed in southern flying squirrels, such that a small proportion of the hosts carried a large proportion of the worm population. In addition, we found S. robustus to be present in northern flying squirrels when the species were sympatric, but not where southern flying squirrels were absent in New York. However, there was no association between S. robustus and the body condition of flying squirrels. We detected a potential parasite community interaction, as S. robustus abundance was positively associated with P. peromysci.

Lack of Population Response by Eastern Chipmunks (Tamias striatus) to Forest Fragmentation

Abstract We compared age- and sex-class structure between two populations of eastern chipmunks (Tamias striatus) occupying study plots within uncut (reference) and managed (fragmented) forest sectors in central Pennsylvania from 1992–1995. In addition, we compared reproductive condition, weight and length of time chipmunks remained on study plots between the two populations. There was no difference (P > 0.05) in age class, sex class or reproductive condition between the populations occupying each sector. Chipmunks remained on plots in both uncut and managed forest sectors for an average of 2.2 and 2.3 mo, respectively. Weights of individual chipmunks did not differ (P > 0.05) between the two populations and averaged 81.5 g. Chipmunks in both populations, however, weighed significantly (P ≤ 0.05) less in 1993 following a poor acorn crop in 1992 than in other years. Although eastern chipmunks primarily inhabit mature eastern deciduous forests, fragmentation had no apparent influence on the demography of populations of this sciurid.

Using Ecological Indicators and a Decision Support System for Integrated Ecological Assessment at Two National Park Units in the Mid-Atlantic Region, USA

We implemented an integrated ecological assessment using a GIS-based decision support system model for Upper Delaware Scenic and Recreational River (UPDE) and Delaware Water Gap National Recreation Area (DEWA)—national park units with the mid-Atlantic region of the United States. Our assessment examined a variety of aquatic and terrestrial indicators of ecosystem components that reflect the parks’ conservation purpose and reference condition. Our assessment compared these indicators to ecological thresholds to determine the condition of park watersheds. Selected indicators included chemical and physical measures of water quality, biologic indicators of water quality, and landscape condition measures. For the chemical and physical measures of water quality, we used a water quality index and each of its nine components to assess the condition of water quality in each watershed. For biologic measures of water quality, we used the Ephemeroptera, Plecoptera, Trichoptera aquatic macroinvertebrate index and, secondarily, the Hilsenhoff aquatic macroinvertebrate index. Finally, for the landscape condition measures of our model, we used percent forest and percent impervious surface. Based on our overall assessment, UPDE and DEWA watersheds had an ecological assessment score of 0.433 on a −1 to 1 fuzzy logic scale. This score indicates that, in general, the natural resource condition within watersheds at these parks is healthy or ecologically unimpaired; however, we had only partial data for many of our indicators. Our model is iterative and new data may be incorporated as they become available. These natural parks are located within a rapidly urbanizing landscape—we recommend that natural resource managers remain vigilant to surrounding land uses that may adversely affect natural resources within the parks.

Animal Behavior in Fragmented Landscapes

Concepts from island-biogeography theory (MacArthur and Wilson 1967) have been instrumental in testing and understanding current patterns of faunal distribution in fragmented landscapes. The species-area curve, for instance, has enabled us to examine the relationship between patch size and species richness in various landscapes (e.g., Robbins et al. 1989). The effects of fragmented landscapes on community structure (e.g., Friesen et al. 1995; Yahner 1997), reproductive success (e.g., Robinson et al. 1995), and population demographics (e.g., Wauters et al. 1994; Litvaitis and Villafuerte 1996; Wolff et al. 1997; Mahan and Yahner 1998) have been examined. These previous studies are vital to natural resource managers and conservation biologists concerned with biological conservation and ecosystem management. However, an important and largely untapped area of research is the effects of fragmented landscapes on animal behavior (Yahner and Mahan 1997a).

Sustainable Remediation of Legacy Mine Drainage: A Case Study of the Flight 93 National Memorial

Abstract Pollution from mining activities is a global environmental concern, not limited to areas of current resource extraction, but including a broader geographic area of historic (legacy) and abandoned mines. The pollution of surface waters from acid mine drainage is a persistent problem and requires a holistic and sustainable approach to addressing the spatial and temporal complexity of mining-specific problems. In this paper, we focus on the environmental, socio-economic, and legal challenges associated with the concurrent activities to remediate a coal mine site and to develop a national memorial following a catastrophic event. We provide a conceptual construct of a socio-ecological system defined at several spatial, temporal, and organizational scales and a critical synthesis of the technical and social learning processes necessary to achieving sustainable environmental remediation. Our case study is an example of a multi-disciplinary management approach, whereby collaborative interaction of stakeholders, the emergence of functional linkages for information exchange, and mediation led to scientifically informed decision making, creative management solutions, and ultimately environmental policy change.

Habitat Characteristics and Revised Gap Landscape Analysis for the Northern Flying Squirrel (Glaucomys sabrinus), a State Endangered Species in Pennsylvania

Abstract We quantified the habitat characteristics associated with capture sites (2003–2006) of the state endangered northern flying squirrel (Glaucomys sabrinus) in Pennsylvania to develop management recommendations that help ensure its continued persistence in the Appalachians. In addition, we used this refined understanding of northern flying squirrel habitat to update the Pennsylvania Gap analysis model for this species. We examined habitat at both the landscape and local level and determined that northern flying squirrels preferred sites that contained mature (>95 y old) mixed coniferous forests and were adjacent to a permanent water source. In addition, sites where northern flying squirrels were captured contained significantly more overstory trees (all species), saplings and rock cover. After using these data to refine the Pennsylvania Gap model for northern flying squirrels, we reduced the primary or core habitat predicted for this species in the state by 90%. Our findings further support the reliance of this species on specialized habitat in the Appalachians and help reinforce the need to conserve and manage mature mixed-coniferous forest stands, which are threatened by exotic pests and human development throughout the region.

Natural resource assessment: an approach to science based planning in national parks.

We conducted a natural resource assessment at two national parks, New River Gorge National River and Shenandoah National Park, to help meet the goals of the Natural Resource Challenge—a program to help strengthen natural resource management at national parks. We met this challenge by synthesizing and interpreting natural resource information for planning purposes and we identified information gaps and natural significance of resources. We identified a variety of natural resources at both parks as being globally and/or nationally significant, including large expanses of unfragmented, mixed-mesophytic forests that qualify for wilderness protection, rare plant communities, diverse assemblages of neotropical migratory birds and salamanders, and outstanding aquatic recreational resources. In addition, these parks function, in part, as ecological reserves for plants in and wildlife. With these significant natural resources in mind, we also developed a suite of natural resource management recommendations in light of increasing threats from within and outside park boundaries. We hope that our approach can provide a blueprint for natural resource conservation at publically owned lands.