BIOLOGICAL CONSERVATION 130 (2006) 230– 238 available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/biocon Population decline of northern dusky salamanders at Acadia National Park, Maine, USA Michael S. Banka,*, Jeffrey B. Crockerb, Shirley Davisc, David K. Brothertond, Robert Cooke, John Behlerd, Bruce Conneryf aDepartment of Environmental Health, Harvard School of Public Health, Landmark Center West, Fourth Floor, 401 Park Drive, P.O. Box 15677, Boston, MA 02215, USA bDepartment of Plant and Soil Science, Center for Forestry and Ecology, Alabama A&M University, Normal, AL 35762, USA c64 Gardner Road, Orono, ME 04473, USA dWildlife Conservation Society, Bronx, NY 10460, USA eCape Cod National Seashore, National Park Service, Wellfleet, MA 02667, USA fAcadia National Park, National Park Service, Bar Harbor, ME 04609, USA ARTICLE INFO ABSTRACT Article history: We investigated and reviewed the current and historic distribution of northern dusky sal- Received 12 July 2005 amanders (Desmognathus fuscus fuscus) in Acadia National Park (ANP), Maine, USA during Received in revised form 1938–2003. Historical data indicate that northern dusky salamanders were once widespread 28 November 2005 and common in ANP. We conducted intensive surveys for stream salamanders during 2000– Accepted 20 December 2005 2003 and observed only two adult northern dusky salamanders on one stream. No eggs or Available online 21 February 2006 larvae were observed. Although the cause of the observed population decline is unknown, we identify multiple potential stressors including stocking of predatory fishes, fungal Keywords: pathogens, substrate embeddedness, and widespread pollution (i.e., from atmospheric pol- Amphibian declines lutants) of surface waters at ANP. Our data suggest that ANP streams may no longer be suit- Conservation biology able for northern dusky salamanders. This investigation is the first to document the decline Desmognathus fuscus fuscus of a stream dwelling amphibian species in a national park (i.e., areas that are not subject to Habitat obvious habitat loss or major changes in land use) with widespread mercury contamina- Headwater streams tion of its surface waters. Ó 2006 Elsevier Ltd. All rights reserved. 1. Introduction Worldwide amphibian declines are well documented (Pounds et al., 1997; Houlahan et al., 2000; Stuart et al., 2004; The physical conditions of habitats are critically important in Beebee and Griffiths, 2005). These declines include popula- lotic environments. In general, headwater streams are con- tions from national parks and natural wilderness areas that sidered more susceptible to watershed degradation than are not subject to obvious habitat loss or major changes in land other ecosystems (Power et al., 1988) primarily because of use (Fellers and Drost, 1993). Population declines have been their small size and close linkage with both atmospheric attributed to multiple stressors (Semlitsch, 2003) including and local watershed conditions. In aquatic ecosystems, signs habitat loss and degradation, UV–B radiation, contaminants of environmental stress and deterioration are often initially including mercury (Hg), exotic species, global climate change, detected at the population level and usually affect sensitive and fungal pathogens and disease (Blaustein et al., 1994; Steb- species first (Odum, 1992; Rapport and Reiger, 1995). bins and Cohen, 1995; Alford and Richards, 1999; Semlitsch, * Corresponding author: Tel.: +1 617 384 8544; fax: +1 617 384 8728. E-mail address: [email protected] (M.S. Bank). 0006-3207/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.biocon.2005.12.033 BIOLOGICAL CONSERVATION 130 (2006) 230– 238 231 2003; Unrine et al., 2004; Stuart et al., 2004; Bank et al., 2005, in (Picea rubens), and balsam fir (Abies balsamea). Dominant press; Beebee and Griffiths, 2005). Amphibians play an impor- deciduous tree species include paper birch (Betula papyrifera), tant role in many aquatic and terrestrial environments, and trembling and big-toothed aspen (Populus tremuloides and Pop- therefore their declines may have significant, negative effects ulus grandidentata), red maple (Acer rubrum), and red oak (Quer- on ecosystem functions (Burton and Likens, 1975; Gibbons, cus rubra). In 1947, a human-caused fire swept through Bar 1988; Stebbins and Cohen, 1995; Davic and Welsh, 2004) such Harbor, Maine, severely burning 6880 ha of northeast MDI. as nutrient cycling in aquatic and terrestrial ecosystems. In ANP, aquatic salamanders (Eurycea bislineata bislineata, Des- Anthropogenic habitat loss and degradation (i.e., from mognathus fuscus fuscus) inhabit small stream and seep envi- contaminants, pollution and other sources) are believed to ronments, although D. fuscus fuscus are now considered be primary threats to the health and persistence of amphib- extremely rare while E. bislineata bislineata is still common ian populations (Alford and Richards, 1999; Semlitsch, 2003; and widely distributed throughout ANP (Bank, 2005). Stuart et al., 2004; Beebee and Griffiths, 2005). Amphibians in general are considered to be sensitive to disturbance in 2.2. Fish stocking in Acadia National Park both aquatic and terrestrial environments, primarily because of their complex life histories, specialized physical adapta- The objectives of the National Park Service’s (NPS) recrea- tions, and micro-habitat requirements (Bury, 1988; Vitt et al., tional fisheries program are to protect native fish species 1990; Wake, 1990; Olson, 1992; Blaustein, 1994; Blaustein and aquatic ecosystems and provide recreational angling et al., 1994; Stebbins and Cohen, 1995; Davic and Welsh, opportunities for the public. In the nutrient limited lakes of 2004). In contrast to vernal pool amphibian species, whose Acadia NP, this requires a careful balance between protection larval period is short, stream salamander larvae are often of native species, and the stocking of fish to enable viable rec- slow-growing (Petranka, 1998). Larval development of these reational fishing by the public. The NPS together with the salamanders occurs in streams, and larvae are strictly aquatic Maine Department of Inland Fisheries and Wildlife (MDIFW) during this life history stage, relying on gills for breathing. regulate and manage freshwater fishing in Acadia National However, after metamorphosis, adults can often be found in Park, although the MDIFW is largely responsible for supervis- streamside habitats in leaf litter or at the interface of the ing the fish stocking programs. The fish communities of Aca- stream channel under partially submerged rocks. Their long dia have been altered by humans for >100 years. Increases in life span, high relative abundance and vagility, philopatric recreational fishing during the second half of the 1900s led to behavior (Daugherty and Sheldon, 1982; Welsh and Lind, an extensive fish introduction program, including the stock- 1992), and stable populations (Hairston, 1987) make stream ing of native and non-native predatory fishes (Stone et al., salamanders ideal indicators of environmental stressors 2001). Recently stocking programs have focused on the intro- including contaminants in lotic ecosystems (Welsh and Olli- duction of salmonid species (Moring, 1999), and only Bear vier, 1998; Bank, 2003; Southerland et al., 2004; Bank et al., Brook Pond and Duck Pond in Acadia have never been stocked 2005, in press). (Leˆ and Moring, 1999; Stone et al., 2001). The northern dusky salamander is a widespread and ubiq- uitous species found throughout eastern North America and 2.3. Atmospheric pollution at Acadia National Park has been observed throughout most of mainland Maine, ex- cept for the northeastern-most corner (Hunter et al., 1999). Sulfur dioxide, Hg, and nitrogen oxide from power plants and The larval period of the dusky salamander is approximately other sources are likely having adverse effects on surface 9–14 months and is influenced by local abiotic and biotic con- waters in ANP (Bank et al., 2005). Acadia’s thin rocky soils pro- ditions including climate, temperature, food availability, com- vide little buffering capacity against acid rain damage to petition and predation (Petranka, 1998). The specific objective headwater streams, ponds, and lakes and Hg contamination of this study was to synthesize existing data related to the of ANP biota is well documented (Burgess, 1997; Bank et al., spatial and temporal distribution patterns of northern dusky 2005, in press). Acidification of surface waters, including salamanders at Acadia National Park (ANP), Maine. We also headwater streams, can reduce species diversity and can ex- discuss the potential causes of population decline at ANP. ert adverse effects on aquatic biota such as fish and salaman- ders, primarily as a result of direct effects of decreases in pH 2. Methods that can cause elevated concentrations of highly toxic alumi- num and Hg (Schindler et al., 1985; Cronan and Schofield, 2.1. Study site 1990; Driscoll and Postek, 1995; MacAvoy and Bulger, 1995; Driscoll et al., 2003; Bank et al., 2005). Episodic acidification ANP (44°210N, 68°130W) encompasses 15,233 ha, with of headwater streams, likely caused by the interaction be- 12,260 ha on Mount Desert Island (MDI) and 2973 ha in sur- tween marine salt deposition and ANP’s acidic soils, has been rounding parcels (Fig. 1). ANP has 26 mountains, and 20% documented with a pH < 5.0 (Kahl et al., 1985; Heath et al., of the park is classified as wetland habitat including marshes, 1992). The pH of precipitation