Amphibian Monitoring on the Manitou Islands ...

U.S. Department of the Interior National Park Service Great Lakes Network Office Ashland, Wisconsin

Amphibian Monitoring on the Manitou Islands, Sleeping Bear Dunes National Lakeshore Kenneth D. Bowen and Erik A. Beever National Park Service Great Lakes Inventory and Monitoring Network

Great Lakes Network Report GLKN/2008/01

January 2008

Suggested Citation: Bowen, K. D. and E. A. Beever. 2008. Amphibian Monitoring on the Manitou Islands, Sleeping Bear Dunes National Lakeshore. National Park Service, Great Lakes Inventory and Monitoring Network Report: GLKN/2008/01 ii

Contents Introduction..................................................................................................................................... 1 Methods........................................................................................................................................... 2 Results............................................................................................................................................. 3 Discussion and Recommendations ................................................................................................. 8 Literature Cited ............................................................................................................................. 10

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Abstract Long-term monitoring of amphibian populations is necessary to obtain accurate estimates of distribution and abundance. We used the USDA Natural Resource Conservation Service Soil Survey Geographic (SSURGO) Database to identify a priori potential habitat for aquaticbreeding amphibians on North and South Manitou Islands, Sleeping Bear Dunes National Lakeshore, Michigan, USA. Our goal was to identify sites for long-term monitoring of amphibian species. We also made use of two effective survey techniques, perimeter walking surveys and daytime call surveys, which are valuable for remote wilderness areas, especially for wetlands where there is high concern about introduction of exotic invasions. We detected four species of amphibian (two salamanders and two anurans) on each island, and identified a number of potential long-term survey sites. Our techniques allow for easy a priori identification of numerous high-quality survey sites and rapid but effective field surveys that require a minimum of manpower, equipment, and disturbance, both of which are necessary for surveys in protected areas.

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Introduction In 1999 the National Park Service (NPS) formed the Great Lakes Inventory and Monitoring Network (GLKN). The GLKN is one of 32 networks nationwide that are intended to inventory and monitor natural resources within NPS units that have similar geography and contain “significant natural resources”. As such, in 2006 the GLKN began long-term monitoring of specific “vital signs” within network management units, drawing on the medical analogy that these metrics might indicate the health (i.e., biological integrity) of park ecosystems. Vital signs were chosen in part on the basis of their ability to represent the overall condition of park resources and the effects of both naturally-occurring and anthropogenic stressors (Route and Elias 2007). Amphibians constitute one of the vital signs chosen for initial monitoring by GLKN. Although amphibians are integral components of many diverse ecosystems (Gibbons et al. 2006), their populations are known or thought to be declining worldwide (Wake 1991; Houlahan et al. 2000; Lannoo 2005). The exact causes of documented declines are often unknown, but amphibians are susceptible to harm from a wide variety of environmental stressors (McCallum 2005; Boone et al. 2007; Davidson and Knapp 2007). For these and other reasons, amphibians have often been suggested for use as indicators of environmental health (Wake 1991; Welsh and Droege 2001; Bank et al. 2007). Several aspects of amphibian biology require long-term monitoring to elucidate true population trends. First, the detection probability for many organisms such as amphibians is often less than one (Bridges and Dorcas 2000; Kéry 2002; MacKenzie et al. 2002; Weir et al. 2005). Repeated visits to a site increase the probability that a given species will be detected, if it is in fact present. In addition, population dynamics of many amphibian species are characterized by relatively common extinction and colonization events (Skelly et al. 1999). Finally, recruitment and population size of some species of amphibian are known to vary widely over short time periods (Pechmann et al. 1991). While protected areas have correctly been championed as potential reservoirs of amphibian species diversity (Gibbons et al. 2006; Brander et al. 2007), such areas are not immune from environmental stressors and correlated population decline and extinction (Wake 1991; Davidson and Knapp 2007). Monitoring is thus necessary in areas both with and without legal protection. Frequent monitoring of amphibian populations in protected areas comes with a special set of problems however, as such areas may be subject to use limitations, logistical difficulties (i.e. travel to remote or isolated locations), or both. Research methods that minimize these problems while allowing for useful monitoring techniques are often necessary. In 2006 and 2007 the GLKN began pilot work surveying for amphibians within network management units. Here we describe our approach to establishing a network of sites for longterm monitoring of amphibians in an area that is managed as wilderness: North and South Manitou Islands, Sleeping Bear Dunes National Lakeshore. We also discuss which species are the most reliably identified and more-easily detected, and therefore hold the most promise for long-term monitoring.

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Methods Study Area The Manitou Islands are located in Eastern Lake Michigan and are the southernmost islands in an archipelago that stretches ca. 90 km from the Leelanau Peninsula in the south to the Straits of Mackinaw in the north. North and South Manitou Islands first appeared in glacial Lake Algonquin ca. 9000-10,000 calendar years before the present (hereafter, c.y.b.p.) and were connected to what is now the Lower Peninsula of Michigan during the Lake Chippewa stage (ca. 4000 to 8000 c.y.b.p.). The islands have been separated from the mainland since the Lake Nipissing stage (ca. 3000 to 4000 c.y.b.p.), during which time all but the highest areas were submerged. The water level then gradually fell to that of present-day Lake Michigan (Hatt et al. 1948; Dietrich 1978). North Manitou Island has a surface area of ca. 5286 ha while South Manitou Island is ca. 2037 ha in area (Hatt et al. 1948). Both islands are ca. 10 km from the Lower Peninsula of Michigan at the nearest point. Land-use history of both islands includes intensive logging and farming since at least the 1800s; however, the islands are now managed as wilderness by the National Park Service. Dominant plant communities on the islands are described in detail by Hazlett and Vande Kopple (1983). Identification of Survey Sites We used the Natural Resource Conservation Service’s (NRCS) SSURGO soil survey data (scale = 1:12,000; minimum map unit = 1 ha) to identify soil polygons that were either all hydric soils, or possessed at least some portion of the map-unit polygon as hydric soils (i.e., “partially hydric”). We used presence of hydric soils not only because NRCS soil surveys are broadly available across the entire Great Lakes ecoregion, but more importantly because hydric soils are one of three conditions used to identify wetlands in assessments in the U.S. (Janisch and Molstad 2004). Furthermore, whereas National Wetlands Inventory or similar wetlands maps may provide locations of where wetlands currently occupy the landscape (with a typical accuracy of approximately 55-70%; e.g., see Peterson et al. 2005), hydric soils provide a fundamental predictor of wetlands, independent of historic and recent land-use activities (such as agriculture) that may have altered the landscape (Janisch and Molstad 2004). Among that subset of map units, we focused our sampling in units for which either the primary or the secondary drainage classes were poorly drained (i.e., “somewhat poorly drained,” “poorly drained,” or “very poorly drained”). These map units were most commonly mucks, but occasionally were sands, loamy sands, or silty loams. This effort identified a total of 18 target map units on North Manitou Island and seven target map units (hereafter referred to as “target sites” or “sites”) on South Manitou Island. Field Methods During 2007, we visited each island once during each of three seasons that corresponded to peak activity of the various amphibian species. Because dates of transportation to, between, and from the islands were dictated by schedules of maintenance-crew activities, we had only ca. 24 hours in which to complete each sampling event. Our visits occurred during 25-27 April (Early Spring), 22-24 May (Late Spring), and 19-21 June (Summer) 2007. Within each target site, 2

surveying began by navigating with handheld GPS units (Garmin GPS V or Garmin GPSMAP 76CSx unit) and a printed map of the island to the centroid of the polygon. Once there, search strategy was a function of topography, wetness of the area, and shape of the site. If standing water was present or if it appeared that standing water might be present at other times of year (i.e., in the case of ephemeral wetlands), a call survey and a perimeter search were conducted. Call surveys consisted of standing in an open location on the periphery of the site and listening for calling anurans. Most call surveys were ten minutes in duration (i.e., two successive 5-minute surveys) and were performed during daylight hours, but otherwise followed Weir and Mossman (2005). We noted the species calling, if any, and the maximum calling index value (Weir and Mossman 2005) for each species. We also recorded the ambient temperature, barometric pressure, relative humidity, and average wind speed during call surveys with Kestrel® 3500 weather meters (Nielsen-Kellerman Co., Boothwyn, PA). Perimeter surveys consisted of walking along the land-water interface of the site or, alternatively, along the edge of the wetland basin if it was clearly defined. Perimeter surveys were terminated after 20 minutes or when the site had been circumnavigated, whichever came first. We scrutinized the land/water interface for adult amphibians, larvae, and egg masses, and also looked under logs and other potential cover objects adjacent to the wetland. We recorded the species observed and the abundance of each species.

Results We visited 14 of 18 target sites on North Manitou Island during 2007. Four sites were considered marginal before ground-truthing because either the primary or secondary drainage class consisted of somewhat excessively drained soils. We were unable to visit two of these sites (NMan 32 and NMan 58); the other (NMan 75) was a wetland that held water until at least late May. The majority of the target sites contained very poorly drained soils in both the primary and secondary drainage class (10 out of 18 sites), and these sites ranged from areas with hydric soils but no standing water, to ephemeral wetlands, to a lake (Table 1). On South Manitou Island, soil information revealed few areas with poorly drained soils in both drainage classes (only two of seven identified sites). We visited each of the seven target sites from one to three times during 2007. Both of the sites with poorly drained soils in both the primary and secondary drainage class (SMan 7 and SMan 12) were suitable for aquatic breeding in at least one season. Two sites had poorly drained soils as either the primary or secondary classification, and one of these was potentially suitable for aquatic breeding in at least one season (SMan 15). Three sites had somewhat poorly drained soils as the primary or secondary classification, and ground-truthing visits indicated that none of these sites were suitable for aquatic-breeding amphibians (Table 2). Call surveys were performed more often during the day (vs. during the night) on North Manitou Island than on South Manitou Island, in part because the larger area and more rugged terrain of North Manitou Island made night travel difficult. Amphibians were heard calling at two sites and across all three seasons on North Manitou Island and at three sites across all three seasons on South Manitou Island. The Spring Peeper (Pseudacris crucifer) was the most commonly detected 3

species during call surveys in 2007 and was the only anuran heard calling on South Manitou (Table 3; Table 4). Perimeter surveys and call surveys detected four and two species respectively. Perimeter surveys performed on North Manitou Island during the summer season detected no amphibians; no perimeter surveys were performed during this season on South Manitou Island. Across all seasons, the same four species (Bufo americanus, Pseudacris crucifer, Ambystoma maculatum, and Plethodon cinereus) were detected on each island, and all life stages (i.e., egg, larva, adult) were encountered. Salamander species were more commonly detected than were anuran species (Table 5; Table 6).

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Table 1. Description of sites surveyed for amphibians on North Manitou Island (Sleeping Bear Dunes National Lakeshore, Michigan, USA) in 2007. All UTM coordinates are in zone 16, map datum NAD83. Site Soil Description a UTM coordinates Seasons in Which Site Description Name Sampled b NMan 37 VPD 4994093N 575497E ES, LS, Su Deciduous Swamp NMan 42 VPD 4994533N 575625E ES, LS, Su Lake/Stream NMan 46 VPD 4995753N 577646E ES Cedar Swamp NMan 49 VPD 4995970N 576966E ES Cedar Swamp NMan 50 VPD 4995934N 574183E LS, Su Open Ephemeral NMan 56 VPD 4996626N 576024E LS Cedar Swamp NMan 59 VPD 4996562N 576944E ES, LS Deciduous Swamp NMan 60 VPD 4997085N 576228E LS Wooded Ephemeral NMan 64 VPD 4997638N 576439E LS Wooded Ephemeral NMan 74 VPD 4998787N 577033E LS Deciduous Forest NMan 53 PD 4996018N 574267E LS, Su Deciduous Swamp NMan 28 SPD 4992164N 578447E ES Seep NMan 34 SPD 4993723N 575743E ES, LS Deciduous Forest NMan 78 SPD 4999989N 578586E Not Visited NMan 32 SED/SPD 4993274N 576133E Not Visited NMan 38 SED/SPD 4993969N 575450 E Not Visited NMan 58 SED/SPD 4996747N 575468E Not Visited NMan 75 SED/SPD 4998925N 578028E ES, LS Open Marsh a SPD = somewhat poorly drained, PD = poorly drained, VPD = very poorly drained, SED = somewhat excessively drained b ES = Early Spring, LS = Late Spring, Su = Summer

Table 2. Description of sites surveyed for amphibians on South Manitou Island (Sleeping Bear Dunes National Lakeshore, Michigan, USA) in 2007. All UTM coordinates are in zone 16, map datum NAD83. Site Name Soil Description a

Seasons in Which Site Description Sampled b SMan 12 VPD 4985339N 569636E ES, LS Open Ephemeral SMan 7 SPD 4983972N 569190E ES, LS, Su Lakeshore SMan 15 ED/PD 4985072N 569474E ES, LS Open Ephemeral SMan 18 ED/PD 4985098N 570483E ES, LS Ridge/Swale SMan 2 SED/SPD 4983578N 568895E ES, LS Deciduous Forest SMan 5 SED/SPD 4984119N 567702E LS Ridge/Swale SMan 6 SED/SPD 4984256N 567465E ES Deciduous Forest a SPD = somewhat poorly drained, VPD = very poorly drained, SED = somewhat excessively drained, PD = poorly drained, ED = excessively drained b

UTM coordinates

ES = Early Spring, LS = Late Spring, Su = Summer

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Table 3. Results of amphibian call surveys for sites surveyed on North Manitou Island (Sleeping Bear Dunes National Lakeshore, Michigan, USA) in 2007. Site Name Time of Survey NMan 37 NMan 42

Day Day

Season a

Species b

Su LS

None Pc Ba None Pc None None None None None None Pc Pc

Maximum Call Index c 0 1 1 0 3 0 0 0 0 0 0 1 3

Day Su Night Su NMan 50 Day LS Day Su Night Su NMan 56 Day LS NMan 59 Day ES Day LS NMan 75 Day LS Night ES a ES = Early Spring, LS = Late Spring, Su = Summer b Pc = Pseudacris crucifer, Ba = Bufo americanus c After Weir and Mossman (2005); Zero indicates no species were detected

Table 4. Results of amphibian call surveys for sites surveyed on South Manitou Island (Sleeping Bear Dunes National Lakeshore, Michigan, USA) in 2007. Site Name Type of Survey

Season a

Species

SMan 2 SMan 7

b

Maximum Call Index c 0 0 1 1 0 3 0 3 0 0

Day ES None Night ES None Day LS Pc Night Su Pc SMan 12 Day ES None Night ES Pc SMan 15 Day ES None Night ES Pc SMan 18 Day ES None Night Su None a ES = Early Spring, LS = Late Spring, Su = Summer b Pc = Pseudacris crucifer c After Weir and Mossman (2005); Zero indicates no species were detected

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Table 5. Results of perimeter surveys for sites surveyed for amphibians on North Manitou Island (Sleeping Bear Dunes National Lakeshore, Michigan, USA) in 2007. Species b Life Stage Abundance None None None None NMan42 Egg masses 14 Am Adult Unknown Pc Unidentified Egg masses 12 LS Adult 1 Pc Adult 1 Ba Su None NMan 46 ES Egg masses 8 Am NMan 49 ES Egg masses 12 Am NMan 50 LS None Su None NMan 56 LS None NMan 59 ES None LS None NMan 75 ES Adult 3 Plc LS Unidentified Larva 1 a ES = Early Spring, LS = Late Spring, Su = Summer b Pc = Pseudacris crucifer, Ba = Bufo americanus, Am = Ambystoma maculatum, Plc = Plethodon cinereus Site Name NMan 28 NMan 34 NMan 37

Season a ES ES ES Su ES

Table 6. Results of perimeter surveys at sites surveyed for amphibians on South Manitou Island (Sleeping Bear Dunes National Lakeshore, Michigan, USA) in 2007. Species b Life Stage Abundance Adult 3 Plc None None Egg Masses 10 Am Adult Unknown Pc LS Adult 1 Pc Adult 1 Ba Unidentified Adult 2 SMan 12 ES Adult 3 Plc SMan 15 ES Unidentified Egg Masses Unknown SMan 18 ES Adult 3 Plc a ES = Early Spring, LS = Late Spring, Su = Summer b Pc = Pseudacris crucifer, Ba = Bufo americanus, Am = Ambystoma maculatum, Plc = Plethodon cinereus; the two unidentified adults were decomposed anurans. Site Name SMan 2 SMan 5 SMan 6 SMan 7

Season a ES LS ES ES

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Discussion and Recommendations Previous Surveys The vertebrate fauna of the islands of Eastern Lake Michigan have attracted scientific attention for over 150 years (Strang 1855). The first attempt at a comprehensive survey was made in the 1930s (Hatt et al. 1948), and surveys on North and South Manitou Islands were conducted as recently as the 1980s (Scharf 1973; Scharf and Jorae 1980; Case and Scharf 1985; Linton et al. 1988). There are currently 7 amphibian species documented from North Manitou Island and 6 species from South Manitou Island. It is not known whether additional species remain to be discovered, nor whether some previously documented species have persisted to the present (Bowen and Gillingham 2004). In addition to species found here, previous surveys (see references in previous paragraph) found Bullfrogs (Rana catesbeiana), Green Frogs (Rana clamitans) and Wood Frogs (Rana sylvatica) on North Manitou Island and Red-spotted Newts (Notophthalmus viridescens) and Leopard Frogs (Rana pipiens) on South Manitou Island. Although we visited the islands during periods designed to increase the detection probability of anuran species, at this time we cannot state with confidence that any of the above species are no longer present on the islands. We also cannot state that there are no more “new” species yet to be detected on the islands. More surveys will be necessary, particularly night-time call surveys for anurans, before a definitive species list can be completed for either island (see Kéry 2002). Utility of Site-Selection and Survey Methods Selecting sites based on soil classification allowed us to quickly narrow down the list of potential survey sites, and identified sites that would not have been readily apparent based on existing maps and aerial photographs. Sites with very poorly drained soils generally yielded the best potential breeding habitat for aquatic amphibians, in that these sites more often held standing water during at least part of the year. We recommend that these types of sites receive the primary focus in future studies that use this method. Where feasible however, sites with “drier” soils (i.e. somewhat poorly drained, poorly drained, or with excessively drained soils as part of the soil classification) should also be evaluated because such sites can contain suitable breeding habitat. Most previous surveys for breeding amphibians have involved night-time call surveys (Mossman et al. 1998; Johnson and Batie 2001, Weir et al. 2005). While this type of survey is well-suited to detecting the vocalizations of adult anurans, it has a number of disadvantages. First, night surveys rarely provide reliable estimates of population size or actual reproductive activity (Nelson and Graves 2004; Stevens and Paszkowski 2004). In addition, night-time call surveys exclude non-vocal species such as salamanders, which require different survey methods (for example see Heyer et al. 1994 or Crawford and Semlitsch 2007) for their detection. Finally, as evidenced by this study, night surveys can be difficult to perform in locations without roads or trails. In backcountry situations, off-trail night-time surveys incur greater hazards (e.g., plant defenses such as spines, topographic hazards such as steep drop-offs, unstable footing as in swamps or mucks or rocky areas), and are recommended only with great familiarity of the area. We therefore agree with Fellers and Kleeman (2006) that both nocturnal and diurnal surveys are important if the objective is to maximize detections, and we advocate the use of multiple survey 8

types when searching for amphibians (see Casper 2004). The perimeter surveys used in this study are advantageous in that they require little manpower, few pieces of equipment, and can be completed quickly. Furthermore, while night-time call surveys are more likely to successfully detect amphibians than are daytime call surveys, daytime call surveys do yield detections. We advocate the use of day call and perimeter surveys in locations such as the Manitou Islands where night call surveys are potentially dangerous. Future Surveys Based on species detections and apparent quality of habitat, continued monitoring is warranted at the following sites on North Manitou Island: NMan 28, NMan 42, NMan 50, and NMan 75. Potential alternative sites are NMan 46/49 and NMan 59. We recommend further monitoring at SMan 7, SMan 12, and SMan 15 on South Manitou Island. SMan 2 and SMan 18 may be suitable sites for monitoring terrestrial salamanders. It is important to note that our site descriptions (Table 1; Table 2) are cursory. While we have selected those sites that we believe hold the most promise, other sites should be periodically re-evaluated as time and resources allow. Few species were detected during the Summer season on either island, suggesting that time and resources should be concentrated on surveying during the Early Spring and Late Spring seasons. However, we recommend that surveys be conducted during the summer season, even if only on an irregular basis. The summer season is the best time to detect species such as Bullfrogs and Green Frogs (Harding 1997), which may or may not be present on the islands. Spring Peepers were the most commonly and easily detected aquatic-breeding species during call surveys, which is in agreement with the results of some previous studies (Mossman et al. 1998; Weir et al. 2005). The large, distinctive egg masses of Spotted Salamanders (Ambystoma maculatum) were also easily detected during perimeter surveys. Both species tend to breed in early spring (Harding 1997), further suggesting an emphasis on Early Spring and Late Spring sampling. Red-backed Salamanders (Plethodon cinereus) were the only terrestrial species encountered. This species is a strong candidate for long-term terrestrial monitoring on the islands (Welsh and Droege 2001).

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Weir, L. A., and M. J. Mossman. 2005. North American Amphibian Monitoring Program (NAAMP). Pages 307-313 in M. J. Lannoo, editor. Amphibian declines: the conservation of United States species. University of California Press, Berkeley. Weir, L. A., J. A. Royle, P. Nanjappa, and R. E. Jung. 2005. Modeling anuran detection and site occupancy on North American Amphibian Monitoring Program (NAAMP) routes in Maryland. Journal of Herpetology 39:627-639. Welsh, H. H., and S. Droege. 2001. A case for using plethodontid salamanders for monitoring biodiversity and ecosystem integrity of North American forests. Conservation Biology 15:558-569.

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