Historic and current amphibian and reptile distributions in the island region of western Lake Erie.
The island region of western Lake Erie includes taxa and biological communities not found elsewhere and thus makes a unique contribution to the biota of Ohio and Ontario (Clapp, 1916; Conant and Clay, 1937; Boerner, 1984; Downhower, 1988; Catling and Brownell, 1995). The region is underlain by limestone and dolomite which resisted glaciation (Calkin and Feenstra, 1985), resulting in a series of islands that range from 0.5 - 4261 ha, [less than]2-21 m above mean lake level, and 0.3-22.4 km from the nearest mainland point. The biota of the island region has a long history of investigation (Downhower, 1988; Bolsenga and Herdendorf, 1993) and as a consequence, the distribution of amphibians and reptiles (and other taxa) is known in considerable detail. The Ohio State University's F. T. Stone Laboratory on Gibraltar and South Bass islands has provided a base for biological research since 1895 and early herpetological work in the region includes that of Roger Conant (Conant, 1982) and Charles Walker (staff member and herpetology instructor at the F. T. Stone Laboratory 1938-1947; Langlois, 1949). Since European settlement in the early 1800s, islands and adjacent mainland areas have been much modified by human activity (wetland drainage, quarrying, grazing, crop production, recreation; Kaatz, 1955; Hatcher, 1971) and a variety of organisms have undergone changes in distribution and abundance as a consequence (Duncan and Stuckey, 1970; Weseloh et al., 1988). Our purpose was to document historic and current distributions of amphibians and reptiles in the island region of western Lake Erie, to draw attention to population declines and extirpations that have occurred on some islands, and to provide baseline data for monitoring future changes in distribution. In addition, we review four unusual components of the island region's amphibian and reptile fauna. Finally, we consider distribution patterns in a biogeographical context.
We compiled amphibian and reptile records for mainland Ontario (Essex County exclusive of the islands), mainland Ohio (Erie and Ottawa counties exclusive of the islands) and 19 Lake Erie islands [ILLUSTRATION FOR FIGURE 1 OMITTED]. Three small unvegetated islands (Big Chicken, Little Chicken and Chick islands) for which we know of no amphibian or reptile records were excluded. All of the islands included lie in the western basin of Lake Erie except Johnsons Island which is located in Sandusky Bay and is separated from the other islands by the Catawba/Marblehead peninsula. Island areas and perimeters were determined from lake charts and topographic maps using a digitizing pad and SigmaScan software (Jandel Scientific). Distances between islands and the nearest mainland point were determined from NOAA chart #14830. [Island areas reported here differ only slightly from those reported in King (1987, 1988b) except for Johnsons Island for which the value reported previously was in error.]
Amphibian and reptile records came from a data base compiled by M.J. Oldham and W. F. Weller for the Ontario Herpetofaunal Summary (OHS), a data base compiled by D. Wynn for the Ohio Department of Natural Resources (ODNR) and a data base compiled by R. B. King (RBK) for this study. The OHS data base consists of amphibian and reptile records for the province of Ontario obtained from museums (see Appendix 1 for museums included), publications, field journals and field volunteers (Weller and Oldham, 1988; Oldham, 1990; Oldham and Weller, 1992). Records for Essex County, which includes the Ontario islands and adjacent mainland, were extracted for this study (3984 records). The ODNR data base consists of museum records of amphibian and reptiles collected in Ohio since 1950 (see Appendix 1 for museums included; older museum records are summarized in Conant, 1938, 1951; Walker, 1946; and Pfingsten and Downs, 1989). Records for Erie and Ottawa counties, which include the Ohio islands and adjacent mainland, were extracted for this study (675 records). The data base compiled by RBK consists of amphibian and reptile records for Essex County, Ontario and Erie and Ottawa counties, Ohio based on observations and specimens collected during field work from 1979-1996, communication with biologists working in the region, and museum and literature records (2874 records; see Appendix 1 for museums included, Appendix 2 for published sources, and Appendix 3 for voucher specimens). These databases were used to compile lists of amphibian and reptile species for the Ontario mainland (Essex County exclusive of the islands), the Ohio mainland (Erie and Ottawa counties exclusive of the islands), and each of the islands and to determine in what years a given species could be documented, from each island or mainland area. Requests for information contained in the OHS database should be addressed to MJO; in the ODNR database to Ohio Department of Natural Resources, Division of Wildlife, Fountain Square, Columbus, Ohio, 43224; and in the RBK database to RBK. Our use of common names follows Collins (1990).
RESULTS AND DISCUSSION
Fifty species of amphibians and reptiles (12 salamanders, 11 frogs and toads, one lizard, eight turtles, 18 snakes) were documented from island and mainland areas included in this study (Table 1). Thirty-five species (eight salamanders, eight frogs and toads, seven turtles, 12 snakes) were recorded on at least one island (Table 1). Number of species per island ranged from one to 24 and number of islands on which a given species occurred ranged from one to 19.
Our earliest record was a 1793 report of "rattlesnakes" on Middle Bass Island (McDermott, 1947), although the true identity of these snakes is uncertain (see "Questionable Records"). Our earliest records based on specimens were an eastern hognose snake (Heterodon platirhinos) collected in Erie County, Ohio, in 1886 (OSUZM833) and a Lake Erie water snake (Nerodia s. insularum) collected on South Bass Island in 1893 (USNM40068). All but three species (Ambystoma laterale, A. texanum, Storeria occipitomaculata) were recorded from the region by 1950. However, records for individual islands have continued to accumulate (Table 1).
Records of uncertain validity were enclosed in parentheses and denoted with a question mark in Table 1 and are explained more fully below.
Coluber constrictor. - Records of racers on West Sister Island (C. B. Stein, 1974, unpubl. rep. to the U.S. Department of the Interior; D. Alexander, 1975, unpubl. student paper on file at the F. T. Stone Laboratory) are not supported by specimens, photos or additional observations. Racers have been collected or observed on several other islands (Table 1) although none are close to West Sister Island.
Crotalus horridus. - Records of timber rattlesnakes on Pelee, Middle Bass, Rattlesnake and Mouse islands (McDermott, 1947; Langlois, 1964; C. A. Campbell, 1971, unpubl. rep. to the Ontario Department of Lands and Forests; 1976, unpubl. rep. to the Ontario Ministry of Natural Resources Division of Parks) are apparently not based on specimens or direct observation, nor are we aware of other records from these sites. Specimens of timber rattlesnakes are known from South Bass Island and the Catawba/Marblehead peninsula of the Ohio mainland.
Diadophis punctatus. - A record of a ringneck snake on Pelee Island (D. Alexander, 1975, unpubl. student paper on file at the F. T. Stone Laboratory) is not supported by specimens or additional observations. Ringneck snakes have been collected regularly on South Bass Island and a single individual was captured, photographed and released on Middle Bass Island (King, 1987, 1988b).
Elaphe vulpina. - A record of fox snakes on Sugar Island (Mr. Keny, pers. comm. to RBK) is not supported by specimens or additional observations but fox snakes are common on nearby Middle Bass Island and are proficient swimmers (Conant, 1951).
Lampropeltis triangulum. - Records of milksnakes on Pelee and East Sister island (Jones, 1912; D. Alexander, 1975, unpubl. student paper on file at the F. T. Stone Laboratory) are not supported by specimens or additional observations nor have milksnakes been reported from any other islands.
Sistrurus catenatus. - Records of massasaugas on Pelee Island (C. A. Campbell, 1971, unpubl. rep. to the Ontario Department of Lands and Forests; 1976, unpubl. rep. to the Ontario Ministry of Natural Resources Division of Parks) are apparently not based on specimens or direct observations nor have massasaugas been reported from other islands.
Thamnophis sirtalis. - A record of "black snakes" on North Harbor Island (Jones, 1902) may refer to melanistic garter snakes (see "Unusual Components of the Island Region's amphibian and reptile fauna"). This record is not supported by specimens or additional observations but garter snakes are common on nearby East Sister Island.
Ambystomatid salamanders. - Because of changes in taxonomy and the occurrence of hybridization (Uzzell, 1964; Oldham, 1984a), we have listed records of Ambystoma jeffersonianum, A. laterale and A. texanum not based on morphometrics, karyology, serology or molecular genetics together with records of known hybrids (including the Kelleys Island salamander, A. nothagenes; Kraus, 1985a) as "Hybrid and unidentified Ambystoma" in Table 1. Records of A. laterale and A. texanum that are based on morphometrics, karyology, serology or molecular genetics and records of A. maculatum, A. opacum and A. tigrinum are listed separately.
Records known to be based on misidentification were excluded. Records of Kirtland's snake (Clonophis kirtlandii, Langlois, 1964) and red-bellied water snake (Nerodia erythrogaster fasciata; Morse, 1904; Jones, 1912) represent misidentified Lake Erie water snakes (N. sipedon insularum; Conant, 1934; Conant and Clay, 1937). A record of a smooth green snake (Opheodrys vernalis) from South Bass Island appears in the card catalog of the Royal Ontario Museum (ROM5799). However, this card is marked "Delete and Destroyed - Discarded" and along with other cards similarly annotated, apparently refers to a discarded specimen for which reliable identification was not possible (R. MacCulloch, pers. comm.).
INTRODUCTIONS AND COLONIZATIONS
Distributions of several amphibian and reptile species may have changed over the period for which we have records due to natural or human-assisted introductions and colonizations.
Rana catesbeiana. - Langlois (1964) reports releasing bullfrog tadpoles into a pond on Middle Bass Island in 1932, but suggests that this species may have been present before that date. A record of bullfrogs on Pelee Island in 1910 (Jones, 1912) supports this suggestion. Thus, it is unclear whether bullfrog records for some islands represent natural populations, descendants of introduced individuals or both.
Terrapene carolina. - Eastern box turtle records for the Ontario mainland and Pelee Island are thought to represent escaped or released pets, although the possibility that a native population exists at these sites cannot be ruled out (Cook, 1984; Oldham, 1984b).
Diadophis punctatus. - A single record of a ringneck snake on Middle Bass Island may represent a recent colonization event (King, 1987, 1988b). Ringneck snakes are present on nearby South Bass Island (Langlois, 1953, 1964) and the adjacent Catawba/Marblehead peninsula of the Ohio mainland (Conant, 1938).
Regina septemvittata. - Queen snakes are known from Kelleys Island only since 1980 and may have recently colonized the island, presumably from the Ohio mainland (King, 1987, 1988b). Queen snakes were not recorded from Essex County, Ontario, until 1985 (Oldham, 1986) but records for Erie and Ottawa counties, Ohio, date from 1908 (Table 1).
Two additional lines of evidence attest to the colonization ability of some amphibians and reptiles found on the Lake Erie Islands. First, high rates of gene flow occur among island and mainland populations of water snakes (Nerodia sipedon) and garter snakes (Thamnophis sirtalis) (King and Lawson, 1995; Lawson and King, 1996). Second, some species found on the Lake Erie islands (Ambystoma jeffersonianum, Plethodon cinereus, Bufo americanus, Hyla versicolor, Pseudacris crucifer, Chrysemys picta, Elaphe vulpina, Nerodia sipedon, Thamnophis sirtalis) have colonized islands in the upper Great Lakes that were formerly inundated by high water levels (King, 1988b).
WAIFS AND TRANSIENTS
Amphibians and reptiles represented by a single observation or specimen from a given island may represent waif or transient individuals rather than representatives of resident breeding populations. This is especially likely for pond-breeding amphibians and for turtles on islands lacking inland aquatic habitats (Acris crepitans on Gibraltar Island, Bufo americanus [TABULAR DATA FOR TABLE 1 OMITTED] on Middle and Sugar islands; B. woodhousii on Gibraltar Island; Rana catesbeiana on Middle, Rattlesnake, East Sister, Green and Gibraltar islands; R. clamitans on Middle Island; R. pipiens on West Sister Island; Apalone spinifera on Gibraltar Island; Chelydra serpentina on East Sister and Middle islands; Emydoidea blandingii on Green Island; Graptemys geographica on Gibraltar Island).
POPULATION DECLINES AND LOCAL EXTIRPATIONS
Population declines and local extirpations have affected a number of amphibian and reptile species in the Lake Erie area (e.g., Ehrlich and Camin, 1960; Conant and Clay, 1963; Conant, 1982; Kraus and Schuett, 1982). Some declines have been the intentional result of human activities (extermination of snakes by pigs and humans, Ehrlich and Camin, 1960; Hatcher, 1971; Conant, 1982). Others may be a secondary result of human activities (e.g., habitat modification) or natural processes.
Pond-breeding amphibians. - Recent records (post-1960) are lacking for some pond-breeding amphibians on islands from which they were previously recorded (e.g., ambystomatid salamanders from South Bass and North Bass islands, Notophthalmus viridescens from Kelleys and South Bass islands, Acris crepitans from Kelleys and North Bass islands, Pseudacris crucifer from Pelee Island, Rana pipiens from South Bass, Middle Bass and North Bass islands). Although some species may have been overlooked during recent field work, degradation and loss of breeding habitat (inland ponds) may have resulted in extirpation of pond-breeding amphibians at some sites (Downs, 1978; King, 1993a). Population declines of A. crepitans on Pelee Island and the Ontario mainland have led to provincial protection in Ontario (Oldham, 1992).
Necturus maculosus. - Mudpuppies are encountered infrequently in waters of the island region (e.g., by ice anglers or as prey of water snakes, Oldham, 1988; King, 1993a). Apparent decreases in Lake Erie mudpuppy populations are reported by Pfingsten and Downs (1989).
Graptemys geographica. - Common map turtles once were abundant at Terwilliger's Pond adjacent to the F. T. Stone Laboratory on South Bass Island (Langlois, 1964), but none have been recorded on that island since 1968. Common map turtles persist in small numbers on Pelee and Johnsons islands and on the Ohio and Ontario mainland.
Coluber constrictor. - Racers are found on several of the larger islands (Table 1) but because Pelee Island is the only Ontario location where racers persist, this species has been given provincial protection (McKeating and Bowman, 1977).
Crotalus horridus. - Timber rattlesnakes found on South Bass Island and the Catawba/Marblehead peninsula of mainland Ohio were often killed (Langlois, 1951, 1964) and no records more recent than 1961 are known. Timber rattlesnakes appear to have been extirpated from the island region although fox snakes (Elaphe vulpina) are sometimes mistakenly identified as rattlesnakes by island residents and visitors. Because the region is well isolated from other timber rattlesnake populations (e.g., in southern Ohio and western Pennsylvania; Conant and Collins, 1991), natural recolonization of the island region by this species is unlikely.
Heterodon platirhinos. - Eastern hognose snakes continue to be recorded on Kelleys Island. However, records from South Bass and Pelee islands date from the 1920s and 1930s (Table 1) and it seems unlikely that hognose snakes persist at these sites.
Nerodia sipedon. - Water snakes are the most widely distributed species included in this study; specimens have been collected from each of the 19 islands (Table 1). However, no water snakes were found during repeated searches on West Sister and Green islands and shorter searches on Middle Sister and North Harbour islands by RBK, MJO and coworkers during the 1980s and 1990s, suggesting that this species has been extirpated on these islands. Declines in water snake numbers have occurred on those islands where populations persist (King, 1986), resulting in provincial protection on Canadian islands and proposed federal protection on U.S. islands (McKeating and Bowman, 1977; Eldridge and Winsor, 1993). Water snakes persist on Rattlesnake and Middle islands despite past eradication efforts (Conant, 1982; Ehrlich and Camin, 1960); either these efforts were not completely successful or water snakes recolonized these islands. We are unaware of recent field work on Mouse or Starve islands and the current status of water snakes (and other amphibians and reptiles) on these islands is unknown.
UNUSUAL COMPONENTS OF THE ISLAND REGION'S AMPHIBIAN AND REPTILE FAUNA
Ambystomatid salamanders. - Ambystomatid salamanders from the island region exhibit unusual patterns of polyploidy, hybridization and unisexual reproduction (Downs, 1978; Bogart et al., 1985; Kraus, 1985a, 1985b, 1989; Bogart and Licht, 1986; Bogart et al., 1987; Bogart, 1989; Licht, 1989; Lowcock, 1989; Hedges et al., 1992). On Pelee Island, A. laterale and A. texanum occur together with unisexual diploid, triploid and tetraploid hybrids conmining genomes from A. laterale and A. texanum; on Kelleys Island, A. texanum and A. tigrinum occur together with unisexual diploid, triploid and tetraploid hybrids containing genomes from A. laterale, A. texanum and A. tigrinum; on Middle Bass Island, A. texanum occurs together with unisexual diploid and triploid hybrids containing genomes from A. laterale and A. texanum; and on North Bass Island, unisexual diploid and triploid hybrids containing genomes from A. laterale and A. texanum occur. Interestingly, there are no verifiable records of one or more parental species from some islands with hybrid populations (A. laterale apparently is absent from Kelleys, Middle Bass and North Bass islands; A. texanum apparently is absent from North Bass Island), warranting further work on these islands. Unfortunately, it is uncertain whether ambystomatid populations persist on North Bass Island; no records since 1972 are known to us. Colonization events and changes in distribution are thought to have been particularly important in promoting interspecific hybridization in ambystomatid salamanders (Lowcock, 1989).
Plethodon cinereus. - The redback salamander occurs as a striped redback morph and a stripeless leadback morph (Conant and Collins, 1991). Morph frequencies vary geographically, perhaps due to an association between color morph and physiology (Lotter and Scott, 1977; Moreno, 1989). Although P. cinereus is locally abundant on South Bass island, redback morphs are exceedingly rare (0 of 144 salamanders, Pfingsten and Walker, 1978; 1 of 132 salamanders, Reichenbach, 1981; 0 of 100 salamanders, RBK, pers. observ.). Recently discovered populations on Rattlesnake and Middle Sister islands also consist of leadback morphs (Rattlesnake Island: n = 5, RBK, pers. observ.; Middle Sister Island: n = 5, Oldham, 1996). Redback morphs are more common in nearby Ohio mainland populations (7-80%, n = 22-230, Pfingsten and Walker, 1978) and it is unknown whether differences in morph frequency between island and mainland populations are the result of natural selection imposed by climatic differences or stochastic processes resulting from isolation.
Nerodia sipedon. - Reduction in color pattern among island water snakes relative to mainland populations has led to designation of island populations as N. s. insularum, distinct from mainland N. s. sipedon (Conant and Clay, 1937; 1963). Color pattern variation is genetically based and island-mainland differences appear to represent a balance between natural selection favoring a reduced pattern along rocky island shorelines and gene flow from populations inhabiting mainland marshes where patterned morphs are favored (King, 1993b, 1993c; King and Lawson, 1995).
Thamnophis sirtalis. - Populations of garter snakes in the Lake Erie area include high frequencies (up to ca. 50%) of jet-black melanistic individuals (King, 1988a; Lawson and King, 1996). Melanistic morphs have an apparent thermoregulatory advantage in cool, lakeshore habitats but may suffer higher predation than typical striped morphs (Gibson and Falls, 1979, 1988). Geographic variation in the relative advantage of striped vs. melanistic color pattern together with gene flow among populations may be responsible for variation in morph frequency among sites in the Lake Erie area (Lawson and King, 1996).
Most of the amphibians and reptiles found in the island region as defined here are found in other lakeshore counties of Ohio, Michigan and Ontario (Conant, 1938, 1951; Walker, 1946; Kraus and Schuett, 1982; Weller and Oldham, 1988; Holman et al., 1989; Pfingsten and Downs, 1989; Harding and Holman, 1990, 1992). However, two species recorded from mainland Essex County, Ontario, were lacking from mainland Erie and Ottawa counties in Ohio. Ambystoma laterale has been recorded in nearby Lucas County, Ohio (Kraus, 1985b; Pfingsten and Downs, 1989), but Storeria occipitomaculata is absent from all Ohio counties bordering Lake Erie (Conant, 1951). Twelve species recorded from mainland Erie and Ottawa counties, Ohio, were lacking from mainland Essex County, Ontario. Of these, Desmognathus fuscus, Eurycea bislineata, Plethodon glutinosus, P. richmondi, A. opacum, A. texanum, Clonophis kirtlandii are distributed mostly S or E of the area included here (Conant and Collins, 1991) and their absence from Essex County is not surprising. Notophthalmus viridescens, Rana palustris, R. sylvatica and Diadophis punctatus are found in neighboring Kent County, Ontario, and in lakeshore counties in Michigan (Weller and Oldham, 1988; Harding and Holman, 1992; Holman et al., 1989) and their absence from mainland Essex County is unexplained. The worm snake, Carphophis amoneus, is unusual in that it has been recorded from a single locality in Erie County (a marl prairie N of Castalia, Ohio) that is isolated by more than 150 km from other known worm snake localities in the southern third of Ohio (Conant, 1951). Six specimens were collected from the Erie County site by C. F. Walker in 1941 and 1942 (F. T. Stone Laboratory herpetological collection #775, 795, 922-924) and by N. B. Green in 1945 (UMMZ 95933) but the current status of this population is unknown.
On a larger scale, species found in the island region exhibit a variety of biogeographic patterns. Some species are distributed nearly continuously across much of eastern North America (e.g., Chelydra serpentina, Chrysemys picta, Nerodia sipedon, Thamnophis sirtalis), whereas others have restricted ranges centered near the southern Great Lakes (e.g., Clonophis kirtlandii, Elaphe vulpina, Thamnophis butleri) (Conant and Collins, 1991). The extension of prairie habitat (the 'prarie peninsula') into western Ohio may explain the presence in the Lake Erie area of some species with more western distributions (e.g., Ambystoma texanum, A. tigrinum, Acris crepitans) as well as gaps SW of Lake Erie in the distribution of other species (e.g., Notophthalmus viridescens, Storeria occipitomaculata, Diadophis punctatus).
Except for snakes, most species of amphibians and reptiles were restricted to the five largest islands (Table 1). Exceptions include apparent waifs and transients noted earlier; Plethodon cinereus, the single terrestrially breeding salamander found on the islands; and Necturus maculosus, which is a lake (rather than island) resident. Among snakes, four species stand out as being widely distributed on islands of all sizes: Elaphe vulpina, Nerodia sipedon, Storeria dekayi and Thamnophis sirtalis.
On islands, number of species is according to Island Biogeography Theory often positively correlated with island area and negatively correlated with distance to the mainland. Such a pattern is expected when species numbers result from an equilibrium between colonization and extinction: extinction rates should decrease with increasing population size, and [TABULAR DATA FOR TABLE 2 OMITTED] hence island area, and colonization rates should decrease with increasing distance from source populations (MacArthur and Wilson, 1967). However, other factors (habitat diversity, island age) may also be important determinants of species number. A previous analysis of reptiles on nine Lake Erie islands showed a positive relationship between species number and island area but no relationship between species number and distance to the mainland (King, 1987, 1988b). Extending this analysis to include additional islands and taxa corroborates this result: species number is significantly positively correlated with island area but uncorrelated with distance to the nearest mainland point regardless of whether all amphibian and reptile records are included or only recent (1980 or later) records are included (Table 2). Because different taxa (e.g., salamanders, frogs, turtles, snakes) may exhibit different species-area and species-distance relationships, we also analyzed each taxon separately. For all four taxa, species number was significantly positively correlated with island area (Table 2). For frogs, turtles and snakes, species number was not correlated with distance to the mainland, whereas for salamanders there was a significant negative correlation between species number and distance to mainland (Table 2).
On land-bridge islands, a positive correlation between species number and island area but no correlation between species number and distance to the mainland can occur when insufficient time has elapsed for species numbers to decline to a extinction-colonization equilibrium (Wilcox, 1978; Case, 1983). This may be the case for islands in Lake Erie which have been isolated from the mainland for only about 4000 yr (Calkin and Feenstra, 1985). However, there may be other reasons why the number of amphibian and reptile species on the Lake Erie islands is uncorrelated with distance to the mainland. Some islands are close to other islands that could serve as sources of colonists, masking any species-distance relationship based on island-mainland distances. For example, Gibraltar Island, which has nine species of amphibians and reptiles compared to just four or fewer species on other similarly sized islands, lies nearly 8 km from the nearest mainland point but is just 0.2 km from South Bass Island with 22 species, and 1.4 km from Middle Bass Island with 19 species. In addition, species lists for some islands may be incomplete or inflated by inclusion of nonresident (waif or transient) species.
Other components of the Lake Erie island biota also show a positive correlation between species number and island area and provide examples of colonization and local extinction (e.g., vascular plants: Duncan and Stuckey, 1970; Klinkenberg, 1988; isopods: Dexter et al., 1988; spiders: Beatty, 1988; beetles: Will et al., 1995; butterflies: Nault et al., 1989; colonial waterbirds: Weseloh et al., 1988; mammals: Campbell et al., 1988; Jackson, 1988). As with amphibians and reptiles, changes in distribution of these taxa reflect habitat changes resulting from human activities (Duncan and Stuckey, 1970; Weseloh et al., 1988). Although it is unlikely that human impacts can be prevented entirely, data such as we present here are valuable in assessing and potentially mitigating these impacts.
Acknowledgments. - Field work by RBK was supported by the Gaige Fund of the American Society of Ichthyologists and Herpetologists, National Science Foundation (DEB-9107382 to R. B. King and R. Lawson), Ohio Department of Natural Resources, Ontario Ministry of Natural Resources, Sigma Xi, Society for the Study of Amphibians and Reptiles and Theodore Roosevelt Memorial Fund of the American Museum of Natural History; access to field sites was granted by the Essex Region Conservation Authority, Johnsons Island, Inc., Ohio Department of Natural Resources, Ontario Ministry of Natural Resources, Ottawa National Wildlife Refuge and Winous Point Shooting Club; logistical support was provided by the F. T. Stone Laboratory; assistance in the field was provided by T. Bittner, R. Lawson, T. Near and A. Queral-Regil. Compilation of the OHS data base was supported in part by the Essex Region Conservation Authority, Ontario Ministry of Natural Resources, Ontario Natural Heritage Information Centre and World Wildlife Fund. Compilation of the ODNR data base was supported by a ODNR nongame fund grant (to DW) with the cooperation of G. Casper, J. Condit, G. Coovert, P. Daniel, P. Flynn, G. Foley, R. Kennedy, C. McCoy, S. Moody, T. Pauley, G. Schneider, K. Tighe, S. Vessey and G. Watkins-Colwell. We thank J. P. Bogart, C. A. Campbell, R. Conant, F. R. Cook, F. Kraus, L. Lowcock, R. Pfingsten and an anonymous reviewer for their contributions.
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Museum collections included in the OHS, ODNR, and RBK data bases: American Museum of Natural History, New York, New York (ODNR, RBK); Bowling Green State University, Bowling Green, Ohio (ODNR); California Academy of Sciences, San Francisco, California (RBK); Canadian Museum of Nature, Ottawa, Ontario (OHS, RBK); Carnegie Museum of Natural History, Pittsburgh, Pennsylvania (OHS, ODNR); Chicago Academy of Sciences, Chicago, Illinois (OHS, RBK); Cincinnati Museum of Natural History, Cincinnati, Ohio (ODNR, RBK); Cleveland Museum of Natural History, Cleveland, Ohio (ODNR, RBK); College of Wooster, Wooster, Ohio (ODNR); Cornell University, Ithaca, New York (OHS, RBK); Dayton Museum of Natural History, Dayton, Ohio (ODNR); Defiance College, Defiance, Ohio (ODNR); Ehrhart Museum, Antwerp, Ohio (ODNR); Field Museum of Natural History, Chicago, Illinois (RBK); Florida State Museum, University of Florida, Gainesville, Florida (RBK); F. T. Stone Laboratory, Put-in-Bay, Ohio (RBK); Illinois Natural History Survey, Urbana, Illinois (RBK); Louisiana State University Museum of Zoology, Baton Rouge, Louisiana (RBK); Marshall University, Huntington, West Virginia (ODNR); Miami University, Oxford, Ohio (RBK, ODNR); Milwaukee Public Museum, Milwaukee, Wisconsin (OHS, ODNR); Montgomery County Herpetological Survey, Ohio (ODNR); Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts (OHS, RBK); Museum of Vertebrate Zoology, University of California, Berkeley, California (RBK); National Museum of Natural History, Washington, District of Columbia (OHS, ODNR); Natural History Museum of Los Angeles County, Los Angeles, California (RBK); Ohio State University Museum of Zoology, Columbus, Ohio (ODNR, RBK); Ohio University, Athens, Ohio (ODNR); Royal Ontario Museum, Toronto, Ontario (OHS, RBK); University of Guelph, Guelph, Ontario (OHS); University of Illinois Museum of Natural History, Urbana-Champaign, Illinois (RBK); University of Kansas Museum of Natural History, Lawrence, Kansas (RBK); University of Michigan Museum of Zoology, Ann Arbor, Michigan (OHS, ODNR, RBK); University of Ottawa, Ottawa, Ontario (OHS); University of Western Ontario, London, Ontario (OHS); Wilfrid Laurier University, Waterloo, Ontario (OHS).
Published sources of records included in the RBK data base: Bogart and Licht (1986), Bogart et al. (1985); Bogart et al. (1987), Camin and Ehrlich (1958), Camin et al. (1954), Catling and Freedman (1980a, 1980b), Conant (1938, 1951, 1965, 1982), Conant and Clay (1937), Cook (1964, 1984), Dance and Campbell (1981), Downs (1978), Ehrlich and Camin (1960), Green (1989), Hamilton (1951), Jones (1902, 1912), King (1985), Kraus (1985a; 1985b), Kraus and Schuett (1982), Langlois (1964), Licht and Bogart (1990), Logier (1925), Logier and Toner (1961), Lowcock and Bogart (1992), McDermott (1947), Mineau and Markel (1981), Morse (1904), Oldham (1986), Patch (1919), Pfingsten and Downs (1989), Pfingsten and Walker (1978), Reichenbach (1981), Taverner (1914), Thomas (1949), Uzzell (1962), Walker (1946).
Voucher specimens included in the RBK data base and deposited in the Field Museum of Natural History (FMNH) and California Academy of Sciences (CAS) (specimens in the FMNH are part of the snake stomach-contents collection and are not individually cataloged): Ambystoma sp. (larvae) - FMNH; Emydoidea blandingi - CAS (photos); Coluber constrictor - CAS198602-198603; Diadophis punctatus - CAS (photos); Elaphe vulpina - CAS198470, 198605; Heterodon platirhinos - CAS198604; Necturus maculosus - FMNH; Nerodia sipedon - CAS198467-198469, 198484, 198506-198515, 198546-198573, 198578-198580, 198582, 198595-198601; Plethodon cinereus - CAS198606-198609; Rana catesbeiana - FMNH; Rana pipiens - FMNH, Regina septemvittata - CAS (photos); Storeria dekayi - CAS197642-197879, 1987881-197882; Storeria occipitomaculata - CAS197641; Thamnophis butleri - CAS197638-197640; Thamnophis sirtalis - CAS197638-197640, 198460-198466, 198471-198483, 198485-198505, 198516-198545, 198574-198577, 198581, 198583; 198588-198594.