COSEWIC Assessment and Update Status Report on the Northern Cricket Frog Acris crepitans in Canada – 2001

Photo of the Northern Cricket Frog Acris crepitans.

Endangered – 2001

Table of Contents

Document Information

List of Figures

List of Tables

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Document Information

COSEWIC – Committee on the Status of Endangered Wildlife in Canada

COSEWIC status reports are working documents used in assigning the status of wildlife species suspected of being at risk. This report may be cited as follows:

Please note: Persons wishing to cite data in the report should refer to the report (and cite the author(s)); persons wishing to cite the COSEWIC status will refer to the assessment (and cite COSEWIC). A production note will be provided if additional information on the status report history is required.

COSEWIC. 2001. COSEWIC assessment and update status report on the Northern Cricket Frog Acris crepitans in Canada. Committee on the Status of Endangered Wildlife. Ottawa. v + 14 pp.

Britton, D. 2001. COSEWIC update status report on the Northern Cricket Frog Acris crepitans in Canada in COSEWIC assessment and update status report on the Northern Cricket Frog Acris crepitans in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. 1-14 pp.

Previous report(s):

Oldham, M.J. and C.A. Campbell. 1990. COSEWIC status report on the Northern Cricket Frog Acris crepitans in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. 33 pp.

Production note:
Northern Cricket Frog Acris crepitans was, for several years, designated by COSEWIC as Blanchard’s Cricket Frog Acris crepitans blanchardi.

For additional copies contact:

COSEWIC Secretariat
c/o Canadian Wildlife Service
Environment Canada
Ottawa, ON
K1A 0H3

Tel.: (819) 997-4991 / (819) 953-3215
Fax: (819) 994-3684
E-mail
Website

Cover illustration/photo:
Northern Cricket Frog -- ©Suzanne L. Collins.

© Her Majesty the Queen in Right of Canada, 2011.
Catalogue No.
ISBN

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COSEWIC

Assessment Summary

Assessment Summary – May 2001

Common name
Northern Cricket Frog

Scientific name
Acris crepitans

Status
Endangered

Reason for designation
Due to continuing declines in the extent of the species’ occurrence, area of occupancy, extent of habitat and number of individuals, any remaining individuals of this frog species would exist in a single small population on Pelee Island.

Occurrence
Ontario

Status history
Designated Endangered in April 1990. Status re-examined and confirmed in May 2001. Last assessment based on an update status report.

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COSEWIC
Executive Summary

Northern Cricket Frog
Acris creptitans

Although widespread in the United States, the Northern Cricket Frog (Acris crepitans) is known in Canada exclusively from the extreme southwest of Ontario where its existence has been confirmed only at Point Pelee and Pelee Island. The Point Pelee population, known from a handful of historical records, was never well known and is believed to be extirpated. On Pelee Island, A. crepitans was documented from as many as twenty sites during the early 1970’s. However, during that decade, these underwent a precipitous decline, until, after 1977, A. crepitans was known to persist in Canada at only a single site on Pelee Island: Fish Point Provincial Nature Reserve, located at the southern tip of the island.

Damage to habitat, including the drainage of marshes, the dredging of drainage canals that were used as breeding sites and the scouring of coastal marshes during severe storms are believed to be key reasons for the decline of A. crepitans on Pelee Island. Other factors that may have contributed to the species’ decline include predation by birds, reptiles, bullfrogs and fish, and use of pesticides and herbicides. Habitat destruction has also been identified as the major cause of recent declines of the species in the American Midwest.

Over the last two decades, observations and auditions of A. crepitans have been reported sporadically from Fish Point, including one as recently as 1997. Unfortunately, none of these more recent reports are supported by photographs or audio recordings of calling frogs. The lack of confirmed reports, coupled with the relatively small size of Fish Point and the short lifespan of individual frogs has led a number of authors to suggest that A. crepitans has been extirpated from Canada. Nevertheless, it may be premature to consider the species extirpated and thus it is recommended that the status of A. crepitans in Canada remain as endangered.

COSEWIC History
The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list. On June 5, 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

COSEWIC Mandate
The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) determines the national status of wild species, subspecies, varieties, and nationally significant populations that are considered to be at risk in Canada. Designations are made on all native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fish, lepidopterans, molluscs, vascular plants, lichens, and mosses.

COSEWIC Membership
COSEWIC comprises representatives from each provincial and territorial government wildlife agency, four federal agencies (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biosystematic Partnership), three nonjurisdictional members and the co-chairs of the species specialist groups. The committee meets to consider status reports on candidate species.

Definitions

Species
Any indigenous species, subspecies, variety, or geographically defined population of wild fauna and flora.

Extinct (X)
A species that no longer exists.

Extirpated (XT)
A species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E)
A species facing imminent extirpation or extinction.

Threatened (T)
A species likely to become endangered if limiting factors are not reversed.

Special Concern (SC)*
A species of special concern because of characteristics that make it particularly sensitive to human activities or natural events.

Not at Risk (NAR)**
A species that has been evaluated and found to be not at risk.

Data Deficient (DD)***
A species for which there is insufficient scientific information to support status designation.

* Formerly described as “Vulnerable” from 1990 to 1999, or “Rare” prior to 1990.
** Formerly described as “Not In Any Category”, or “No Designation Required.”
*** Formerly described as “Indeterminate” from 1994 to 1999 or “ISIBD” (insufficient scientific information on which to base a designation) prior to 1994.

The Canadian Wildlife Service, Environment Canada, provides full administrative and financial support to the COSEWIC Secretariat.

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Update COSEWIC Status Report on the Northern Cricket Frog Acris crepitans in Canada – 2001

Introduction

The Northern Cricket Frog (Acris crepitans) is a small treefrog of the family Hylidae widespread throughout eastern North America. In Canada, its occurrence has only been confirmed at two localities: Point Pelee and Pelee Island in extreme southwestern Ontario.

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Distribution

Acris crepitans is distributed widely in the eastern and central United States. It ranges from Texas to southeastern South Dakota in the western part of its range, and from the Gulf states to southeastern New York in the east. It is absent from much of the Appalachian region, the southern Atlantic Coastal Plain and from the Florida panhandle where it is replaced by the morphologically similar Southern Cricket Frog (Acris gryllus). In the Great Lakes region, A. crepitans has been recorded in southern Wisconsin, southern Michigan, western Ohio and in extreme southwestern Ontario. Taxonomically, A. crepitans is divided into three subspecies based on geographic variation in colouration and morphology (Conant and Collins, 1991): the Northern Cricket Frog (A.c. crepitans) in the eastern portion of its range, Blanchard’s Cricket Frog (A.c. blanchardi) in the western part of its range, including southwestern Ontario, and the Coastal Cricket Frog (A.c. paludicola) in the coastal marshes of Louisiana and eastern Texas.

In Canada, A. crepitans has been recorded only in extreme southwestern Ontario (Fig. 1; Tables 1 and 2). The first confirmed Canadian record of this species comes from an individual collected by a National Museum of Canada expedition in 1913 at Point Pelee (Oldham and Campbell, 1990). Point Pelee, which is protected by its designation as a national park, is the southernmost point in mainland Canada, and consists of a narrow sand spit that extends sixteen kilometers into western Lake Erie. In 1950, A. crepitans was also collected from several sites on Pelee Island (J. Baillie, field notes, as cited in Oldham and Campbell, 1990). This 4,000 ha island (Fig. 2) is Canada’s most southerly inhabited land mass and is located in Lake Erie, approximately 30 kilometers southwest of the tip of Point Pelee. By the early 1970’s, A. crepitans had been recorded from 20 specific sites on the island, all located close to the shore (Table 2).

In addition to those from Point Pelee and Pelee Island, there have been a number of unconfirmed reports of A. crepitans on the mainland of southwestern Ontario made during the 1970’s and 1980’s (Fig. 1, Table 1): in Essex County at Lighthouse Cove, the mouth of the Canard River, the Comber Sewage Lagoon and at Big Creek Marsh at Holiday Beach; and in Haldimand-Norfolk Regional Municipality at Long Point and Turkey Point (Oldham and Campbell, 1990; Natural Heritage Information Centre, 1998). However, because none of these sightings have been confirmed with photographs, audio recordings of calling frogs, or voucher specimens, and because subsequent searches at these locations have failed to yield further records, their status remains dubious. Oldham and Campbell (1990) speculated that some sightings may be cases of confusion between A. crepitans and the Western Chorus Frog (Pseudacris triseriata) which is widespread in southern Ontario and is superficially similar to A. crepitans in appearance.

Figure 1.  Distribution of the Northern Cricket Frog (Acris crepitans) in Ontario.

Map of the distribution of the Northern Cricket Frog in Ontario.

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Table 1.  Mainland Ontario records for A. crepitans (Fig. 1).
Question marks indicate unconfirmed reports. From Oldham and Campbell (1990).
LocalityYears in which observations were recorded
Point Pelee, Essex Co.1913, 1920, 1972(?)
Lighthouse Cove, Essex Co.1979(?), 1980(?)
Comber Sewage Lagoon, Essex Co.1985(?)
Canard River, Essex Co.1981(?)
Big Creek Marsh, Essex Co.1962(?)
Long Point, Haldimand-Norfolk R.M..1976(?), 1984(?)
Turkey Point, Haldimand-Norfolk R.M.1985(?)

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Figure 2. Distribution of the Northern Cricket Frog (Acris crepitans) on Pelee Island.

Map of the distribution of the Northern Cricket Frog on Pelee Island.

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Table 2.  Pelee Island records for A. crepitans (Fig. 2).
Question marks indicate unconfirmed records. Modified from Oldham and Campbell (1990).
 LocalityYears in which observations were recorded
1Northwest Lagoon1970, 1972, 1976
2Northeast Lagoon1972
3Mosquito Point1970
4Mosquito1970
5West Road ditches1970, 1972
6Lizard Point1970
7Lighthouse Point Lagoon1970, 1976
8Northwest Quarry1972, 1973
9South Marsh (Curry Swamp1970, 1972, 1973, 1974, 1976, 1977
10Peregrine Pond (also known as Fox Pond or South Swamp1971, 1972, 1973, 1983, 1984, 1987, 1989, 1993(?), 1997
11Girl Guide CampNo records
12Base of Lighthouse Point1972
13Moelles-Kamp Property1972
14No data recorded 
15East of South Marsh1972, 1976
16Lake Henry1974, 1976
17Rollo’s1977
18West of South Marsh1976
19Northwest Canal1976, 1977
20East Beach Road canals1970

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Protection

Acris crepitans is designated as Endangered by the Ontario Ministry of Natural Resources, and is protected in Ontario by regulations made under the Ontario Endangered Species Act which protects both endangered species and their habitat. Under the Nature Conservancy system, A. crepitans is ranked G5 and SH meaning that it is considered globally common, but provincially it is known only from historical records. On Pelee Island two A. crepitans breeding locations, at Lighthouse Point and Fish Point, are protected from development by their designation as Provincial Nature Reserves (Fig. 2). Acris crepitans has previously been designated Endangered by COSEWIC (Oldham and Campbell, 1990).

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Population Size and Trend

Aside from the historical records of sightings, there are no quantitative data on the A. crepitans population that was once extant at Point Pelee. Subsequent to the initial collection of one individual in 1913, there is only one other specimen record, when a single calling male was collected in 1925 (Logier, 1925). More recently, in 1972, another calling male was reported (Rivard and Smith, 1972) but this record was not substantiated by a photograph, audio recording or voucher specimen. Despite several concerted searches at this site since 1972 (Oldham and Campbell, 1990), and the intense attention the area receives from naturalists and Parks Canada staff, there have been no further sightings or auditions of A. crepitans at Point Pelee and there is general agreement that the species has been extirpated from this site (Cook, 1984; Oldham and Campbell, 1990).

On Pelee Island, the record of A. crepitans’ presence has been more thoroughly documented. Its existence on the island was first established in 1950 when seventeen individuals were collected by a Royal Ontario Museum field party, and numerous others were heard (J.L. Baillie, as cited in Oldham and Campbell, 1990). Subsequently, single individuals were collected in 1961 and 1963. In 1970, C.A. Campbell began visiting Pelee Island and kept detailed field notes on A. crepitans calling sites (Oldham and Campbell, 1990). Although his surveys were not standardized in terms of search effort or the time of year conducted, and are therefore not suitable for any statistical analysis of population trends, they constitute a unique and valuable record of the population decline of A. crepitans on Pelee Island. In the early seventies, Campbell verified the presence of A. crepitans at 20 localities on Pelee Island, all located on, or close to, the shore of the island. However, throughout the seventies, A. crepitans populations on Pelee Island experienced a precipitous decline. Campbell’s field notes document the disappearance of A. crepitans from many of its known localities on Pelee Island throughout the 1970’s until, after 1977, the species was known to persist at only one location: Peregrine Pond (previously known as Fox Pond or South Swamp) located in Fish Point Provincial Nature Reserve at the southernmost tip of Pelee Island. During the 1980’s there were sporadic reports of A. crepitans at Fish Point, most notably when an estimated 30 males were heard calling there in 1984. The species was not recorded during 1985, 1986, or 1988, but calling males were reported from Peregrine Pond in 1987 and 1989 (Oldham and Campbell, 1990). In 1992, all known A. crepitans breeding sites on Pelee Island were re-surveyed (Kellar et al., 1997), but no sign of the species was found. However, in 1993, another report of calling males, and possible sightings of adults was recorded, again at Peregrine Pond (Kellar et al., 1997).

The most recent report of A. crepitans on Pelee Island is from September 11, 1997. The frog was found under a small piece of wood at Fish Point along the interpretive trail that leads from the parking area to the tip of the point about 100 m south of the parking area where the trail passes Peregrine Pond. The observer, Rick Simek, is a biologist from the University of Michigan Natural Sciences Department who was visiting Pelee Island. Although he had never seen A. crepitans in the field before, he had conducted frog surveys in Michigan and is familiar with the frog species in the Great Lakes area. He described the frog as small, about the size of a spring peeper, but perhaps even smaller, quite dark in colouration with small bumps, smaller than the protuberances on a toad (R. Simek, pers. comm.). Furthermore, on a subsequent outing in Florida, he observed the Southern Cricket Frog, A. gryllus, which was very similar to the frog he observed on Pelee Island and confirmed in his mind that what he observed on Pelee Island was A. crepitans. The observer was not aware that A. crepitans was a significant species on Pelee Island, nor that Peregrine Pond is the site where the species was last recorded (R. Simek, pers. comm.).

On June 18, 1999 the author visited Peregrine Pond and spent three hours searching the pond and adjacent area. No trace of A. crepitans was found. Recently, a interpretive plaque has been erected at the wooden observation deck that overlooks the pond. This plaque indicates that this is the last known site for A. crepitans in Canada but that, with the recent sighting, there is optimism that a small population might still be extant at Peregrine Pond.

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Habitat and General Biology

Acris crepitans are semi-aquatic by nature and individuals generally remain in, or close to, permanent water bodies. Throughout their range, they are found in a wide variety of permanent water bodies including lakes, ponds, rivers and streams, especially in shallow water near shore where there is substantial vegetative cover (Conant and Collins, 1991; Vogt, 1981). On Pelee Island, A. crepitans were found in shoreline marshes, pools, and lagoons, drainage canals used for agriculture, ditches, and flooded fields (Oldham and Campbell, 1990).

All of the sites at which A. crepitans were recorded on Pelee Island are located near the shoreline. Campbell (1971, as cited in Oldham and Campbell, 1990) speculated that A. crepitans originally inhabited a large 2,800 ha marsh that occupied the centre of Pelee Island prior to the late 1800’s. In the 1880’s this marsh was diked and drained to provide land for agricultural use and, as a result, the frogs may have been driven to the remaining shoreline marshes around the periphery of the island.

In the southern portion of its range, A. crepitans may begin calling as early as February (Conant and Collins, 1991). On Pelee Island, at the northern edge of its distribution, calling males were recorded from early June until late July (Oldham and Campbell, 1990). Eggs are laid in a small clusters attached to vegetation. The tadpole stage is believed to last from 5 to 10 weeks (Burkett, 1984). On Pelee Island, one individual caught on 16 September, 1972 had a tail stub, indicating that it had recently transformed (Oldham and Campbell, 1990).

Demographic studies of A. crepitans have shown that, like other small frogs such as Spring Peepers (Pseudacris crucifer) or Chorus Frogs (Pseudacris sp.), they have a very short lifespan, generally living as adults for only one year, during which time they breed only once (Johnson and Christiansen, 1976; Burkett, 1984). As a result, factors that reduce breeding success for even one season can potentially decimate a population, which may account for the precipitous and rapid decline that occurred on Pelee Island over a few short years in the late 1970’s.

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Limiting Factors

Oldham and Campbell (1990) suggest a number of factors that may have played a role in the decline of Acris crepitans on Pelee Island, the most important of which are habitat degradation and predation. Damage to A. crepitans breeding habitat could have accrued from a number of sources. For example, the drainage of marshes for agricultural purposes is suspected to have eliminated a population at Curry Marsh on the southern shore of Pelee Island. The frogs were also known to breed extensively in drainage canals, but artificial dredging and draw-down of these canals to keep them clear of vegetation may be responsible for eliminating these populations. A. crepitans were not recorded at Lighthouse Point after 1972, when severe waves and storms breached and scoured the shoreline marshes there (Oldham and Campbell 1990). Additionally, the widespread use of fertilizers and pesticides for agricultural purposes may be a factor in the decline as A. crepitans are known to be susceptible to increased pesticide levels (Minton, 1972). Campbell (1978, as cited in Oldham and Campbell 1990) analyzed seven Pelee Island A. crepitans for several types of pesticides and found that these individuals contained levels of DDE and PCB's that were considered to be higher than normal.

Predation on A. crepitans may have also been a factor in their decline. Wading birds such as Great Blue Herons (Ardea herodias), Black-crowned Night Herons (Nycticorax nycticorax) and Common Bitterns (Botaurus lentiginosus) are known to prey on frogs (Ehrlich et al., 1988) and all are present on Pelee Island. A heronry was formerly located adjacent to Peregrine Pond, and when the herons relocated in the late 1980’s there was some optimism that this might spur a recovery of the waning A. crepitans population there (Oldham and Campbell, 1990). Instead, the relocation of the herons apparently resulted in an increase in Bullfrog (Rana catesbeiana) numbers. Bullfrogs are highly predaceous on smaller frogs and tadpoles (Bury and Whelan, 1984) and this increase in their numbers may have actually resulted in increased predation pressure on the already flagging A. crepitans population. Other potential predators on Pelee Island include large spiders and odonate larvae, which prey on tadpoles, Common Carp (Cyprinus carpio), Eastern Garter Snake (Thamnophis sirtalis sirtalis), Lake Erie Water Snake (Nerodia sipedon insularum), Snapping Turtle (Chelydra serpentina), Midland Painted Turtle (Chrysemys picta marginata), and Blanding’s Turtle (Emydoidea blandingii).

The Ontario decline in this species is apparently part of a larger pattern of decline in the northwestern portion of its range. Throughout the American Midwest, drastic declines in this species have been reported since the late 1970’s. Once widespread, A. crepitans is now restricted to a few isolated populations in Illinois (Mierzwa, 1998) and Wisconsin (Hay, 1998), where it has been listed as an endangered species since 1982. Acris crepitans have apparently also been extirpated from Indiana (Brodman and Kilmurry, 1998) and Minnesota (Moriarty, 1998). Habitat loss is foremost among those factors suggested as the primary reason for the decline, especially the elimination of wetland habitats for agricultural land-use.

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Special Significance of The Species

In terms of its significance to humans, A. crepitans is probably mainly of interest to naturalists and researchers and, even in these circles, it would take a measure of experience to differentiate this species from other small frogs. Its aquatic habits would rarely bring it into contact with humans and Oldham and Campbell (1990) suggest that it was never common enough to have been collected widely for bait on Pelee Island.

The Canadian populations are biogeographically significant in that they are among the most northerly known populations of the species and occur at the very edge of A. crepitans’ range. Such populations are of interest to biologists because of the significant demographic and genetic processes that occur at the periphery of a species’ range (Pulliam, 1988; Green et al., 1996). Genetic studies have shown that peripheral populations tend to be less genetically variable than populations in the core of a species range (Highton and Webster, 1976) and island populations tend to be less genetically variable than mainland populations (Frankham, 1997). As a result, the Pelee Island populations of A. crepitans may have been depauperate in genetic variation compared to more southerly, mainland populations.

Without any formal scientific investigation, it is difficult to say to what extent the Canadian populations of A. crepitans were genetically or morphologically distinct from other A. crepitans populations. Acris crepitans most likely reached Pelee Island through dispersal from populations located on the islands and mainland of Ohio. As the islands in the western Lake Erie basin have only been above lake level for approximately the last 4,000 years (Calkin and Feenstra, 1985), the Pelee Island population has probably not been isolated for sufficient evolutionary time to accrue large-scale neutral genetic differences from its parent population.

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Evaluation

With the last confirmed sighting occurring in 1925, and the general attention that is paid to the area both from visiting naturalists and Parks Canada staff, there is general agreement (Cook 1984; Oldham and Campbell, 1990) that A. crepitans has been extirpated from Point Pelee. As for other records of the species on the mainland of southern Ontario, the lack of confirmation through photographs, audio recordings or voucher specimens, and the lack of repeated records from these sites, suggest that these may be cases where A. crepitans has in fact disappeared and other frog species have been mistaken for it.

For Pelee Island, if a population does persist, it almost certainly does so only at Peregrine Pond in Fish Point Provincial Nature Reserve since the species has not been recorded elsewhere on the island for over two decades. A number of searches of this area by qualified individuals over the past ten years have failed to detect the species (Oldham and Campbell, 1990; Kellar et al., 1997). This fact, combined with the relatively small size of Peregrine Pond and the short lifespan of the individual frogs has suggested to some researchers that the species may be extirpated from Canada (Kellar et al., 1997). Nevertheless, there have been two unconfirmed reports of A. crepitans from this site over the last decade, in 1993 and 1997.

The 1997 report, in particular, seems reliable, especially given that the observer is a biologist with experience identifying frogs and toads and his report is augmented by his subsequent field experience with A. gryllus. Moreover, when he made his report, he was unaware of both the conservation status of A. crepitans on Pelee Island and the fact that the last confirmed sightings came from Peregrine Pond, which removes potential bias resulting from the expectation of finding them there. This sighting has certainly stimulated a degree of optimism among local naturalists (Meleg and Tiessen, 1997), which is borne out by the recently erected interpretive plaque at Peregrine Pond.

In conclusion, although it is certainly possible that A. crepitans has been extirpated from Canada, in light of the relatively short time span since the last confirmed report, as well as sporadic unconfirmed reports in the interim, it seems wisest to err on the side of caution and entertain the possibility that it still remains in this country.

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Acknowledgements

In preparing this status report update, I am is very much in debt to Mike Oldham and Craig Campbell for preparing the original COSEWIC status report on A. crepitans in 1990. This excellent document is one of the very few published reports dealing with Canadian populations of this species, and is far and away the most exhaustive. It was an invaluable resource in preparing this update, as the number of times it is cited in this document will bear out. I would also like to thank Jim Bogart, Mike Oldham, Ben Porchuk, Kent Prior, Ron Tiessen and Rick Simek for assistance, information and advice in preparing this manuscript. Reviewers David Green, Dave Galbraith, Don Rivard and Tom Herman also provided many useful suggestions.

Funding for this status report provided by the Canadian Wildlife Service, Environment Canada.

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Literature Cited

Brodman, R., and M. Kilmurry. 1998. Status of Amphibians in Northwestern Illinois. Pp. 131-141. In: Status and Conservation of Midwestern Amphibians. M.J. Lannoo (Ed.), University of Iowa Press, Iowa City.

Burkett, R.D. 1984. An ecological study of the Cricket frog, Acris crepitans. In: Vertebrate ecology and systematics, R.A. Siegel, L.E. Hunt, J.L. Knight, L. Malaret, and N.L. Zuchlag eds. Museum of Natural History, University of Kansas. Lawrence.

Bury, R.B., and J.A. Whelan. 1984. Ecology and management of the Bullfrog. U.S. Fish and Wildlife Service, Resource Publication No. 155. Washington.

Calkin, P.E., and B.H. Feenstra. 1985. Evolution of the Erie-basin Great Lakes. In: Quaternary Evolution of the Great Lakes, P.F. Karrow and P.E. Calkin (Eds.), Geological Association of Canada Special Papers. St. John’s.

Conant, R., and J.T. Collins. 1991. A field guide to the reptiles and amphibians. Eastern/central North America. 3rd ed. Houghton and Mifflin Co. Boston.

Cook, F.R. 1984. Introduction to Canadian amphibian and reptiles. National Museum of Natural Sciences. Ottawa.

Ehrlich, P.R., D.S. Dobkin and D. Wheye. 1988. The birder’s handbook. Simon and Schuster. New York.

Frankham, R. 1997. Do islands have less genetic variation than mainland populations? Heredity 78: 311-327.

Green, D.M., T.F. Sharbel, J. Kearsley, and H. Kaiser. 1996. Postglacial range fluctuation, genetic subdivision and speciation in the western North American spotted frog complex, Rana pretiosa. Evolution 50(1): 374-390.

Highton, R., and T.P. Webster. 1976. Geographic protein variation in populations of the salamander Plethodon cinereus. Evolution 30: 33-45.

Johnson, B.K., and J.L. Christiansen. 1976. The food and food habits of Blanchard’s Cricket frog, Acris crepitans blanchardi (Amphibia, Anura, Hylidae), in Iowa. Journal of Herpetology 10: 63-74.

Hay, R. 1998. Blanchard’s Cricket frog in Wisconsin: A Status Report. pp. 79-82. In: Status and Conservation of Midwestern Amphibians. M.J. Lannoo (Ed.), University of Iowa Press, Iowa City.

Kellar, T., G. Waldron, C. Bishop, J.P. Bogart, D. Kraus, M. McLaren, and M. Oldham. 1997. National Recovery Plan for Blanchard’s Cricket frog. Report No. 16. Recovery of Nationally Endangered Wildlife Committee, Ottawa.

Logier, E.B.S. 1925. Notes on the herpetology of Point Pelee. Canadian Field-Naturalist 39(5): 91-95.

Meleg, E., and R. Tiessen. 1997. A Guide to Exploring Pelee Island. Pelee Island Heritage Centre, Pelee Island.

Mierzwa, K.A. 1998. Status of Northeastern Illinois Amphibians. pp. 116-130 In: Status and Conservation of Midwestern Amphibians. M.J. Lannoo (Ed.), University of Iowa Press, Iowa City.

Minton, S.A., Jr. 1972. Amphibians and reptiles of Indiana. Indiana Academy of Science Monograph No. 3. Indianapolis.

Moriarty, J.J. 1998. Status of Amphibians in Minnesota. pp. 166-191 In: Status and Conservation of Midwestern Amphibians. M.J. Lannoo (Ed.), University of Iowa Press, Iowa City.

Natural Heritage Information Centre, 1998. NHIC Element Report: Acris crepitans blanchardi. Natural Heritage Information Centre, Peterborough.

Oldham, M.J., and C.A. Campbell. 1990. The Status of Blanchard’s Cricket frog, Acris crepitans blanchardi, in Canada. Committee on the Status of Endangered Wildlife in Canada Status Report. Ottawa.

Pulliam, H.R. 1988. Sources, sinks and population regulation. American Naturalist 132: 652-661.

Rivard, D.H., and D.A. Smith. 1972. A herpetological inventory of Point Pelee National Park, Ontario. Unpublished report to the Department of Indian Affairs and Northern Development. Ottawa.

Vogt, R.C. 1981. Natural history of amphibians and reptiles of Wisconsin. Milwaukee Public Museum. Milwaukee.

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The Author

David Britton received his Bachelor of Science in Zoology from the University of Guelph in 1993. In 1998 he received a Masters of Science, also in Zoology from the University of Guelph, where he studied the island biogeography of amphibians and reptiles in Georgian Bay and the population genetic structure of insular populations of amphibians. His time at Guelph also afforded him the opportunity to work in the field in locales as far-flung as Colombia and Thunder Bay. David is currently working in Ottawa on Parliament Hill in the Office of the Secretary of State (Rural Development; Federal Economic Development Initiative for Northern Ontario) where he is responsible for legislative and parliamentary matters.