Western Painted Turtle (Chrysemys Picta Bellii)
- Assessment Summary
- Executive Summary
- COSEWIC History, Mandate, Membership and Definitions
- List of Figures
- Species Information
- Population Sizes and Trends
- Limiting Factors and Threats
- Special Significance of the Species
- Existing Protection or Other Status Designations
- Technical Summary
- Acknowledgements, Authorities Contacted, and Information Sources
- Biographical Summary of Report Writer and Collections Examined
Population Sizes and Trends
There are 496 known Western Painted Turtle records in Canada: 219 in Ontario, 129 in B.C., 101 in Saskatchewan, 25 in Manitoba, and 22 in Alberta. These records, which date from 1920 to 2005, represent about 320 locations (some locations have several records). High numbers of records in Ontario and B.C. may simply reflect higher human population densities and the correspondingly greater number of citizens detecting or looking for turtles. Ontario has a relatively thorough coverage of turtles in the province because the Ontario Herpetofaunal Summary Atlas (OHS) has been in existence since 1984 (Ontario MNR 2005). Given that there are few potentially turtle-bearing wetlands in Alberta, this province’s small collection of records is probably relatively complete as well.
Most of the Western Painted Turtle records that have been used in delineating range limits and understanding distribution patterns in Canada are the result of nonsystematic searches and reports. Exceptions to this sporadic collection/ observation method are as follows: (1) 16% of Ontario records were the results of a more thorough wetland inventory of Ontario; (2) there has been a fairly systematic reconnaissance of the South Okanagan wetlands over the course of several years (43% of B.C. records by local herpetologist Mike Sarrell); (3) the Saskatchewan Wetland Conservation Corporation funded turtle surveys in 2002 and 2003 (26% of SK records); (4) a recent systematic survey of critical wetland habitats was conducted along the Souris River, as part of an environmental impact assessment for the Saskatchewan Watershed Authority (39% of SK records).
In summary, the records probably give a reasonable index of range, distribution, and abundance within each province except in Manitoba (the scant number of records do not reflect this province’s profusion of interconnected wetlands).
Painted Turtles are generally the most abundant turtle species wherever they occur in Canada (Cook 1984; Ernst et al. 1994) but their densities can be quite variable, ranging from a few to several hundred individuals/ha. The overall abundance of Western Painted Turtles in Canada is unknown. NatureServe (2004) considers this species secure in Canada and the U.S. (N5) because it can be abundant in suitable habitats, there are many large sub-populations throughout its range, its numbers appear to be relatively stable, and threats (habitat degradation, mortality on roads, human-induced rise in predation) are moderate and often localized. However, given the increase in road density, intensive drainage of wetlands, the propensity of nesting females to use roads and the species’ long-lived life history, it may be that these threats are having a greater effect than has been supposed. As pointed out by Congdon (J. Congdon pers. comm. 2005), just because this species has a wide range does not mean it does not respond to these threats in the same manner as other long-lived vertebrates.
In light of the wide variation in local abundance, it may be more useful to examine the number of Western Painted Turtle ‘occurrences’. An occurrence (location as defined by COSEWIC) is a sub-population that is separated from all others by barriers such as (1) busy highways; (2) highways with obstructions to crossings (e.g., concrete dividers); (3) untraversable topography (e.g., cliffs); or (4) extensive urban or dry areas lacking wetted habitats (NatureServe 2004). In the absence of such barriers, a sub-population can be viewed as separate if species records are: (1) 10 km apart in more or less continuously joined suitable habitat; (2) three km apart across upland habitat (so that females on nesting migrations from separate ponds do not overlap); or (3) five km apart in intermediate situations (NatureServe 2004).
Chrysemys picta bellii is assessed as secure (S4) in northwestern Ontario and Manitoba because human impacts are not severe in these areas (compared to southern Ontario), wetlands abound, and there are more than 100 occurrences in each province (M. Oldham pers. comm. 2004; J. Duncan pers. comm. 2004).
In Saskatchewan, C. p. bellii is also secure (S4; J. Pepper pers. comm. 2004) because it is found in four large watersheds; there are 101 records from about 40 different places, which implies that there are at least 40 known occurrences in the province. Threats to the species in Saskatchewan include habitat loss and alteration (J. epper pers. comm. 2004).
Chrysemys p. bellii has a tenuous hold in Alberta with probably fewer than 100 individuals belonging to few, if any, viable occurrences in the Cypress Hills, lower Milk River, and Oldman River basins (Alberta Conservation Data Centre 2004). It is thought that more northern Western Painted Turtle records (e.g., Lethbridge, Edmonton) represent individuals released from the pet trade (R. Quinlan pers. comm. 2004).
In British Columbia, C. p. bellii is considered vulnerable (S3S4). There appear to be on the order of 100 occurrences. However, roads often bisect nesting areas in British Columbia, because suitable wetlands, turtles, and roads all tend to be confined to valleys between mountain ranges. Although the species appears to be widespread and secure in eastern B.C., with up to 60% of the wetlands in the Columbia River basin protected through conservation initiatives (Krebs pers. comm. 2005), wetland habitat loss, degradation and fragmentation, and road construction and use continue to increase in the Southern Interior and on the South Coast (Lower Mainland; Vancouver Island). In these latter areas, numbers of turtles are small and appear to be declining (M. Sarell pers. comm. 2005; P. Gregory pers. comm. 2005, Bunnell 2005).
In the Okanagan, Sarell (M. Sarell pers. comm. 2005) and Brown (J. Brown pers. comm. 2005) stated that “natural” habitat loss (loss of numerous small lakes and ponds from recent extended droughts) has probably destroyed not only those turtle populations but connectivity between populations that remain. In addition, there is a significant loss of wetlands due to filling and draining to increase land for cultivation and development. Sarell also observed many Western Painted Turtles killed on roads and dead from injuries from being hooked by fishermen. Recent expansion of the raccoon (Procyon lotor) has likely reduced nesting success and led to increased mortality of hatchlings and nesting females.
On Vancouver Island and the lower mainland, Painted Turtles have always been very uncommon (P. Gregory pers. comm. 2005, L. Friis pers. comm. 2005), and Gregory stated that he had not seen one in years. There has been some question whether the Painted Turtle is native or introduced to Vancouver Island, but this debate seems based mainly on the fact that the turtles have always been rare. However, records do go back to at least the early 1900s, and likely the Western Painted Turtle should be considered a native subspecies (F. Cook pers. comm.)
There are no data on population trends for the Western Painted Turtle. Although the species appears to be stable overall (K. Griffin pers. comm. 2005; J. Krebs pers. comm. 2005), it seems to be experiencing significant declines in certain areas in the far west. Based on habitat trends (e.g., Nichol et al. 2001), the Western Painted Turtle has likely suffered significant declines in: (1) the lower Fraser Valley (Vancouver Region); (2) the southeast coast of Vancouver Island (Victoria Region); and (3) the Okanagan and Similkameen River Valleys. A recent survey of 29 wetlands for turtles in lower Fraser River valley found Western Painted Turtles at only one site (Burnaby Lake) even though the species had previously been reported form six of the 29 surveyed sites (Bunnell 2005). The species also seems to be declining locally in other parts of its Canadian range (e.g., Clark and Grueing 2002), where roads or human activities significantly impact certain wetlands or turtle nesting grounds.
Dispersal among populations of Western Painted Turtles is likely high in Ontario, Manitoba, and eastern Saskatchewan, where the extensive, interconnected complex of lakes and wetlands undoubtedly facilitates metapopulation dynamics (e.g., Lake of the Woods in Ontario drains into Lake Winnipeg via Winnipeg River; a significant proportion of the turtle-bearing watercourses of Saskatchewan are connected to Lake Winnipeg by the Assiniboine River).
Although southwest Saskatchewan and southeastern Alberta have fewer lakes and wetlands, sub-populations appear to be linked through watersheds to source populations in the U.S. (e.g., the Frenchman River of Saskatchewan merges with the Milk River headwater of Missouri River in Montana and the Milk River extends into Alberta). The Western Painted Turtle is not at risk in the neighbouring, agricultural states of North Dakota, Montana and Minnesota (NatureServe 2004). Presumably, landscape fragmentation and wetland degradation is moderately low in this part of the U.S. because human population densities are low to moderate (10 families/km or less based on the Hammond Atlas of Canada and the World year).
Southeast British Columbia is not heavily populated and the landscape between this region and the moderately populated, agricultural land of northern Idaho is fairly continuous; C. picta is apparently secure in Idaho (NatureServe 2004). Conversely, human activity levels are high on southern Vancouver Island, the Lower Mainland region (Vancouver and vicinity), and the Okanagan Valley and there are matching human densities across the border with the U.S.A. (Spokane, Seattle and suburbs), at least for the coastal mainland. The ensuing level of habitat loss, degradation, and fragmentation across the border implies that there is a low potential for natural turtle dispersal/recolonization across the border. Wetlands in less populated areas of the Southern Interior ecoprovince could perhaps serve as source populations for the Okanagan Valley, but coastal sub-populations have few sources of colonists.
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