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Western Painted Turtle (Chrysemys Picta Bellii)

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COSEWIC
Executive Summary

Western Painted Turtle
Chrysemys Picta Bellii

Pacific Coast population
Intermountain – Rocky Mountain population
Prairie/Western Boreal – Canadian Shield population

Species Information

The Painted Turtle, Chrysemys picta, is a small freshwater turtle with a smooth, dark carapace (upper shell) and outstanding red and yellow patterns on its limbs and plastron (ventral shell). There are three subspecies in Canada. The Western Painted Turtle, C. p. bellii, is distinct from the other subspecies in being the largest, and in possessing a large central mark that extends along the plastral seams and covers much of the red/orange plastron.

Distribution

Chrysemys picta bellii occurs in wetlands in low elevation forests and grasslands of western and central North America. In Canada, its range extends from southwest of Lake Nipigon, Ontario, across the southern portion of the prairies, to the low-lying valleys of southern Interior and southwest British Columbia and Vancouver Island.. Range expansion appears to be limited by the length of the turtle’s active season, mean ambient temperature during egg incubation, and, perhaps, mean winter temperature.

Habitat

This aquatic species is found in the shallow waters of ponds, lakes, sloughs, and slow-moving stream reaches. Suitable wetlands have muddy substrates, an abundance of emergent vegetation, and numerous basking sites. Chrysemys p. bellii habitat also includes riparian zones bordering wetlands; females nest up to 150 m away from water, in loose, warm, well-drained soils.

Biology

Western Painted Turtles mate in shallow water, probably throughout the active season. Females may mate with a single male prior to egg-laying, but there is evidence of multiple paternity in some clutches. Nesting usually takes place at dawn or dusk during June. Once a female has traveled to her chosen nest site, she digs a 10-cm hole, deposits up to 23 eggs, and covers them. Incubation lasts roughly 76 days, and the temperature regime in the nest will determine the sex of the offspring. Constant temperatures above 29°C produce all females and those below 27°C produce males; at the pivotal temperature of 28°C, both sexes are produced. Hatchlings usually overwinter in the nest and emerge the following spring. They resist winter freezing by supercooling, or they survive by tolerating freezing. Mortality is high when nest temperatures are lower than about -4C.

There is no post-hatching parental care in this species, and few hatchlings survive to adulthood. The survival rate of juveniles and adults is relatively high and constant. Sexual maturity is attained in 8-10 years in males and 12-15 years in females. Adult lifespan is likely over 50 years and possibly much longer. Aside from hatchlings, all life stages lie dormant on the muddy substrate of ponds during winter. They become active as soon as ice cover melts and the surface of the water body has some open water. During the growing season, turtles bask to raise their temperature to facilitate foraging and mating. They may bask several times a day, and the basking period will vary with temperature, age (size), and activity (females may bask longer prior to the nesting season).

Population Sizes and Trends

Globally, the Western Painted Turtle is secure, with more than 300 locations with a dozen to several hundred individuals per hectare. In Canada, Chrysemys p. bellii is apparently secure in Ontario (> 100 locations) and Manitoba (> 100 locations); wetlands are abundant and interconnected in these provinces. The species is also considered secure in Saskatchewan (21-100 locations). Chrysemys p. bellii has a tenuous hold in Alberta (S1), with small numbers in a handful of isolated locations near the U.S. border. In British Columbia, the species has been reported from over 30 locations, most in the Okanagan Valley. The species is ranked as S3S4 (of concern). Some populations appear stable; but most are vulnerable because roads intercept nesting areas, and because wetland degradation/loss through urbanization and filling in for vineyards is on the rise in large parts of the species’ range in British Columbia (Okanagan, lower mainland, Fraser River Valley, Vancouver Island).

Limiting Factors and Threats

Given this species’ low adult recruitment, delayed maturity, and high adult survival, chronic added mortality of juveniles and adults could eliminate local populations. Factors contributing to this cumulative diminishment of older turtles include road kills of turtles, particularly gravid females during the nesting season, increased predation on dispersing turtles during drought years (or in reservoirs with low water levels), and increasing depredation of nests. Habitat loss is also a threat to turtles, and may rise significantly with climate change, particularly in the drier prairies. Wetland and riparian degradation is prevalent in landscapes where human activity is extensive, intensive or frequent. Habitat threats include water pollution, habitat fragmentation, drainage of wetlands, increased predation of eggs and juveniles particularly by higher populations of raccoons, and introduction of exotic turtle species and their associated diseases and parasites.

Special Significance of the Species

Chrysemys p. bellii is one of only two extant, native freshwater turtle species west of Ontario, which makes it a significant element in the overall biodiversity of the western provinces. Western Painted Turtles undoubtedly play an important role in the ecology of some wetlands. Populations at range limits are critical sources of genetic variation for potential, future adaptation to changing environmental conditions.

Existing Protection

Provincial wildlife acts protect turtles from killing and/or collection. A number of protected areas occur within the species’ range though few are in the dry prairie belt, especially Alberta. In many protected areas, individuals are still vulnerable to collection, nest disturbance and road mortality. Federal fish regulations, provincial management initiatives and municipal by-laws can also protect turtles.