|
Canadian Herpetological Society Société d'Herpétologie du Canada |
|---|
Blanding's Turtle
Emydoidea blandingii
Family: Emydidae
COSEWIC status:- Endangered (Great Lakes / St. Lawrence population)
- Endangered (Nova Scotia population)
- Endangered (Great Lakes / St. Lawrence population)
- Endangered (Nova Scotia population)
- Endangered
Description
Blanding's Turtles have a smooth, domed carapace (upper shell) that is black or dark brown with small tan or yellow flecks, although these markings may be absent or faded on some individuals. The plastron (lower shell) is yellow with a large dark blotch in the corner of each scute (the enlarged scales on the shell), but may be almost entirely black. The plastron has a hinge that allows the front portion to be pulled closed when the turtle retracts its head and legs into its shell. The top of the head and the limbs are brown to black with yellow flecks, and the chin and throat are bright yellow. Adults can reach a maximum carapace length of 28 cm. Hatchlings have a carapace length of 3–4 cm and resemble adults in colour but their carapace is very flat and becomes more domed as they age. Adult males can be easily differentiated from adult females by their concave plastron and larger tail.
Similar Species
No other Canadian turtles have a bright yellow chin and throat. Spotted Turtles have large yellow spots rather than small yellow flecks on their shell. Painted Turtles and Map Turtles have yellow or red lines on the face, neck and legs and comparatively flat shells. Wood Turtles have orange on the chin and neck and their shell is highly sculpted rather than smooth.
Distribution
Click for larger image
The Great Lakes / St. Lawrence Blanding’s Turtle population comprises the majority of the species’ distribution in Canada and occurs in southern and central Ontario and a few locations in southwestern Quebec. There is also a smaller, isolated population in Nova Scotia. Blanding’s Turtle occurs in the northeastern United States from Maine west to South Dakota and Nebraska and south to Illinois and Indiana.
Habitat
Blanding's Turtles occupy wetlands and other aquatic habitats with shallow water, little-to-no flow and organic substrates, such as fens, bogs, swamps, marshes, permanent or temporary ponds, creeks and shallow bays of lakes. They are typically found in areas with abundant aquatic vegetation and plenty of basking sites, such as hummocks, logs and vegetated shorelines with low canopy cover. Individuals overwinter, sometimes communally, in the soft bottoms of small wetlands or ponds. Females dig their nests in open-canopy habitat with high sun exposure, such as in forest clearings, meadows, shorelines, rock outcrops, agricultural fields and the shoulders of roads. The nest sites are typically within a few hundred metres of a wetland or water body.
Biology
In Canada, Blanding’s Turtles are dormant during the winter and are active from late March or April until late September or October, depending on latitude. Females nest in late May or June. Females may travel over 6 km to reach their nesting site, often moving extensive distances over land through forests, fields and other terrestrial habitats. The female excavates a nest cavity in soil, sand or gravel substrate and deposits 3–25 elliptical eggs. Hatchlings emerge in September or October. The sex of the offspring is temperature-dependant; warmer incubation temperatures produce females and cooler temperatures produce males. Blanding’s Turtles do not reach sexual maturity until they are 17–25 years of age, and females reproduce every 1–3 years. Blanding’s Turtles are very long-lived, and individuals can live for over 80 years. Blanding’s Turtles are primarily carnivorous and forage for fish, frogs and frog eggs, carrion and a wide range of invertebrates, including crayfish, insects, slugs, worms, snails and bivalves. When feeding, Blanding’s Turtles suck food into the mouth by expanding a chamber in the mouth to create a negative pressure. Blanding’s Turtles bask regularly in the spring, especially on sunny days. Individuals typically travel between several wetlands or other aquatic habitats throughout the active season, and home ranges can often be several kilometres in length.
Threats
The extensive conversion of natural areas to urban and agricultural uses in southwestern Ontario has resulted in the loss of Blanding’s Turtle populations from most of that region, and ongoing habitat loss continues to threaten this species throughout its Canadian range. The rapid spread of the highly invasive European Common Reed (Phragmites australis australis) is also causing the widespread conversion of this species’ habitat into largely unsuitable areas. Blanding’s Turtles are especially susceptible to mortality on roads due to the extensive terrestrial movements that are common to this species, well as the tendency for females to nest on gravel roads or road shoulders. Since Blanding’s Turtles are naturally long-lived and reproductive potential is very low, increases in annual adult mortality of as little as 1–5% can cause populations to decline. Nest predation by subsidized predators (e.g., Raccoon, Skunk) and illegal collection for the pet trade or for human consumption also threaten some populations, and climate change poses a potentially serious future threat to Canadian turtles.