Species Profile: Northern Map
Turtle (Graptemys geographica)
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| Northern Map Turtle - Nancy Barrett |
During a visit in mid-July, I came
across a small Northern Map Turtle sunning itself on a sunken log not far from
the platform overlooking the pond. I have seen adult Map Turtles sunning
themselves, usually on the far side of the pond, so this was a great
opportunity to observe and photograph this one. As a young individual, no
more than 9-10 cm in length, it was still brightly marked.
This turtle is named for the
markings on its shell, which look like contour lines on a topographical map.
The head and legs have a pattern of bright yellow lines, with a yellow
spot behind the eyes, and the carapace (upper shell) has an obvious raised
"keel" or ridge along the centre. Other similar species found in the
park include the native Midland Painted Turtle and, unfortunately, the
non-native Red-eared Slider which is the most commonly released "pet
store" turtle species in Ontario. They act like the neighbourhood
bullies to our native species, often released by owners once they begin growing
to 33 cm in length with a lifespan up to 30 years.
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| Midland Painted Turtle - Nancy Barrett |
Their habitat includes large lakes
and rivers with slow-moving water and a soft bottom, and they require high-quality
water that supports the females' favoured prey, molluscs (females can grow much
larger than males, up to 27 cm compared with 13 cm for the males).
Female Map Turtles may take more
than 10 years to reach maturity, nest from June through July, and lay a single
clutch of up to 17 eggs. The incubation temperatures of the eggs
determines the gender of the hatchlings.
Map Turtles are known for their
communal basking, and many individuals can be found piled up together.
They have very strong jaws; the females eat snails, clams and crayfish;
males and juveniles eat insects and crayfish. Some individuals of this
species can live more than 20 years.
Water pollution poses a serious
threat as it can cause massive die-offs of molluscs, the primary food item of
female Map Turtles. Habitat loss and degradation due to shoreline
development are additional threats.
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| Red Eared Slider - Nancy Barrett |
The Northern Map Turtle is listed as
a species of Special Concern under the Ontario Endangered Species Act 2007 and
the Species at Risk Act. It is also considered a Specially Protected
Reptile under the Ontario Fish and Wildlife Conservation Act.
Because this species is not very
common in our area, and because our reptiles and amphibians are experiencing
global declines of 20 and 40 percent respectively, I've always considered it
somewhat special. One way to help is to consider becoming a volunteer
citizen scientist and submit your sightings, and not just the rare ones.
You can do this by downloading the Ontario Reptile and Amphibian Atlas
App on your smartphone--it's also a digital pocket guide for all of Ontario's
reptiles and amphibians.
Find more information at www.ontarionature.org;
source material courtesy Ontario Nature;
