Graptemys geographica (LeSueur 1817) – Northern Map Turtle, Common Map Turtle

Abstract

The Northern Map Turtle, Graptemys geographica (Family Emydidae), is a mediumsized sexually dimorphic freshwater turtle species (female carapace length to 292 mm, males to 160 mm) and the sister taxon to all other map turtle species. It is often common in rivers and lakes within its North American range. The turtles make extensive movements within their habitats for nesting, basking, and feeding. Mating occurs in fall and spring; hibernation lasts from October to mid-April in northern regions, and most hatchlings overwinter in the nest. Northern Map Turtles are primarily carnivorous, feeding predominately on snails, bivalves (including invasive dreisennid mussels), and aquatic insect larvae. Two to three clutches of 6 to 20 eggs are laid each year between late May and mid-July. Because males mature after about 4 years and females require about 10 years, adult sex ratios are often skewed towards males. Sex ratios are also influenced by nest temperatures, with warmer nests producing females and cool nests producing males. Direct and indirect human activities, including fisheries by-catch mortality, appear to be responsible for some population declines of this species in some regions, but G. geographica is not at this time considered Threatened.distRiBution. -Canada, USA. Southwestern Quebec and southeastern Ontario to central Alabama, northern Louisiana, west to central Minnesota and eastern Kansas and Arkansas, with scattered isolated populations in the northeastern USA in Vermont, New York, New Jersey, and Pennsylvania.

High Conservation Value of an Urban Population of a State-Endangered Turtle

“…The Northern Map Turtle is a widely-distributed species, ranging from southern Canada south to Alabama and northern Louisiana and as far west as Kansas and Oklahoma [19]. Abundant in much of its range, the species faces declines in some areas due to habitat loss, pollution, and commercial collecting [20][21][22]. In Maryland, Northern Map Turtles are found only in the Susquehanna River and its immediate drainages, between the Maryland/Pennsylvania state line and Chesapeake Bay.…”

Burying in lake sediments: A potential tactic used by female northern map turtles to avoid male harassment

“…During these 2 days, we observed 32 turtles: 29 adult females, one adult male, one immature female, and one turtle we could not sex because it was too far in the field of view. Turtles could easily be sexed from the ROV recordings due to the pronounced sexual dimorphism in body size, head size, tail length, and body shape in northern map turtles (Vogt et al., 2018). Of the 29 adult females observed, three (10%) were moving along the bottom and 26 (90%) were immobile on the bottom.…”

The overwintering behaviour and physiology of Northern map turtles (Graptemys geographica) in Ontario

“…Males may also have a reproductive incentive to move in winter. Northern map turtles mate just before and after the winter (Vogt et al 2018), and in lake Opinicon mating occurs at communal overwintering sites within days of the spring ice melt (Bulté et al 2018;Bulté et al 2021). Male Northern map turtles prefer larger females over smaller ones (Bulté et al 2018) and also appear to consider the potential for sperm competition when selecting mates (Bulté et al 2021).…”