SCIENTIFIC NAME: Graptemys ernsti
Description: The Escambia map turtle is a large aquatic turtle exhibiting a remarkable degree of sexual dimorphism. The female carapace may reach 11 inches while males typically are smaller at 5 inches. Females develop massive heads that appear disproportionate to bodies; males retain the juvenile feature of a narrow head. The carapace has a median keel accentuated by prominent, black-tipped spines or knobs on the second and third vertebral scutes. The spines are retained by males but become inconspicuous in adult females. Old females often develop an anterior hump. The carapace typically is olive green to tannish with light yellow and with circular to C-shaped markings on pleural and marginal scutes; these markings are frequently obscured in older females as the ground color darkens. The plastron is pale yellow and unmarked except for narrow dark lines along the seams. The head has an olive green background with a large, yellowish, pale green, or tan blotch behind each eye. The inter-orbital blotch of head is not connected to post-orbital blotch and the post-orbital blotch terminates in a three-pronged nasal trident. The chin has lateral spots. Supraoccipital spots are often present. In the Graptemys pulchra species group, a group of Gulf Coast map turtles in which the females develop broadly expanded jaw surfaces, extreme sexual dimorphism is exhibited, and vertebral scutes develop into a spine-like keel. The characters that distinguish Escambia map turtles from the other species in the group are the presence of a nasal trident, supraocciptal spots and lack of a curved or transverse bar on the underside of the chin.
Distribution: Escambia map turtles were previously thought to be restricted to rivers draining into Escambia Bay, including the Conecuh, Escambia, Yellow, and Shoal, the species has since been discovered in the Pea and Choctawhatchee rivers. An individual, an unidentified Graptemys, was first observed in the Choctawhatchee River in 1996; Barbour’s map turtle was documented from the Pea River (Choctawhatchee River system) in 1997. This species was previously considered to be endemic to the Escambia River system (Conecuh and Yellow Rivers in Alabama, Escambia and Shoal Rivers in Florida). Putative hybrids of Barbour’s and Escambia map turtles also have been collected.
Habitat: Escambia map turtles are found exclusively in rivers and associated habitats. The greatest numbers occur along stretches with abundant logs and limbs for basking, sandbars for nesting, and molluscan prey, such as native bi-valve mollusk and the non-native Asian clam. Occasionally they may be found in impoundments, but these habitats are suboptimal.
Feeding Habits: Escambia map turtles are wholly carnivorous. The diets of males and small females consist primarily of aquatic insects. Adult females use massive head musculature and expanded oral crushing surfaces to feed almost exclusively on native unionid mollusks (bi-valve mussels) and the introduced Asian clam.
Life History and Ecology: Nesting occurs during late spring and early summer with peak nesting in June. Average number of clutches per season is four; older females may nest six to seven times per season. Average clutch size is 7.2 eggs, typically laid in a cavity an inch or two beneath the surface, within 10 – 50 feet of the water, on sandbars and riverbanks. Males mature in three years, females in 14 and longevity of females may exceed 50 years.
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AUTHORS: Mark S. Sasser, Certified Wildlife Biologist, Alabama Division of Wildlife & Freshwater Fisheres and James C. Godwin, Zoologist, Alabama Natural Heritage Program