Distribution: This group includes one species with seven recognized races or subspecies. The diamondback terrapin ranges along the Atlantic and Gulf coasts from Cape Cod, Massachusetts, to southern Texas, including the Florida Keys (Ernst, Lovich, and Barbour 1994). This species was released during the 1940's into San Francisco Bay, but did not become established (Taft 1944; Hildebrand and Prytherch 1947). Records for this species in Mexico have not been confirmed (Smith and Smith 1979). Individual variation is great, and some forms are confusingly alike; therefore it is best to depend heavily on geography in matching identifications.

Habitat: The diamondback terrapin seldom strays from salt or brackish water and inhabits coastal marshes, tidal flats, coves, estuaries, and inner edges of barrier beaches (Conant and Collins 1998). Juveniles spend the first years of their life under mats of tidal wrack and flotsam (Pitler 1985).

Behavior: Diamondback terrapins spend the day feeding in the marsh and basking on the banks of tidal creeks and apparently spend the night buried in the mud (Ernst, Lovich, and Barbour 1994). The annual activity cycle of diamondback terrapins varies because of the extensive latitudinal distribution of the species. In the northern part of the range along the Atlantic Coast, terrapins enter hibernation from November through December and emerge between April and May. The active season is generally from March to November. Terrapins in the southern part of its range may emerge from hibernation on any warm days; however, northern terrapins remain dormant throughout winter. Yearicks et al. (1981) reported terrapins hibernating individually or in small groups resting on the bottom under water, buried in the mud atop creek banks near the high tide line, and beneath undercut banks. Little is known regarding the movement patterns of diamondback terrapins but some studies have indicated remarkable site fidelity from year to year (Hurd et al. 1979, Lovich and Gibbons 1990). This species meets the osmotic challenges of a saline environment with several behavioral, physiological, and anatomical adaptations.

Reproduction: Males mature at about 9 cm before the end of their third year and females mature after the sixth year at about 13.2 - 17.6 cm (Cagle 1952, Montevecchi and Burger 1975, Seigel 1984, Lovich and Gibbons 1990). Timing of reproductive activities varies throughout their range. Generally courtship and mating occur in March and April and the nesting season extends through July. However, this may vary widely for those in the southern part of the range. The general sites selected for nesting are located in areas above high tide with minimum erosion (Burger 1977). Nesting occurs at night. Clutch size ranges from 4 to 18 eggs and incubation time ranges from 61 to 104 days (Burger 1977). Hatchlings may overwinter in the nest (Gibbons and Nelson 1978, Lazell and Auger 1981). Gender determination is temperature-dependent.

Food habits: Because of their large heads, diamondback terrapins are capable of eating hard-shelled prey including gastropods, crabs, and mussels (Conant and Collins 1998). Other food items include carrion, fish, marine annelids, and some plant material.

Populations: Population declines for diamondback terrapin are directly attributed to overharvesting for food (turtle soup) and the pet trade as well as habitat destruction. During the 1920's, many populations near coastal metropolitan areas were almost extirpated. Virtually nothing is known about diamondback terrapins from the time they leave the nest until they reach sexual maturity.