The name originally was used by early European settlers in North America to describe these brackish-water turtles that inhabited neither freshwater habitats nor the sea.

[17] Terrapins also exhibit unusual and sophisticated behavior to obtain fresh water, including drinking the freshwater surface layer that can accumulate on top of salt water during rainfall and raising their heads into the air with mouths open to catch falling rain drops.

[24] It is unclear why terrapins do not inhabit the upper reaches of rivers within their range, as in captivity they tolerate fresh water.

[30] Female terrapins can mate with multiple males and store sperm for years,[31] resulting in some clutches of eggs with more than one father.

[32] Hatchlings sometimes stay on land in the nesting areas in both fall and spring and they may remain terrestrial for much or all of the winter in some places.

Hatchlings have lower salt tolerance than adults and Gibbons et al.[26] provided strong evidence that one- and two-year-old terrapins use different habitats than do old individuals.

Limited data suggest that terrapins hibernate in the colder months in most of their range, in the mud of creeks and marshes.

[41][42][43][44][45] At high densities the terrapin may eat enough invertebrates to have ecosystem-level effects, partially because periwinkles themselves can overgraze important marsh plants, such as cordgrass (Spartina alterniflora).

Adult females, due to their powerful, defined jaw, will occasionally feed on crustaceans such as crabs and are more likely to consume hard-shelled mollusks.

[48] The population also decreased due to the development of coastal areas, terrapins being susceptible to wounds from the propellers on motorboats.

[49] The Wetlands Institute estimates that a minimum of 14,000 to 15,000 terrapins drown in crab traps annually set along the New Jersey coast alone.

[51] Among two such abandoned crab pots in a tidal marsh in Georgia, a study found 133 dead terrapins, according to the Center for Biological Diversity.

[52] Further, an increase in seawalls and bulkheads being built for storm and erosion control, exacerbated by climate change and sea level rise, inadvertently eliminate terrapin's nesting habitat on beaches and upland areas with soft shorelines.

The diamondback terrapin is listed as a "high priority species" under the South Carolina Wildlife Action Plan.

[57] There is limited protection for terrapins on a state-by-state level throughout its range; it is listed as Endangered in Rhode Island and Threatened in Massachusetts.

[citation needed] Diamondback terrapins are the only U.S. turtles that inhabit the brackish waters of estuaries, tidal creeks and salt marshes.

With a historic range stretching from Massachusetts to Texas, terrapin populations have been severely depleted by land development and other human impacts along the Atlantic coast.

This program allows volunteers to explore the coastal sprawl of New Jersey's Ocean County on Barnegat Bay, one of the most extensive salt marsh ecosystems on the East Coast, in search of this ornate turtle.

Veteran turtle scientists Dr. Hal Avery, Dr. Jim Spotila, Dr. Walter Bien and Dr. Ed Standora are overseeing this program and the viability of terrapin populations in the face of growing environmental change.

[59] The conservation status was heavily impacted by the consumption of diamondback terrapins in the 1900s when their sweet meat eventually became a multi-million dollar industry for gourmet restaurants.

[60] Gastrointestinal studies have identified the presence of ingested PST in their tissues which causes the muscle weakness, paralysis, etc.

People tend to build their cities on ocean coasts near the mouths of large rivers and in doing so they have destroyed many of the huge marshes that terrapins inhabited.

Nests, hatchlings, and sometimes adults[65] are commonly eaten by raccoons, foxes, rats[32][66][67] and many species of birds, especially crows and gulls.

Terrapins are killed by cars when nesting females cross roads[69] and mortality can be high enough to seriously affect populations.

In Maryland, diamondback terrapins were so plentiful in the 18th century that slaves protested the excessive use of this food source as their main protein.

Late in the 19th century, demand for turtle soup claimed a harvest of 89,150 pounds from Chesapeake Bay in one year.

In 1899, terrapin was offered on the dinner menu of renowned Delmonico's Restaurant in New York City as its third most expensive item.

[74] On July 8, 2009, flights at John F. Kennedy Airport in New York City were delayed for up to one and a half hours as 78 diamondback terrapins had invaded one of the runways.

The turtles, which according to airport authorities were believed to have entered the runway in order to nest, were removed and released back into the wild.

[79] Recent anthropogenic habitat modification, such as the construction of docks, roads, and housing developments, as well as activities such as crab-trapping, likely play a role in low annual survivorship.