Types of Sea Turtles in Delaware

Loggerhead sea turtles can weigh 200 to 350 pounds and have shells typically 2.5 to 3 feet long, with a reddish-brown carapace. Their heads are distinctly large and block-shaped, visible even from a distance. Diamondback terrapins are much smaller, averaging 5 to 9 inches in shell length, and weigh less than a pound. Terrapins have a darker, more patterned carapace with concentric rings on each scute. The terrapin's head is proportionally smaller and more delicate. Loggerheads are ocean-going reptiles that travel thousands of miles; terrapins rarely leave their home bay.

Loggerheads that reach Delaware in summer are typically juveniles born on beaches in Florida and other southeastern states 5 to 10 years earlier. They spend their early years in the open Atlantic Ocean feeding on sargassum and jellyfish, then gradually migrate northward as they grow. By the time they reach Delaware's Delaware Bay and coastal waters, they are 2 to 3 feet long and actively foraging. Adult loggerheads from nesting populations as far south as Central America also occasionally pass through Delaware waters during long-distance migrations between feeding grounds and nesting beaches. These journeys span years and thousands of miles, making each sighting a snapshot of a much larger Atlantic-wide movement.

Leatherbacks are the largest sea turtles and the only species with a shell lacking hard bone plates. Instead, their carapace is a thick, leathery skin stretched over a framework of small bony ossicles, giving them a smooth, dark appearance with no visible scutes like other turtles. They can exceed 4 feet in length and weigh over 1000 pounds, making them instantly recognizable by their size and texture. Leatherbacks have a narrower, more pointed head than loggerheads and seven prominent ridges running along their carapace. In Delaware, leatherbacks are extremely rare, showing up only in late August or September during the warmest water years. Most Delaware visitors will never see one, but identifying features make them unmistakable if encountered.

A juvenile loggerhead arriving in Delaware is typically 20 to 24 inches in shell length and weighs 5 to 10 pounds. A diamondback terrapin, by contrast, is roughly 6 inches long and weighs a few ounces. The young loggerhead is still small enough to fit in an adult human's hands, but it is always substantially larger than any terrapin you might see. At a distance, the confusion most often comes from seeing dark water-loving shapes and mistaking terrapins in a creek for a young sea turtle, especially if visibility is poor. Up close, the loggerhead's larger size, scalier appearance, and flipper-like limbs instantly separate it from the terrapin's stubby, clawed feet and compact form.

Diamondback terrapins are brackish-water specialists, living year-round in salt marshes, tidal creeks, and estuary bottoms throughout Delaware. They are the state's most common turtle in these habitats. Loggerheads, by contrast, are open-water ocean turtles that prefer deeper offshore environments and only venture into Delaware's shallow bays during their summer feeding migrations. Terrapins remain largely stationary in their home creek or marsh, while loggerheads are nomadic across entire ocean basins. Terrapins bask on mud banks and log snags in marshes; loggerheads rarely emerge and are observed mostly from boats in deeper channels or during occasional strandings. Both are cold-intolerant and disappear or become dormant as soon as water temperatures drop below 50 degrees in late fall.

Sea turtles are ectothermic reptiles with body temperatures controlled by their environment. When water temperatures fall below 55 degrees Fahrenheit, their metabolism slows dramatically, and they cannot feed or move effectively. Delaware Bay water reaches maximum temperature in August (around 74 degrees) and drops rapidly by October, falling below 50 degrees by November. Juvenile loggerheads arriving in May and June to feed on small fish and crustaceans must depart by early autumn before the water cools. Leatherbacks, which are slightly more cold-tolerant due to their large size and thermoregulation abilities, can linger into late September or early October in warm years. By contrast, terrapins that remain year-round in marsh bottoms survive winter dormancy in the mud, emerging only when spring warming returns.

Kemp's ridley sea turtles and green sea turtles have been recorded as extremely rare vagrants in Delaware, mostly as stranded juveniles or sub-adults during unusually warm water years. These occurrences are sporadic and unpredictable, averaging fewer than one confirmed sighting every several years. Kemp's ridleys are the smallest sea turtles and are generally restricted to the Gulf of Mexico and southern Atlantic waters, making Delaware far outside their normal range. Green sea turtles primarily inhabit tropical and subtropical waters and are even rarer in Delaware than Kemp's ridleys. For practical identification and observation purposes, loggerheads and occasional leatherbacks represent the only sea turtles you are likely to encounter during a summer visit to Delaware's coast.

Loggerheads have a relatively smooth, reddish-brown to tan carapace with minimal patterning compared to other sea turtle species. Each scute (plate) on the shell is uniform in color with only subtle edges visible between them. Green sea turtles, if they ever reached Delaware, would show more olive to dark coloring with radiating pattern lines on the scutes. Leatherbacks have seven ridges running lengthwise along their carapace, creating a distinctly ridged appearance. Kemp's ridleys, if encountered, would show a heart-shaped carapace that is relatively shorter and wider than a loggerhead's. The loggerhead's shell is roughly oval and proportionally longer, and the reddish tint is the most reliable field mark even from a distance in poor visibility.

Delaware's shallow bays and inlet areas provide ideal feeding grounds for both species during the warmest months. A visitor or researcher observing loggerheads in Cape Henlopen or Delaware Bay may also spot diamondback terrapins basking or foraging in the same general region, simply because both are present during summer. Terrapins are far more numerous and active during daytime hours, while loggerheads are generally submerged and only occasionally surface or beach themselves. In academic surveys and casual observation, both are documented in the same locations because the habitat, shallow, food-rich estuary water, benefits both. However, a single observation will most likely show either terrapins or loggerheads in isolation rather than both in the same moment.