Spring’s approach means turtles are on the move

I enjoy a snowy winter, but the quiet atmosphere invites me to look for subtle signs of change that mean spring is on its way. Skunk cabbage sprouting in the wetlands? A soaring osprey? Naturally attracted to water, I sight my envoys of spring lounging on logs and mud banks: the eastern painted turtle (Chrysemys picta picta) and the northern diamondback terrapin (Malaclemys terrapin). Surfing our watersheds, these two native swimmers pass the baton as water flows east, down a gradual incline, to the Atlantic Ocean.

At the headwaters, the eastern painted turtle thrives in freshwater. Many of our streams or branches, from Millsboro to Milford, were dammed to power gristmills. These mill ponds are ideal habitat for this turtle: a muddy bottom, plenty of aquatic plants and invertebrates to eat, and exposed banks or logs for basking (sunbathing) sites. A medium sized turtle (4-6 inches), the painted turtle has 13 olive-brown scutes (scales) on an oval-shaped carapace (top shell). All turtles have a spine, which grows with the carapace, and each vertebrae is visible on the inside of an empty shell. A bridge (bone) on each side welds the carapace to the yellow plastron (bottom shell). Two prominent yellow spots on the head, and red stripes on the neck and limbs distinguish this turtle from the exotic red-eared slider (Trachemys scripta elegans). The slider has an elongated red patch behind the eye and a sharply keeled carapace.

Turtles have lungs and breathe air above the water. Driving by a frozen Wagamons Pond, I am reminded that a painted turtle may find a pocket of air and swim under the ice (much to the surprise of a young ice skater). Water temperatures are often more stable and above freezing under a layer of ice. Research indicates that painted turtles are inactive at the bottom of a pond during extreme drops in water temperature, yet they are able to take in dissolved oxygen underwater through their skin and mouth lining. As reptiles, turtles are ectothermic. Their body temperature varies according to the external air or water temperature. As the fickle weather of March warms into April, turtles jockey for space on a log to soak up the sun and jump-start their metabolic activity.

On the way to the sea, fresh water meets salt water, and they mix to become brackish. The diamondback terrapin prospers in tidal estuaries from Slaughter Beach to the Indian River Bay, where the salinity is constantly changing. Equipped with a gland behind the eye, these turtles are able to get rid of excess salt by “crying” salty tears. 

Like a fingerprint, each diamondback terrapin has distinct diamond-shaped rings on its scutes, and a unique white-and-black-patterned head and neck. At maturity, females are a hefty 4.45 pounds, with a 7.5-8-inch-long, narrow plastron; males weigh in at 1.1 pounds with a 5-inch plastron. Since 2001, a Delaware recreational fishing regulation requires each crab pot to have a TED (turtle excluder device) to reduce the accidental drowning of male terrapins.

In the ice-encrusted creeks weaving among the saltmarsh cordgrass (Sporobolus alterniflorus), the terrapin is inactive during brumation (not a true hibernation) and remains submerged. As March arrives, look for these exceptional swimmers feeding on crabs, mussels and saltmarsh snails, and basking at low tide. A species of “special concern” in Delaware, the diamondback terrapin is a keystone species supporting a healthy saltmarsh. To learn more about local diamondback terrapin surveys, visit the Delaware Center for the Inland Bays website, inlandbays.org.

In late spring, mature female turtles leave the water in search of the perfect sandy berm to excavate and deposit their eggs. The nest cavity will hold an average of eight to 12 offspring in pliable, leathery eggshells. Subterranean temperatures in the natal nest determine the ratio of male to female hatchlings. Diamondback terrapins emerge in 60 days, and painted turtles hatch in about 72 days. During July and August, quarter-sized hatchlings surface and scramble to the water, avoiding cars and predators. Occasionally, September nests produce hatchlings that overwinter underground and emerge on a warm day in March or April.

Female turtles of all species will be on the move in April, May and June, so keep an eye out for them! Watch for turtles crossing inland back roads near ditches, ponds and rivers. Be aware of diamondback terrapins cruising across coastal byways and navigating traffic through Delaware Seashore State Park along Route 1. For a list of native turtle species, visit delawarenaturally.org.