Sea Turtles

Loggerhead resting on the beach. source: NOAA

Loggerhead resting on the beach. source: NOAA

There are relatively few reptile species that have adapted to the challenges of the marine environment. Unlike mammals, most reptiles cannot maintain a constant body temperature (endothermic); their body temperature changes with the environment around them (ectothermic).

On land, reptiles often have many options to regulate their temperature by changing their behavior: getting out of the cold by burrowing or perching on sunny rocks, for example. In high latitudes, cold seasons drive them into torpor or hibernation giving them a few, warm months to feed and reproduce. Temperature becomes especially important during incubation (most reptiles produce eggs, not live young). Buried in rotting vegetation or soil in a sunny patch ensures that the eggs will be warm enough to develop. Slight changes in temperature can spell disaster for the clutch or even change the sex of developing embryos.

In aquatic and marine environments, many organisms have had to find ways of dealing with the cold: water absorbs heat four times as quickly as the air. It is a wonder that there are any marine reptiles at all. For the most part, marine reptiles keep warm by changing their behavior. They may haul out on land to bask, use warm water currents or migrate with the seasons. All, or some of these adaptations may be used. The diversity of adaptations mirrors the diversity of marine reptiles. They include the full range of reptile types: alligators and crocodiles, marine iguanas and, of course, sea turtles.

All sea turtles are well adapted to life at sea: they have strong armor against predators: a carapace on top and the plastron beneath. Long, stiff fore flippers pull them through the water while the hind flippers steer. Large eyes gather light in dark depths. The nostrils are placed high on the tip of the beak to catch a breath quickly at the surface. Despite these adaptations, sea turtles, like seals, must come ashore: their eggs need the warmth that only sunny beaches can provide. And like whales, their feeding grounds are often at great distances from their breeding grounds. There is growing evidence that long distance migrations may be guided by magnetic cues.

The records of five species of marine turtles are the only representatives of reptiles on the Bank. Only one of these species, the leatherback, is considered to be cold adapted: they can maintain a body temperature well above the surrounding sea temperature using many of the same adaptations that marine mammals use. The other species use the Bank during the short season of late summer, visit sporadically with warm water episodes or are juveniles, lost from wandering or tossed by storms. Most sea turtle species are in considerable danger from human activity. They show up as bycatch or are entangled in some types of fishing gear; they are founded strangled or gagged in human debris; their nesting beaches have been razed by development; their meat or other body parts are consumed. Many researchers are surprised that some of the species still exist. All of the species mentioned below are listed as endangered by the U.S. Endangered Species Act except for the loggerhead, which is considered threatened.

On Stellwagen and the surrounding coasts, there has been considerable interest in sea turtles, especially in fall when cold stunned individuals may wash ashore. These individuals can, in some instances, be rehabilitated and transported south to warmer environs. In some instances (such as the Kemp’s ridley) helping individuals may positively affect the population as a whole. This also gives researchers a chance to answer some basic gaps in our knowledge of their biology. Where do some species spend their early and late juvenile stages (leatherbacks and Kemp’s Ridley)? Do some species actually use this area as a regular part of their feeding area, or are they found here only incidentally (Kemp’s Ridley, loggerhead and green)?

If you do come across a sea turtle on beaches along the Massachusetts southeast coast you should cover the individual with sea weed or beach grass, mark the spot with something prominent and contact the Massachusetts Audubon Society in Wellfleet, on Cape Cod at (508) 349-2615 or, for other regions of Massachusetts, the New England Aquarium in Boston.