NATURALIST'S 



NOTEBOOK 



the early 1900s. Many of the finer 

 restaurants closed during Prohibition. In 

 addition, the harvest of wild stock 

 diminished as the populations rapidly 

 declined. The practice of selecting for 

 large, sexually mature females over the 

 years had reduced the breeding popula- 

 tion. 



Today, the North Carolina Wildlife 

 Resources Commission has given the 

 species a "special concern" designation. 

 Eggs in the nests are broken and young 

 hatchlings are killed by raccoons, foxes, 

 otters, marsh rice rats and seabirds. 

 Adults fall prey to otters and other large 

 predators. Human activity contributes to 

 two causes of mortality: road kills, 

 common where a highway separates 

 sandy nesting sites from tidal creeks, 

 and incidental drownings in gill nets and 

 crab pots. 



Gilbert Grant, a Sea Grant researcher 

 with the University of North Carolina at 

 Wilmington, is testing an excluder device 

 for crab pots that will reduce the acciden- 

 tal take of diamondback terrapins. 

 Preliminary studies have shown that crab 

 pots equipped with excluders and located 

 more than 75 feet from the shore may 

 significantly reduce terrapin bycatch 

 mortality. Grant hopes to develop a 

 design that excludes terrapins without 

 reducing the catch of blue crabs. 



Perhaps the major reason for the 

 recent diamondback decline is the 

 deterioration and loss of its natural 

 habitat. Possible causes include develop- 

 ment and bulkheading marsh shorelines, 

 thus reducing nesting sites; increased 

 sedimentation; nutrient enrichment; 

 boating disturbances; and filling and 

 draining marshes. 



To help the diamondback survive 

 these threats, researchers must know as 

 much as possible about its life history. 

 But much remains to be learned about 

 this marsh creature. For example, its 

 feeding behaviors are unclear. North 

 Carolina terrapins eat fiddler crabs, but 

 other populations appear to prefer 

 periwinkle snails. They are also known to 



eat juvenile blue crabs, mummichogs 

 (marsh minnows) and other fish. Large 

 diamondbacks will even "limb crop" — 

 bite the legs off adult blue crabs. 



Phil Spivey, a graduate student at 

 the University of Georgia, has noted that 

 males in the Davis marsh prefer 

 Melampus snails, tiny, thin-shelled land 

 snails that hang around high-tide debris, 

 whereas females tend to select larger 

 juvenile blue crabs. While most scientists 

 believe that diamondbacks feed under- 

 water, it is unclear where they capture 

 fiddler crabs, which are intertidal critters. 



The terrapins' reproductive behavior 

 is a little more clear. Late spring brings 

 them into courtship, and mating takes 

 place in tidal creeks. Soon after, females 

 search for nesting sites in sandy spots 

 above the high tides. Like loggerhead 

 turtles, diamondback terrapins dig a hole 

 in the sand with their back legs. They 

 deposit six to 1 2 soft, white, elliptical 

 eggs into the hole, and hatchlings emerge 

 50 to 70 days later. Females nest 

 throughout the summer in North 

 Carolina, but researchers do not know 

 whether they produce two or three 

 clutches each season. 



Once the hatchlings climb through 

 the sand to the surface, their fate presents 

 another mystery. Some reports indicate 

 that the young crawl back into the 

 subtidal mud until the following year and 

 do not feed at all until the next spring. 

 Others indicate that early-hatching young 

 do feed. Alvin Braswell, curator of 

 herpetology at the North Carolina State 

 Museum of Natural Sciences, says their 

 behavior for the first several years of 

 their lives remains a mystery. 



To solve one part of the mystery, 

 Spivey is attempting to determine how 

 widely diamondbacks travel. With a spot 

 of epoxy cement, he attaches small 

 transmitters to the backs of terrapins in 

 the Davis marsh and tracks them with 

 radiotelemetry. One female ranged up to 

 a mile, but always returned to a home 

 location. By interpreting these move- 

 ments, Spivey can one day define the 



terrapins' home ranges. He has already 

 found that they are more active during 

 the day. 



The diamondback' s future is as 

 uncertain as some of its habits. In areas 

 with few roads or crab pots and many 

 tidal creeks or old mosquito ditches 

 (narrow channels once used to drain 

 marshes), their numbers have slowly 

 increased. In other places, habitat loss 

 and human population pressures 

 continue to reduce the population. 

 A successful comeback depends on 

 humans maintaining the diamondback' s 

 habitat and preventing additional loss of 

 breeding females. 



As denizens of intertidal muds and 

 tidal creeks, diamondback terrapins 

 push boldly through the salt marsh grass 

 and bask lazily on sandy banks, unaware 

 of the concern for their survival. Warm 

 weather creatures, they will bury 

 themselves at the first chilly touch of 

 winter. If their marshy homes are 

 preserved, they will continue their cycle 

 and emerge from the mud again, hungry 

 and seeking the sun. □ 



TERRAPIN 

 TIDBITS 



• Range: Gulf Coast of Texas to 

 Cape Cod, Mass. 



• Size: Female carapace reaches up 

 to 9 inches while male carapaces 

 extend no more than 5 inches. 

 Females weigh about 1,200 grams, 

 while males weigh in at 225. 



• Sexual dimorphism: Females are 

 larger, have a rounder head, deeper 

 shell and shorter tail than males. 



• Markings: The carapace varies 

 from a uniform black to light 

 brown, marked by distinct dark 

 concentric rings. The head, upper 

 lip, neck and limbs can have black 

 spots on dark gray, greenish-gray 

 or dark brown skin with margins 

 of orange or yellow. □ 



COASTWATCH 33 



