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For the past three summers Tom Wolcott has 

 been chasing ghost crabs up and down the beaches 

 of North Carolina. Armed with a transistor radio 

 and a starlight telescope, he works from dusk to 

 dawn. 



Wolcott, assistant professor of zoology at North 

 Carolina State University in Raleigh, developed a 

 consuming interest in ghost crabs (Ocypode quad- 

 rata) when he moved to North Carolina five years 

 ago. "The question I asked in the beginning was 

 'Just how important are these guys?' " he explains. 

 In order to find out, Wolcott had to determine what 

 the ghost crabs eat. 



"So I spent a lot of time walking up and down 

 the beach stalking every crab that was eating and 

 then stopping ter see what he was eating," said 

 Wolcott. 



These strange antics have resulted in some sur- 

 prising discoveries about the ghost crab's place in 

 the food chain of the beach. Wolcott contends that 

 the ghost crab is not the scavenger it was once 

 believed to be. Until recently, it was assumed that 

 ghost crabs picked their meals from rotting sea- 

 weed and trash which washed up high on the dry 

 sand. 



But Wolcott believes that the crab disdains such 

 fare. What he found after many nights of observa- 

 tion was that these creatures spend all their feed- 

 ing hours below the drift line, digging for the 

 other two crustaceans on the beach — the coquina 

 (butterfly clam) and the emerita (mole crab). In 

 fact, Wolcott's studies have shown that the ghost 

 crab consumes half or more of the population of 

 both species. That makes it the biggest predator on 

 the North Carolina beaches. 



The ghost crab probably got its name from its 

 habit of scampering silently across the beach at 

 night and disappearing into a hole in the sand if 

 threatened. During the day crabs stay in their 

 individual burroughs underground. At night they 

 come out to feed. 



Early in his studies, Wolcott did a burrough 

 census and discovered that the crabs are very num- 

 erous on North Carolina's beaches. During the 

 summer months as many as 20 crabs may inhabit 

 a one-meter wide swatch of the beach from the 

 dunes to the ocean. "That's dull work, I tell you — 

 counting every hole on the beach," Wolcott ob- 

 served. 



So far, most of Wolcott's work has been done on 

 50-meter wide stretches of beach at Shackleford 

 Banks and Ft. Macon State Park. During the sum- 

 mers he relocates at the beach, using an office at 

 the Marine Fisheries Lab in Beaufort. He takes 

 with him his research vessel, affectionately called 

 the "RV Sears," a 12-foot plastic boat. 



But more important than the boat in his track- 

 ing of crabs are the tiny transmitters Wolcott 

 makes. At about dusk on observation nights, he 

 traps two or three crabs and tapes the transmit- 

 ters to their backs. The equipment gives out 

 rhythmic signals which Wolcott picks up on his 

 souped-up transistor radio. Perched high on a 

 dune, he can locate the crabs and observe them 

 with his starlight telescope. The telescope ampli- 

 fies light so that he can see the crabs from a dis- 

 tance. 



"You can drive yourself crazy doing that. One 

 crab may go 300 meters one way, while another 

 scampers 100 yards in another direction," said 

 Wolcott. 



The ghost crabs do not seem to have any natural 

 predators on the North Carolina beaches, though 

 they are occasionally cannibalistic. Wolcott sus- 

 pects that racoons might be interested in eating 

 ghost crabs, but he can find no racoon tracks on 

 the beach. 



This particular species of crab ranges from 

 Rhode Island to Brazil. The top weight of crabs in 



Census-taking will 

 Result in bird atlas 



The University of North Carolina Sea Grant 

 College Newsletter is published monthly by the 

 University of North Carolina Sea Grant College 

 Program, 1235 Burlington Laboratories, Yarbor- 

 ough Drive, North Carolina State University, 

 Raleigh, N.C. 27607. Vol. 3, No. 4, April, 1977. 

 Dr. B. J. Copeland, director. Written and edited 

 by Karen Jurgensen and Mary Day Mordeeai. 

 Second-class postage paid at Raleigh, N.C. 27611. 



Ghost crabs: 

 Beach predators 



(Continued from p. S) 



this area is about 40 grams. If an average-sized 

 crab (about 20 grams) is allowed to eat all it wants, 

 it would consume two grams of meat per day. 

 That's the equivalent of one good-sized emerita or 

 about a dozen coquinas. 



One of the most startling pieces of information 

 that Wolcott has uncovered has to do with how 

 ghost crabs obtain water. After October the ghost 

 crabs disappear from the beaches. Their burroughs 

 close over with sand and they don't bother to dig 

 out again until May. Nobody knows exactly what 

 happens to them. 



Wolcott contends that they don't eat during this 

 time. But they must have water. In testing the 

 crabs, he discovered that they can get all the water 

 they need from the moist sand. They use their setal 

 tufts to extract water and then suck it into their 

 brachial chambers. 



"They are sucking, which we all know crabs 

 can't do," chuckled Wolcott. 



The census revealed 12 species of ground nesters 

 in the coastal area. There were 76,000 birds all 

 together and about 83 percent of them nested on 

 dredge islands. The most abundant of these was the 

 Royal Tern, with over 16,000 nests. The most rare 

 was the Great Black-backed Gull which is just be- 

 ginning to nest in North Carolina. 



Parnell and Soots have also found some sur- 

 prises in their research. Until they started work, 

 no one knew that there were any Herring Gull 

 colonies in North Carolina. The researchers dis- 

 covered a colony of over 300 pairs of birds. Forsters 

 Terns, Caspian Terns and Great Black-backed 

 Gulls were also recorded for the first time in North 

 Carolina. 



An abnormal amount of rain on the coast made 

 last summer a difficult one for birds and ornithol- 

 ogists. Many of the birds that nest on the beaches 

 were repeatedly washed out. "A lot of herons died 

 last summer. We found the young dead of exposure 

 by the dozens. They just can't make it in wet 

 weather," Parnell noted. 



Parnell and Soots are hoping for average 

 weather this summer so that they can complete 

 their census. They will compile the final statistics 

 into an atlas of maps, pinpointing the locations of 

 various colonial bird colonies on the coast. The 

 maps will be valuable for local governments, de- 

 velopers and bird lovers. 



University of North Carolina 

 Sea Grant College Program 

 1235 Burlington Laboratories 

 North Carolina State University 

 Raleigh, N.C. 27607 



