Burke et al.: Diet of Lepidochelys kempn 



Discussion 



The analysis of fecal samples from live turtles and 

 of gut contents from dead specimens strongly sug- 

 gests that crabs are the main dietary component for 

 Kemp's ridleys in New York waters. Crab parts were 

 present in 18 of the 19 turtles from which fecal 

 samples were obtained and were the predominant 

 food item by dry weight analysis. The analysis of 

 fecal material, however, may be biased because it 

 examines only that material which has not been 

 fully digested. This could cause overrepresentation 

 of less digestible components. 



The gastrointestinal tract results (which are less 

 susceptible to such bias) support the results of the 

 fecal sample analysis. Of the 18 stranded turtles 

 which contained identifiable food items, 13 con- 

 tained crab parts in their guts. Gut contents can 

 potentially be biased because of differential diges- 

 tion. However, from our qualitative observation of 

 the condition of the intestinal contents during dis- 

 section, we believe the components described herein 

 are representative of the diet. 



One difference between the fecal and intestinal 

 samples was the source of the turtles. Most fecal 

 samples were obtained from turtles captured in the 

 Peconic Bays, but most stranded turtles were recov- 

 ered on beaches adjacent to Long Island Sound. 

 Presumably the dietary samples reflect feeding ac- 

 tivities near the location of capture (or stranding). 

 Thus, the observation of spider and rock crabs as the 

 predominant components in the diets of both live- 

 captured and stranded turtles emphasizes their 

 importance as food items. 



The dietary components observed during the 

 study may be related to the relative abundance of 

 the prey species in the environment. Of the four 

 species of crab that were identified, the spider crab 

 was both the most frequently encountered fecal com- 

 ponent and the predominant crab identified in the 

 gut contents of dead turtles. During the course of 

 our studies we have noted that the nine-spined spi- 

 der crab was one of the most common crabs in the 

 waters where the turtles occurred. We have observed 

 local commercial fishermen retrieving thousands of 

 spider crabs while hauling in their nets. The Atlan- 

 tic rock crab was also frequently encountered in the 

 feces and gut contents of the turtles. The rock crab 

 is also abundant in many of the areas in which the 

 turtles occur. 



Not all of the dietary make-up observed in this 

 study can be explained by prey abundance. The 

 green crab (Carcinus maenus) is very common in 

 many of Long Island's estuaries but was not present 

 in any of the turtles examined. This species usually 



inhabits shallower, rocky intertidal and subtidal 

 habitats (Ropes, 1968; Williams, 1984), and our re- 

 search on turtle behavior indicates that the Kemp's 

 ridleys typically forage in deeper waters (Standora 

 et al., 1990). 



While we have commonly encountered lady crabs 

 in the waters where turtles forage, this species was 

 represented in only a few samples. Also rare in the 

 samples was the locally and commercially harvested 

 blue crab. Both the lady crab and the blue crab are 

 portunid crabs, capable of swimming very quickly. 

 This characteristic differentiates the portunids from 

 the slower walking crabs, such as the spider and 

 rock crabs. 



The only molluscs consumed by turtles examined 

 during this study included a few fragments of rela- 

 tively thin-shelled blue mussels (Mytilus edulis) and 

 bay scallops (Argopectin irradians), and entire shells 

 of the small three-lined mud snail (Nassarius 

 trivitattus). These mud snails are scavengers and 

 can be found locally in association with dead fish 

 and crabs (Long Island Shell Club, 1988). Their oc- 

 currence in four turtles, all of which had been cold- 

 stunned, may indicate that the turtles were scaveng- 

 ing during periods of low water temperature. 



Because sea turtles were obtained from different 

 sources in New York waters, it was possible to ob- 

 tain dietary information on a larger number of 

 Kemp's ridleys. In many of the previous studies 

 presented in Table 1, portunid crabs were indicated 

 as a main dietary component for Kemp's ridleys. 

 Although this crab family was observed in some 

 New York turtles, it was of secondary importance to 

 the walking crabs. 



In terms of the overall life cycle of Kemp's ridleys, 

 it appears that post-pelagic juveniles exploit the 

 benthic environments of Long Island's estuaries, 

 preying mainly on walking crabs. Data from our 

 ongoing research indicate that sea turtles emigrat- 

 ing from New York inshore waters travel to south- 

 ern coastal areas. Kemp's ridleys exhibiting this 

 behavior may join the more southerly portion of the 

 Atlantic population. Therefore, management plans 

 for Kemp's ridleys should consider factors that af- 

 fect benthic fauna, especially the abundant crab 

 populations in the northeastern region. Such im- 

 pacts could have far-reaching effects on a critical 

 stage in the lives of these endangered sea turtles. 



Acknowledgments 



This study was supported by a grant from the Na- 

 tional Marine Fisheries Service under contract num- 

 ber 40AANF902823. We thank Phil Williams for his 

 encouragement and support. Long-term support for 



