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Marine Turtle Newsletter 37:7-8, © 1986
Anne Meylan1 and Sam Sadove2
1Department of Herpetology, American Musuem of Natural History,
Central Park West and 79th St. New York, New York 10021 USA
2Okeanos Ocean Research Foundation, P. O. Box 776, Hampton Bays, NY 11946 USA
During late 1985 and early 1986 the Okeanos Ocean Research Foundation recovered 52 stranded sea turtles from the waters of Long Island Sound, New York (USA). The strandings coincided with several episodes of unusually cold weather. Most of the turtles were found washed ashore in the tidal wrack or floating passively in the surf along the northern coast of Long Island. As far as we are aware, no strandings occurred on the opposite shore of the Sound, in Connecticut. Eighteen turtles were still alive when recovered. Most responded to gradual exposure to warmer temperatures; eleven survived.
Three observations led us to suspect that cold temperatures were responsible for the stranding:
Large-scale cold-stunning events involving sea turtles have been recorded in Florida in 1894-95 (Wilcox 1896) and again in 1977, 1981, and 1985 (Ehrhart 1983, Witherington and Ehrhart 1985), but to our knowledge no event of comparable magnitude has been previously recorded elsewhere in US waters.
What made the cold-stunning episode in Long Island all the more unusual was that most of the turtles were Kemp's ridleys (Lepidochelys kempi). We positively identified 39 ridleys and two other specimens unseen by us are believed to have been ridleys. Ridleys are one of the rarer species of sea turtles observed in New York waters in any season. Okeanos, which has had the responsibility for recording strandings for the state of New York since 1979, has recovered only nine other specimens. The primary range of L. kempi is considered to be the Gulf of Mexico (Carr 1952; Hildebrand 1980; Ogren, pers. comm.), although evidence has been accumulating that ridleys regularly occupy habitats in eastern Florida and along the eastern seaboard as far north as the Chesapeake Bay (Byles, pers. comm.; Ogren, pers. comm.). There are a considerable number of recent and historical records of strandings in the area of Cape Cod. These have always been difficult to explain in view of the eastern-trending currents in the northern Atlantic and the location of the sole nesting beach at Rancho Nuevo, Mexico. Some authors consider that most of the turtles found in New England waters have been swept out of their normal range by Gulf Stream currents (Hildebrand 1980); the question of their viability as members of the breeding population has not yet been resolved (Carr 1980).
The ridleys recovered in this event were remarkably similar in straight carapace length, measured notch-to-notch (mean = 28.2cm; range = 22.1-33.0; SD = 2.69; N = 37); all can be considered immature. Five of the nine that survived were flown to the Florida Keys, where four were tagged and released by the National Marine Fisheries Service. Four others are being held through the winter and will be radio-tagged and released in the Northeast in late spring.
We are faced with several puzzling questions about the distribution and migratory behavior of Kemp's ridleys. Is Long Island Sound a normal but unrecognized developmental habitat, or is their presence there in 1985-86 an anomalous event? Given the critical survival status of the species, the importance of answering this question is obvious. Although it seems likely that ridleys would have been spotted previously in the Sound if they occur there on a regular basis, we are hesitant to make this assumption. An important developmental habitat for green turtles and loggerheads went unrecognized in Florida until cold-stunning events occurred there (Ehrhart 1983).
An alternative hypothesis is that ridleys do not normally inhabit the Sound, but were brought there by some external factor such as the warm-core eddies of the Gulf Stream (Carr 1980). Unfortunately, we have no information as to whether the turtles arrived in the Sound one-by-one over a period of time, or simultaneously. They also might be part of a developmental migration - an hypothesis supported by the uniformity of their sizes.
The green turtle is also uncommon in New York waters. From 1979 until the present cold-stunning event, only two others had been recovered by Okeanos. The two that were recovered in the present event were both immature (28.3 and 29.0 cm straight carapace length, notch-to-notch). One survived and was released in Florida with the ridleys.
The nine loggerheads ranged from 36.0 to 58.3 cm straight carapace length, notch-to-notch (mean = 48.7; SD = 6.56). Based on stranding records, loggerheads are the second most common species in New York (the leatherback, Dermochelys coriacea, is most common). Most of the loggerheads recovered previously by Okeanos were taken in Summer and early Fall. Data on the seasonal migrations of immature loggerheads in US waters are lacking, but adults are thought to be absent from waters of the northern states during the winter months (Shoop et al. 1981; Meylan and Bjorndal 1983). The presence of apparently healthy, immature specimens in New York in November-January is both puzzling and unexpected.
None of the 52 turtles recovered during the cold-stunning event showed evidence of having carried a tag. For the ridleys, this is important because it indicates that they are part of the wild population rather than members of the group head-started at Galveston, Texas. Moreover, given their small size, they most likely hatched at Rancho Nuevo since government protection began in 1966. It is an encouraging sign to find this many ridleys anywhere away from the nesting beach.
All turtles that succumbed in the cold-stunning event have been donated by Okeanos to the American Museum of Natural History, where they will be available for study by interested researchers.
Carr, A. 1952. Handbook of Turtles. Cornell University Press, Ithaca, New York. 542pp.
Carr, A. 1980. Some problems of sea turtle ecology. Amer. Zool. 20:489-498.
Ehrhart, L. M. 1983. Marine turtles of the Indian River Lagoon system. Florida Scientist 46:337-346.
Hildebrand, H. 1980. A historical review of the status of sea turtle populations in the western Gulf of Mexico. In K. Bjorndal (ed.) Biology and Conservation of Sea Turtles. Smithsonian Institution Press, Washington DC.
Meylan, A. and K. Bjoprndal. 1983. Sea turtle nesting at Melbourne Beach, Florida, II. Post-nesting movements of Caretta caretta. Biological Conservation 26:79-90.
Shoop, C. R., T. L. Doty and N. E. Bray. 1981. Sea turtles in the region between Cape Hatteras and Nova Scotia in 1979. In A Characterization of Marine Mammals and Turtles in the Mid- and North Atlantic areas of the U.S. and Outer Continental Shelf. Cetacean and Turtle Assessment Program, Univeristy of Rhode Island Annual Report for 1979. Bureau of Land Management, Washington DC.
Wilcox, W. A. 1896. Commercial fisheries of Indian River, Flordia. Rept. U. S. Comm. Fish Fish. 22:249-262.
Witherington, B. E. and L. M. Ehrhart. 1985. Hypothermic stunning of marine turtles in Florida east-coast lagoons in January 1985: a comparison with two previous cold-stunning eposides. Abstr. SSAR/Herp. League Meeting, 4-9 August 1985. Tampa, FL.