Date Awarded

1993

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Virginia Institute of Marine Science

Advisor

J. A. Musick

Abstract

Flipper-tagging, aerial surveys, and satellite telemetry was used to investigate the occurrence, migratory routes, distances traveled, swimming speeds, diving behavior, and the relation of water temperature to movements and timing of migration of wild loggerhead (Caretta caretta) and Kemp's ridley (Lepidochelys kempii) sea turtles. The behavior and movements of head-started loggerhead turtles was investigated with satellite telemetry and compared to wild turtles. Flipper-tagged loggerhead and Kemp's ridley turtles inhabit Chesapeake Bay during the warm months and many return in subsequent seasons. Aerial surveys showed that loggerhead turtles migrate from south of Cape Hatteras to northern waters during May and June, and return to the south of Cape Hatteras in the autumn, usually during October or November. Satellite telemetry supported aerial survey data, and showed that loggerhead and Kemp's ridley turtles migrate nearshore to the south of Cape Hatteras in the autumn, although one loggerhead became pelagic in the North Atlantic. Kemp's ridleys and some loggerheads migrate as far south as Florida for the winter months, while some loggerheads overwinter in the Gulf Stream off North Carolina. Loggerheads which returned to Chesapeake Bay used similar migratory routes during the northerly and southerly migrations. Loggerhead and Kemp's ridley turtles spent up to 94% of 12 h periods submerged (ridley mean = 81%, loggerhead mean = 88%), and mean dive durations ranged from 13 to 124 min (ridley mean = 66 min, loggerhead mean = 74 min), making 13 to 38 dives over a 12 h period (ridley mean = 25, loggerhead mean = 25). Temperatures measured by satellite transmitters attached to Kemp's ridley turtles ranged from 13-23 C (mean = 17 C), while loggerhead temperatures ranged from 6-33 C (mean = 20 C). Movements of turtles appear to be mitigated by temperatures about 15 C. Movements and diving behavior of head-started loggerheads were different than wild turtles. Some head-started turtles entered the Gulf Stream and traveled eastward across the Atlantic, while others wandered in various directions. Head-started loggerheads made more (mean = 69) and shorter dives (mean = 21 min) over a 12 hr period than wild turtles, and spent significantly less time submerged (mean = 54%) than wild turtles.

DOI

https://dx.doi.org/doi:10.25773/v5-jbgm-bf23

Rights

© The Author

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