Migratory and reproductive behavior of the olive ridley turtle, Lepidochelys olivacea (Eschscholtz, 1829), in the eastern Pacific Ocean Thesis uri icon

abstract

  • The olive ridley turtle (Lepidochelys olivacea Eschscholtz, 1829) is the most abundant sea turtle, yet very little is known about its non-nesting life cycle, or its unique synchronous mass emergent nesting behavior (termed arribada). The main objectives of this study were to (1) determine what factors affect the timing and occurrence of arribadas; (2) monitor the movements and behavior of females and males in and from their nearshore breeding area; (3) test the group migration hypothesis; (4) document migration routes and migratory corridors; (5) characterize the distribution and behavior of L. olivacea in relationship to the physical nature of its marine environment; and (6) describe the diving behavior of females and males. Arribadas at Nancite Beach, Costa Rica most often occurred between the last quarter moon and the new moon. Rain was the only apparent factor that affected arribada timing and occurrence. Excessive rainfall appeared to mask, erase, or otherwise negate the cues that trigger an arribada and resulted in a delayed synchronous nesting emergence. Pre-egglaying developmental arrest may occur so that females delaying nesting retain their eggs in the oviduct until environmental conditions are suitable and the appropriate cues are present. Results from telemetry indicate that females who were spatially associated during arribadas on Nancite Beach did not remain associated in the Gulf of Papagayo during the inter-nesting period, but may re-associate on Nancite Beach during subsequent arribadas. This suggests that females are independently (of each other) attracted to the beach and that environmental/physiological cues experienced by individuals serve to trigger responses that result in their assembly. Females departed the Gulf of Papagayo after oviposition of one or two egg clutches when their ovaries were depleted and serum testosterone levels were reduced. Males used the Gulf of Papagayo as a breeding area until September when the largest arribadas commenced and most females already have mated. Females spatially associated during arribadas on Nancite Beach did not remain spatially associated during post-nesting migrations. Similarly, males captured at the Gulf of Papagayo breeding area were not spatially associated during post-breeding migrations. The turtles were notably oceanic in their migrations which spanned thousands of km, as far north as Mexico and south to Peru. Turtles left the breeding area and travelled to a series of oceanic feeding areas. The slow swimming speeds, continual movements, tendency to spend short periods of time in an area before moving elsewhere, and lack of migratory corridors leading towards common feeding areas characterize L. olivacea as a nomadic migrant. Lepidochelys olivacea likely are assisted by currents and other surface circulation features during their migrations, but they do not appear to be directly guided in whole nor passively transported in this manner. Lepidochelys olivacea occupied areas where upwelling was prevalent. Changes in the areas occupied by L. olivacea during 1990-1991 and 1991-1992 suggest that the El Nino-Southern Oscillation influences their distribution. The diving behavior of the turtles corresponded well with their reproductive and migratory behaviors and with the water depth of their habitat. Females were relatively inactive during the inter-nesting period, while males were very active during the breeding period. Female and male dive behavior changed after the breeding season when they migrated to deep oceanic waters. Females and males spent a lot of time at the surface, where they feed, rest, and bask.

author list (cited authors)

  • Plotkin, P. T.

complete list of authors

  • Plotkin, PT

publication date

  • January 1994