Nesting ecology of E ast P acific green turtles at P laya C abuyal, G ulf of P apagayo, C osta R ica

Abstract

East P acific green turtles ( C helonia mydas ), often referred to as black turtles, are smaller and exhibit a lower reproductive output than other populations of green turtles in the A tlantic, I ndian and W estern P acific O ceans. Knowledge of nesting ecology of E ast P acific green turtles is limited to general descriptions. We conducted an exhaustive analysis of the nesting ecology of E ast P acific green turtles at P laya C abuyal, N orth P acific C osta R ica. Compared with other populations of green turtles, E ast P acific turtles exhibited smaller clutch sizes (mean ± SD : 76.9 ± 18.2 eggs per clutch), but the number of clutches (estimated clutch frequency ( ECF ): 4.3 ± 2.3 clutches) fell within the upper limit reported for green turtles. Clutch size and seasonal reproductive output (409 ± 135 eggs per female), but not ECF , increased with female size. The observed internesting period ( OIP ) between consecutive oviposition events (mean ± SD : 15.4 ± 2.9 days) increased as the season progressed and was approximately 2 days longer than the mean OIP reported for the species. Most clutches were laid in the upper vegetated part of beach (zone 3, 75%) and within this zone, tended to be located underneath trees (79%). Hatching success of clutches laid underneath trees was significantly higher (0.89 ± 0.17) than that of clutches laid in the exposed areas of zone 3 (0.75 ± 0.33). Mean duration of the nesting process (3:14 h) was on average 45 min longer than previously reported for the species. Frequency of false crawls was high (49% of nesting activities), and nesting success was low (54% of nesting attempts). Poaching of eggs, tourism and predation by dogs were important threats to this population. Conservation actions were being successfully implemented at the local level due to presence of beach patrollers, but official protection is needed for the preservation of the nesting population into the future.

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