Nesting ecology of East Pacific green turtles at Playa Cabuyal, Gulf of Papagayo, Costa Rica

Abstract

East Pacific green turtles (Chelonia mydas), often referred to as black turtles, are smaller and exhibit a lower reproductive output than other populations of green turtles in the Atlantic, Indian and Western Pacific Oceans. Knowledge of nesting ecology of East Pacific green turtles is limited to general descriptions. We conducted an exhaustive analysis of the nesting ecology of East Pacific green turtles at Playa Cabuyal, North Pacific Costa Rica. Compared with other populations of green turtles, East Pacific 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.

The Black Sea Turtle (Chelonia mydas agassizii) at Lobos de Tierra Island, Northern Peru: High Densities in Small Areas

“…the Galapagos Archipelago, Ecuador (Marquez, 1990;Zárate, 2003); Revillagigedo Islands, Mexico (Holroyd and Trefry, 2010) and some important new reported nesting sites in northwestern Costa Rica, in Guanacaste peninsula (Blanco et al, 2012;Santidrián Tomillo et al, 2014). Marquez (1990) reported coastal primary foraging areas from San Diego Bay, USA to Mejillones, Chile and more recently, its southward distribution was extended to Valparaíso, Chile (Troncoso and Urbina, 2007).…”

Are thermal barriers "higher" in deep sea turtle nests?

“…Additionally, olive ridley and leatherback nests may suffer from hydric stress [ 41 ]. These species nest on the open beach, as opposed to green turtles that tend to select vegetated areas that shade the nests [ 30 , 52 ]. As a result, olive ridley and leatherback clutches may be more sun-exposed and water content at nest depth must be lower.…”

“…Leatherback turtles are the largest sea turtle species [ 28 ] and have a mean curved carapace length (CCL) in the eastern Pacific of 147.0 cm [ 29 ]. East Pacific green and olive ridley turtles have mean CCLs of 86.2 cm [ 30 ] and 65.9 cm [ 31 ] respectively at the study sites. Mean nest depths are related to turtle size and at the study sites depths are 82.2, 68.1 and 47.3 cm respectively for leatherback, green and olive ridley turtle nests.…”

The impacts of extreme El Niño events on sea turtle nesting populations

“…where AH was the mean annual production of hatchlings, ECF corresponded to the mean estimated clutch frequency (number of clutches laid in a season) for the nesting population (estimated as the mean ECF of all turtles for which it has been estimated), cs to the clutch size (mean number of eggs in a clutch), f 1 and f 2 to the frequencies of extreme and regular ENSO years, respectively, over a decade, and H 1 and H 2 to hatching success under extreme and regular ENSO conditions, respectively. Mean (± SD) clutch size and ECF were obtained from the long-term monitoring project at Playa Grande for leatherback turtles (66 ± 16.6 eggs and 6.1 ± 3.1 clutches, respectively) and from published articles available for the area for green (76.9 ± 18.2 eggs and 4.3 ± 2.3 clutches) (Santidrián Tomillo et al 2015a) and olive ridley turtles (87.5 ± 33.6 eggs and 2.2 ± 1.1 clutches) (Van Buskirk and Crowder 1994;Dornfeld et al 2015). Values of ECF, cs, and H 1 were obtained by randomly picking one value within the standard deviation of their mean to account for natural stochasticity.…”