Document Type

Event

Start Date

28-3-2014 10:00 AM

End Date

28-3-2014 10:55 AM

Faculty Sponsor

Dr. Frank Paladino

Department/Program

Department of Biology

University Affiliation

Indiana University-Purdue University Fort Wayne

Award Winner

First

Abstract

We investigated emergence rate of leatherback turtle hatchlings from in situ clutches over the course of three nesting seasons (October-December) during 2008-9, 2011-12 and 2012-13 at Playa Grande, Parque Nacional Marino Las Baulas, Guanacaste, Costa Rica. We focused on hatchlings, which emerged from their eggshell yet failed to emerge from the nest during the two-day period between the first hatchlings emerging and the nest excavation being performed. We measured the distance from the head of the hatchling to the surface of the sand to determine whether measured variables had an impact on where in the sand column above the nest hatchlings were found at the time of excavation. These variables included: temperature in the week prior to emergence, depth of dry sand above the nest (dry front), hatching success of the individual clutch, number of eggs in the clutch, and total depth of nest. Emergence rate (hatchlings that emerge from a nest related to total number of eggs that hatched) of hatchlings significantly declines as the season progressed in all years of this study. The depth of the dry front significantly increased during the course of all three seasons, and the temperatures in the centre of each clutch also increased through the season; this indicates that the nest environment may become less suitable for emergence as the season advances. This conclusion was supported by results from 2008-9 and 2011-12 seasons where the depth of the dry front had the strongest correlation with emergence rate respectively, and in 2012-13 both dry front depth and temperature were significantly correlated to emergence rate. There was also a significant effect of weeks into the hatching season on the number of dead hatchlings found in the dry front which also supports this conclusion. Seasonal progression had an impact on the number of hatchlings found in the nests during excavations, and the proportion of these hatchlings that were still alive. The depth of the dry front was significantly correlated to number of hatchlings failing to emerge in all years investigated; this suggests that water content of the sand or sand consistency may be contributing factors to lowering leatherback hatchling emergence rate. By identifying factors responsible for reduced emergence rate we could potentially implement conservation strategies to alter environmental conditions within the nest, therefore increasing hatchling production. We would like to thank all the field biologists and Earthwatch volunteers responsible for collecting the data used in this investigation, the Park rangers at Parque Nacional Marino Las Baulas, the Leatherback Trust, and the Goldring-Gund Marine biology station.

Keywords

leatherback turtle, Dermochelys coriacea

Included in

Biology Commons

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Mar 28th, 10:00 AM Mar 28th, 10:55 AM

Emergence of Leatherback (Dermochelys coriacea) Hatchlings from the Nest at Playa Grande, Costa Rica

We investigated emergence rate of leatherback turtle hatchlings from in situ clutches over the course of three nesting seasons (October-December) during 2008-9, 2011-12 and 2012-13 at Playa Grande, Parque Nacional Marino Las Baulas, Guanacaste, Costa Rica. We focused on hatchlings, which emerged from their eggshell yet failed to emerge from the nest during the two-day period between the first hatchlings emerging and the nest excavation being performed. We measured the distance from the head of the hatchling to the surface of the sand to determine whether measured variables had an impact on where in the sand column above the nest hatchlings were found at the time of excavation. These variables included: temperature in the week prior to emergence, depth of dry sand above the nest (dry front), hatching success of the individual clutch, number of eggs in the clutch, and total depth of nest. Emergence rate (hatchlings that emerge from a nest related to total number of eggs that hatched) of hatchlings significantly declines as the season progressed in all years of this study. The depth of the dry front significantly increased during the course of all three seasons, and the temperatures in the centre of each clutch also increased through the season; this indicates that the nest environment may become less suitable for emergence as the season advances. This conclusion was supported by results from 2008-9 and 2011-12 seasons where the depth of the dry front had the strongest correlation with emergence rate respectively, and in 2012-13 both dry front depth and temperature were significantly correlated to emergence rate. There was also a significant effect of weeks into the hatching season on the number of dead hatchlings found in the dry front which also supports this conclusion. Seasonal progression had an impact on the number of hatchlings found in the nests during excavations, and the proportion of these hatchlings that were still alive. The depth of the dry front was significantly correlated to number of hatchlings failing to emerge in all years investigated; this suggests that water content of the sand or sand consistency may be contributing factors to lowering leatherback hatchling emergence rate. By identifying factors responsible for reduced emergence rate we could potentially implement conservation strategies to alter environmental conditions within the nest, therefore increasing hatchling production. We would like to thank all the field biologists and Earthwatch volunteers responsible for collecting the data used in this investigation, the Park rangers at Parque Nacional Marino Las Baulas, the Leatherback Trust, and the Goldring-Gund Marine biology station.