Analysis of climate change on leatherback (Dermochelys coriacea) nesting patterns at Parque Nacional Marino las Baulas, Costa Rica

Sara E Valentine, Purdue University

Abstract

This study examines whether there is a relationship between sea surface temperature (SST) and the peak for the majority of female leatherback turtles (Dermochelys coriacea) at Parque Nacional Marino Las Baulas (PNMB), Costa Rica. Similar studies with loggerhead sea turtles ( Caretta caretta) in Florida and Greece demonstrated the median Julian date (MJD) was earlier in the season as SST increased. Leatherbacks have also been shown to respond to increased SST by departing North Atlantic foraging grounds earlier (Sherrill-Mix et al., 2008). Unlike the results in the Atlantic loggerhead population, eastern Pacific leatherbacks had a delay in the peak median nesting date as SST's increased. The ecological implications of this shift in the nesting season caused by climate change is that the incubated nest are more susceptible to the hotter and dryer conditions that prevail during the dry season (Santidrián-Tomillo et al., 2010). The averaged SST data from fifty-nine individual Eastern Pacific buoy locations during a 16-year period showed an increasing SST trend. This study of leatherback nesting data demonstrated that the MJD peak tends to occur later in the nesting season (MJD varied from Julian day 340 to 366.5) as SST's increased. This finding could be explained because of the nature of the El Niño Southern Oscillation (ENSO) with warm El Niño phases and cooler La Niña events every few years. ENSO could be affected by future scenarios of climate change resulting in more frequent and stronger El Niño events that would affect the nesting season of leatherbacks by delaying their arrival to the nesting beach. While the overall SST for the buoys studied in this eastern Pacific array did not change significantly over time, there is a strong trend between increasing SST and increases in MJD (p-value = 0.165). The MJD; however, was delayed over the study period (p-value = 0.073), and if current trends continue and SST's rise in the future, this study predicts that the MJD could shift to later in the season leading to lowered reproductive productivity. In addition, 8 of 9 nesting seasons showed that as SST's rose, the number of successful nesting events (emerging turtles that actually deposited eggs) decreased with an increase in aborted nesting events. This interaction of rising SST and successful nesting indicated there was a compression of the leatherback nesting season with a lowered rate of successful nesting events as SST's increased during El Niño years.

Degree

M.S.

Advisors

Paladino, Purdue University.

Subject Area

Wildlife Conservation|Ecology|Climate Change|Biological oceanography

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