Editorial Type:
Article Category: Research Article
 | 
Online Publication Date: 18 Dec 2012

Emergence Success and Sex Ratio of Natural and Relocated Nests of Olive Ridley Turtles from Alas Purwo National Park, East Java, Indonesia

,
, and
Page Range: 738 – 747
DOI: 10.1643/CH-12-088
Save
Download PDF

The nest environment, in particular sand temperature, is critical to the breeding ecology of sea turtles which lack parental care during their early stages of life. We investigated the effects of sand temperature on emergence success and sex ratio of Olive Ridley (Lepidochelys olivacea) hatchlings in in situ and relocated nests in Alas Purwo National Park (APNP), East Java, Indonesia. Over two years of observation no in situ nests survived due to predation, while emergence success in relocated nests varied between the years. Temperatures above 34°C experienced by the nests over at least three consecutive days during incubation (T3dm) had decreased emergence success in both years. These high temperatures occurred as a result of metabolic heating of developing embryos combined with high sand temperatures. The indirect method of determining sex ratios from nest temperature profiles indicated that the hatchery at APNP generated more male hatchlings than female. Our study provides justification for on-going egg relocation to the hatchery as a conservation management strategy. Therefore the nest environment inside the hatchery needs to be carefully managed so that temperatures do not exceed the viable limit nor unnaturally skew the sex ratio of embryos.

Copyright: 2012 by the American Society of Ichthyologists and Herpetologists
Fig. 1. 
Fig. 1. 

Study site. Pancur and Marengan Beaches, Alas Purwo National Park, East Java, Indonesia.

Fig. 2. 
Fig. 2. 

Frequency distribution of nest construction throughout the year and monthly beach sand temperatures during the peak nesting season for the Alas Purwo National Park Olive Ridley turtle rookery for 2009 and 2010. Nest frequency data obtained from Alas Purwo National Park management records.

Fig. 3. 
Fig. 3. 

Monthly precipitation from January–December 2009 and 2010 recorded by the local Bureau of Meteorology and Geophysics, Banyuwangi (2010).

Fig. 4. 
Fig. 4. 

Sand temperatures in the eastern and western sections of the Alas Purwo National Park hatchery during the 2009 and 2010 nesting seasons.

Fig. 5. 
Fig. 5. 

Mean daily nest temperatures for Olive Ridley turtle nests in the Alas Purwo National Park hatchery during the 2009 and 2010 nesting seasons.

Fig. 6. 
Fig. 6. 

Mean emergence success of Olive Ridley turtles plotted against mean maximum temperatures over three consecutive days during incubation (T3dm). There was no relationship between T3dm and emergence success for T3dm < 34°C in 2009 (R2  =  0.089, P > 0.05, n  =  31 nests), but there was a relationship for T3dm > 34°C in 2009 and 2010 (R2  =  0.278, P < 0.001, n  =  78 nests).

Fig. 7. 
Fig. 7. 

Relationship between mean nest temperatures and incubation period for Olive Ridley turtles in the 2009 and 2010 nesting seasons (R2  =  0.546, r  =  −0.739, P < 0.001, n  =  109 nests, incubation period (days)  =  116.6–2.106*incubation temperature).

Fig. 8. 
Fig. 8. 

Frequency distribution of Olive Ridley turtle nests over each temperature interval during the middle third of incubation period in the Alas Purwo National Park hatchery (2009 and 2010 nesting seasons).

Contributor Notes

Associate Editor: K. Martin.

Received: 26 May 2012
Accepted: 30 Jul 2012
  • Download PDF