Journal
JOURNAL OF THERMAL BIOLOGY
Volume 37, Issue 1, Pages 6-14Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jtherbio.2011.10.010
Keywords
Crocodylus acutus; Nest temperature; Temperature-dependent sex determination; Embryo survival; Incubation length; Mexico
Funding
- Banco Chinchorro Biosphere Reserve (CONANP)
- El Colegio de la Frontera Sur (ECOSUR)
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Crocodilians have temperature-dependent sex determination (TSD) in which incubation temperature determines sex of embryo. Global warming is expected to alter hatchling sex ratio, leading to the extinction of small populations. Regional climate influence on crocodile nest microclimate and hatchlings' characteristics is poorly known. Here, microclimate in natural nests of American crocodile (Crocodylus acutus) and its relation with incubation length, hatchling sex and nesting success was studied in Banco Chinchorro Biosphere Reserve (Mexico) from 2007 to 2010. Temperature and relative humidity in different locations within and outside the nests were registered by data loggers. Incident solar radiation above nest was calculated from hemispheric photographs. Incubation length, proportion of hatchling reaching complete development and hatchling sex were determined at hatching. Nest temperatures exhibited a cyclic daily fluctuation due to solar radiation, which is the major heat source for nests. Clutch temperature was relatively stable and its daily amplitude was negatively correlated with clutch depth and size. Rainfall was the major source of clutch temperature decrease. Clutch and metabolic temperatures increased significantly during incubation. A small sample size failed to demonstrate a statistical relationship between length of incubation and mean clutch temperature. Proportion of embryos reaching complete development depended on maximum and minimum clutch temperature, maximum daily amplitude of clutch temperature and maximum decrease in clutch temperature on a period <= 4 day. Results confirmed a Female-Male-Female TSD pattern for C. acutus, with 31 and 32.5 degrees C as possible pivotal temperatures. Population and hatchling sex ratios were male-biased and fate of crocodiles of Banco Chinchorro could depend on the magnitude of temperature increase in the future. (C) 2011 Elsevier Ltd. All rights reserved.
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