Reproductive ecology and hatchling growth rates of the American crocodile (Crocodylus acutus) on Coiba Island, Panama

Sergio A. Balaguera-Reina, Miryam Venegas-Anaya, Oris Imperio Sanjur, Harilaos A. Lessios, Llewellyn D. Densmore

Research output: Contribution to journalArticle

9 Scopus citations

Abstract

Abstract. We assessed the reproductive ecology of the American crocodile (Crocodylus acutus) on Coiba Island, Panama from January-December 2013. We examined nest site characteristics from January-April and hatchling survivorship from April-December. Ten nests were examined at three nesting localities where 30% of the nests were found under forest canopies and 70% were exposed to sunlight (distance to nearest tree = 280 ± 110 cm). Half of the nests were built closer to the sea and the other half closer to bodies of freshwater (700 ± 360 cm). The nest dimensions were 17.5 ± 7.8 cm from the top of the clutch to the surface, 42.9 ± 9.9 cm from the bottom of the clutch to the surface, and 35.9 ± 3.6 cm wide at the top of the nest cavity. The average soil conditions in the nests consistently had high concentrations of potassium (69.3 mL/L) and manganese (9.2 mg/L), moderate concentrations of phosphorus (6.6 mg/L) and iron (3.7 mg/L), and low concentrations of zinc (0.5 mg/L) and copper (0.0 mL/L). Cation exchange capacity showed consistently high concentrations of calcium (2.2 cmol/kg), moderate of magnesium (1.1 cmol/kg), and low in aluminum (0.1 cmol/L). Volumetric water content was about 25.0 ± 2.6% at the bottom and 22.8 ± .3% in the middle of the clutches. Hatching success was 88.9%, of which 68.3% hatched by themselves or with the mother's aid and 20.6% hatched with our aid. Mean size of the mother was 219 ± 6.2 cm total length (TL) and 115.9 ± 3.0 cm snout-vent length (SVL). The incubation period was estimated to be 85-88 days. TL and SVL growth rate of those individuals were 0.03-0.16 cm/day and 0.00-0.09 cm/day, respectively. Population size was estimated to be 218.6 hatchlings in 22.4 km2; the hatchling population declined 65.7% after the first 2 months (May and June) and 95.9% by July, leaving only 0.5% remaining by December. This is the first study to assess nest-site characteristics and estimate hatchling survival in a Pacific population of American crocodiles.

Original languageEnglish
Pages (from-to)10-22
Number of pages13
JournalSouth American Journal of Herpetology
Volume10
Issue number1
DOIs
StatePublished - Apr 1 2015

Keywords

  • Parental care

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