Title
Size estimation, morphometrics, sex ratio, sexual size dimorphism, and biomass of Crocodylus acutus in the coastal zone of Belize
Author(s)
Platt, S. G.; Rainwater, T. R.; Thorbjarnarson, J. B.; Martin, D.
Published
2011
Publisher
Salamandra
Abstract
We used morphometric data from 151 Crocodylus acutus captured in the Coastal Zone of Belize to develop predictive models for deducing body size (total length [TL] and snout-vent length [SVL]) from measurements of single attributes (dorsal cranial length [DCL], cranial width [CW], snout length [SL] and width [SW], body mass [BM], and rear foot length [RFL]), quantify sexual size dimorphism, examine ontogenetic changes in cranial morphology, and estimate standing crop biomass of crocodiles on an offshore atoll. Strong positive allometric relationships were found between measurements of body length and other morphometric attributes, and provide a reliable means to estimate body length from tracks, skulls, and body parts. The maximum DCL:CW ratio of 2.4 was attained at a body size that coincided with a dietary shift from invertebrates to larger vertebrate prey. The SL:SW ratio of C. acutus partially overlapped that of C. moreletii, and consequently this attribute was not useful for distinguishing these two morphologically similar, sympatric species. The mean DCL:TL ratio was 0.15 and remained constant across body sizes ranging from hatchlings to large adults. Both overall and adult sex ratio (female:male) were not significantly different from parity. The mean SVL of males (111.3 ± 20.7 cm) was significantly greater than that of females (101.0 ± 6.2 cm). A compressed sexual size dimorphism index (SDI) of 2.10 was calculated for C. acutus in coastal Belize. Crocodylus acutus in coastal Belize appear to attain a smaller body size than reported for other populations. Standing crop biomass of C. acutus in the Turneffe Atoll was estimated to be 0.92 kg/ha. © 2011 Deutsche Gesellschaft für Herpetologie und Terrarienkunde e.V. (DGHT).
Keywords
Body size; Cranial morphology; Crocodylia; Crocodylus acutus; Morphometrics; Ontogenetic change; Standing crop biomass
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