SREL Reprint #2107

 

 

 

 

GROWTH MODELS FOR TWO SPECIES OF FRESHWATER TURTLE, CHELODINA RUGOSA AND ELSEYA DENTATA, FROM THE WET-DRY TROPICS OF NORTHERN AUSTRALIA

ROD KENNETT

Wildlife Research, Conservation Commission of the Northern Territory, PO Box 496, Palmerston N.T. 0831, Australia

ABSTRACT: Chelodina rugosa is a fast-growing, carnivorous turtle that occupies seasonally ephemeral habitats, whereas Elseya dentata is relatively slow-growing, largely herbivorous, and confined to permanent water. The relationship between carapace length and growth rate for each species was modeled using "split-stick" regression. The regression procedure estimated the carapace length at which the slope of the growth rate-body size relationship changed from rapid juvenile growth to slow adult growth. This estimate of body size at maturity compared favorably with estimates of size at maturity based on independent criteria. The von Bertalanffy growth model provided the best fit to recapture data, and the age-size curve closely matched individual ages obtained by counting plastral annuli. Both species are sexually dimorphic in body size at maturity and at maximum size, with females being the larger. On average, males of C. rugosa mature at 3.9 yr and 165 mm in carapace length and reach a maximum size of 250 mm, whereas females mature at 6.5 yr and 210 mm and reach a maximum size of 300 mm. Males of E. dentata mature at 8.6 yr and 220 mm and reach a maximum size of 280 mm, whereas females mature at 13.5 yr and 276 mm and reach a maximum size of 330 mm. The rapid growth and early maturity of C. rugosa reflects its high protein diet and occupancy of highly productive ephemeral environments where selection for rapid growth may be intense. The slower growth and late maturity of E. dentata, despite year-round warm temperatures, suggests that its growth may be energetically limited by a largely herbivorous, protein-poor diet.

Key words: Chelidae; Chelodina; Elseya; Turtle; Growth; Maturity; Food-limited; Australia

SREL Reprint #2107

Kennett, R. 1996. Growth and maturity of two freshwater turtles, Chelodina rugosa and Elseya dentata, from the wet-dry tropics of Northern Australia. Herpetologica 52:383-395.

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