Monday, August 13, 2012

Survivorship in Hatchlings of Two Species of Emydid Turtles.

A hatchling Blanding's Turtle, Emydoidae blandingii

Turtles are one of the most endangered reptile clades worldwide and information about their population ecology is essential for species recovery. Although adult spatial ecology and demography of several turtle species is well studied, little is known about early life stages. The small size, soft shell, and limited mobility of hatchling turtles may result in differences in survivorship and habitat selection when compared to compared adults.

Paterson et al. (2012)  tested the hypothesis that hatchling turtles select habitat as they move away from nests to reduce the risk of predation and desiccation. They  examined survivorship, behaviour and habitat selection in hatchling Blanding’s turtles (Emydoidea blandingii) and wood turtles (Glyptemys insculpta) in 2009 and 2010, using radio-telemetry. In addition, temperatures of sites used by hatchlings during winter were compared with those at haphazard stations in various habitats.The study was done in Algonquin Provincial Park, Ontario, Canada.

 They found the hatchling mortality rate was high, with only  42% of Blanding's Turtles and 11% of of wood turtle hatchlings surviving to winter; most mortality was caused by predation. Behavioural observations for both species were mostly  of individuals hiding under cover. Both species showed evidence of macrohabitat and microhabitat selection as they dispersed from nests towards overwintering sites, and important variables in the models differed between species. Likewise, the adult stages of these two species differ in their macrohabitat specialisation. There was also evidence that hatchlings chose overwintering sites on the basis of temperature. Despite significant differences in survivorship between hatchlings and adults, resource selection was similar between these two demographic stages, and conservation plans based on adult habitat use should simultaneously protect hatchlings. Understanding habitat selection by juveniles is important for testing hypotheses about ontogenetic shifts in resource selection and for protecting habitat for species at risk.

Citation:
Paterson, J. E., Steinberg, B. D., and Litzgus, J. D. (2012) Revealing a cryptic life-history stage: differences in habitat selection and survivorship between hatchlings of two turtle species at risk (Glyptemys insculpta and Emydoidea blandingii). Wildlife Research 39, 408–418.

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