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)

Abstract

Context Turtles are one of the most imperilled taxonomic groups worldwide and information about population ecology is essential to species recovery. Although the spatial ecology and demography of adults of several turtle species have been well studied, little is known about early life stages. The small size, soft shell, and limited mobility of hatchling turtles may cause differences in survivorship and habitat selection compared with adults. Aims We tested the hypothesis that hatchling turtles select habitat as they move away from nests, so as to reduce the risk of predation and desiccation. Methods We examined survivorship, behaviour and habitat selection at two spatial scales in hatchling Blanding’s turtles (Emydoidea blandingii) and wood turtles (Glyptemys insculpta) in 2009 and 2010, using radio-telemetry in Algonquin Provincial Park, Ontario, Canada. In addition, temperatures of sites used by hatchlings during winter were compared with those at haphazard stations in various habitats. Key results The mortality rate was high, with 42% of E. blandingii and 11% of G. insculpta hatchlings surviving to winter; most mortality was caused by predation. Most behavioural observations for both species were 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. Conclusions 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. Implications Understanding habitat selection by juveniles is important for testing hypotheses about ontogenetic shifts in resource selection and for protecting habitat for species at risk.

Potential sources of intra-population variation in painted turtle (Chrysemys picta) hatchling overwintering strategy

“…Perhaps hatchlings remain in nests that keep them cool, concomitant with a reduced metabolic rate overwinter, while still being at temperatures above the limit for freeze tolerance. Paterson et al (Paterson et al, 2012) also found evidence that hatchling Emydoidea blandingii and Glyptemys insculpta selected overwintering sites with cooler temperatures than those in random plots. This begs the question, how might hatchlings in the autumn sense the future temperature conditions in their nest?…”

“…Data loggers recorded hourly temperatures at a depth of 10 cm within the marsh substrate at putative hatchling overwintering sites and some known adult overwintering sites. Previous observations indicate that turtle hatchlings overwinter at a substrate depth of 2 to 15 cm within water bodies Paterson et al, 2012). In total, 44 data loggers were placed in 12 marshes; from each marsh, 2-5 data loggers were retrieved in April 2012.…”

Water exchange relationships predict overwintering behavior in hatchling turtles

“…Tuttle and Carroll (2005) tracked hatchling G. insculpta from nests to streams, but did not observe overwintering sites. G. insculpta hatchlings have been reported to overwinter "on the shores of a creek" (Paterson et al 2012). However, Dragon (2014) …”

Identification of Factors Affecting Predation Risk for Juvenile Turtles Using 3D Printed Models

“…Juvenile turtles have lower estimated survival than adults [14], likely in part due to increased vulnerability to predators resulting from smaller body sizes and incomplete hardening of the shell [15]. Their primary anti-predator strategy appears to entail habitat selection facilitating concealment such as burrowing in substrate or seeking cover (e.g., under woody structure, leaf litter, or dense vegetation) [16]. However, it is not well understood how this mitigates predation risk, especially considering risk is often temporally and spatially variable based on predator groups present [17][18][19].…”