Movement and habitat use of captively-reared southwestern snake-necked turtle (Chelodina oblonga) hatchlings

Liz Whatmore

Turtles are one of the most threatened groups of vertebrates worldwide. Many species of freshwater turtles suffer from poor hatchling recruitment rates owing to nesting females, their eggs and hatchlings being vulnerable to anthropogenic threats such as vehicle strikes and subsidised predators. Ex-situ conservation strategies of artificial incubation and headstarting can supplement recruitment, however, environmental conditions of release sites that optimise survival are unknown for many species. This study aimed to quantify movement and habitat use of artificially incubated and headstarted southwestern snake-necked turtle hatchlings (Chelodina oblonga); a species endemic to southwestern Australia whose populations are suffering from poor recruitment. The study investigated the effects of egg collection method (nest or harvested from deceased females), egg incubation conditions (wet or dry), hatchling release weight and release habitat on hatchling movement and habitat use. Thirty-nine hatchlings were released into two separate Typha orientalis and Schoenoplectus tabernaemontani plant communities in Bibra Lake, Western Australia and tracked using radio-telemetry for up to 19 days. Headstarted C. oblonga hatchlings exhibited 90% survival over the tracking period indicating early success. Incubation treatment had the largest effect on mean daily movement per day, with larger hatchlings and hatchlings incubated in wet conditions having increased movement. Hatchlings favoured habitats with high vegetation cover, either above or below water. Radio-telemetry proved a viable option for hatchling tracking, however high vegetation density and deep water reduced tag detection range. The findings suggest that C. oblonga hatchlings should be incubated in wet conditions and headstarted to greater than 15 g weight to maximise their mobility post-release. However, further studies of incubation conditions and headstarting time, including a comparison between natural nests, direct-released and headstarted hatchlings, is recommended to identify any physiological and behavioural effects. This study represents an important first step in understanding the effects of headstarting on the movement, habitat use and survival of C. oblonga and better informs the use of this technique to help mitigate extinctions of freshwater turtles worldwide.

Movement and habitat use of captively-reared southwestern snake-necked turtle (Chelodina oblonga) hatchlings

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