Eastern snake-necked turtles (Chelodina longicollis)
About Chelodina longicollis
Chelodina longicollis is an east Australian species of snake-necked turtle that inhabits a wide variety of water bodies and is an opportunistic feeder. It is a side-necked turtle (Pleurodira), meaning that it bends its head sideways into its shell rather than pulling it directly back.
Eastern snake-necked turtles (Chelodina longicollis) move from main river channels onto inundated floodplain wetlands and remain in those habitats while suitable resources are available. When those resources become limited C. longicollis aestivates in off-stream terrestrial habitats, surviving by living off their fat reserves, for up to 7 months. After aestivating individuals must migrate back to permanent water holes or main river channels if conditions in off-stream wetlands remain unfavourable.
Upon return to the main channel the turtles are forced to compete with other predatory species that are better suited to catch fast moving prey. That period, as well as migration to and from main river channels, are thought to result in higher rates of mortality for the species and therefore represents a risk to C. longicollis populations.
This model uses a flow time series along with an overbank threshold of flow to identify floodplain inundation events. A wetland dry out phase is determined by an understanding of local condition and is specified by the user. Aestivation is assumed to commence at the end of the dry out phase and the duration of aestivation can be specified by the user. After the Aestivation period, turtles enter a period of high stress which continues until a subsequent floodplain inundation event occurs.
The purpose of the model is to analyses long times series of modelled flow to determine if the risk to successful breeding events for Eastern snake-necked turtles is adversely affected by proposed water resource development (represented in the modelled flow).
This model, describing floodplain connectivity requirements for Chelodina longicollis, has been developed using quantitative information from the literature and expert opinion.
It was developed to support the Queensland Department of Environment and Resource Management’s ecological risk assessment for Water Resource Plan (WRP) reviews.
This model and its default parameters were created for application in the Condamine River, Queensland.
However, the model parameters could be edited to suit other locations where Chelodina longicollis, occurs or to apply it for other turtle species (such as Chelodina canni) with similar requirements.
Suitable conditions are defined when
- Wetlands have water (defined by the time since an overbank connection event and the time required for a wetland to dry). (suitability score = 1)
- During periods following a wetland drying, and within the aestivation period (7 months) a suitability score of 0.5 applies.
- Following the aestivation period and up until the next wetland reconnection event the suitability score is 0.
This model produces continuous daily results (suitability score – 0, 0.5, 1). These results are then aggregated to a binary daily result, then to a binary yearly result, and then further to a binary temporal result based on the defined assessment parameters.
The temporal results are then analysed across locations to report an overall landscape risk by considering the simultaneous occurrence of failures across the system.
- Daily flow data
- Flow parameters – define the flow requirements for suitable conditions. This includes a flow threshold (or ARI calculated flow), a drying period and an aestivation period.
- Daily time series of suitability (0, 0.5, 1).
- Daily time series of assessment results
- Yearly time series of assessment results
- Temporal time series of assessment results
- Spatial time series of assessment results
This plugin is written in Python and its underlying code is publicly available from the Eco Risk Projector computation repository.
DSITIA 2013. Review of Water Resource (Warrego, Paroo, Bulloo and Nebine) Plan 2003. Review of Water Resource (Warrego, Paroo, Bulloo and Nebine) Plan 2003 and Resource Operations Plan: Environmental risk assessment for selected ecological assets. Department of Science, Information Technology, Innovation and the Arts, Brisbane.
Burgin, S, Emerton, S & Burgin, M 1999, ‘A comparison of sample and total census data for a population of the Eastern Longneck Turtle Chelodina longicollisin a farm dam north west of Sydney, NewSouth Wales’,Australian Zoologist, vol. 31, no. 1, pp. 161–165.
Chessman, BC 1983, ‘A note on the aestivation in the snake-necked turtle, Chelodina longicollis(Shaw) (Testudines: Chelidae)’, Herpetofauna, vol. 14, pp. 96–97.
Georges A, Norris RH & Wensing, L 1986, ‘Diet of the freshwater turtle Chelodina longicollis(Testudines: Chelidae) from the coast dune lakes of theJervis Bay Territory’, Australian Wildlife Research, vol. 13, no. 2, pp. 301–308.
Georges, A & Thomson, S 2010, ‘Diversityof Australasian freshwater turtles, with an annotated synonymy and keys to species’, Zootaxa, vol. 2496, pp. 1–37.
Kennett, RM & Georges, A 1990, ‘Habitat utilization and its relationship to growth and reproduction of the eastern long-necked turtle, Chelodina longicollis(Testudinata: Chelidae), from Australia’, Herpetologica, vol. 46, pp. 22–33.
Kennett, R & Georges, A 1995, ‘The Eastern Long-necked Turtle: Dispersal is the key to survival’ pp.104–106. In GCho, A Georges & R Stoujesdijk (eds) Jervis Bay: A place of cultural, scientific and educational value, Australian Nature Conservation Agency, Canberra.
Parmenter, CJ1976, ‘The natural history of the Australian freshwater turtleChelodina longicollis Shaw (Testudinata, Chelidae)’.PhD thesis, University of New England, Armidale.
Parmenter, CJ1985, ‘Reproduction and survivorship ofChelodina longicolllis (Testudinata: chelidae)’,pp. 53–61. InGGrigg, R Shine and & H Ehmann (eds)Biology of Australasian Frogs and Reptiles, Surrey Beatty & Sons,Chipping Norton