The southwestern snake-necked/oblong turtle (Chelodina colliei) is a species of freshwater turtle endemic to the southwest of Western Australia (ranging from Kalbarri in the north to Esperance in the south). The species can be found in both permanent and seasonal freshwater systems, and although it predominantly spends its time in freshwater it has the ability to aestivate during dry periods and departs the water for nesting. Thankfully many local councils are aware of the migration onto dry land for nesting and help educate the community through community news articles.
Although the species is quite widespread it is not immune to threats, including that of introduced predators, more specifically the red fox (Vulpes vulpes). Two recent studies by Dawson et al. (see further reading) have helped fill some key knowledge gaps concerning the predation of both adult turtles and their eggs by introduced red foxes. One method the researchers used was to swab depredated adult turtle carapaces as well as egg-shell fragments for DNA. Of three carapaces that were tested the researchers were able to identify fox DNA from one of the carapaces (33% of samples tested). To support this observation 16 samples of egg-shell fragments were also tested, with 9 of these returning a positive result for fox DNA (69% of samples tested). Camera traps were also set up to monitor the nest sites in which several foxes were observed excavating nests, further reinforcing the findings. Another aspect of the research was the establishment of artificial nests with chicken eggs and the ground sprayed with swamp water. This was compared with sites without eggs and just swamp water sprayed, sites with just eggs present and no swamp water sprayed, and sites with just the ground excavated and refilled. The presence of eggs and swamp water was significant in determining the depredation by foxes with 53% of sites being depredated, where as only 38% of sites without eggs or swamp water were excavated by foxes. The nests were also more likely to be excavated when they were more obvious, located in sparse vegetation and closer to the shoreline. This led the authors to conclude that foxes use both visual and olfactory cues to help locate nests. Despite all the evidence of foxes predating on both the adult turtles and eggs, when scats from foxes were analysed only 4% of those samples had any shell fragments or turtle remains. The scats were filled with remains from anthropogenic sources such as fruit (e.g. figs, melons), as well rodents and sheep. Unfortunately this does not mean the impact on freshwater turtles will be minimised, purely that foxes have become experts are thriving in urban and modified environments. If anything the exposure of foxes to anthropogenic food sources allows them to multiply to greater numbers, potentially applying greater pressure on the freshwater turtles. Findings such as these are key in the management and conservation of our native species, as well as for the control of introduced predators. Further reading
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AuthorMy name is Garry and I am extremely passionate about the environment. I have completed my BSc. Conservation and Wildlife Biology with First Class Honours and have worked in the Environment sector since 2009. Archives
September 2019
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Photos used under Creative Commons from sean.kelleher1, BioDivLibrary, BioDivLibrary