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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The Western Quoll also known as the Chuditch (Dasyurus geoffroii) was once widespread but the current range is dramatically reduced to a small pocket in the south-west of Western Australia. They are commonly encountered in the Jarrah forests of the south-west, with occasional records in the Wheatbelt, the Goldfields region, and the Swan Coastal Plain. The species was though to be "locally extinct" from the Swan Coastal Plain by around the 1930's and is listed as Vulnerable under the Wildlife Conservation Act 1950 (now replaced with the Biodiversity Conservation Act 2016). Recent evidence however suggests they are slowly returning to areas on the Swan Coastal Plain. Unfortunately some of this evidence has come in the form of dead specimens. Click here for a news article from last year on the discovery of one outside a primary school within the City of Melville.
The Chuditch is the largest endemic carnivore across its range and is a generalist predator, feeding on a range of prey from brushtail possums & southern brown bandicoots to reptiles & birds. They are approximately the size of a domestic cat and have occasionally been referred to as a native cat, despite not being a cat in any way, shape or form. The introduction of predators such as feral cats and foxes have thought to be one of the major reasons for the decline of the Chuditch throughout its range (through predation and competition for resources). Fox control has been documented to favour Chuditch populations however due to the presence of feral cats the flow on effects of fox control are less understood. Thankfully conservation efforts are assisting this species with a reintroduction program returning the Chuditch to the Flinders Ranges National Park in South Australia. The species was thought to be locally extinct from the park in 1880, and after the 130+ year absence, a new population was introduced in 2014 and supplemented over the next couple of years. The reintroduced population appear not only to be surviving, but thriving, with approximately half of the population now thought to have been born in the park. Further reading
The burrowing bettong (Bettongia lesueur) also known as a Boodie, is a nocturnal marsupial that was once widespread across most of Australia. Unfortunately since European settlement the species has declined dramatically in range and until recently was only present on islands off mainland Australia. Thankfully conservation efforts are assisting this fascinating species, with re-introduced populations now thriving in several predator-free sanctuary enclosures on the mainland as well as several re-introduced island populations. I had the pleasure of assisting AWC monitor their population on Faure Island in Shark Bay and it was an experience i'll never forget.
The Boodie faces several threats, with one long standing theory being their decline was attributed to competition for food resources with introduced herbivores, such as the European rabbit. A study by Robley and colleagues examined the diet of populations of both the Boodie and European Rabbit at Heirisson Prong in Shark Bay. Some key findings from this research were the significant differences in diet between the two target species. In winter the dietary overlap was only 43% and in summer it was 56%. Bettongs were able to vary their diet in response to environmental conditions (e.g. hypogeal fungi, fruit, forbs, seeds, stems etc.) more so than the European rabbits which relied more heavily on grasses (large numbers perished in the second summer of the study). The type of dietary shift seen in Bettongs is suggested by Optimal Foraging Theory, and leads to the conclusion that the dramatic decline in range suffered by the species, is not likely due to competition for food resources with introduced herbivores. More recently it has been suggested that another threat may be responsible for the decline, introduced predators (e.g. feral cats and European fox). As mentioned above, many of the current populations now only thrive in predator-free enclosures on the mainland, or on islands that have had predator control or never had predators introduced. An issue with establishing new populations without predator control is the issue of prey naïveté. The marsupials of Australia, included the Boodie, did not co-evolve with these introduced predators and as such do not generally have the right anti-predator behavioural responses needed to survive. A recent study on the species however is trying to change this! Rebecca West and colleagues studied populations of the species in South Australia as part of the Arid Recovery project. As part of their research a population was exposed to a small number of cats (at a density of only 0.03-0.15 cats per square kilometre). During the same period a population was introduced into a predator-free enclosure. Throughout the study several responses were examined, flight initiation distance, trap docility, and behaviour at feeding trays. After 12 months, flight initiation distance was significantly different between the two populations, with the Boodie populaton that was exposed to cats fleeing sooner when approached (e.g. further away from a predator). After 18 months the pattern was still the same for flight initiation distance, and also for behaviour at feeding trays (those exposed to cats approached more cautiously). These findings highlight the benefits of predator training in conservation programs and it could be the key to saving many of our iconic species. Did you know?
Further reading
* Please note this blog in no way condones the shaking of any animals ... merely a play on words! :P |
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