Western bobtails (Tiliqua rugosa rugosa) on the move through the suburbs are a sure sign spring is on the way in Perth Western Australia. Unfortunately with this extra movement comes added risk, with one of the largest risks for bobtails in suburban areas being roads. In the last two weeks I have found two dead bobtails just around the corner from where I live, both victims of vehicle strikes. Living in a quiet area surrounded by a regional park, I find this staggering and have to question, was it purely just an accident? Is it complacency of people living here? Or do they simply not care? Thankfully during the same period I have had the pleasure of relocating two bobtails back to the bush from our street ... these were the lucky ones (see one of them in the image below).
Now as bobtails are a common sight in Perth, I do wonder if people really appreciate what we have right on our door step. They truly are an amazing species, so with this blog I hope to provide a bit of an insight into the fascinating biology of the bobtail. The species is a short-tailed (hence the name bobtail) blue-tongued skink found across much of Australia with four subspecies recognised (three of which are found in Western Australia). Bobtails are slow moving so their diet, although varied, consists largely of plants or slow moving animals (e.g. snails and beetles). Mating occurs between September and November, during which time, monogamous pairs of bobtails will seek each other out to reunite and mate once more. This period is one of the most high risk for the species; as it is their peak activity season they become more vulnerable to predation (including from domestic cats and dogs) and vehicle strikes. Outside of this period bobtails will generally live a solitary existence before repeating the cycle of reuniting with their mate each spring for several years. Unlike many reptiles, the bobtail gives birth to live young! This occurs approximately three to five months after mating and the female will usually give birth to two or three young. Amazingly the young are born fully developed and ready to disperse on their own within a matter of days! Often when bobtails are observed in the suburbs they appear to be "lost" wandering haphazardly on roads and up peoples drive ways. Research by Auburn et al. (2009) may help provide some clues as to why this is. To test the visual perception range of bobtails a cleared arena was created with a 0.5 m bush placed at three different distances from a release site, 10 m, 20 m and 30 m. The researchers found that when the bush was placed at 0.5 m bobtails were more likely to seek shelter, however, when the bush was 30 m away, no bobtails were able to find the bush. Interestingly when the bush was 30 m away several individuals did not even move from the release point indicating they could not see the shelter opportunity. The data from this research suggested that bobtails had a visual perception range of up to 20 m, which is perfectly adapted for their life in uncleared bushland which typically has large bushes for shelter at average intervals of 10.5 m. This however becomes much more problematic in fragmented landscapes such as urban areas and care needs to be taken to minimise our impact on these magnificent creatures within such areas. Did you know? The four subspecies of the bobtail are
You can also keep bobtails as pets, however, they must be purchased from a licensed store/breeder (DO NOT take them from the wild - see an article here about a haul of bobtails found by Perth Airport Border Force) and you must have the appropriate DPaW/DBCA License. Further reading
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The dugite (Pseudonaja affinis) is a fascinating diurnal (active mainly during the day) snake with a broad diet, including frogs but with a preference for reptiles, birds and mammals (including the introduced house mouse - which may explain why it loves urban areas ... well and we built our homes on top of theirs!). Interestingly the species is also known to be cannibalistic - feeding on other snakes. Check out a news article highlighting this fascinating behaviour here.
The species is widespread in the South-west occupying a range of habitats including coastal dunes, heathlands, shrublands, and inland wetlands. The mainland species can reach lengths of up to 2 m but more commonly encountered snakes are often in the 1-1.5 m range. The males can mature as early as 58 cm (snout-vent length*) and the females mature as early as 68 cm (snout-vent length). During mating season (winter-early spring) males will combat each other by entwining their bodies together. Females will lay a clutch of eggs in late spring-early summer, ranging from as few as 11 eggs to as much as 35!! Snakes can often get a bit of a bad reputation and the dugite in Perth is no exception. More often than not I see stories on the news highlighting another person that has been bitten (often due to trying to pick up the snake and move it), or I hear from people that had one in the back garden so they killed it to protect their child or dog. So I want to finish this blog off with a bit of education now that the warmer months are fast approaching. Now although they are indeed a venomous snake and should be treated with respect, there are many precautions you can easily take to minimise the risk with snake interactions highlighted on the DPAW (DBCA) website. One such precaution is "Keep a watchful eye on the ground about a metre ahead of where you are walking, and avoid entering areas of long grass, rushes and undergrowth." You would be amazed by how short this "long grass" can be in order for the dugite to disappear right before your eyes (see image at the bottom of the blog - seconds after this photo was taken it completely disappeared from view). If you find them on your property ensure the snake is not accessible to any pets or children, and before you think about reaching for your shovel to kill it, your next step should be contacting the Wildcare Helpline (08) 9474 9055 which can refer you to local reptile removers that will happily come by your place and relocate the snake. With a little care and respect we can co-exist with these amazing creatures. *Snout-vent length - The measurement from the tip of the nose (snout) to the anus (vent) excluding the tail Did you know?
Further reading
The south-west of WA is home to a large number of freshwater crayfish, many of which people will not be aware of. There are a total of eleven species of freshwater crayfish native to the south-west (plus one introduced species - the Yabby, Cherax destructor); these include five species from the burrowing Engaewa genus and six species from the Cherax genus including the Koonac (Cherax preissii) and the well known Smooth Marron (Cherax cainii).
Catching freshwater crayfish is a past-time of many people in the south-west region, with the Marron season running each year from early January to early February. Unfortunately however, in their attempts to catch the introduced Yabby or native Marron, many people use illegal traps such as opera house / cathedral traps. The use of these traps can unwittingly trap turtles (see image at the end of the blog - caution: image may cause distress) and water rats endangering both species to a fate of drowning. The Smooth Marron is widespread and probably the most well known species of freshwater crayfish in WA, however, it has a close "relative" in the Hairy Marron (Cherax tenuimanus). The Hairy Marron is distinct in appearance from the Smooth Marron, with the most notable characteristic being the presence of short hairs along the head and occasionally the tail. Unfortunately the Hairy Marron is listed as Critically Endangered and according to the Department of Fisheries it is estimated that less than 1,000 hairy marron are left in the wild (to put this number into perspective, the Panda, one of the most well known endangered animals in the world, has a current population estimate of just over 1,800 remaining in the wild). The current population of Hairy Marron in the Margaret River is under threat on many fronts, with the most pressing being competition with the Smooth Marron which was introduced to the Margaret River in the 1980's. The Smooth Marron not only outcompetes the Hairy Marron through aggressive interactions, but it also has the ability to cause hybridisation through breeding with the current population. The Hairy Marron is now extinct from the lower reaches of the Margaret River but can still be found in the head waters. Thankfully there is ongoing research trying to reduce this threat and to help bring the species back from the brink. The species is currently being captive-bred at the Pemberton Freshwater Research Centre with the aim of increasing the gene pool and establish a breeding population. If you have seen suspected illegal fishing activities (e.g. fishing for Marron out of season, the use of illegal traps) get in touch with the FishWatch phone line at the Department of Fisheries on 1800-815-507 and provide as much information to them as possible, such as the number of people involved, what you observed including equipment used, precise location if possible - if GPS location is not possible you can use landmarks, intersections with roads etc. Further reading
The nightfish (Bostockia porosa) is a species of freshwater fish endemic to south-western Australia (meaning it is found no where else in the world!) and as the name suggests is active mostly at night. The nightfish is carnivorous and has been documented feeding on a range of taxa, including ostracods, gastropods, amphipods and even decapods (e.g. consuming parts of freshwater crayfish). The species has had limited research, with the biology of the species only being described in a paper in 1990. However, more recent broad sampling by freshwater ecologists has begun to decipher the mystery and expose the threats the nightfish faces.
A study by Beatty and colleagues published in 2014 documented large downstream movements of juvenile nightfish in tributaries of the Blackwood River (e.g. Milyeannup Brook) during November and December, as well as migration in the species being significantly associated with surface water discharge. The findings of movement predominantly in the tributaries of the Blackwood River supports earlier research by Dave Morgan and colleagues. A paper published in 2003 found increasing salinity in the Blackwood River had caused the extinction or massive decline in a number of species from the main river channel itself. Whereas the tributaries containing natural forest vegetation and lower salinity levels still contained species such as the nightfish. Although the nightfish is one of the most widespread native freshwater fish in the south-west region, salinization is an ongoing threat and is causing the decline in populations in many of the river catchments. The problem is unfortunately exacerbated by climate change in the south-west where average rainfall has declined drastically since the 1970s leading to even greater decreases in runoff/discharge and altered groundwater levels. The protection of the species in the south-west is now reliant on the preservation of high quality habitat, particularly in areas that remain uncleared, as well as the potential for intervention through the creation of artificial wetlands within the natural environment. Fun fact! The nightfish is one of several native species of fish that host the glochidia (parasitic larvae) of the native freshwater mussel (Westralunio carteri) Further reading
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
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 The Stimson's Python (Antaresia stimsoni) is a relatively small python (usually only growing to 1m in length - see images above and below of two Stimson's I was fortunate enough to find in the Pilbara). The species is widely distributed from the Kimberley region in northern Western Australia, to south of Perth around Waroona, and extending inland through the Goldfields all the way across to the eastern states of Australia. Throughout their range they are found across a variety of habitats, but in the Perth region will generally prefer the rocky outcrops and forests in the hills. See an article here about a surprising find of a Stimson's python in Craigie!
In its natural environment the Stimson's Python feeds on a wide range of vertebrates such as frogs, other reptiles, and small terrestrial mammals (including the introduced house mouse Mus musculus - which is also commonly fed to captive pythons). In the wet warm months in the Pilbara and central Australia, the species is more active and therefore more commonly encountered. As well as being beneficial from a physiological point of view (e.g. avoiding dehydration), it is likely the pythons themselves encounter a larger availability of food resources. Many of the ground-dwelling frogs in the region burrow into the ground and aestivate during dry periods. When the rains occur the population abundance of these frogs appears to explode, providing the Stimson's Python with a reliable food source during the wet season. As well as being a fascinating species in the wild, the Stimson's Python can also be kept as a pet in Western Australia (with the appropriate license). It has been possible for reptiles & amphibians to be kept as pets in Western Australia since 2003 - see here for the most up to date approved reptile keeping list. Fun fact! Did you know the Stimson's Python (along with a suite of other critters) are regularly found taking diurnal refuge in the termite mounds throughout the Pilbara. See the following two papers for further reading on the surprising finds in termite mounds!
The short-tailed pygmy monitor (Varnus brevicauda) is found in the central and western deserts of Australia, inhabiting spinifex country (including near Onslow, WA - where I was fortunate enough to take the image below). Despite being diurnal (active during the day) the species is not well understood and research has been limited. The species is carnivorous and has been found to feed on insects, arthropods, carrion, and even other small lizards and their eggs. The short-tailed pygmy monitor also undergoes rather rapid sexual maturation (males have been reported to be sexually mature at just 10 months of age at 7cm in snout-vent length). Whilst the males mature rapidly, the females take there time and generally will not be sexually mature until the following year at approximately 22 months of age and reached a snout-vent length of 8-9cm.
The short-tailed pygmy monitor was until recently, thought to be the world's smallest monitor lizard. It was only in late 2014 when the title was handed to a newly described species, the Dampier Peninsula monitor (Varnus sparnus). Seen in the image below, the species (V. brevicauda) comfortably fits in my hand, and when you consider it comes from the same family as the largest lizard in the world, the Komodo dragon, it really sinks in just how remarkable this is. It truly is a pygmy among giants! Fun fact!
Population growth is bringing with it urban sprawl across the globe, and Perth Western Australia is no exception. Although many species are pushed out with the expansion, some species hang on in isolated pockets of remnant bushland. Around Perth, the southern brown bandicoot (Isoodon obesulus fusciventer) also known as the Quenda, is one such species that is hanging on, in some cases quite literally in our backyards (see the image below - one I was fortunate enough to take when translocating the species).
The Quenda grows to approximately 300-330mm in length and can weigh up to 1.8kg depending on the condition of the individual. The species is widely distributed from Guilderton to east of Esperance, however due to land clearing and development the distribution is quite patchy. They can be found in a range of habitats including swampy areas with dense shrub, woodland & forests, and are often seen utilising peoples gardens along the coast and in the Perth Hills. The species unfortunately still faces many threats including introduced predators such as foxes (Vulpes vulpes) and domestic/feral cats. In the forest/woodland habitats away from development, the control of predators such as foxes and feral cats is crucial to maintain the populations of Quenda. Juvenile Quenda are particularly susceptible to predation by both cats and foxes. In more urban environments you can reduce the impact on Quenda by keeping your domestic cats indoors at night, and keeping dogs on a lead. Habitat loss through the ongoing development and expansion has also brought with it a new threat in vehicle impacts. Thankfully many new highways that are being constructed, are being built with underpasses for fauna to use (including the Mitchell Freeway Extension - currently under construction). A recent study by Harris and co-authors documented the use of an underpass by several Quenda during construction and after completion. They also identified a range of other species using the same underpasses including the Western grey kangaroo (Macropus fuliginosus ocydromus), brushtail possum (Trichosurus vulpecula), Gould's monitor (Varanus gouldii), and dugites (Pseudonaja affinis). For further reading on this, feel free to check out their research here. Fun fact: Although the southern brown bandicoot/Quenda is not a rodent, the name bandicoot is originally derived from the Indian/Telugu language word for pig-rat (pandi kokku). |
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