Academic literature on the topic 'Chelodina longicollis'

Turtles face a variety of threats (e.g. habitat destruction, introduced predators) that are pushing many species towards extinction. Vehicle collisions are one of the main causes of mortality of adult freshwater turtles. To conceptualise the level of threat that roads pose to Australians turtles, we analysed data gathered through the citizen science project TurtleSAT along the Murray River. We recorded 124 occurrences of turtle road mortality, which included all three local species (Chelodina expansa, Chelodina longicollis, and Emydura macquarii). Chelodina longicollis was the most commonly reported species killed on roads. We found that rain and time of year affect the likelihood of C. longicollis being killed on roads: increased turtle mortality is associated with rain events and is highest during the month of November, which coincides with their nesting season. Chelodina longicollis was most likely to be killed on the Hume Highway and roads around major urban centres; therefore, we recommend that governing bodies focus management practices and increase awareness at these locations. The degree of road mortality that we detected in this study requires mitigation, as it may contribute to the decline of C. longicollis along the Murray River.

Activity cycles of Chelodina expansa, C. longicollis and Emydura macquarii were inferred from captures in baited traps set in the Murray River and Lake Boga. C. expansa and E, macquarii were caught only from October to April, while C. longicollis was taken in all months but June and July. Minimum water temperatures at capture were highest for C. expansa and lowest for C. longicollis. Diel cycles of catch rate were often weak, but tended to be bimodal for all species, with peaks near dawn and in the afternoon or evening. Unlike the Chelodina species, E. macquarii was ofen caught near midnight. In the laboratory (at c.24�C with light:dark 12:12 h), the average diel pattern of locomotor activity was weakly bimodal in C. expansa, strongly bimodal in C. longicollis and unimodal in E. macquarii.

Preferences of Chelodina expansa, Chelodina longicollis and Emydura macquarii (Testudines : Chelidae) for different types of aquatic habitat on the Murray River flood plain in south-eastern Australia were inferred from catch statistics. E. macquarii was the species most often caught in the river itself and river backwaters, whereas C. longicollis formed the majority of captures from oxbow lakes, anabranches, ponds, rain pools and a swamp. Relative abundance of E. macquarii was significantly positively correlated with water body depth, transparency, persistence during dry conditions and flow speed, and negatively correlated with remoteness from the river. C. longicollis demonstrated the opposite pattern, and the proportional catch of C. expansa was weakly correlated with environmental variables. The capacity of C. longicollis for colonising and surviving in small, remote and ephemeral ponds and pools relates to its ability to aestivate and resist desiccation and its propensity for overland migration.

Вивчення розвитку нюхового аналізатора рептилій є дуже важливим в еволюційному та порівняльно-анатомічному аспектах. Нюховий аналізатор різних рептилій має суттєві відмінності в будові. У ящірок та змій нюховий аналізатор анатомічно розділений на основну та додаткову (вомероназальну) системи. Нюховий орган черепах має відмінні риси організації. У більшості черепах в нюховому органі відсутнє морфологічне розмежування основного нюхового та вомероназального органа.У роботі описано ключові стадії розвитку структур нюхового органа східної довгошийої черепахи (Chelodina longicollis). Нюховий орган складається з присінка, власне нюхової порожнини та носоглоткового каналу, який відкривається в ротову порожнину хоанами. Носова порожнина розмежована вузькою ділянкою несенсорного епітелію на дорсальну частину, яка вистелена нюховим епітелієм, та вентральну, яка вистелена вомероназальним епітелієм. Вентральна частина носової порожнини утворює медіальне впячування, що значно збільшує об’єм вомероназального епітелію. Нюховий епітелій має чисельні залози Боумена, які відсутні у вомероназальному епітелії. Протока латеральної нюхової залози впадає на межі переходу присінка в носову порожнину та зволожує основний нюховий епітелій, який найбільше контактує з повітрям. Доказом наявності вомероназальної системи у черепахи слугує наявність вомероназального нерва, окремі волокна якого йдуть від вентральної частини носової порожнини до медіальної поверхні нюхової цибулини.

Chelodina longicollis is an opportunistic carnivore that obtains its food from a wide variety of sourcesplankton, nekton, benthic macro-organisms, carrion, and terrestrial organisms that fall upon the water. Although there are some quantitative differences between the littoral components of the diet and the composition of the littoral fauna, these can be attributed to differences in accessibility or 'noticeability' among prey species. There is no evidence to suggest that C, longicollis is selective in what it eats, within the confines of carnivory. Comparison of the diet of C. longicollis with those of other sympatric chelids reveals considerable overlap; the relevance of this to geographic variation in abundance of the species is discussed.

Oxygen consumption () of Chelodina expansa, C. longicollis and Emydura macquarii (Pleurodira: Chelidae) was measured at rest and during induced exercise at 8, 13, 18, 22, 26, 30 and 34°C. Resting varied significantly among species, being lowest in C. expansa, which is the most sedentary of the three species in nature, and highest in E. macquarii, which is the most energetic, but active did not differ significantly among the three species overall. For both Chelodina species, resting was appreciably lower than expected from regression of on body mass for non-marine turtles globally, a result that reinforces previous evidence of low resting metabolism in Australian chelid turtles. Active of all three species at higher temperatures was similar to reported for active freshwater cryptodires. Resting of all three species increased similarly with temperature, but active and aerobic scope did not. In C. expansa and E. macquarii, active and aerobic scope increased over the full temperature range assessed but in C. longicollis these variables reached a plateau above 22°C. Projected increases in freshwater temperatures in south-eastern Australia as a result of global warming are likely to enhance activity, feeding and growth of the three species (subject to food availability), especially in cooler seasons for C. longicollis and warmer seasons for C. expansa and E. macquarii. However, other aspects of predicted climate change, especially increased drought, are likely to be detrimental.

The abilities of freshwater turtles to control their body temperatures by behavioural means have implications for activity, food ingestion and digestion, growth, reproduction and potential responses to climate change. I compared various forms of basking in nature, and responses to aquatic and aerial photothermal gradients in the laboratory, among three species of Australian chelid turtles: Chelodina expansa, C. longicollis and Emydura macquarii. Proclivity for behavioural thermoregulation varied substantially among these species, being highest in C. longicollis and lowest in C. expansa. However, C. expansa had a thermophilic response to feeding. For C. longicollis and E. macquarii, behavioural thermoregulation may enhance colonisation of more southerly latitudes or higher elevations as climatic warming proceeds. However, increasing air temperatures may pose a hazard to turtles dispersing or sheltering terrestrially (for example, when water bodies dry during drought). C. longicollis appears the best placed of the three species to avoid this hazard through its abilities to thermoregulate behaviourally and to aestivate in terrestrial microenvironments that are buffered against temperature extremes.

Trypanosome infections are often difficult to detect by conventional microscopy and their pleomorphy often confounds differential diagnosis. Molecular techniques are now being used to diagnose infections and to determine phylogenetic relationships between species. Complete small subunit rRNA gene sequences were determined for isolates of Trypanosoma chelodina from the Brisbane River tortoise (Emydura signata), the saw-shelled tortoise (Elseya latisternum), and the eastern snake-necked tortoise (Chelodina longicollis) from southeast Queensland, Australia. Partial sequence data were also obtained for T. binneyi from a platypus (Ornithorhynchus anatinus) from Tasmania. Phylogenetic relationships between T. chelodina, T. binneyi and other species were examined by maximum parsimony and likelihood methods. The Australian tortoise and platypus trypanosomes did not exhibit any close phylogenetic relationships with those of mammals, reptiles or amphibians, but were closely related to each other, and to fish trypanosomes. This contra-indicates their co-evolution with their vertebrate hosts but does not exclude co-evolution with different groups of invertebrate vectors, notably insects and leeches.

Eastern long-necked turtles, Chelodina longicollis, are known to lack heteromorphic sex chromosomes and to lack temperature-dependent sex determination when incubated under constant conditions. This study determined whether sex ratios of hatchlings emerging from natural nests of C. longicollis were different from that expected from constant temperature experiments. Temperatures in the eight nests monitored varied considerably each day (by 1.7-12.6�C), with eggs at the top of the nest experiencing the greatest variation (mean range 9.0�C) and eggs at the bottom experiencing least variation (mean range 5.3�C). Temperatures experienced by the top and bottom eggs differed by as much as 5.7�C at any one time. No monotonic seasonal trend was evident, but rainfall caused a sharp drop in nest temperatures. Sex ratios in hatchlings from 14 field nests of C. longicollis did not differ significantly from 1:1, a result in agreement with previous studies conducted at constant incubation temperatures in the laboratory.

Most studies of wetlands tend to focus on the biotic and abiotic interactions within the aquatic habitat. Though wetlands and associated biota may appear to be somewhat isolated from the influence of the wider landscape, wetland habitats are critically linked with adjacent terrestrial habitats and other wetlands through the two-way flows of energy and nutrients and provision of structure. While an understanding of these inter-habitat linkages is breaking down the perceived boundaries between "aquatic" and "terrestrial" ecosystems, there is more limited knowledge on the ecology of wetland animals that must meet critical needs in both aquatic and terrestrial habitats at some time during their life or seasonal cycles. Here, I examine the terrestrial ecology of a freshwater turtle, the eastern long-necked turtle (Chelodina longicollis) in the temporally dynamic and heterogeneous landscape of Booderee national park in south-east Australia by 1) providing a description of terrestrial behaviours, 2) identifying the factors driving terrestrial behaviour and its functional significance, 3) examining factors that may limit or constrain terrestrial behaviour and 4) demonstrating how various terrestrial behaviours can factor prominently in the overall biology of a nominally aquatic animal. Chelodina longicollis used terrestrial habitats for reasons other than nesting, including aestivation and movements between wetlands. Radio-telemetry of 60 turtles revealed that nearly 25 % of all locations were in terrestrial habitats up to 505 m from the wetland, where turtles remained for extended periods (up to 480 consecutive days) buried under sand and leaf litter in the forest. Individuals also maintained an association with a permanent lake and at least one temporary wetland within 1470 m, though some inter-wetland dispersal movements were much longer (5248 m). As a result of their associations with several wetlands and terrestrial aestivation sites, C. longicollis traversed large areas and long distances (13.8 +/- 2.8 ha home range, 2608 +/- 305 m moved), indicating that this species is highly vagile. In fact, a three-year capture-mark-recapture study conducted in 25 wetlands revealed that 33% of the population moved overland between wetlands. After scaling this rate to the number of generations elapsed during the study, C. longicollis moved between discrete water bodies at a rate of 88-132% per generation. This rate is not only high for freshwater turtles, but is among the highest rates of inter-patch movement for any vertebrate or invertebrate. Chelodina longicollis demonstrated an impressive capacity for individual variation in nearly every aspect of its behaviour examined. Most of the variation in space use, movements, terrestrial aestivation and activity could be attributed to extrinsic local and landscape factors, seasonal influences and rainfall, whereas intrinsic attributes of the individual such as sex, body size, body condition and maturity status were less important. Turtles increased movement distance and home range size in regions where inter-wetland distances were farther and with increasing wetland size. Individuals spent more time in terrestrial habitats with decreasing wetland hydroperiod and increasing distance to the nearest permanent lake. Overland movements between wetlands were correlated with rainfall, but the directionality of these movements and the frequency with which they occurred varied according to the prevalent rainfall patterns; movements were to permanent lakes during drought, but turtles returned to temporary wetlands en masse upon the return of heavy rainfall. However, deteriorating conditions in drying wetlands forced turtles to move even in the absence of rainfall. Captures at a terrestrial drift fence revealed that immature turtles as small as 72.3 mm plastron length may move overland between wetlands with similar frequency as larger adults. Taken together, these results suggest that C. longicollis behaviour is in part conditional or state-dependent (i.e., plastic) and shaped by the spatiotemporal variation and heterogeneity of the landscape. Perhaps the most surprising aspect of individual variation was the alternate responses to wetland drying. Turtles either aestivated in terrestrial habitats (for variable lengths of time), or moved to other wetlands. Movement to other wetlands was the near universal strategy when only a short distance from permanent lakes, but the proportion of individuals that aestivated terrestrially increased with distance to the nearest permanent lake. When long distances must be travelled, both behaviours were employed by turtles in the same wetland, suggesting that individuals differentially weigh the costs and benefits of residing terrestrially versus those of long-distance movement. I propose that diversity in response to wetland drying in the population is maintained by stochastic fluctuations in resource quality. The quality of temporary wetlands relative to permanent wetlands at our study site varies considerably and unpredictably with annual rainfall and with it the cost-benefit ratio of each strategy or tactic. Residency in or near temporary wetlands is more successful during wet periods due to production benefits (high growth, reproduction and increased body condition), but movement to permanent wetlands is more successful, or least costly, during dry periods due to the fitness benefits of increased survival and body condition. I used the doubly-labelled water (DLW) method to provide the first estimates of water and energy costs of aestivation and overland movement for any freshwater turtle behaving naturally in the field. Chelodina longicollis remained hydrated while terrestrial with water flux rates (14.3-19.3 ml kg-1 d-1) on par with those of strictly terrestrial turtles, but field metabolic rate during aestivation (20.0-24.6 kJ kg-1 d-1) did not indicate substantial physiological specializations in metabolism during aestivation. Energy reserves, but not water, are predicted to limit survival in aestivation to an estimated 49-261 days, which is in close agreement with the durations of natural aestivation. The energy costs of overland movement were 46-99 kJ (kg d)-1, or 1.6-1.7 times more expensive than aestivation. When a wetland dries, a turtle that foregoes movement to other wetlands can free sufficient energy to fuel up to 134 days in aestivation. The increasing value of this energy "trade-off" with travel distance fits our behavioural observations of variance in response to wetland drying. Taken together, this evidence indicates that terrestrial habitats provide more than just organic and structural inputs and filtering services and that nearby wetlands are important for reasons other than potential sources of occasional colonists to a population. Terrestrial habitats are used for aestivation in response to wetland drying and different wetlands are diverse in their functions of meeting the annual or life-cycle requirements of C. longicollis in temporally dynamic wetland systems. As overland movements between these various habitat types are in response to spatiotemporal variation in habitat quality and associated shifts in the fitness gradient between them, I suggest that terrestrial and different aquatic habitats in Booderee offer complementary resources contributing to regional carrying capacity and population persistence of the turtle population. Thus, important ecological processes regulating C. longicollis in a focal wetland should not be viewed as operating independently of other nearby wetlands and their adjacent terrestrial habitats. Collectively, these findings highlight the complex and dynamic associations between a population of freshwater turtles and the wider terrestrial and aquatic landscape, demonstrating that turtle populations and the factors that impact them can extend well beyond the boundaries of a focal wetland.

With 226-343 individual/ha, population density of Chelodina longicollis in the dams of the University of Western Sydney-Hawkesbury Richmond campus were in the range of other studies around Australia. Their size extremes (24.3 -223.3 mm) were within the range of previous studies, and the overall sex ratio was skewed toward males. The annual growth rates varied and were weakly correlated with animal size. Scute shedding occurred between September and April and peaked in December. Turtles were generally in excellent condition, indicating that sufficient food resources were available in local habitats. Only 3.4% of the population were in poor condition and few animals (8.8 %) carried signs of past injury. No gross abnormalities were recorded, however, there has been low levels of recruitment to the population compared with other Australian studies. Despite a maximum distance dams sampled of 2.8 km and ample evidence of interchange between dams, there was a great variation in animal size, cohort structure, sex ratio among dams. There are a range of factors which have the potential to bias sampling results. Turtles were not influenced by a dominance hierarchy or by the presence of eels, however, they appeared to be capable of avoidance behaviour when nets are set at a specific location. Different cohorts were caught differentially and this varied with month, season and year. In addition, catchability varied among cohorts. Juveniles were least likely, and sub-adult males were most likely, to be recaptured. In some dams there was evidence that animals moved at random while in others movement did not conform to this pattern. These results could not be accounted for in terms of dam size, physical structure of the dam or the distribution and abundance of vegetation.
Master of Science (Hons)

Australia’s largest and most important waterway- the Murray-Darling Basin (MDB) - is under threat owing to predicted increases in temperature extremes and reduction in rainfall - runoff in the coming decades. Management strategies are required that incorporate an understanding of dispersal patterns of the MDB fauna and flora. Patterns of dispersal have typically been studied through direct organismal studies but genetic approaches, in which the movement of genes in the landscape is used as a correlate of species dispersal, can provide a more comprehensive view by investigating at a much larger temporal and spatial scale. Genetic connectivity (dispersal) is influenced by the biology of the species, and by flow regime and the dendritic pattern of the network in riverine landscapes. An understanding of the relative influence of each on connectivity is required to deliver informed management strategies. Decisions regarding whether management for conservation is necessary also require an understanding of a species susceptibility to a changing environment. Species already exhibiting deleterious trajectories under current flow regimes in the basin may require more drastic measures than those that have remained unaffected.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
Full Text

It is well documented that humans may have a major impact on native ecosystems including the animals that reside within them. In Australia, over the past 200 years there have been major changes to the landscape, including land clearing, habitat fragmentation, urbanisation, the creation of roadways, and the introduction of exotic species. Freshwater turtles are one taxon that has been affected by both terrestrial and aquatic changes. The long-necked turtle Chelodina longicollis (Shaw 1794) is the most widespread, and abundant freshwater turtle in Australia. Because of their broad geographic range, their ability to survive within a diversity of aquatic habitats, urban and rural, and because they have a penchant for terrestrial movement, they are an appropriate species to use as a case study on the effect of urbanisation on the long-term viability of freshwater turtles. In addition, because C. longicollis represent the largest vertebrate biomass in many impoundments, their demise is likely to have a major impact on the functioning of these systems. This study was undertaken in Sydney, the largest city in Australia, in areas that have had significant habitat change due to urbanisation, and continue to have rapid change due to increasing density and extent of urbanisation. It was observed that C. longicollis remain the ubiquitous freshwater turtle, although recruitment to the population varied both at different human population density, and among wetlands, and there was little to no recruitment in the urban and suburban sites. Another native freshwater turtle, Emydura macquarii was found at all three sites (urban, suburban and peri urban). In the peri urban site there were very few of this species netted, whilst at both the urban and suburban sites they were in greater numbers, with E. macquarii in greater density than C. longicollis in the urban area. Successful recruitment of E. macquarii was only observed to have occurred in the suburban site and not in the other two sites (suburban, peri urban). A potential impact on C. longicollis was competition from other species such as Trachemys scripta elegans the feral red-eared slider that has demonstrated to outcompete native species in many areas of the world, including Australia. In the peri-urban area it was found that wetland characteristics were influencing the population structure in wetlands, and juveniles were more prevalent in wetlands with low dissolved oxygen and higher percentages of emergent vegetation. It was also observed that over the decade of the study, there was a shift in the population structure to a female bias in the population. Females were also shown to have greater site fidelity than males. Approximately 15% of females were recaptured in the wetland of first capture 13 years after they were first netted in the wetland, although no males were recaptured after this length of time. These females were also in better condition than those that had been netted only in the more recent study period. Vehicle collision impacted both sexes of C. longicollis in all stages of their lifecycle. Females were killed in higher numbers in the nesting season (spring) than at other times, potentially exacerbating the impact on local populations. Casual observation may indicate that C. longicollis, and where they are present, Emydura macquarii, have viable populations, even within wetlands within the most densely populated area of Sydney. However, in these long-lived animals, lack of, or limited, recruitment to the population, losses due to vehicle collision during terrestrial movement, supplementary feeding, water quality, and loss of wetlands in the urbanising areas, question whether the populations over the longer term are viable in the urbanised/rapidly urbanising areas of the Sydney Basin. Without knowledge of longevity and age of senescence, it is effectively impossible to predict when the population will become non-sustainable. However, without intervention such as raising the awareness of the plight of freshwater turtles, the provision of safe nesting sites, mitigation measures to reduce vehicle collision, and removal of exotic animals, the population will decline over time.

With 226-343 individual/ha, population density of Chelodina longicollis in the dams of the University of Western Sydney-Hawkesbury Richmond campus were in the range of other studies around Australia. Their size extremes (24.3 -223.3 mm) were within the range of previous studies, and the overall sex ratio was skewed toward males. The annual growth rates varied and were weakly correlated with animal size. Scute shedding occurred between September and April and peaked in December. Turtles were generally in excellent condition, indicating that sufficient food resources were available in local habitats. Only 3.4% of the population were in poor condition and few animals (8.8 %) carried signs of past injury. No gross abnormalities were recorded, however, there has been low levels of recruitment to the population compared with other Australian studies. Despite a maximum distance dams sampled of 2.8 km and ample evidence of interchange between dams, there was a great variation in animal size, cohort structure, sex ratio among dams. There are a range of factors which have the potential to bias sampling results. Turtles were not influenced by a dominance hierarchy or by the presence of eels, however, they appeared to be capable of avoidance behaviour when nets are set at a specific location. Different cohorts were caught differentially and this varied with month, season and year. In addition, catchability varied among cohorts. Juveniles were least likely, and sub-adult males were most likely, to be recaptured. In some dams there was evidence that animals moved at random while in others movement did not conform to this pattern. These results could not be accounted for in terms of dam size, physical structure of the dam or the distribution and abundance of vegetation.