Cutaneous Lesions in Freshwater Turtles (Emydura macquarii krefftii and Myuchelys latisternum) in a Rainforest Creek in North Queensland, Australia

Freshwater turtles inhabit most rivers and creeks on the east coast of Australia, but some species are only found in specific catchments, which makes them vulnerable to extinction. During annual fieldtrips to Alligator Creek, North Queensland, the resident population of Myuchelys latisternum and Emydura macquarii krefftii in a natural pond, just outside Bowling Green National Park, have been surveyed for a number of years and demographic data recorded against tagged turtles. Rounded, cutaneous lesions on individual animals were first noted in August 2016, three years after the first survey of the population. Turtles living in the upstream sections of the creek were not affected. An initial investigation into the cause of the lesions ruled out pollutants and although the bacterial communities appeared to be different on turtles with lesions, a causative agent was not identified. Attempts to isolate virus in culture was not successful and specific PCRs for ranavirus, papillomavirus, adenovirus and herpesvirus did not identify their presence. Blood biochemical parameters, body condition and activity levels were not significantly different between affected turtles and those without lesions. The turtles in this pond were monitored regularly over the following three years with 249 M. latisternum and 192 E. m. krefftii captured, tagged and released. The prevalence of the lesions fluctuated with season from 0 to 77 and 68% respectively, but did not vary significantly between species or sex in adults. There was a tendency for larger animals to be more likely to have lesions. The position of the lesions on the turtles was mostly on dorsal surfaces, distally on the legs and proximal on the tales of males, indicating that the initial lesion may have been associated with a behaviourally induced trauma. Recaptured animals (n = 43) during this period, provided records of lesion progression over time and while some healed up between capture events, others persisted for up to 24 months. Some turtles were repeatedly captured without lesions. Intra-species aggression associated with seasonal behaviours could potentially be the primary cause of skin trauma, followed by a secondary invasion of an unusual pathogen present in the environment.

The influence of a new water infrastructure development on the relative abundance of two Australian freshwater turtle species

Development of water infrastructure benefits water security and agriculture but poses risks to habitat and aquatic fauna. Wyaralong Dam was constructed on Teviot Brook in 2010 to provide future urban water supplies for South East Queensland, Australia. Construction of the dam created a large impoundment area and environmental impact assessment predicted significant impacts upon resident freshwater turtle species and their habitats. Differences in habitat requirements, life-history characteristics and sensitivity to change between the Macquarie River turtle (Emydura macquarii macquarii) and the common saw-shelled turtle (Myuchelys latisternum) were expected to influence the impact of the dam on the spatial and temporal abundance of these species. The relative abundance of each species was monitored at sites located within, upstream and downstream of the impoundment across wet and dry seasons during the dam’s first five years of operation. The results of this monitoring program indicate that spatial and temporal variability in the relative abundance of E. macquarii macquarii and M. latisternum occurred during the study but not all expected impacts were realised. Contrary to expectation, the relative abundance of E. macquarii macquarii did not increase over time within, upstream or downstream of the dam. M. latisternum showed greater temporal variability at some sites; however, no clear relationship between relative abundance and operational years was observed during the monitoring program. Spatial variability in relative abundance between sites was dependent upon season, with trends generally consistent across both turtle species. Where differences between species were observed, these are suspected to have resulted from the influence of environmental conditions on species-specific movement behaviours. The monitoring program confirmed the use of the upper limits of the impoundment and the plunge pool below the dam wall by both turtle species but relative abundance within the main body of the impoundment remained low throughout monitoring. The results of the study allow for consideration of the suitability of predefined management measures and the development of recommendations for future monitoring programs prescribed for water infrastructure developments.

Food abundance and diet variation in freshwater turtles from the mid-Murray River, Australia

Consumers usually respond to variations in prey availability by altering their foraging strategies. Generalist consumers forage on a diversity of resources and have greater potential to ‘switch’ their diet in response to fluctuations in prey availability, in comparison to specialist consumers. We aimed to determine how the diets of two specialist species (the eastern long-necked turtle (Chelodina longicollis) and the broad-shelled turtle (Chelodina expansa) and the more generalist Murray River short-necked turtle (Emydura macquarii) respond to variation in habitat and prey availability. We trapped and stomach-flushed turtles, and compared their diets along with environmental variables (turbidity, macrophyte and filamentous green algae cover, and aquatic invertebrate diversity and abundance) at four wetlands in north-central Victoria. Diets of E. macquarii differed from those of both Chelodina species, which overlapped, across all four sites. However, samples sizes for the two Chelodina species were too small to compare among-wetland variation in diet. Dietary composition of E. macquarii was variable but did not differ statistically among sites. Emydura macquarii preferentially selected filamentous green algae at three of the four sites. Where filamentous green algae were rare, total food bolus volume was reduced and E. macquarii only partially replaced it with other food items, including other vegetation, wood, and animal prey. Many turtles at these sites also had empty stomachs. Thus, filamentous green algae may be a limiting food for E. macquarii. Although E. macquarii has previously been described as a generalist, it appears to have limited ability to replace filamentous green algae with other food items when filamentous green algae are rare.

Population structure and allometry of Podocnemis unifilis (Testudines, Podocnemididae) in a protected area upstream Belo Monte dam in Xingu River, Brazil

Amazon river turtles are increasingly threatened by habitat loss and alteration due to the Brazilian energy policy based on construction of hydroelectric dams, meanwhile, populational studies remain scarce. We described the population structure, and established body allometric relationships of Podocnemis unifilis in the Terra do Meio Ecological Station in the Iriri River, tributary of the Xingu River upstream the Belo Monte dam under construction Turtles were captured by hand net and diving in 2012 and 2013 dry seasons, and 2013 rainy season. A total of 728 males, 296 females and four juveniles were captured. Adult sex ratio was male-biased by 9.15 ♂:1 ♀. Females were significantly larger than males. Mean straight carapace length was 268.9 ± 46.7 mm (165 - 403) for females; and 232.7 ± 24.8 mm (167 - 303) for males. The sexes were morphologically distinct in function of a proportionally larger plastron, and higher carapace, on females. Allometric relationships between straight carapace length and other morphometric traits were strong for males (R2 range = 0.87 - 0.96 and females (R2 range =0.79 - 0.98. Exploitation of P. unifilis in biomass extirpated from the Middle Xingu River may be estimated from body parts found post-consumption by the presented regressions.

A risk assessment approach to manage inundation of Elseya albagula nests in impounded waters: a win-win situation?

A risk assessment process was used to trial the impact of potential new operating rules on the frequency of nest inundation for the White-throated snapping turtle, Elseya albagula, in the impounded waters of the Burnett River, Queensland, Australia. The proposed operating rules would increase the barrage storage level during the turtle nesting season (May-July) and then would be allowed to reduce to a lower level for incubation for the rest of the year. These proposed operating rules reduce rates of nest inundation by altering water levels in the Ben Anderson Barrage impoundment of the Burnett River. The rules operate throughout the turtle reproductive period and concomitantly improve stability of littoral habitat and fishway operation. Additionally, the proposed rules are expected to have positive socio-economic benefits within the region. While regulated water resources will inherently have a number of negative environmental implications, these potential new operating rules have the capacity to benefit the environment while managing resources in a more sustainable manner. The operating rules have now been enacted in subordinate legislation and require the operator to maintain water levels to minimize turtle nest inundation.