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Invasive mammalian predators are efficient at driving native animal declines. The red fox (Vulpes vulpes) kills millions of endemic reptiles in Australia each year. In areas of south‐eastern Australia, the eastern long‐necked turtle (Chelodina longicollis) and Murray River turtle (Emydura macquarii) have declined by more than 50%. High rates of nest predation by foxes limit the recruitment of young turtles in these populations, but previous methods of fox control have been ineffective at protecting turtle nests. Here, we tested the effectiveness of plastic mesh for protecting artificial turtle nests from predation by foxes, in the mid‐Murray catchment, Victoria. We also tested whether protecting a large number of artificial nests in a given area encourages foxes to give up foraging following predictions from giving‐up density theory. We made a series of plots, each containing 32 artificial turtle nests. In each plot, we covered a percentage (0%, 25%, 50%, 81% or 100%) of the nests with either 1 or 2 sheets of plastic mesh. We used remote cameras to photograph and identify any predator that attacked nests in the plots. The cameras also allowed us to estimate the amount of time a fox was visible on each plot, as a metric of how much effort foxes expended on protected nests. Nest survival rate was not increased by either 1 or 2 sheets of mesh, and increasing the number of protected nests on a plot did not reveal a giving‐up density (GUD) value for fox foraging behaviour. Our study demonstrates that plastic mesh is not effective for protecting artificial turtle nests from foxes in this region. [ABSTRACT FROM AUTHOR]

Common demographic parameters such as survival and fecundity are regularly estimated in freshwater turtles, but large-scale manipulative and comparative experiments are rare. The resilience of a population to stage-specific predation is dependent on density-dependent inversity or compensation. Some species are also more susceptible to predation because of their life-history strategies. Nest predation by introduced red foxes ( Vulpes vulpes) on Australian freshwater turtles is a major source of mortality, but its full impact has yet to be evaluated. Freshwater turtles are long lived, and a population decline resulting from nest predation by foxes may take a long time to become evident. We evaluated the impact of foxes on the population growth and patterns of survival of two widely distributed Australian freshwater turtles in the Murray River, where nest predation rates have previously been reported at above 95%. We estimated densities and survivorship ofEmydura macquariiandChelodina expansafrom the nest to adult stage. We then conducted a fox removal program (before-after control-impact design) to determine the impact of foxes on populations of these species. We found a contrast in life-history strategies between the two sympatric species.C. expansawas five times less abundant thanE. macquarii. A type III survivorship curve described the life history ofE. macquariibecause nest predation and adult survival rates were>0.9. Densities ofC. expansanests were low and situated away from shore. Consequently, nest predation rates were half those ofE. macquarii.Projection matrices predicted thatE. macquariipopulations may be declining slowly but are likely to respond to changes in adult survival, which has the greatest elasticity value. Foxes destroyed a proportion of nesting adult females each year; however, there appears to be no density-dependent compensation in adult survival, and foxes potentially regulate these populations.E. macquariipopulations had low productivity and relied on a standing crop of turtles for population maintenance, whereasC. expansahad relatively more juveniles in the population and was less reliant on adult survival. Despite its vulnerable status, C. expansais relatively more stable thanE. macquarii, primarily because there were proportionally more juveniles in the population. Management options focusing on reducing adult mortality in both species will be most effective. [ABSTRACT FROM AUTHOR]

Gregarious behavior among oviparous female animals just prior to oviposition can be explained by several mechanisms, including a benefit to offspring survival. By clustering eggs together in one area, females may dilute the probability of egg predation. We tested the hypothesis that nest density influences egg survival in the Pig-Nosed Turtle (Carettochelys insculpta) along a river in northern Australia. Beaches with multiple nests were three times more likely to experience a predation event than beaches with single nests. However, the number of nests on a beach did not influence the probability of predation of individual nests, when considering either beaches with single versus groups of nests, or when comparing beaches with single nests, small groups of nests (n = 2-5), and large groups of nests (n = 6-8). Therefore, gregarious behavior of reproductive females during the nesting period did not dilute predation risk to nests. Four other hypotheses might explain the behavior: (1) nesting areas are limited; (2) nesting in groups dilutes predation risk to nesting females; (3) nesting in groups dilutes predation risk to hatchlings; and (4) social interactions in aggregations of nesting females provide additional information on nesting beaches/sites, reducing some cost associated with independent assessments of nesting beaches/sites. [ABSTRACT FROM AUTHOR]