Ineffectiveness of plastic mesh for protecting artificial freshwater turtle nests from red fox (Vulpes vulpes) predation

Abstract

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.