Conservation implications of turtle declines in Australia's Murray River system

Area of Science:

• Ecology
• Conservation Biology
• Zoology

Background:

• Turtles are a highly endangered vertebrate group, with nearly half of all species facing extinction.
• Invasive predators, like the red fox (Vulpes vulpes), pose a significant threat to turtle populations, particularly through nest predation.
• Previous predictions in the 1980s indicated that fox predation would lead to declines in turtle populations in Australia's Murray River.

Purpose of the Study:

• To assess the current population status of three turtle species (broad-shelled turtle, eastern long-necked turtle, and Murray River turtle) in the Murray River.
• To determine if the predicted declines due to invasive fox predation have occurred.
• To evaluate the recruitment success and population age structure of these turtle species.

Main Methods:

• Field surveys were conducted in the Murray River and associated waterways to assess turtle populations.
• Population assessments included determining species rarity, presence/absence, and age structure.
• Nest predation by invasive foxes was considered as a primary driver of observed population trends.

Main Results:

• All three studied turtle species (broad-shelled turtle, eastern long-necked turtle, and Murray River turtle) are rare in the lower Murray River region.
• Populations of the Murray River turtle (Emydura macquarii) exhibited significant aging, indicating poor recruitment, likely due to fox nest destruction.
• Eastern long-necked turtles (Chelodina longicollis) also showed signs of population aging at some sites.
• Turtle populations were undetected in numerous locations in South Australia, suggesting a severe decline.

Conclusions:

• The predicted turtle declines in the Murray River due to invasive fox predation are occurring and have not been mitigated.
• Sustained low recruitment, driven by nest predation, is leading to aging populations and risks future population collapse.
• Failure to mitigate threats has resulted in a worst-case scenario, potentially leading to the loss of a vital vertebrate guild crucial for aquatic ecosystem health.