The influence of fence design on the movement patterns of eastern long-necked turtles

Abstract

<p>Fences disturb the movements of terrestrial species, altering migration patterns, limiting access to vital resources, and reducing genetic diversity. With almost 40% of the Earth's land surface converted for agriculture, farm fencing to protect crops and corral livestock is expected to stretch into the millions of kilometers. As semi-terrestrial ectotherms, freshwater turtles are threatened by fences that limit access to resources and increase risks of desiccation, entanglement, and overheating, often resulting in death. To determine the effect of fences, we quantified the movement patterns for a population of eastern long-necked turtles (Chelodina longicollis) inhabiting an agricultural landscape near Armidale, New South Wales, Australia from November 2022 to September 2023. There was considerable variation in the distance traveled, home range size, and movement corridor selection between turtles that was not explained by the morphological factors of size, mass, or the loss of a limb (likely due to predation attempts). On average, 38%±4.70 (±SE) of turtle movements were terrestrial (overland) during their active season (spring and summer) during which they encountered fences frequently because of a complex matrix of paddocks. Fence design dictated the distance turtles traveled to locate a suitable passage point. The majority of fences allowed turtles to pass (turtle-friendly fences, 71.4% of total fence distance) as opposed to turtle-unfriendly fences (28.6% of total fence distance). Turtles were required to travel almost 4 times the distance to locate a suitable crossing point (a gap or fault in the fence) when they encountered an unfriendly fence (85.32 m±29.81) compared to a turtle-friendly fence (25.85 m±3.58). Our results highlight the need for land managers to avoid small-diameter exclusion fencing and fence designs containing chicken wire that extend to or below ground level. In settings where small-diameter wire fencing is required, we recommend the installation of turtle gates for small terrestrial fauna or elevating bottom wires at least 50 mm above ground level to facilitate fence permeability.</p>