Oral Presentation- Symposium 12th International Mammalogical Congress

Bridging the gap for the western ringtail possum (Pseudocheirus occidentalis): Rope bridges provide safe passage across roads for a critically endangered marsupial (#312)

Roberta Bencini 1 , Kaori Yokochi 2
  1. School of Agriculture and Environment, University of Western Australia, Perth, Western Australia, Australia
  2. School of Life & Env. Sciences, Faculty of Sci Eng & Built Env, Deakin University, Burwood, Victoria, Australia

The western ringtail possum (Pseudocheirus occidentalis) is a critically endangered arboreal marsupial endemic to the south west of Western Australia, the only biodiversity hotspot on mainland Australia, and one of its most rapidly growing regions. A population viability analysis on its last stronghold population living along Caves Road, between Busselton and Dunsborough, predicted a risk of extinction as high as 92% in the next 20 years. Mortality on the road was contributing to its rapid decline, with the removal of road mortality events from the model reducing the extinction risk to 32%. To address road mortality, a rope bridge was installed across Caves Road in 2013 and we monitored its use using motion sensor cameras and microchip readers to identify factors influencing the crossings. We analysed the crossing data using generalised linear models that included factors such as days since installation, breeding season, wind speed and temperature. Possums started investigating the bridge even before installation was completed and made the first complete crossing only 36 days after the installation, with crossing rate reaching to 8.9 ± 0.59 crossings per night. Mothers were observed crossing with young that continued to cross after they reached independence. Possums crossed the bridge less on windy nights and warm nights probably due to the risk of being blown away and heat stress on warmer days. Breeding season did not influence the crossings. Our results demonstrate that rope bridges have a potential as an effective mitigation measure against the negative impacts of roads on this species.