Are wildlife escape ramps needed along Australian highways?

Abstract

Summary Road escape ramps are structures developed in the USA to enable large mammals that become trapped on the roadside of a wildlife fence to escape the road and avoid vehicle collision. They are now commonly installed in eastern Australia to enable the Koala (Phascolarctos cinereus) and other fauna to escape through a roadside exclusion fence and return to the forest. We investigated the use of seven of 14 escape ramps over three years on the Oxley Highway at Port Macquarie in New South Wales. The Swamp Wallaby (Wallabia bicolor) was the most frequently detected species, traversing the escape ramps on 502 occasions, followed by bandicoots (Isoodon macrourus and Perameles nasuta) on 148 occasions. Various other species were detected but no Koalas. Swamp Wallabies moved through the escape ramps in the reverse direction (i.e. towards the road) in 53% of detections of that species and bandicoots in 14% of their detections. There was no obvious pattern by these species of proportionately higher use of ramps closer to the end of the exclusion fences. The large number of reverse passages through the escape ramps reveals a poor design of these structures. Trials with taller ramps are required to determine how to minimise reverse passages. Concurrent monitoring of three underpasses detected numerous crossings by large mammals including Swamp Wallabies, and some crossings by Koalas. We believe evidence is needed to demonstrate the necessity for escape ramps along Australian highways.

Roadkill mitigation is paved with good intentions: a critique of Fox et al. (2019)

“…Indeed, the occurrence of any wildlife on roadsides, despite the loud noises and bright lights produced by passing vehicles, illustrates the strength of this phenomenon (e.g. Ben-Ami and Ramp 2013, Goldingay et al 2018. Inspection of the monthly roadkill rates recorded by Fox et al (2019, fig.…”

Patterns and composition of medium and large vertebrate roadkill, based on six annual surveys along two adjoining highways in south-eastern Queensland, Australia

“…Efforts to mitigate roadkill losses are drawing increasing attention, and protection of Australia's unique fauna has been a major focus of this work (e.g. Dwyer et al 2016;Goldingay et al 2018;Shima et al 2018). More species-specific research is needed in order to better tailor mitigation efforts to the behavioural ecology of particular species.…”

“…Australian efforts to mitigate animal-vehicle collisions are of increasing priority, particularly where iconic or endangered species are impacted (e.g. koalas: see Goldingay et al 2018;cassowaries: see Dwyer et al 2016; Lumholtz's tree kangaroos: see Shima et al 2018; eastern quolls, Tasmanian devils: see Jones 2000). Klöcker et al (2006) point out that collisions with vehicles substantially impact kangaroo populations.…”

Use of road underpasses by mammals and a monitor lizard in eastern Australia and consideration of the prey‐trap hypothesis

“…This comprised a standard 1.5‐m floppy top fence at Port and 1.2 m stock fence with chicken wire at Grafton. At Port, there were seven pairs of escape ramps, spaced 250–650 m apart, within the exclusion fence (see Goldingay et al, 2018).…”