Facilitated movement over major roads is required to minimise extinction risk in an urban metapopulation of a gliding mammal

Abstract

Context Urbanisation is recognised as a primary cause of biodiversity loss. Roads are an inherent element of this, creating partial or complete barriers to animal movement. Urban landscapes of eastern Australia are typified by a dense road network interspersed with remnant patches of bushland. Inter-patch movement by tree-dependent gliding mammals may be halted and, consequently, population viability threatened, when canopy gaps over roads exceed gliding ability. Aims We test the notion that a metapopulation of the squirrel glider (Petaurus norfolcensis) in southern Brisbane can persist within a highly fragmented urban landscape with large road canopy gaps. Methods We used the population modelling software VORTEX to investigate the influence of inter-patch movement (dispersal) and wildfire on the probability of extinction. Wildfire is an inherent characteristic of this landscape. Key results Our modelling suggests that a lack of inter-patch movement as a result of road barriers, in tandem with wildfire, is associated with a high probability of local extinction. However, a small rate of inter-patch movement can substantially reduce the likelihood of extinction. Conclusions Road-crossing structures are the most plausible means available to link remnants to enable inter-patch movement for squirrel gliders in this landscape because of inadequate road-side tree height. Simulation studies such as the present study that test population viability are critical to convince land managers that action must be taken. Implications The need to conserve urban biodiversity will increase over time, so land managers must consider the likely benefits to population persistence conferred by installing wildlife crossing structures into existing roads.