Effects of different management strategies on long-term trends of Australian threatened and near-threatened mammals

Abstract

Monitoring is critical to assess management effectiveness, but broadscale systematic assessments of monitoring to evaluate and improve recovery efforts are lacking. We compiled 1,808 timeseries from 71 threatened and near-threatened terrestrial and volant mammal species and subspecies in Australia (48% of eligible threatened mammal taxa), to compare relative trends of populations subject to different management strategies. We adapted the Living Planet Index to develop the Australian Threatened Mammal Index and track aggregate trends for all sampled threatened mammal populations, and for small (<35 g), medium (35-5,500 g) and large mammals (>5,500 g), between 2000 and 2017. Unmanaged populations (42 taxa) declined by 63% on average between 2000 and 2017, with unmanaged small mammals suffering the greatest declines (96%). Populations of 17 taxa in havens (islands and fenced areas that excluded or eliminated introduced red foxes and domestic cats) increased by 680%. Outside havens, populations undergoing sustained predator baiting initially declined by 75% but subsequently increased to 47% of their abundance in 2000. At sites where predators were not excluded or baited but other actions like fire management and introduced herbivore control occurred, populations of small and medium mammals declined faster, but large mammals slower, than unmanaged populations. Only 13% of taxa had data for both unmanaged and managed populations, but Index comparisons for this subset showed that taxa with populations increasing inside havens declined outside havens, but taxa with populations subject to predator baiting outside havens declined at a slower rate than populations with no management, then increased while unmanaged populations continued to decline. More comprehensive and improved monitoring (particularly encompassing poorly represented management actions and taxonomic groups like bats and small mammals) is required to understand if, and where, management has worked. Improved implementation of management for threats other than predation is critical to recover Australia's threatened mammals.