Notes on a newly discovered population of the Pygmy Copperhead Austrelaps labialis (Jan, 1859) in the Adelaide Hills, South Australia

ABSTRACT The Pygmy Copperhead Austrelaps labialis is South Australia’s only endemic snake, being native to the Adelaide Mount Lofty Ranges and Fleurieu Peninsula; with an additional allopatric population on Kangaroo Island. Within the AMLR, it inhabits stringybark forests and adjacent dense vegetation, occupying a total area of ~150 km2. Here, we document a newly discovered and seemingly isolated population at the north-eastern extent of its known mainland distribution. We visited Lobethal Bushland Park from 2013–2018 and observed snakes of varying age and size, while documenting their ecology and behaviour. In late 2019, the site was decimated by catastrophic wildfire and its persistence here remains unknown. Alongside descriptions of our observations, we suggest measures for the conservation of this vulnerable population in its remnant habitat if it has survived the impacts of wildfire.

Population ecology of the nectar-feeding squirrel glider (Petaurus norfolcensis) in remnant forest in subtropical Australia

Context. Nectar is a temporally variable food resource. However, because few studies describe the population dynamics of nectar-feeding non-flying mammals, it is unclear how such populations are influenced by resource availability. Aims. We investigated the population ecology of the squirrel glider (Petaurus norfolcensis) in remnant forest in Brisbane, Australia, where nectar was a dominant food item. Methods. We used 36 tree-mounted traps to census a squirrel glider population inhabiting a 47-ha urban remnant over a 4-year period. Key results. A total of 201 gliders was captured 705 times in 3729 trap-nights (19% trap success). Population density peaked in the first year at ~1.6 individuals ha–1, and declined down to ~0.5 individuals ha–1 by the final year. This change in population density appeared to be mediated by annual variation in flowering intensity. Births occurred from March to November, peaking between April and July. All females >1 year old bred in each year of the study, with a mean litter size of 1.7 (n = 122). The overall natality rate was 1.9, indicating that females occasionally bred twice per year. The sex ratio was at parity in the pouch and in the trappable population. Gliders first entered the trappable population at 4 months of age, and persisted for a mean of 32 months. The maximum longevity was at least 6 years. Conclusions. The demographic characteristics of this squirrel glider population within remnant forest surrounded by urban development were similar to those reported elsewhere. Variation in nectar availability appears to have a substantial influence on the dynamics of squirrel glider populations. Implications. The substantial variation in population size driven by food availability raises concerns regarding the viability of small populations of nectarivorous non-flying mammals inhabiting remnant habitat.

Extinction debt: origins, developments, and applications of a biogeographical trope

The concept of the extinction debt has two components: a direct timelag between an environmental perturbation and the consequent extinction of a species and the idea that among species going extinct the strong competitors/weak colonizers go extinct first. Although the term was first used in 1994 in the context of metapopulation models, its roots go back to general systems theory and the theory of island biogeography. It has been qualified and elaborated since 1994, mostly in terms of the effects of spatial pattern on the outcomes. The strongest critiques of the concept emphasize that the direct trade-off between competition and colonization abilities is not simple. The original application was to remnant habitat patches, but it could be applied to spatially heterogeneous habitats that are subject to climate change or invasive species. As a guide to conservation practice, extinction debt remains a general cautionary principle rather than a specific prescription, but the raising of awareness is nevertheless significant.