Indistinct changes in the mammal fauna between 1986-2017 at Judbarra-Gregory National Park, Northern Territory

Abstract

The mammal fauna in many parts of northern Australia has undergone dramatic changes in the past 20-30 years, though longitudinal data that spans this period are limited and largely from coastal and high rainfall regions. We examined data from Judbarra-Gregory National Park that has been collected in a systematic manner (once in 1986 and then 2005-2017), including two years where camera trapping was included (2015 and 2017). We standardised this data in a simple manner (i.e., species by relative abundance and site frequency) to examine if there were any stark changes over this time span. We also undertook some simple modelling of mammal pattern with respect to fire and fractional green and bare cover metrics. Though we recognise some limitations in our comparisons (i.e., spatial variation in sites and methods), the data indicated that the mammal fauna had generally not changed substantially in composition, relative abundance or frequency across sites. There were meaningful models correlating mammal pattern to fire frequency, time since fire, fraction green and bare parameters. However, some species symptomatic of small mammal decline elsewhere (i.e., Rattus tunneyi) may have become less common, whereas other species were recorded for the first time in more recent years (2010-2017), particularly by camera traps (i.e., Trichosurus vulpecula, Isoodon macrourus, Melomys burtoni). We postulate that change in the mammal fauna on the semi-arid fringe of tropical savannas may have occurred prior to the 1980s, with a long history of cattle grazing a possible contributing factor. The mammal fauna there, is also perhaps naturally sparse and heterogeneous in spatial and temporal distribution.