Brushtail possum terrestrial activity patterns are driven by climatic conditions, breeding and moonlight intensity

Abstract

Ecological studies of common brushtail possums (Trichosurus vulpecula) in their extant range have been limited by technology and the species’ nocturnal habit. However, camera traps now allow the investigation of possum ethology without observer interference. Here, we analysed terrestrial possum activity patterns using a large dataset collected over 3 years from 133 camera traps in mesic eucalypt woodland and open forest in three national parks on the New England Tablelands, New South Wales, Australia. We investigated how weather and moonlight intensity influenced possum activity patterns throughout the night, and across seasons and years, by using the timestamps assigned to each detection by the camera trap. Terrestrial possum activity increased as ambient temperatures decreased in autumn and peaked in winter when females were rearing offspring. Nightly possum detections decreased significantly with rain and increasing mean temperature. Possums were almost exclusively nocturnal, with most terrestrial activity earlier in the evening in winter and later at night in summer. During longer nights, higher temperatures also delayed activity. While nightly detection rates were not affected by lunar phase, possums preferred parts of the night with the highest moonlight intensity, and this effect was stronger on brighter nights. Overall, brushtail possums were most active on the ground when temperatures were mild and moonlight bright, presumably assisting foraging and predator avoidance, and during the breeding season; they avoided rain. These patterns suggest that reproduction, thermoregulation and risk of predation strongly shape the nocturnal activity cycle. Furthermore, our research adds to the evidence that camera traps can help greatly expand our knowledge of the ecology and behaviour of nocturnal mammals.