Population dynamics of dasyurid marsupials in dryland Australia: Variation across habitat and time

Abstract

The irruptive population dynamics of rodents are a globally renowned wildlife phenomenon; however, the dynamics of other small mammals with which rodents are sympatric are poorly understood. Dryland Australia supports a high diversity of small (<200 g) arthropod-eating marsupials (Dasyuridae). Here, we test the hypothesis that dasyurid marsupials do not exhibit the same degree of irruptive population dynamics that are shown by rodents. We addressed this question by sampling small mammal assemblages on 20 permanent trapping sites in the Simpson Desert on 20 occasions from 2007 to 2017. Sampling was stratified across three broad habitat types: sandridge, gibber plain and clay plain. We captured 478 dasyurid marsupials of nine species, ranging in mean body mass from 5.75 to 93.50 g, at a capture rate of 1.71 per 100 trap-nights. Capture rate varied across habitat and over time and the interaction between these two effects was also significant. Capture rate was highest on clay plain (3.35 captures/100 trap-nights), followed by gibber plain (2.16 captures/100 trap-nights) and lowest on sand habitat (0.54 captures/100 trap-nights). Each species had a clear preference for one of the dominant habitat types. Dasyurid assemblages responded to high rainfall pulses in November-December 2008 and January 2015; however, the largest rainfall period in 2010-2011 resulted in very low captures. Likewise, a peak in abundance occurred in April 2008 although it was not preceded by high rainfall. We conclude that, although dasyurid marsupial capture rates varied up to 34 fold during the study period, population changes are not strongly tied to rainfall. Heterothermic physiology in this family, in particular the ability to use daily torpor to save energy, may be central to the decoupling of population dynamics from rainfall-driven primary productivity.

Landscape monitoring reveals initial trends in occupancy and activity of bats in multiple‐use forests

“…Yet longitudinal studies of desert marsupial insectivores have revealed their abundance is not strongly tied to rainfall (Pavey et al . 2020), unlike that found for rodents (Greenville et al . 2016).…”

“…This relationship was unexpected given that the Pilliga is a dry forest, and we suspected drought conditions and associated effects on productivity, as measured by NDVI, would be more important (Watson 2011;Rodhouse et al 2015). Yet longitudinal studies of desert marsupial insectivores have revealed their abundance is not strongly tied to rainfall (Pavey et al 2020), unlike that found for rodents (Greenville et al 2016). Instead, Pavey et al (2020) suggested that the ability of dasyurids to enter torpor to save energy may decouple population dynamics from rainfall-driven primary productivity.…”

“…Yet longitudinal studies of desert marsupial insectivores have revealed their abundance is not strongly tied to rainfall (Pavey et al 2020), unlike that found for rodents (Greenville et al 2016). Instead, Pavey et al (2020) suggested that the ability of dasyurids to enter torpor to save energy may decouple population dynamics from rainfall-driven primary productivity. Bats also use torpor on a regular basis, both after fire (Doty et al 2016) and in hot, dry environments (Bondarenco et al 2016), and this may reduce the effect of lower productivity during droughts on populations.…”

“…Instead, Pavey et al . (2020) suggested that the ability of dasyurids to enter torpor to save energy may decouple population dynamics from rainfall‐driven primary productivity. Bats also use torpor on a regular basis, both after fire (Doty et al .…”

Using bioindicators to inform effective predator management for threatened species protection

“…Previous research has also suggested that small to medium dasyurids may be unable to rapidly respond and take advantage of increased resource availability or improved environmental conditions (Dickman et al, 2001). Longer-term monitoring has shown that small to medium dasyurids display a delayed response to large rainfall events (Pavey et al, 2020) and small dasyurids respond to the larger dasyurid predator, the mulgara, rather than invasive predators, such as feral cats and foxes (Greenville et al, 2017). In contrast, Pedler et al (2016) found a substantial increase in the distribution of the crest-tailed mulgara (Dasycercus cristicauda) following a rabbit haemorrhagic disease virus (RHDV) outbreak that suppressed rabbit populations and consequently reduced feral cat and fox numbers.…”