Habitat and introduced predators influence the occupancy of small threatened macropods in subtropical Australia

Abstract

Australia has had the highest rate of mammal extinctions in the past two centuries when compared to other continents. Frequently cited threats include habitat loss and fragmentation, changed fire regimes and the impact of introduced predators, namely the red fox (Vulpes vulpes) and the feral cat (Felis catus). Recent studies suggest that Australia's top predator, the dingo (Canis dingo), may have a suppressive effect on fox populations but not on cat populations. The landscape of fear hypothesis proposes that habitat used by prey species comprises high to low risk patches for foraging as determined by the presence and ubiquity of predators within the ecosystem. This results in a landscape of risky versus safe areas for prey species. We investigated the influence of habitat and its interaction with predatory mammals on the occupancy of medium‐sized mammals with a focus on threatened macropodid marsupials (the long‐nosed potoroo [Potorous tridactylous] and red‐legged pademelon [Thylogale stigmatica]). We assumed that differential use of habitats would reflect trade‐offs between food and safety. We predicted that medium‐sized mammals would prefer habitats for foraging that reduce the risk of predation but that predators would have a positive relationship with medium‐sized mammals. We variously used data from 298 camera trap sites across nine conservation reserves in subtropical Australia. Both dingoes and feral cats were broadly distributed, whilst the red fox was rare. Long‐nosed potoroos had a strong positive association with dense ground cover, consistent with using habitat complexity to escape predation. Red‐legged pademelons showed a preference for open ground cover, consistent with a reliance on rapid bounding to escape predation. Dingoes preferred areas of open ground cover whereas feral cats showed no specific habitat preference. Dingoes were positively associated with long‐nosed potoroos whilst feral cats were positively associated with red‐legged pademelons. Our study highlights the importance of habitat structure to these threatened mammals and also the need for more detailed study of their interactions with their predators.

Short‐term response of threatened small macropods and their predators to prescribed burns in subtropical Australia

“…Measures of percentage ground cover and shrub cover were taken at 1‐m intervals using a 20 cm × 50 cm chequered coverboard (see Monamy & Fox 2000). Ground cover was measured from 0 to 0.5 m from the ground, and shrub cover was measured from 1 to 1.5 m from the ground (see McHugh et al 2019). Foliage projective cover (FPC percentage) was measured along each transect using an FPC sighting tube, with fine cross‐wires (see Specht et al 2006).…”

“…We tested three main hypotheses relating to macropod and predator activity following the implementation of prescribed burns: We predicted that Long‐nosed Potoroo activity would be lower in burn blocks relative to their reference blocks following burn implementation (Claridge & Barry 2000; Norton et al 2015; McHugh et al 2019). We predicted that the larger cursorial macropods, the Black‐striped Wallaby ( Macropus dorsalis ) and Red‐legged Pademelon, would have higher levels of activity in burn blocks following the burns, relative to reference blocks, due to open areas of habitat becoming available and new growth of grasses (Vernes 1995; Evans 1996; Baxter et al 2001).…”

“…High fire frequency regimes in forested plant communities generally diminish understory and mid‐story species and have the potential to transform plant communities from a shrubby understory to a grassy understory with limited structural complexity (Catling et al 2001; Watson & Morris, 2006). Increasing time since fire allows plant communities to recruit understory and mid‐story species, which over time allows shrub and mid‐story layers to re‐develop (Stone et al 2008; Silver & Carnegie 2017) which provides ideal habitat for small macropods (Claridge & Barry 2000; Norton et al 2011; McHugh et al 2019).…”

“…The Long‐nosed Potoroo ( Potorous tridactylus ) and Red‐legged Pademelon ( Thylogale stigmatica ) both have large and patchy distributions and occupy a range of different vegetation communities that vary in their fire management requirements. For example, Long‐nosed Potoroo occupies coastal sandy wet heathlands, moist inland woodlands and dry forests in temperate ecosystems (Claridge et al 2007; Norton et al 2011) and heathlands, heathy woodlands, wet sclerophyll forests, dry sclerophyll forest and rainforest within subtropical ecosystems (Andren et al 2013; McHugh et al 2019). To our knowledge, there have been no experimental studies to determine the response of Long‐nosed Potoroo and its predators to prescribed burns in subtropical Australia, yet this region provides stronghold populations of Potoroos (Andren et al 2013; McHugh et al 2019).…”

“…For example, Long‐nosed Potoroo occupies coastal sandy wet heathlands, moist inland woodlands and dry forests in temperate ecosystems (Claridge et al 2007; Norton et al 2011) and heathlands, heathy woodlands, wet sclerophyll forests, dry sclerophyll forest and rainforest within subtropical ecosystems (Andren et al 2013; McHugh et al 2019). To our knowledge, there have been no experimental studies to determine the response of Long‐nosed Potoroo and its predators to prescribed burns in subtropical Australia, yet this region provides stronghold populations of Potoroos (Andren et al 2013; McHugh et al 2019). Recent investigations in temperate Australia suggest that prescribed burning in the presence of mesopredators (European Red Fox ( Vulpes vulpes ) and feral Cat ( Felis catus )) can have deleterious effects on medium‐sized mammals including Long‐nosed Potoroo (Robley et al 2016; Hradsky et al 2017).…”