Supplementary refuge as a tool for recovering small mammals and reptiles after fire

Abstract

Global fire regimes are becoming more frequent, severe, and extensive. Within Australia, this trend was demonstrated by the unprecedented scale and ecological impact of the 2019-2020 Black Summer fires. Small mammals and reptiles are of particular conservation concern due to their reliance on ground-level vegetation and woody debris, and increased vulnerability to predation in burnt landscapes. Despite the importance of post-fire conservation for these species, there are relatively few evidence-based management interventions available to land managers looking to actively conserve native fauna after fire. In the following chapters I aim to address this knowledge gap by systematically mapping the literature to identify potential post-fire management actions (Chapter 2), and conducting a field-based experiment to test the effects of supplementary coarse woody debris (CWD) on small mammal and reptile populations (Chapters 3-5). In Chapter 2 I used a systematic mapping protocol to identify the range of conservation-focused management interventions that have been used in disturbed landscapes globally. I aimed to identify which management interventions have been used in disturbed landscapes to date and whether those interventions could be suitable in response to other types of disturbance, specifically fire. Interventions were most commonly used to address invasive or overabundant species, agriculture, and production forestry. Coarse woody debris manipulation, predator control and revegetation were the most commonly studied interventions. However, understanding suitable management responses to fire represents a significant knowledge gap and only three studies assessed management interventions in post-fire landscapes. In Chapters 3 and 4 I experimentally tested the effects of supplementary CWD on small mammal and reptile populations in areas burnt by the 2020 Orroral Valley Fire in Namadgi National Park, ACT. In a field-based study I established 20 experimental blocks with three treatments: (1) structure only (CWD piles); (2) predation only (strips of chicken wire); and (3) structure + predation (CWD piles covered in chicken wire). A combination of active and visual searches were used to survey reptile populations at each treatment for two consecutive summer seasons, and wildlife cameras were used to continuously monitor small mammal activity for 15 months. Woody debris treatments (i.e., structure and structure + predation) supported significantly higher abundances of reptiles compared to the control. Small mammal abundance and richness was not significantly greater at any treatment compared with the control, and instead increased most significantly with increasing levels of shrub cover. In Chapter 5 I examined the thermal properties of supplementary CWD piles and compared them to the thermal properties of natural refugia in a post-fire landscape. Temperature loggers were used to monitor temperatures within CWD piles, hollow logs and rocky outcrops across seven months. Temperatures within CWD piles were significantly less extreme than ambient maximum and minimum temperatures. In Chapter 6 I synthesise the findings of Chapters 2-5 to answer the question "what should we do after the next fire?". In this chapter I identify the key lessons learned across my research that can help land managers make more informed decisions after future fires. Overall, supplementary CWD was proven to support a higher abundance of reptiles in areas burnt at high and low fire severity across our study. CWD piles without chicken wire were the most cost-effective treatment tested, and the simplicity of their construction provides an opportunity to involve citizen scientists and community members interested in post-fire recovery efforts. Show more