The response of marsupial carnivores to production forest landscapes and operations
Creators: name: Jones, Evie
Publisher: name: University of Tasmania
Year: 2024

description: In a world increasingly dominated by modified landscapes, finding ways to protect threatened wildlife beyond protected areas is a priority. Forestry can degrade landscapes and impact biodiversity, but production forests often support more biodiversity than other land uses such as agriculture. Understanding how wildlife species use production forests can inform management practices to improve their conservation. <br>Mammalian carnivores are often sensitive to habitat modification due to large home ranges, high energy requirements and conflict with humans. Carnivores play important roles in ecosystems such as regulating prey and smaller predators and carrion recycling, roles that are often suppressed in modified landscapes. While there is plenty of research on the use of production forests by placental carnivores, how marsupial carnivores use these landscapes is less well understood. I aimed to identify the response of two endangered marsupial carnivores, Tasmanian devils and eastern quolls, to production forest landscapes and operations, and place my results in the context of global literature on carnivores and forestry. <br>First, I conducted a systematic literature review of the use of production forest landscapes by carnivores globally. Carnivores generally show higher use of native and unharvested forests and lower use of agricultural land than production forests. Threatened species and large carnivores respond more negatively to production forests. Surprisingly, a high proportion of carnivore species use clearfelled more than unharvested native forest. In forest with partial harvesting or reduced-impact logging, most species show no difference in use between harvested and unharvested forest. <br>Second, I used a network of camera traps to analyse the abundance of two endangered marsupial carnivores, Tasmanian devils and eastern quolls, across three production forest landscapes. Devil and quoll abundance increased with the extent of timber plantations within production forest landscapes. Overall, devils were positively associated with higher tree density and eastern quolls with indicators of open habitat. Within plantations, devil abundance increased with the volume of windrows (linear piles of harvesting debris), as did eastern quoll abundance in pine plantations. Neither species showed a strong response to logging-related features in native forest such as time since harvest. <br>Third, I used GPS tracking of devils in a eucalypt plantation to identify their habitat selection in three behavioural states. Devils did not show preferences for any of native forest, native grassland, and plantation. Within plantations, devils preferred a plantation age of 4–7 years. Devils preferred roads and plantation edges in all behavioural states, and moved faster on roads and edges than away from them, indicating they use them for foraging and travel. <br>Fourth, I investigated lead exposure to devils in a eucalypt plantation from scavenging on browsing marsupials culled using lead ammunition. To assess lead exposure to devils in the landscape, I used a new method of hair analysis, portable X-ray fluorescence (XRF). I first validated the method by analysing hair samples from 39 road-killed devils across Tasmania using portable XRF and with the traditional method of inductively coupled plasma mass spectrometry (ICP-MS) (validation study). Portable XRF measures of hair lead levels were positively correlated with ICP-MS values (R <sup>2</sup> = 0.61). Lead concentrations were then measured in 61 hair samples collected from a eucalypt plantation landscape using portable XRF only (plantation study). Contrary to expectations, mean lead levels in the plantation study were not significantly different to those in the validation study. <br>To assess the short-term impact of browser culling events on lead exposure to devils, we analysed devil blood lead levels (BLLs) before and after a marsupial culling program, and compared lead isotope signatures in devil blood to those in the culling ammunition. We found no evidence that mean BLLs in devils change after culling, though some individuals showed evidence of lead exposure from culling. Low sample sizes limited the power of our results. While 18% of devil blood lead had an isotope signature that was similar to the ammunition samples, the majority did not, possibly indicating other sources of lead in the landscape. Contrary to expectations, BLLs in our study landscape were similar to published BLLs in wild devils. <br>My research found that devils and eastern quolls are highly adaptable to production forest landscapes, as with other generalist carnivores. Production forests provide important habitat to carnivores worldwide. I highlight several management techniques that are likely to improve the value of production forests to carnivores, such as preserving coarse woody debris including windrows, and creating heterogeneous landscapes.