How high is your hummock? The importance of Triodia height as a habitat predictor for an endangered marsupial in a fire‐prone environment

Fire and seral vegetation succession are known to influence the distribution and abundance of a wide range of arid and semi‐arid mammal species. In Triodia hummock grasslands, the gradual increase in Triodia cover after fire is a significant factor influencing mammal distribution and abundance. However, the height of fire‐adapted hummock grass species is often ignored during habitat preference studies despite the fact that taller hummocks are likely to have improved insulation properties and greater protection from predators. We tested the relative importance of a range of Triodia habitat characteristics in determining the distribution and abundance of a fire‐adapted mammal inhabiting Triodia mallee dune fields in semi‐arid Australia. We sampled 77 sites and collected information on habitat attributes including Triodia cover, height and time since fire. The 90th percentile Triodia height (>400 mm) was the most reliable predictor of sandhill dunnart abundance, and breeding, inferred through the presence of subadults. The presence of adult sandhill dunnarts was best explained by Triodia cover, increasing when cover exceeded 25%. We suggest that while Triodia cover may be an important variable for predicting the presence of adult sandhill dunnarts, the height of Triodia is important for breeding, when tall Triodia are possibly sought for nesting sites. These Triodia height and cover requirements were not recorded at sites until at least 10 years post fire but the relationship between fire and Triodia cover and height was inconsistent; after 20 years Triodia cover declined with increasing fire age while the 90th percentile Triodia height remained relatively constant. This incongruence may explain why the presence of sandhill dunnarts appears more constrained by a minimum rather than maximum time since fire and could help explain patterns of post‐fire distribution in other arid zone mammals. Importantly, the 90th percentile Triodia height highlighted the possible significance of scattered, tall Triodia hummocks for arid zone fossorial mammals.