Diet of the silky mouse (Pseudomys apodemoides) and the heath rat (P. shortridgei) in a post-fire environment

Abstract

Understanding the ecological effects of fire is important for biodiversity conservation in flammable ecosystems. To this end we quantified the winter and spring diet of silky mice (Pseudomys apodemoides) and heath rats (P. shortridgei) at 20 woodland sites ranging from 2 to 55 years post-fire. We tested the hypothesis that diets would differ (shift) between very recently burnt (2–3 years old) and mature (≥17 years old) parts of the landscape. Analyses based on faecal material collected in winter (June) and spring (October) demonstrated that both species ate a broad range of foods, but the diets of silky mice and heath rats differed substantially with respect to monocot, seed and invertebrates. Seasonal changes in diet were also observed. Silky mice demonstrated a distinct diet shift, with fewer flowers and more seeds consumed at very recently burnt sites compared with mature sites. A distinct diet shift was not observed for heath rats as they ate substantial quantities of monocots and forbs regardless of time since fire. However, they did demonstrate a seasonally dependent diet shift with respect to flowers: in winter, more flowers were eaten at very recently burnt sites but in spring more flowers were eaten at mature sites. In line with the diet shift hypothesis, silky mice altered their diet to take advantage of food groups (principally seeds) more readily available shortly after fire. Heath rats did not shift their diet to the same degree, but a focus on food groups (such as monocots and forbs) that are accessible across the time-since-fire spectrum may facilitate rapid post-fire recolonisation by this species.