Exotic Plant Pathogen Reduces Habitat and Foraging Activities of a Digging Mammal

ABSTRACT

The introduced plant pathogen Phytophthora cinnamomi Rands has caused extensive loss of understorey vegetation cover in native ecosystems globally. Vegetation loss likely has cascading impacts on fauna, but these are largely undocumented. One group of plants notably impacted by the pathogen are Xanthorrhoea grasstrees, which provide important habitat for digging mammals, so‐called ‘ecosystem engineers’, such as bandicoots. We examined whether the quenda, Isoodon fusciventer , a bandicoot species endemic to southwestern Australia and an important ecosystem engineer, alters its foraging behaviour in forest infested by P. cinnamomi . We surveyed quenda digging activities in P. cinnamomi ‐infested and adjacent non‐infested jarrah ( Eucalyptus marginata ) forest in peri‐urban reserves and recorded the availability of plant cover and Xanthorrhoea preissii densities that could be used as refuge habitat, to determine if this was the case. We also recorded the availability of truffle‐like fungi, an important food for quenda. Compared to non‐infested forest, P. cinnamomi ‐infested sites had 46% less available quenda habitat in the form of dense, low shrubs. Downturned X. preissii ‘skirts’ of dead leaves touching the ground provide important quenda habitat. Infested sites had 45% fewer habitable (skirted) X. preissii . Infested sites also had 40% more bare ground. Quenda foraging activity was 33% lower within P. cinnamomi ‐infested sites and varied among reserves, suggesting the importance of site factors. We located few truffle‐like fungi, with no significant difference between infested and non‐infested forest, but we did not quantify all food sources used by these omnivores. We interpreted lower foraging in infestations as being due to reduced refuge habitat rather than reduced food availability. Our findings stress the importance of dense‐skirted X. preissii and low‐shrubs as quenda habitat. Management of pathogen spread is essential to retain quenda habitat. We invite further research into identifying pathogen‐resistant shrubs and X. preissii to bolster quenda habitat in P. cinnamomi‐ infested forest.