Rabbit biocontrol and landscape‐scale recovery of threatened desert mammals

Abstract

Funding for species conservation is insufficient to meet the current challenges facing global biodiversity, yet many programs use expensive single-species recovery actions and neglect broader management that addresses threatening processes. Arid Australia has the world's worst modern mammalian extinction record, largely attributable to competition from introduced herbivores, particularly European rabbits (Oryctolagus cuniculus) and predation by feral cats (Felis catus) and foxes (Vulpes vulpes). The biological control agent rabbit hemorrhagic disease virus (RHDV) was introduced to Australia in 1995 and resulted in dramatic, widespread rabbit suppression. We compared the area of occupancy and extent of occurrence of 4 extant species of small mammals before and after RHDV outbreak, relative to rainfall, sampling effort, and rabbit and predator populations. Despite low rainfall during the first 14 years after RHDV, 2 native rodents listed by the International Union for Conservation of Nature (IUCN), the dusky hopping-mouse (Notomys fuscus) and plains mouse (Pseudomys australis), increased their extent of occurrence by 241-365%. A threatened marsupial micropredator, the crest-tailed mulgara (Dasycercus cristicauda), underwent a 70-fold increase in extent of occurrence and a 20-fold increase in area of occupancy. Both bottom-up and top-down trophic effects were attributed to RHDV, namely decreased competition for food resources and declines in rabbit-dependent predators. Based on these sustained increases, these 3 previously threatened species now qualify for threat-category downgrading on the IUCN Red List. These recoveries are on a scale rarely documented in mammals and give impetus to programs aimed at targeted use of RHDV in Australia, rather than simply employing top-down threat-based management of arid ecosystems. Conservation programs that take big-picture approaches to addressing threatening processes over large spatial scales should be prioritized to maximize return from scarce conservation funding. Further, these should be coupled with long-term ecological monitoring, a critical tool in detecting and understanding complex ecosystem change.

Eradicating abundant invasive prey could cause unexpected and varied biodiversity outcomes: The importance of multispecies interactions

“…This is fortunate because these were the parameters in our model with the greatest level of uncertainty. Importantly, our findings are in direct agreement with previous on‐ground studies reporting the bounce back of native small mammals following severe rabbit population crashes in response to the release of a new biocontrol agent (Pedler et al., ). Furthermore, the role of the dingo as a top predator, which facilitates the maintenance of biodiversity in Australian ecosystems, has been shown empirically (Letnic, Ritchie, & Dickman, ); and increased predation by cats on alternative prey has been documented as a consequence of rabbit control (Murphy, Keedwell, Brown, & Westbrooke, ; Norbury, ).…”

“…Ways in which the effects of rabbit removal could cascade through an Australian arid ecosystem. Based on previous studies (Holden & Mutze, ; Pedler et al., ; and Read & Bowen, ), we hypothesise possible flow‐on effects of rabbit removal on the abundances of other key species in the Australian arid ecosystem. We show potential ecosystem states corresponding to different phases of rabbit control: (i) precontrol; (ii) immediate postcontrol; (iii) postcontrol with sustained control; and (iv) postcontrol when control is not sustained.…”

“…Previous studies suggest that successful rabbit control could have wide reaching effects on native biodiversity in Australia (Pedler et al., ), in addition to economic benefits (Cooke, Jones, & Gong, ). However, to date, research has not considered the outcomes of rabbit management at the ecosystem level.…”

Impacts and management of feral cats Felis catus in Australia

“…Disease‐induced declines in rabbit abundance can cause declines in feral cat numbers and recovery of mammal populations (Pedler et al. ). However, there is a risk that once rabbit numbers fall below a critical threshold, feral cats will prey‐switch (Marlow & Croft ), so management of introduced prey populations needs to be carried out carefully.…”

Continental‐scale analysis of feral cat diet in Australia, prey‐switching and the risk: benefit of rabbit control

“…In the 20 years after RHD, two endangered rodents, plains mice ( Pseudomys australis ) and dusky hopping mice ( Notomys fuscus ) and a marsupial micro‐predator, crest‐tailed mulgara ( Dasycercus cristicauda ) increased their geographical range by 2.5‐ to 70‐fold (Pedler et al ., ). The authors attributed this to RHD and noted that species recoveries on this scale are rarely documented in any mammal.…”