European rabbit survival and recruitment are linked to epidemiological and environmental conditions in their exotic range

Abstract

The European rabbit, Oryctolagus cuniculus, is threatened within its native range, yet it is a highly successful colonizing pest species across its worldwide introduced range, causing large economic losses and widespread environmental degradation. To date, there has been no long-term empirical evidence documenting the relative roles of climatic, epidemiological and biological factors in limiting life-history determinants of rabbit range and abundance. Using 12 years of capture-mark-recapture data from their exotic range in Australia, we constructed candidate Cormack-Jolly-Seber models to test the influence of environmental, competition and disease conditions on rabbit survival and recruitment. Our results show that: (i) population-level disease infection rate has the largest overall impact on rabbit survival, explaining 80% of variance in survival rates; (ii) environmental as well as epidemiological conditions constrain rabbit survival, especially for younger animals; (iii) temporal variation in rabbit kitten recruitment patterns are best described by a combination of climate, competition and disease settings (accounting for 68% of variance), while temperature alone has a strong negative influence on kitten recruitment; and (iv) recruitment responds positively to rabbit haemorrhagic disease, but negatively to myxomatosis -the former, probably being mediated through a disease driven effect on intraspecific competition for food. A strengthened understanding of climate change impacts on rabbit range and abundance can be achieved by accounting explicitly for potential synergisms between disease dynamics and climate. In this analysis, we provide the first step towards such an attempt for this important mammal species. Integrated approaches of this kind are essential for future forecasts of rabbit range and abundance, offsetting the conservation threat faced by O. cuniculus in its native range, and achieving effective management in exotic habitats.

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

“…Rabbits in arid Australia are managed using a “press and pulse” type framework (Bender, Case, & Gilpin, ), where rabbits are controlled using viral biocontrol agents ( press ) and episodes of warren ripping and baiting ( pulse ; Wells et al., ). Our finding that a sustained rate of rabbit removal of 40% provides the greatest benefit to small mammals has strong implications for the on‐ground management of rabbits in their invasive range because this press mortality rate corresponds closely to disease‐induced mortality rates following the long‐term establishment of rabbit haemorrhagic disease and myxomatosis in disease‐burdened rabbit populations (Fordham et al., ); the primary biocontrol agents used to manage rabbits in arid Australia. Therefore, if the goal of rabbit management in arid Australia is to provide benefits to small mammal populations (e.g., by facilitating increased population abundances), then it seems clear that the present management strategy, involving a sustained press at intermediate levels of mortality and/or time‐limited removals of higher fractions of the rabbit populations, is appropriate.…”

“…These studies have shown the importance of considering ecological interactions when identifying “whole ecosystem” type responses to species management. For example, Pech and Hood () disentangled the likely effects of a downward pressure on rabbit abundance (caused by rabbit hemorrhagic disease, an important biocontrol for European rabbits in their invasive range; Fordham et al., ) on a mesopredator and a generic small native mammal. Choquenot and Forsyth () used a similar approach to establish the likely effects of controlling dingoes on kangaroo populations, showing the potential for cascading effects of controlling an apex predator.…”

Timing and severity of immunizing diseases in rabbits is controlled by seasonal matching of host and pathogen dynamics

“…With high recovery rates, in turn, we may expect reproductive effort and disease dynamics to have equally important effects on rabbit extinction. This is because in rabbits, density-dependent population regulation is expected to disproportionately affect juvenile survival [33], and seasonally coinciding density-dependent and disease-induced mortality may counterbalance each other.…”

“…We examined seasonal patterns in population counts from Turretfield, using capture-mark-recapture data [33]. We used data imputation to generate a continuous time series (weekly steps) of the minimum number of individuals known to be alive (MNA, based on all capture and carcass-recovery records) in different weeks between 1998 and 2013.…”

“…Rabbits and their diseases have been intensively studied at a long-term field site in South Australia; Turretfield (34833 0 S, 138850 0 E) [33,34] where they have been live-trapped for at least 4-5 consecutive days at 8-12 week intervals since 1996. All live captured animals were marked and surveyed serologically for RHDV and MYXV antibodies [32].…”