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Demographic population structure of European rabbits at Turretfield, South Australia, 1998–2013, shown as a frequency distribution of posterior modes of estimated longevity in days (d) or years (yr). Numbers at the right of each bar represent the average posterior range of individual birth date (BD) and longevity (L) estimates for each age class using credible intervals. Individuals with uncertainty in BD >100 days have been excluded from the plot (i.e., those mainly with age estimates of 7–8 years).
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The effectiveness of invasive species control can be influenced by seasonal fluctuations in reproduction in response to environmental conditions. However, it is difficult to determine how demography and environmental conditions affect the efficacy of different control efforts from field trials alone. We incorporated an ontogenetic growth model into...
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... with only 463 out of 3,736 estimates (12%) having credible intervals of 100 days uncertainty. Because of this uncertainty, longevity was deemed to be unrealistically high, 7-8 years for 31% of individuals. The overall demographic structure of the rabbit population was characterized by up to 60% of recorded individuals dying before 1 year of age (Fig. 2). Capture probabilities varied over seasons and time periods between 0.07 (CI ¼ 0.07-0.08) and 0.37 (CI ¼ 0.35-0.38), being highest in spring (Sep-Nov) and increasing towards the end of the study ...
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Duvaucel's Geckos (Hoplodactylus duvaucelii) are large-bodied, long-lived, and slow-breeding geckos endemic to New Zealand. Translocation is considered an important tool for conservation of this species. The first translocation of these geckos occurred in 1998 when 40 geckos were released on a pest-free island. Despite multiple survey efforts withi...
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... This greatly reduced labour and costs compared with fumigation alone or fumigation before ripping. The implementation of integrated rabbit management in late summerautumn (February-May), before winter rains begin, is also a well-established recommendation for rabbit control (Wells et al. 2016a). This is consistent with when rabbit numbers are naturally at their lowest in their annual cycle and food is short, making rabbits more vulnerable to taking poison baits or surviving if deprived of warrens or other cover. ...
Integrated pest management (IPM) is widely recommended for managing invasive pests to maximise effectiveness. However, the extent to which IPM occurs is typically unknown. We used the rabbit in Australia as a case study to investigate whether land managers apply IPM. Using 7415 control records voluntarily submitted to RabbitScan by land managers, we found evidence of IPM in only 39%. The extent to which integration occurred depended on the control method applied [warren ripping, poison baiting, release of rabbit haemorrhagic disease virus (RHDV), warren fumigation]. Two of four major rabbit control methods were frequently integrated with at least one other method; 73% of warren ripping and 55% of poison baiting records were associated with another different control method. In contrast, only 15% of RHDV releases and 35% of warren fumigations were integrated with another different control method. This confirmed reports that land managers view RHDV release as a ‘silver bullet’ and release it to avoid applying more expensive but more effective control methods. We identified control sequences that were neither biologically appropriate nor cost-efficient. In some situations, where there is a risk to other animals, or land managers lack suitable equipment, it may be difficult to apply IPM in an optimal sequence or at the optimal time. However, a greater level of control and at a proportionally lower cost could result if IPM principals were more rigorously applied, for instance, by focusing on strategic application of control methods in sequences known to be highly effective and cost-efficient.
... However, time-series data for exotic animal control (i.e., capture counts and capture effort) are useful for estimating population parameters (Fukasawa et al. 2013a,b, Wells et al. 2016, Scroggie et al. 2018, including the natural growth rate, density effect on population growth, and capture efficiency. It should be noted that field-based monitoring data are often limited by irregular spatial and temporal arrangements of traps and missing data, among other factors. ...
Optimization of spatial resource allocation is crucial for the successful control of invasive species under a limited budget but requires labor‐intensive surveys to estimate population parameters. In this study, we devised a novel framework for the spatially explicit optimization of capture effort allocation using state‐space population models from past capture records. We applied it to a control program for invasive snapping turtles to determine effort allocation strategies that minimize the population density over the whole area. We found that spatially heterogeneous density dependence and capture pressure limit the abundance of snapping turtles. Optimal effort allocation effectively improved the control effect, but the degree of improvement varied substantially depending on the total effort. The degree of improvement by the spatial optimization of allocation effort was only 3.21% when the total effort was maintained at the 2016 level. However, when the total effort was increased by two, four, and eight times, spatial optimization resulted in improvements of 4.65%, 8.33%, and 20.35%, respectively. To achieve the management goal for snapping turtles in our study area, increasing the current total effort by more than four times was necessary, in addition to optimizing the spatial effort. The snapping turtle population is expected to reach the target density one year after the optimal management strategy is implemented, and this rapid response can be explained by high population growth rate coupled with density‐dependent feedback regulation. Our results demonstrated that combining a state‐space model with optimization makes it possible to adaptively improve the management of invasive species and decision‐making. The method used in this study, based on removal records from an invasive management program, can be easily applied to monitoring data for wildlife and pest control management using traps in a variety of ecosystems.
... This is because ecological mechanisms of range limits and shifts can be better understood using abundance data ) and spatiotemporal estimates of abundance and subsequent variability are frequently used to maximize the efficacy of on-the-ground management efforts to control invasive species (Simberloff 2003). For example, efforts for managing rabbits in their invasive range are often reduced when population size is perceived to be relatively low, allowing resources to be prioritized elsewhere (Wells et al. 2016a). Moreover, time series abundance estimates are important for the development of spatially explicit and dynamic population models for invasive species management (Mellin et al. 2016), enabling management intervention strategies to be directly tested (Fordham et al. 2013a). ...
... Using this information in predictive models to generate high spatiotemporal resolution maps of rabbit abundance will enable more targeted rabbit management at local-to-regional scales, enabling the control of invasive rabbits to potentially be better optimized . This is because invasive species management decisions are typically based on populations in specific habitats and locales, involving time horizons of seasons to decades (Rout and Walshe 2013, Wells et al. 2016a). ...
... Spatial and temporally explicit estimations of abundance are an important component in ecological modeling, because a change in population abundance over time and space is brought about by changes in movement and/or birth and death rates. Identifying and quantifying the temporal variability in populations of invasive species can help to better target management actions (Simberloff 2003), particularly when responses to removal of invasive species happen on varying time scales (Strayer et al. 2006, Cooke 2012, Lurgi et al. 2018, and different control measures will have differing population-level effects (Wells et al. 2016a). Just as importantly, quantifying variability in population abundances across the range of a species can unlock the ecological mechanisms responsible for spatiotemporal variation in abundance across a species geographic distribution (Caughley et al. 1988). ...
The European rabbit (Oryctolagus cuniculus) is a notorious economic and environmental pest species in its invasive range. To better understand the population and range dynamics of this species, 41 yr of abundance data have been collected from 116 unique sites across a broad range of climatic and environmental conditions in Australia. We analyzed this time series of abundance data to determine whether interannual variation in climatic conditions can be used to map historic, contemporary, and potential future fluctuations in rabbit abundance from regional to continental scales. We constructed a hierarchical Bayesian regression model of relative abundance that corrected for observation error and seasonal biases. The corrected abundances were regressed against environmental and disease variables in order to project high spatiotemporal resolution, continent‐wide rabbit abundances. We show that rabbit abundance in Australia is highly variable in space and time, being driven primarily by internnual variation in temperature and precipitation in concert with the prevalence of a non‐pathogenic virus. Moreover, we show that internnual variation in local spatial abundances can be mapped effectively at a continental scale using highly resolved spatiotemporal predictors, allowing “hot spots” of persistently high rabbit abundance to be identified. Importantly, cross‐validated model performance was fair to excellent within and across distinct climate zones. Long‐term monitoring data for invasive species can be used to map fine‐scale spatiotemporal fluctuations in abundance patterns when accurately accounting for inherent sampling biases. Our analysis provides ecologists and pest managers with a clearer understanding of the determinants of rabbit abundance in Australia, offering an important new approach for predicting spatial abundance patterns of invasive species at the near‐term temporal scales that are directly relevant to resource management.
... Although the rabbit has been well-studied over the last 50 years in Australia, the database will help to develop process-based models to inform current pest management strategies, by providing vital information on variation in vital life history traits (e.g. Wells et al. 2016a). The database includes ecological information on rabbit distribution in time and space, including long-term time series abundance data, which inform fine-to-broad-scale predictions about the population dynamics of the rabbit (e.g. ...
... We recommend users to employ statistical approaches that allow for sampling and temporal biases in abundance count data to be identified and explicitly accounted for in their analyses of the database (e.g. Joseph et al. 2009, Wells et al. 2016a. ...
With ongoing introductions into Australia since the 1700s, the European rabbit (Oryctolagus cuniculus) has become one of the most widely distributed and abundant vertebrate pests, adversely impacting Australia's biodiversity and agroeconomy. To understand the population and range dynamics of the species and its impacts better, occurrence and abundance data have been collected by researchers and citizens from sites covering a broad spectrum of climatic and environmental conditions in Australia. The lack of a common and accessible repository for these data has, however, limited their use in determining important spatiotemporal drivers of the structure and dynamics of the geographical range of rabbits in Australia. To meet this need, we created the Australian National Rabbit Database, which combines more than 50 yr of historical and contemporary survey data collected from throughout the range of the species in Australia. The survey data, obtained from a suite of complementary monitoring methods, were combined with high‐resolution weather, climate, and environmental information, and an assessment of data quality. The database provides records of rabbit occurrence (689,265 records) and abundance (51,241 records, >120 distinct sites) suitable for identifying the spatiotemporal drivers of the rabbit's distribution and for determining spatial patterns of variation in its key life‐history traits, including maximum rates of population growth. Because all data are georeferenced and date stamped, they can be coupled with information from other databases and spatial layers to explore the potential effects of rabbit occurrence and abundance on Australia's native wildlife and agricultural production. The Australian National Rabbit Database is an important tool for understanding and managing the European rabbit in its invasive range and its effects on native biodiversity and agricultural production. It also provides a valuable resource for addressing questions related to the biology, success, and impacts of invasive species more generally. No copyright or proprietary restrictions are associated with the use of this data set other than citation of this Data Paper.
... This is because ecological mechanisms of range limits and shifts can be better understood using abundance data ) and spatiotemporal estimates of abundance and subsequent variability are frequently used to maximize the efficacy of on-the-ground management efforts to control invasive species (Simberloff 2003). For example, efforts for managing rabbits in their invasive range are often reduced when population size is perceived to be relatively low, allowing resources to be prioritized elsewhere (Wells et al. 2016a). Moreover, time series abundance estimates are important for the development of spatially explicit and dynamic population models for invasive species management (Mellin et al. 2016), enabling management intervention strategies to be directly tested (Fordham et al. 2013a). ...
... Using this information in predictive models to generate high spatiotemporal resolution maps of rabbit abundance will enable more targeted rabbit management at local-to-regional scales, enabling the control of invasive rabbits to potentially be better optimized . This is because invasive species management decisions are typically based on populations in specific habitats and locales, involving time horizons of seasons to decades (Rout and Walshe 2013, Wells et al. 2016a). ...
... Spatial and temporally explicit estimations of abundance are an important component in ecological modeling, because a change in population abundance over time and space is brought about by changes in movement and/or birth and death rates. Identifying and quantifying the temporal variability in populations of invasive species can help to better target management actions (Simberloff 2003), particularly when responses to removal of invasive species happen on varying time scales (Strayer et al. 2006, Cooke 2012, Lurgi et al. 2018, and different control measures will have differing population-level effects (Wells et al. 2016a). Just as importantly, quantifying variability in population abundances across the range of a species can unlock the ecological mechanisms responsible for spatiotemporal variation in abundance across a species geographic distribution (Caughley et al. 1988). ...
Aim: The European rabbit (Oryctolagus cuniculus) is a notorious economic and environmental pest species in its invasive range. To better understand the population and range dynamics of this species, long-term abundance data has been collected across a broad range of climatic and environmental condition in Australia. We analysed this time series data to determine whether inter-annual variation in climatic conditions can be used to map historic, contemporary, and potential future fluctuations in rabbit abundance from regional to continental scales. Location: AustraliaMethod: We compiled spotlight monitoring data at 116 unique sites, collected over 41 years from locations in different climate and vegetation zones. We constructed a hierarchical Bayesian regression model of relative abundance that corrected for observation error and seasonal biases. The corrected abundances were regressed against environmental and disease variables in order to project high spatiotemporal resolution, continent-wide rabbit abundances. Results: We show that rabbit abundance in Australia is highly variable in space and time, being driven primarily by inter-annual variation in temperature and precipitation in concert with the prevalence of a non-pathogenic virus. Moreover, we show that inter-annual variation in local spatial abundances can be mapped effectively at a continental scale using highly resolved spatiotemporal predictors, allowing “hotspots” of persistently high rabbit abundance to be identified. Importantly, cross-validated model performance was fair to excellent within and across distinct climate zones.Primary conclusion: Long-term monitoring data for invasive species can be used to map fine-scale spatiotemporal fluctuations in abundance patterns when accurately accounting for inherent sampling biases. Our analysis provides ecologists and pest managers with a clearer understanding of the determinants of rabbit abundance in Australia, offering an important new tool for predicting spatial abundance patterns of invasive species at the near-term temporal scales that are directly relevant to resource management.
... Using the survivorship rates from Hern andez-Pacheco et al. (2013), we modeled future population size under 4 management scenarios: culling 50% of subadults and adults, culling 80% of subadults and adults, sterilizing 50% of sexually mature females (3 yrs old), and sterilizing 80% of sexually mature females (3 yrs old). Because the efficacy of management strategies can be influenced by the timing and frequency of implementation (Abrams 2009, Wells et al. 2016, we modeled the 4 management scenarios implemented at 4 timescales: annually, biennially, every 5 years, and every 10 years (code provided in Appendix A). We estimated the number of individuals in the population at each time based on the predicted number of females (from the models) and the predicted female:male ratio. ...
Approximately 12 rhesus macaques (Macaca mulatta) were introduced to the forests along the Silver River, central Florida, USA, between 2 introductions in the 1930s and 1940s to increase tourism; this land is now Silver Springs State Park (SSSP). By the mid-1980s the population along the Silver River reached nearly 400 individuals. Approximately 1,000 animals were trapped and removed from 1984 to 2012 to reduce population growth and mitigate negative macaque-human interactions. This practice was halted due to extensive public controversy, and consequently no population management has been implemented since 2012. To aid in informing management decisions related to rhesus macaques, we estimated the fall 2015 population size within SSSP, developed an age-structured matrix model to estimate the population growth rate, and examined the efficacy of 4 management strategies to regulate this population, including culling (50% or 80% of subadults and adults) and sterilizing adult females (50% or 80% 3 years old). Our assessment suggested there were 176 macaques among 5 social groups within SSSP in fall 2015. We estimated this population was growing and will likely double in size by 2022 without management intervention. Management actions designed to eradicate the macaque population would be most effective by removing 50% of subadults and adults at least biennially. The population could be reduced to about a third of the fall 2015 size by sterilizing 50% of adult females annually or 80% biennially. The rhesus macaque population extends outside of our study site, and thus our results are a proxy for management implications in the region. Managers tasked with rhesus macaque management must carefully weigh the trade-offs of these options in future management of this charismatic, invasive species.
... Using the survivorship rates from Hern andez-Pacheco et al. (2013), we modeled future population size under 4 management scenarios: culling 50% of subadults and adults, culling 80% of subadults and adults, sterilizing 50% of sexually mature females (3 yrs old), and sterilizing 80% of sexually mature females (3 yrs old). Because the efficacy of management strategies can be influenced by the timing and frequency of implementation (Abrams 2009, Wells et al. 2016, we modeled the 4 management scenarios implemented at 4 timescales: annually, biennially, every 5 years, and every 10 years (code provided in Appendix A). We estimated the number of individuals in the population at each time based on the predicted number of females (from the models) and the predicted female:male ratio. ...
... We used a scaling factor to account for unequal time intervals between capture sessions (average length of time intervals = 74 days, 1 SD = 27 days). We used individual measures of body mass b(i,t) for estimating individual age and birth dates using the West-Brown-Enquist ontogenetic model, and we projected all data on a continuous time scale (the first day of the study set to one) to express individual age and ontogenetic growth as Euclidean temporal distances (Wells, Cassey et al., 2016). ...
1. European rabbits (Oryctolagus cuniculus) have been exposed to rabbit haemorrhagic
disease virus (RHDV) and myxoma virus (MYXV) in their native and invasive
ranges for decades. Yet, the long-term effects of these viruses on rabbit population
dynamics remain poorly understood.
2. In this context, we analysed 17 years of detailed capture–mark–recapture data
(2000–2016) from Turretfield, South Australia, using a probabilistic state-space
hierarchical modelling framework to estimate rabbit survival and epidemiological dynamics.
3. While RHDV infection and disease-induced death were most prominent during
annual epidemics in winter and spring, we found evidence for continuous infection
of susceptible individuals with RHDV throughout the year. RHDV-susceptible
rabbits had, on average, 25% lower monthly survival rates compared to immune
individuals, while the average monthly force of infection in winter and spring was ~38%. These combined to result in an average infection-induced mortality rate of 69% in winter and spring.
4. Individuals susceptible to MYXV and immune to RHDV had similar survival
probabilities to those having survived infections from both viruses, whereas individuals susceptible to both RHDV and MYXV had higher survival probabilities
than those susceptible to RHDV and immune to MYXV. This suggests that MYXV may reduce the future survival rates of individuals that endure initial MYXV infection.
5. There was no evidence for long-term changes in disease-induced mortality and infection rates for either RHDV or MYXV.
6. We conclude that continuous, year-round virus perpetuation (and perhaps heterogeneity in modes of transmission and infectious doses during and after epidemics) acts to reduce the efficiency of RHDV and MYXV as biocontrol agents of rabbits
... Rabbits in arid Australia are managed using a "press and pulse" type framework (Bender, Case, & Gilpin, 1984), where rabbits are controlled using viral biocontrol agents (press) and episodes of warren ripping and baiting (pulse; Wells et al., 2016). 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., 2012); the primary biocontrol agents used to manage rabbits in arid Australia. ...
Abundant and widely distributed invasive prey can negatively affect co‐occurring native species by competing for food and/or shelter, removing vegetation cover and reducing habitat complexity (changing predation risk), and by sustaining elevated abundances of invasive mesopredators. However, information regarding the community and trophic consequences of controlling invasive prey and their temporal dynamics remain poorly understood.
We used multispecies ecological network models to simulate the consequences of changing European rabbit Oryctolagus cuniculus abundance in an arid mammalian community. We quantified how changes in the dominant prey (rabbits) affected multiple trophic levels, examining changes in predator–prey interactions through time and how they affected native prey persistence.
Our results suggest that removal of rabbits can benefit native biodiversity immediately at removal rates between 30% and 40%. However, beyond these levels, densities of small native mammals will decline in the short term. The processes underpinning these declines are: (a) increased competition for resources (vegetation) with kangaroos Macropus spp., whose numbers increase due to their release from competition with rabbits and (b) increased predation (prey switching) by feral cats Felis catus . Both effects are mediated by dingoes Canis dingo , a native apex predator.
Importantly, native mammal abundance recovers after a time delay, which is prolonged when high rates of rabbit control are applied. This is likely due to a reduction in hyperpredation by invasive feral cats and red foxes Vulpes vulpes following rabbit removal.
Continued eradication of rabbits in arid Australia will benefit native species due to a decrease in apparent competition for resources and by alleviating hyperpredation from invasive mesopredators. Furthermore, ecosystem‐level conservation benefits of reducing invasive prey abundance are as important as direct control of invasive mesopredators.
Synthesis and applications . Multispecies ecological network models provide wildlife managers with tools to better understand and predict the complex effects of species removal and control on both intact and modified ecosystems. Our results show that management of the Australian arid zone can benefit from controlling invasive prey as well as invasive predators. However, invasive species control can cause unexpected outcomes on native biodiversity. This extends to other systems where dominant prey may play fundamental roles in ecosystem structure and function.
... In relation to rabbit biocontrol, effectiveness is patchy both spatially and temporally (e.g. Richardson et al., 2007;Liu et al., 2014;Wells et al., 2016) and many individuals, and subsequently populations, exhibit varying degrees of resistance to virus strains (e.g. Robinson et al. 2002;Mutze et al., 2010a) which has enabled rabbit numbers to increase over time (Cox et al., 2013). ...
Invasive animals have been linked to the extinctions of native wildlife, and to significant agricultural financial losses or impacts. Current approaches to control invasive species require ongoing resources and management over large geographic scales, and often result in the short-term suppression of populations. New and innovative approaches are warranted. Recently, the RNA guided gene drive system based on CRISPR/Cas9 is being proposed as a potential gene editing tool that could be used by wildlife managers as a non-lethal addition or alternative to help reduce pest animal populations. While regulatory control and social acceptance are crucial issues that must be addressed, there is an opportunity now to identify the knowledge and research gaps that exist for some important invasive species. Here we systematically determine the knowledge gaps for pest species for which gene drives could potentially be applied. We apply a conceptual ecological risk framework within the gene drive context within an Australian environment to identify key requirements for undertaking work on seven exemplar invasive species in Australia. This framework allows an evaluation of the potential research on an invasive species of interest and within a gene drive and risk context. We consider the currently available biological, genetic and ecological information for the house mouse, European red fox, feral cat, European rabbit, cane toad, black rat and European starling to evaluate knowledge gaps and identify candidate species for future research. We discuss these findings in the context of future thematic areas of research worth pursuing in preparation for a more formal assessment of the use of gene drives as a novel strategy for the control of these and other invasive species.
