School of Agriculture, Food and Ecosystem Sciences - Research Publications
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ItemForecasting species range dynamics with process-explicit models: matching methods to applications(WILEY, 2019-11)Knowing where species occur is fundamental to many ecological and environmental applications. Species distribution models (SDMs) are typically based on correlations between species occurrence data and environmental predictors, with ecological processes captured only implicitly. However, there is a growing interest in approaches that explicitly model processes such as physiology, dispersal, demography and biotic interactions. These models are believed to offer more robust predictions, particularly when extrapolating to novel conditions. Many process-explicit approaches are now available, but it is not clear how we can best draw on this expanded modelling toolbox to address ecological problems and inform management decisions. Here, we review a range of process-explicit models to determine their strengths and limitations, as well as their current use. Focusing on four common applications of SDMs - regulatory planning, extinction risk, climate refugia and invasive species - we then explore which models best meet management needs. We identify barriers to more widespread and effective use of process-explicit models and outline how these might be overcome. As well as technical and data challenges, there is a pressing need for more thorough evaluation of model predictions to guide investment in method development and ensure the promise of these new approaches is fully realised.
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ItemFoxNet: An individual-based model framework to support management of an invasive predator, the red fox(WILEY, 2019-06)Invasive predators are a key driver of biodiversity decline, and effective predator management is an important conservation issue globally. The red fox (Vulpes vulpes) poses a significant threat to wildlife, livestock and human health across Eurasia, North America and Australia. Despite worldwide investment in red fox management, decision makers still lack flexible tools for predicting control efficacy. We have developed FoxNet, a spatially explicit, individual‐based model (IBM) framework that can be customised to predict red fox population dynamics, including responses to control and landscape productivity. High‐resolution models can be run across northern and southern hemisphere landscapes. We present four case‐study models to verify FoxNet outputs, explore key sensitivities and demonstrate the framework's utility as a management planning tool. FoxNet models were largely successful in reproducing the demographic structure of two red fox populations in highly contrasting landscapes. They also accurately generated the relationship between home‐range size and fox‐family density for home‐range sizes between 1.0 and 9.6 km², and captured the rapid decline and seasonally driven recovery of a red fox population following poison‐baiting. An exploration of alternative poison‐baiting scenarios for a conservation reserve predicted that current management suppresses red fox density by ~70% and showed that frequent baiting is required to combat recolonisation. Baiting at higher densities or establishing a baited buffer would further reduce red fox density. Predictions were sensitive to home‐range and litter size assumptions, illustrating the value of region‐specific data on red fox movement and biology. Synthesis and applications. We have developed a versatile individual‐based model framework to guide management of the red fox, a globally significant invasive predator. Our framework, FoxNet, can be customised to generate realistic predictions of red fox population dynamics in diverse landscapes, making it immediately applicable to the design and optimisation of predator control programmes at scales relevant to management. Future extensions could explore competitor and prey responses to red fox control and the effects of habitat disturbance on predator population dynamics.
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ItemFactors influencing the residency of bettongs using one-way gates to exit a fenced reserve(Wiley, 2020-11)Understanding the conditions under which small native Australian mammals can persist in the presence of introduced predators remains a key challenge to conservation ecologists. Bettong‐specific one‐way gates were used at a predator‐free reserve in South Australia to allow the burrowing bettong (Bettongia lesueur) – a small potoroid, listed as ‘vulnerable’ nationally – to disperse out of the reserve. We conducted a field experiment to explore the conditions affecting residence time of bettongs that left the reserve. We monitored bettong and mammalian predator activity outside the fence using track surveys across 18 sites over two seasons. We examined the effect of supplementary feeding as a strategy for increasing residence time, as well as the influence of predator presence and habitat quality, using linear mixed models. Bettong activity was positively associated with supplementary feeding, midstorey vegetation cover and shelter availability. After gates were closed, bettong activity near gates declined to almost zero the following weeks, likely either due to death from predation or due to movement away from the sites. To a small extent, mammalian predators were more likely to be present at sites with high bettong activity. Further research on conditions to support persistence of burrowing bettongs and other small mammals, including understanding minimum necessary predator control effort, is required before successful establishment of populations outside of fences can occur.
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ItemPredators, fire or resources: What drives the distribution of herbivores in fragmented mesic forests?(WILEY, 2020-05)Trophic interactions and disturbance events can shape the structure and function of ecosystems. However, the effects of drivers such as predation, fire and climatic variables on species distributions are rarely considered concurrently. We used a replicated landscape‐scale predator management experiment to compare the effects of red fox Vulpes vulpes control, time‐since‐fire, vegetation type and other environmental variables on native herbivore distributions. Occurrence data for four native herbivores and an invasive predator – the red fox – were collected from 240 sites across three baited (for lethal fox control) and three unbaited forest blocks (4659–9750 ha) in south‐western Victoria, Australia, and used to build species distribution models. The herbivore taxa were as follows: red‐necked wallaby Macropus rufogriseus, black wallaby Wallabia bicolour, grey kangaroo Macropus fuligenosus and Macropus giganteus and common brushtail possum Trichosurus vulpecula. Fox control and fire had little effect on herbivore occurrence, despite the literature suggesting it can influence abundance, while climate, proximity to farmland and topography were more influential. This may be because the region’s high productivity and agricultural pastures subsidise food resources for both predators and prey within the forest blocks and so dampen trophic interactions. Alternatively, these drivers may affect herbivore abundance, but not herbivore occurrence. Understanding the drivers of herbivore distributions is an important step in predicting the effects of herbivory on other species, particularly after management interventions such as predator control and prescribed burns.