Predicting the ecosystem-wide impacts of eradication with limited information using a qualitative modelling approach.

Han, Yi; Kristensen, Nadiah P.; Buckley, Yvonne M.; Maple, Dion; West, Jeffrey A.; McDonald‐Madden, Eve

doi:10.1016/j.ecolmodel.2020.109122

Cited by 4 publications

(9 citation statements)

References 29 publications

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“…Predicting the consequences of management interventions in ecosystems that face multiple threats is difficult because they exhibit complex dynamics and knowledge to parameterize these models is often scarce (Geary et al, 2020). Instead of predicting the population state of a threatened species after a management action (as in, e.g., Baker et al [2017], Bode et al [2015], Dambacher et al [2003], and Han et al [2020]), our approach identified the levels of threat that could lead to undesired population trajectories in a threatened species and could thereby trigger a management decision. For example, on Christmas Island, our methods would allow managers to determine whether the current abundance of predators threatens the redtailed tropicbird population; whether managing cats alone is sufficient to protect the birds; and whether and how much additional rat control is necessary.…”

Section: Discussionmentioning

confidence: 99%

“…Although our approach is most easily applied to small ecosystems with 1 threatened component and 2 threats, in reality many more ecosystem components can influence such a small system. For example, the network of species interacting on Christmas Island include a number of other species (Han et al, 2020).…”

Section: Discussionmentioning

confidence: 99%

“…Because cats also eat rats, the 2 threats can interact antagonistically (i.e., the predation by rats may be lower in the presence of cats [Hughes et al., 2019 ; Rayner et al., 2007 ]). Controlling cats therefore has the potential to cause perverse consequences for native species if the reduction of cats leads to a mesopredator release of rats (Baker et al., 2018 ; Beeton et al., 2010 ; Han et al., 2020 ).…”

Section: Methodsmentioning

confidence: 99%

“…On the island, feral cats ( Felis catus ) and invasive black rats ( Rattus rattus ) prey on the threatened red‐tailed tropicbird ( Phaethon rubricauda ) among other species (Beeton et al., 2010 ) (Figure 1 ). Cat removal is already underway, but there is concern that a decrease in the cat population could release predation pressure on rats, potentially leading to increased rat predation on red‐tailed tropicbirds ( Phaethon rubricauda ) (Baker et al., 2020 ; Han et al., 2020 ). Simultaneous rat control has therefore been recommended (Han et al., 2020 ).…”

Section: Introductionmentioning

confidence: 99%

“…Cat removal is already underway, but there is concern that a decrease in the cat population could release predation pressure on rats, potentially leading to increased rat predation on red‐tailed tropicbirds ( Phaethon rubricauda ) (Baker et al., 2020 ; Han et al., 2020 ). Simultaneous rat control has therefore been recommended (Han et al., 2020 ). However, given the uncertainty associated with mesopredator release and the costs and difficulties of rat eradication on tropical islands (Holmes et al., 2015 ), complete rat control is unrealistic in this case.…”

Section: Introductionmentioning

confidence: 99%

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Modeling total predation to avoid perverse outcomes from cat control in a data‐poor island ecosystem

Plein

O’Brien

Holden

et al. 2022

Conservation Biology

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Data‐hungry, complex ecosystem models are often used to predict the consequences of threatened species management, including perverse outcomes. Unfortunately, this approach is impractical in the many systems that have insufficient data to parameterize ecosystem interactions or reliably calibrate or validate such models. We devised a different approach composed of a minimum realistic model that guides decisions in data‐ and resource‐scarce systems. We applied our approach to a case study in an invaded ecosystem from Christmas Island, Australia, where there are concerns that cat (Felis catus) eradication to protect native species, including the red‐tailed tropicbird (Phaethon rubricauda), could release mesopredation by invasive rats (Rattus rattus). We used biophysical constraints (metabolic demand) and observable parameters (e.g., prey preferences) to identify the combined cat and rat abundances that could threaten the tropicbird population. The population of tropicbirds was not sustained when predated by 1607 rats (95% credible interval [CI]: 103–5910) in the absence of cats and 21 cats (95% CI: 2–82) in the absence of rats. For every cat removed from the island, the bird's net population growth rate improved, provided rats did not increase by more than 77 individuals (95% CI: 30–174). Thus, in this context, 1 cat is equivalent to 30–174 rats. Our methods are especially useful for on‐the‐ground predator control in the absence of knowledge of predator–predator interactions to determine whether current abundance of predators threatened the prey population of interest; managing only 1 predator species was sufficient to protect the prey species given potential release of another predator; and control of multiple predator species was needed to meet the conservation goal. With our approach limited information can be used for maximum value in data‐poor systems because it shifts the focus from predicting future trajectories to identifying conditions that impede conservation.

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