Removing Protected Populations to Save Endangered Species

Courchamp, Franck; Woodroffe, Rosie; Roemer, Gary W.

doi:10.1126/science.1089492

Cited by 96 publications

(106 citation statements)

References 6 publications

(5 reference statements)

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“…For example, recovery of endangered island foxes (Urocyon littoralis) may require the lethal removal of protected golden eagles (Aquila chrysaetos; Courchamp et al 2003). In our system, successful removal of G. nobilis is impractical; however, if left undisturbed it is likely that Gambusia will continue to be favoured at the expense of C. bovinus.…”

Section: Discussionmentioning

confidence: 99%

Conservation and conflict between endangered desert fishes

2008

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Conservation of naturally sympatric endangered species requires unique considerations. While impacts of invasive species garner much attention, interactions between endangered species must also be managed. The endangered Leon Springs pupfish, Cyprinodon bovinus, has suffered a population decline due to decreasing natural habitat. As breeding habitat is lost, C. bovinus is also adversely affected by the sympatric, endangered Pecos gambusia, Gambusia nobilis. Here, we document interactions between these species, finding significantly more G. nobilis accumulated at pupfish spawning events than randomly distributed on breeding grounds in the absence of spawning. As a known egg predator, our results suggest that G. nobilis presence at spawnings may further decrease pupfish numbers while also altering the evolutionary dynamics of C. bovinus breeding tactics. Habitat restoration may decrease Gambusia concentrations or influence C. bovinus breeding behaviour and increase the number of territorial males resulting in viable population sizes for both critically endangered fishes.

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Section: Discussionmentioning

confidence: 99%

Conservation and conflict between endangered desert fishes

2008

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“…Encouragingly, such data are increasingly being used in the development of complex solutions for conservation management (14,26,27). We suggest that the management of such programs can be aided by research investigating the role of habitat and climatic gradients on the biology of the perturbed systems in question.…”

Section: Resultsmentioning

confidence: 99%

Spatial heterogeneity of mesopredator release within an oceanic island system

Rayner

Hauber

Imber³

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

230

178

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Predator-prey communities are ubiquitous in ecology, but introduced predators can drive native species to extinction within island systems, prompting the eradication of such exotics. Ecological theory predicts that elimination of top-introduced predators from islands can lead to the counterintuitive decline of native prey populations through the ecological release of smaller introduced species in a process termed ''mesopredator release.'' We show, in accordance with mesopredator release theory and counter to conservation goals for a New Zealand island reserve, that initial eradication of cats on Little Barrier Island led to reduced breeding success of Cook's petrels, which also are vulnerable to predation by a mesopredator, the Pacific rat. The rat's impact on prey productivity varied with elevation within the island. Rat eradication was followed by a rise in petrel productivity, in support of both ecological theory and practical conservation management goals. It appears that interactions among introduced predators, native prey, and environmental gradients can drive counterintuitive and spatially heterogeneous responses to predator eradications from islands. Location-specific, ecosystem-level understanding is essential for predicting the outcomes of such restoration management techniques.habitat gradients ͉ introduced predator eradications ͉ island restoration ͉ trophic cascade ͉ Cook's petrel

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“…It is unknown how fox populations would be affected if the size of the colonizing population varied or if the starting fox populations were small. Similarly, as noted above, we do no yet know how the removal of feral pigs from the island might change predation behavior (Courchamp et al 2003, Dratch et al 2004 or if the foxes have decreased susceptibility to eagles through evolved or learned antipredator responses such as increased nocturnality (Roemer et al 2002). Disease outbreaks have afflicted island fox populations in the past (Timm et al 2000, Clifford et al 2006) and pose a serious threat for the future, but the frequency of recorded epizootics has been so low that any inclusion of them in our models would require undue guesswork.…”

Section: Years Years Yearsmentioning

confidence: 96%

“…While we modeled numbers of eagles present on the northern islands, we have taken pains to refer to these as eagle equivalents or EEs to emphasize that we are simulating the estimated per capita impacts of eagles during the 1990s. We use EEs rather than eagle numbers, despite the intuitive appeal of the latter, because predator-prey dynamics have almost certainly changed with alterations of this ecological community, including the potential for increased per capita eagle predation rates with the decrease in the ungulate prey base across the northern islands (Courchamp et al 2003) or for decreased predation efficacy with the acquisition of anti-predator behaviors by foxes (Roemer et al 2002). Use of EEs also helps to emphasize the reliance of our model outputs on the past space use patterns of eagles.…”

Section: Implications For Island Fox Recoverymentioning

confidence: 99%

Incorporating ecological drivers and uncertainty into a demographic population viability analysis for the island fox

Bakker

Doak

Roemer

et al. 2009

Ecological Monographs

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Abstract. Biometricians have made great strides in the generation of reliable estimates of demographic rates and their uncertainties from imperfect field data, but these estimates are rarely used to produce detailed predictions of the dynamics or future viability of at-risk populations. Conversely, population viability analysis (PVA) modelers have increased the sophistication and complexity of their approaches, but most do not adequately address parameter and model uncertainties in viability assessments or include important ecological drivers. Merging the advances in these two fields could enable more defensible predictions of extinction risk and better evaluations of management options, but only if clear and interpretable PVA results can be distilled from these complex analyses and outputs. Here, we provide guidance on how to successfully conduct such a combined analysis, using the example of the endangered island fox (Urocyon littoralis), endemic to the Channel Islands of California, USA. This more rigorous demographic PVA was built by forming a close marriage between the statistical models used to estimate parameters from raw data and the details of the subsequent PVA simulation models. In particular, the use of mark-recapture analyses and other likelihood and information-theoretic methods allowed us to carefully incorporate parameter and model uncertainty, the effects of ecological drivers, density dependence, and other complexities into our PVA. Island fox populations show effects of density dependence, predation, and El Nin˜o events, as well as substantial unexplained temporal variation in survival rates. Accounting not only for these sources of variability, but also for uncertainty in the models and parameters used to estimate their strengths, proved important in assessing fox viability with different starting population sizes and predation levels. While incorporating ecological drivers into PVA assessments can help to predict realistic dynamics, we also show that unexplained process variance has important effects even in our extremely well-studied system, and therefore must not be ignored in PVAs. Overall, the treatment of causal factors and uncertainties in parameter values and model structures need not result in unwieldy models or highly complex predictions, and we emphasize that future PVAs can and should include these effects when suitable data are available to support their analysis.

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Removing Protected Populations to Save Endangered Species

Cited by 96 publications

References 6 publications

Conservation and conflict between endangered desert fishes

Conservation and conflict between endangered desert fishes

Spatial heterogeneity of mesopredator release within an oceanic island system

Incorporating ecological drivers and uncertainty into a demographic population viability analysis for the island fox

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