Over three days we have posted a collection of blog posts on a topical Forum discussion published in Issue 2 about the methods used in wildlife conservation and in particular the role of dingoes in conservation. Following acceptance of a peer-reviewed Forum critique of another article in the Journal it is the Journal’s process to invite the original authors to write a peer-reviewed response to the critique. Both opinions are then presented side by side in an issue to enable readers to form their own opinions.
In this post Associate Editor, Jacqueline Frair and her postdoc Paul Schuette discuss a Practitioner’s Perspective from Matt Hayward and Nicky Marlow ‘Will dingoes really conserve wildlife and can our methods tell?, and Forum articles from Dale Nimmo and colleagues ‘Dingoes can help conserve wildlife and our methods can tell’ and Matt Hayward and colleagues ‘Ecologists need robust survey designs, sampling and analytical methods’.
Here you can read a post from Dale Nimmo and a post from Matt Hayward. (Please note that although the articles comment on each other the blog posts were received separately and are not intended as comments on the previous post.)
Apex predators are in global decline and humans have played a large part in their imperiled state. Although this statement is generally supported in the ecological literature, uncertainty arises when ecologists and managers attempt to document the magnitude and causal mechanisms of decline and their potential cascading effects on animal and plant species in a complex food web. These uncertainties make it difficult for managers and conservation policy-makers to determine the appropriate course of action.
Conducting research on apex predators is inherently challenging because they are cryptic, nocturnal, and crepuscular and move across vast areas. Because of these limitations, few agencies have the financial capacity to carry out intensive monitoring programs to gather data on population demographics and fine-scale behavioral data to examine species interactions. Without this information, ecologists and managers have a limited ability to describe the ecological, environmental, and anthropogenic factors limiting an apex predator population, let alone the factors affecting co-occurring predator and prey species and other taxa that may be directly or indirectly affected by an apex predator.
Ecologists and managers often rely on animal counts and sign surveys (e.g. tracks, scat) to monitor wildlife population size and distribution for this is the most readily accessible type of data for wide-ranging predators. However, a fundamental problem with these data is that a change in the index may represent a change in the detectability of animals or their sign rather than a change in actual animal numbers. Over the past few decades, collaborations with statisticians have improved upon animal count and sign survey strategies by accounting for imperfect detectability. These collaborations have led to the development and widespread use of robust mathematical models such as distance sampling, mark-recapture, and occupancy modeling. These techniques are able to provide unbiased estimates of species abundance and distribution, or at least detectability-corrected indices of their abundance, to help inform conservation and management decisions at the population, community, and ecosystem level. Use of these robust methods have been on the rise over the past two decades as indicated by the increasing number of peer-reviewed journal articles that include ‘detection probability’ in their title. However, the majority of ecological articles do not account for imperfect detectability (Kellner & Swihart 2014), which indicates these methods are not yet the standard mode of operation for ecologists and managers around the globe.
Recent articles by Hayward & Marlow (2014), Nimmo et al. (2014), and Hayward et al. (2015) highlight the contrasting views on how to efficiently and effectively gather data to inform management decisions in an era of global apex predator declines. Their discussion focuses on the decline of dingoes Canis lupus dingo (apex predator), the rise of non-native red foxes Vulpes vulpes and feral cats Felis catus (mesocarnivores), the potential cascading effects of these changes on small mammal communities, and the challenges of making sound management decisions with available data. Although focused on a unique situation and set of species in Australia, this theme is evident in ecosystems around the world, in places where tigers Panthera tigris, lions Panthera leo, wolves Canis lupus, and other apex predators are far fewer and less widespread than in the past. In each situation, ecologists and managers urgently seek the best available information to guide management policies to secure viable populations of threatened apex predators and ensuring adequate measures are in place to protect biological diversity.
Hayward & Marlow (2014) and Hayward et al. (2015) state that ecologists and managers should use robust methods that account for detection probability (distance sampling, occupancy modeling, mark-recapture), replicated across space and time, to document species trends. They also advocate the use of experimental manipulations to test the role of dingo reintroduction on mesocarnivores, small mammals, and other taxa in this biologically rich rangeland. Newsome et al. (2015) outline how such an experiment could be implemented in Sturt National Park, western New South Wales. Without these more rigorous research strategies, Hayward & Marlow (2014) and Hayward et al. (2015) argue that there are too many uncertainties surrounding species’ abundance, distribution, and behavior, which would make widespread dingo reintroduction risky. Nimmo et al. (2014) argue that track indices, uncorrected for detection probability, are sufficient under the circumstances to justify reintroducing dingoes to help reduce non-native mesocarnivores and protect biological diversity. They suggest that a failure to take immediate action based on the available data could have lasting negative effects on this ecosystem that could ultimately prove more costly down the road.
Moving forward, ecologists, managers, and statisticians should continue to collaborate and develop strategies that provide the best available information to guide management decisions and conservation policy. The momentum is behind field and analytical approaches that account for detection probability, efforts that validate indices against intensive monitoring approaches, controlled experiments when possible, and transparency about the limitations and assumptions associated with field and analytical approaches. Workshops that bring together statisticians, academic researchers, and wildlife managers to discuss the advantages and limitations of current strategies should be encouraged to help develop additional cost-effective, accurate, and easily implemented and repeatable strategies. These types of workshops are increasingly common and should continue to be advertised to wildlife professionals and not just to students and academic researchers.
At the same time, we must also recognize that in some situations, immediate and potentially drastic management actions might be necessary to prevent extinctions or damages that will only get more costly if left unattended. In these situations, experimental introductions of an apex predator in a before-after-control-impact design would be useful, because studying where they are or are not at present may not provide sufficient a priori knowledge of their potential effects in a novel landscape. Ecologists and managers should also conduct risk analyses to determine possible outcomes from reintroductions, and have the necessary logistics and budgets in place to manage unexpected and unintended outcomes associated with these management decisions.
References:
Hayward, M. W., Boitani, L., Burrows, N.D., Funston, P.J., Karanth, K.U., MacKenzie, D.I., Pollock, K.H. & Yarnell, R.W. (2015) Ecologists need robust survey designs, sampling and analytical methods. Journal of Applied Ecology, 52:286–290.
Hayward, M. W. & Marlow. N. (2014) Will dingoes really conserve wildlife and can our methods tell? Journal of Applied Ecology, 51:835–838.
Kellner, K. F. & Swihart, R.K. (2014) Accounting for imperfect detection in ecology: a quantitative review. PLOS ONE, 9:e111436.
Newsome, T. M., Ballard, G-A., Crowther, M.S., Dellinger, J.A., Fleming, P.J., Glen, A.S., Greenville, A.C., Johnson, C.N., Letnic, M, Moseby, K.E. et al. (2015) Resolving the value of the dingo in ecological restoration. Restoration Ecology, DOI: 10.1111/rec.12186.
Nimmo, D. G., Watson, S.J., Forsyth, D.M. & Bradshaw, C.J. (2014) Dingoes can help conserve wildlife and our methods can tell. Journal of Applied Ecology, 52:281–285.
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