An experimental test of a compensatory nest predation model following lethal control of an overabundant native species

Beggs, Richard; Pierson, Jennifer C.; Tulloch, Ayesha I. T.; Blanchard, Wade; Westgate, Martin J.; Lindenmayer, David B.

doi:10.1016/j.biocon.2019.01.003

Cited by 18 publications

(20 citation statements)

References 82 publications

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“…This will be reported elsewhere but we offer preliminary findings here. The limited decline in Noisy Miner abundance achieved in treatment sites led to small increases in rates of detection and foraging of small woodland birds (Beggs et al, unpublished data) and a small decline in artificial nest predation rates (Beggs et al 2019). (5) The possibility of a management action making things worse (Donnelly et al 2003, Walsh et al 2012, Lazenby et al 2015.…”

Section: Culling Uncertainty and Ecological Risks: A General Framewmentioning

confidence: 99%

Patch‐scale culls of an overabundant bird defeated by immediate recolonization

Beggs

Tulloch

Pierson

et al. 2019

Ecological Applications

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Overabundant native animals cause a variety of human–wildlife conflicts that can require management to reduce their social, environmental, or economic impacts. Culling is an intuitively attractive management response to overabundance, but poor monitoring of results and costs means that evidence for successful outcomes is often lacking. Furthermore, many culls worldwide have been ineffective or counterproductive due to ecological release mechanisms or compensatory responses by the overabundant species. We completed a controlled, replicated, costed, and rigorously monitored experimental cull of the endemic Australian honeyeater, the Noisy Miner (Manorina melanocephala). Aggressive exclusion of birds from remnant woodland patches by overabundant Noisy Miners is listed as a Key Threatening Process under Australian conservation legislation due to its impacts on threatened birds. The problem is particularly prevalent in the highly modified agricultural landscapes of eastern Australia. The species impacts avian assemblages at low densities (0.6–0.8 birds/ha) and at a subcontinental scale (>1 million km2). Some ecologists recommend culling as the only management response capable of timely reversal of declines of threatened small woodland birds. We monitored Noisy Miner abundance before and for 12 months after a culling program and found that immediate recolonization from the surrounding landscape negated the impact of the cull. We hypothesize that this is due to a vacuum effect; whereby, birds resident in more marginal habitat around treatment patches move into the vacant territory post‐cull. Modeled mean abundance of Noisy Miners declined by 22% in treatment sites compared to an increase of 4% in control sites in the post‐cull period. Abundance in all sites, however, remained three to five times higher than published ecological impact thresholds. Return on investment analysis indicated no relationship between culling effort and reduction in Noisy Miner abundance. We conclude that culling at a patch scale is not an efficient method of reducing Noisy Miner abundance to levels unlikely to impact threatened woodland birds in the highly modified study landscape, despite estimated costs 18 times lower than another potential management response of revegetation. Our study highlights the importance of building empirical evidence before intuitively attractive but not necessarily ecologically effective management responses are applied more widely.

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Section: Culling Uncertainty and Ecological Risks: A General Framewmentioning

confidence: 99%

Patch‐scale culls of an overabundant bird defeated by immediate recolonization

Beggs

Tulloch

Pierson

et al. 2019

Ecological Applications

Self Cite

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“…However, the data showed no effect of the treatment on the bait intake by other predators (mainly mustelids: the stone marten and the European badger), thus, showing a trend towards bait intake compensation by scavenging. Compensatory predation has been reported in other CFA studies of red foxes (Tobajas et al ., 2020) and also in predator control studies (Holt et al ., 2008; Beggs et al ., 2019 a ), but in our case these species are mainly scavengers and rarely prey on adult rabbits. However, compensatory predation could be a limitation as regards employing the CFA technique in situations in which there are more than one predator species.…”

Section: Discussionmentioning

confidence: 61%

Conditioned odor aversion as a tool for reducing post‐release predation during animal translocations

Tobajas

Descalzo

Villafuerte

et al. 2020

Animal Conservation

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Predation is a key factor in prey population dynamics and could impact population recovery. One common means employed to recover prey populations is that of translocations, but most fail owing to high predation during the early stages. We tested whether conditioned odor aversion can reduce predation during animal translocations by using the predation of the European rabbit Oryctolagus cuniculus by the red fox Vulpes vulpes as a case study. Following a before‐after control‐impact design (BACI), we deployed bait stations monitored using camera‐traps in two zones to which rabbits were translocated. One week before the rabbits were released, microencapsulated levamisole was added to rabbit baits located in the treatment zones, along with vanilla essence as an odor cue. A total of 148 rabbits were distributed in artificial warrens with the odor cue and 68 of them were fitted with radio collars in order to determine their survival rates. The response to the treatment and translocation as regards subsequent rabbit abundance was evaluated using N‐mixture models, while rabbit establishment was evaluated using a warren use index (WUI). The treatment decreased the proportion of baits consumed by foxes, but this decrease was partially compensated by other predators. WUI and rabbit population growth increased significantly more after translocations in the treatment zones than in the control zones. The short‐term survival of translocated rabbits was also higher in the treatment zones than in the control zones. Our study showed that conditioned odor aversion reduced rabbit predation by foxes, and had a positive effect on rabbit population growth after translocation, since there was an increase in rabbit survival and warren establishment. This method could be used as a non‐lethal tool for the recovery of a key prey when carrying out programs concerning the reintroduction of endangered predators or for other vulnerable species requiring translocations.

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“…Improvements in opportunities for foraging and reproduction are essential if vulnerable species are to recover in the longer term. Hence, for this experiment we monitored changes in foraging opportunities (reported here) and reproductive potential (Beggs et al 2019a). In addition, we monitored changes in harassment rates to see if interference competition by the dominant aggressor, or other aggressive species associated with high Manorina melanocephala densities, is the reason that small woodland birds are unable to access resources in sites colonised by Manorina melanocephala.…”

Section: Discussionmentioning

confidence: 99%

“…We chose treatment/control replicates with comparable vegetation characteristics and found no inherent differences between treatment and control sites in response of Manorina melanocephala abundance to the cull (Beggs et al 2019b), in artificial nest predation rates (Beggs et al 2019a), nor in foraging rates in this study. However, we recorded a large difference in pre-cull harassment rates between treatment and control sites (Figure 3; Figure S5).…”

Section: Accepted Ar Ticlementioning

confidence: 95%