Killing wolves to prevent predation on livestock may protect one farm but harm neighbors

Large carnivores, such as gray wolves, Canis lupus, are difficult to protect in mixed-use landscapes because some people perceive them as dangerous and because they sometimes threaten human property and safety. Governments may respond by killing carnivores in an effort to prevent repeated conflicts or threats, although the functional effectiveness of lethal methods has long been questioned. We evaluated two methods of government intervention following independent events of verified wolf predation on domestic animals (depredation) in the Upper Peninsula of Michigan, USA between 1998–2014, at three spatial scales. We evaluated two intervention methods using log-rank tests and conditional Cox recurrent event, gap time models based on retrospective analyses of the following quasi-experimental treatments: (1) selective killing of wolves by trapping near sites of verified depredation, and (2) advice to owners and haphazard use of non-lethal methods without wolf-killing. The government did not randomly assign treatments and used a pseudo-control (no removal of wolves was not a true control), but the federal permission to intervene lethally was granted and rescinded independent of events on the ground. Hazard ratios suggest lethal intervention was associated with an insignificant 27% lower risk of recurrence of events at trapping sites, but offset by an insignificant 22% increase in risk of recurrence at sites up to 5.42 km distant in the same year, compared to the non-lethal treatment. Our results do not support the hypothesis that Michigan’s use of lethal intervention after wolf depredations was effective for reducing the future risk of recurrence in the vicinities of trapping sites. Examining only the sites of intervention is incomplete because neighbors near trapping sites may suffer the recurrence of depredations. We propose two new hypotheses for perceived effectiveness of lethal methods: (a) killing predators may be perceived as effective because of the benefits to a small minority of farmers, and (b) if neighbors experience side-effects of lethal intervention such as displaced depredations, they may perceive the problem growing and then demand more lethal intervention rather than detecting problems spreading from the first trapping site. Ethical wildlife management guided by the “best scientific and commercial data available” would suggest suspending the standard method of trapping wolves in favor of non-lethal methods (livestock guarding dogs or fladry) that have been proven effective in preventing livestock losses in Michigan and elsewhere.

Risk map for wolf threats to livestock still predictive 5 years after construction

Risk maps are spatial models of environmental hazards such as predation on livestock. We tested the long-term validity of a published risk map built from locations where Wisconsin wolves attacked livestock from 1999-2006. Using data collected after model construction, we verified the predictive accuracy of the risk map exceeded 91% for the period 2007-2011. Predictive power lasting 5 years or more substantiates the claim that risk maps are both valid and verified tools for anticipating spatial hazards. Classification errors coincided with verifier uncertainty about which wolves might be responsible. Perceived threats by wolves to domestic animals were not as well predicted (82%) as verified attacks had been and errors in classification coincided with incidents involved domestic animals other than bovids and verifier uncertainty about which wolves were involved. We recommend risk maps be used to target interventions selectively at high-risk sites.

Landscape predictors of wolf attacks on bear-hunting dogs in Wisconsin, USA

Context In Europe and the United States, wolf–human conflict has increased as wolf populations have recovered and recolonised human-dominated ecosystems. These conflicts may lead to negative attitudes towards wolves and often complicate wolf management. Wolf attacks on bear-hunting hounds (hereafter, hounds) are the second-most common type of depredation on domestic animals in Wisconsin, USA, and, typically, the most costly in terms of compensation per individual animal. Understanding the geospatial patterns in which these depredations occur could promote alternative hunting practices or management strategies that could reduce the number of wolf–human conflicts. Aims We compared variables differentiating between wolf attacks on hounds and non-hounds (e.g., pets), we constructed a spatial, predictive model of wolf attacks on hounds, and we explored how the landscape of risk changed over time. Methods We characterised landscape features of hound depredations using logistic regression. We applied the spatial model to a geographic information system (GIS) to display spatial patterns and to predict areas of risk for wolf attack. Key results Our model correctly classified 84% of sites of past depredations, 1999–2008, and 78% of nearby random-unaffected sites. The model correctly predicted 82% of recent (2009–11) depredation sites not used in model construction, thereby validating its predictive power. Risk of wolf attack on hounds increased with percentage area of public-access land nearby, size of the nearest wolf pack, proximity of the nearest wolf pack, and decreased with percentage of human development. National and county forest lands had significantly (P < 0.001) more hound depredations than did other land-ownership types, whereas private lands had significantly fewer. Conclusions Risk of wolf attacks on hounds had distinctive temporal and spatial signatures, with peak risk occurring during the black bear hound training and hunting seasons and in areas closer to the centre of wolf pack territories, with larger wolf packs and more public access land and less developed land. Implications Our analysis can help bear hunters avoid high-risk areas, and help wildlife managers protect wildlife and recreational use of public lands, and reduce public costs of predator recovery. We present a risk-adjusted compensation equation. If wildlife managers choose, or are required, to provide compensation for hounds attacked by wolves, while hunting on public lands, we suggest that managers consider adjusting compensation payments on the basis of the relative landscape of risk.