Understanding the science on wolf-livestock conflict

New research highlights the importance of using multiple tactics, from range riders to targeted lethal removal, to reduce and resolve conflicts between wolves and livestock.

Key takeaways from recent wolf-livestock research:

• The science does not support general public wolf hunting as a solution for reducing cattle depredations in areas where wolves and livestock overlap.
• Wolf-livestock conflict can be predictable in that it often recurs in areas where prior conflicts have taken place. Conflicts also predictably happen more frequently in forested areas further from towns and cities, and in areas where there is greater density and overlap of wolves and livestock.
• The current body of science does not support the conclusion that lethal removal of wolves by wildlife agencies increases future conflict.
• Targeted lethal removal can effectively stop chronic depredations on livestock, at least for a few years given the propensity for conflict to reoccur in a given area. This underscores the importance of using proactive non-lethal conflict deterrence methods to keep losses of wolves and livestock to a minimum, and validates the use of lethal removal as a tool for resolving persistent conflicts.

Read on for more!

BY JAY SHEPHERD, PH.D, WOLF PROGRAM LEAD and the consErvation northwest wolf team

A recent paper in the Journal of Wildlife Management by Nicholas DeCesare et al. titled Wolf-Livestock Conflict and the Effects of Wolf Management helps explain some of the factors driving wolf-livestock conflicts, and highlights the need for both proactive non-lethal deterrence tactics and reactive lethal removal to reduce and resolve conflicts in the interest of wolf conservation and human tolerance for wildlife.

The study, which draws from a long-term dataset of wolf depredations on livestock in areas of Montana where wolves and domestic cattle share territory on public and private lands (much like they do in Eastern Washington), sheds light on these factors, but also cautions against relying on some long-held beliefs.

One such assumption common in wolf country from the Great Lakes to the Pacific Northwest is that public wolf hunting will significantly reduce and alleviate wolf-livestock conflict. Instead, the authors’ review of data from 2005 to 2015 concludes that “we were unable to support a hypothesis that public [wolf] harvest has been a primary factor influencing [decreases in livestock depredations]” {DeCesare et al., 2018, p. 721}.

Another theory, or controversy, that this paper addresses is the relationship between targeted lethal wolf removal and livestock depredations the following year.

Does lethal removal actually increase conflict?

In a 2014 paper, Washington State University researchers Robert Wielgus and Kaylie Peebles argued that depredations increased the year after lethal removal, referencing data from publicly available reports in the Northern Rocky Mountain States. Their analysis was at a macro scale, and in a statistical reanalysis of the same data published in 2016, University of Washington researchers Niraj Poudyal, Nabin Baral and Stanley Asah were unable to replicate Wielgus and Peebles’ conclusions. Both this study and a second reanalysis by Lyudmyla Kompaniyets and Marc Evans published in 2017 found that after taking autocorrelation (in this case time and increasing wolf populations) into account, livestock depredations by wolves actually decreased after targeted lethal removal.

It’s notable that this is also the conclusion reached by a 2015 paper, Effects of wolf removal on livestock depredation recurrence and wolf recovery in Montana, Idaho, and Wyoming, authored by Elizabeth Bradley et al., which analyzed the same data at a wolf pack scale concluding that lethal removal did in fact reduce livestock depredations the following year.

Getting back to the latest research by DeCesare and his co-authors, their paper also took autocorrelation into account by treating targeted lethal removal by wildlife agencies as an interaction factor. Consistent with the Bradley and Kompaniyets papers, they concluded that targeted lethal removals reduce livestock depredations the following year {DeCesare et al., p. 721}.

In summary, at least three separate peer-reviewed scientific papers have contradicted the notion that lethal removal increases conflict between wolves and livestock, with additional analysis questioning the conclusions of the original 2014 paper by Wielgus and Peebles. This is not to say that repeated removals don’t have the potential to disrupt the social bonds of wolf packs and cause dispersal to new areas, which may or may not lead to more depredations on livestock, just that as of now, there is more statistical support for the conclusion that targeted removal can effectively reduce depredations in subsequent years.

Limiting conflict through rapid response

The 2018 DeCesare paper also indicates that targeted removal of depredating wolves fairly quickly after they have preyed on livestock helps reduce further depredations. As we very much want to reduce deaths of both wolves and livestock, keeping wolf packs intact with minimal losses whenever possible, this is worth consideration. 

In Washington, the Wolf-Livestock Interaction Protocol developed and agreed to by the Wolf Advisory Group and others requires that livestock producers employ “at least two proactive deterrence measures that are appropriate to their operation”. Lethal wolf removal is then considered after acute or chronic depredation thresholds are met, the most basic of which is three livestock depredations within a 30-day period. We support these thresholds as appropriate, and as Washington wildlife managers and stakeholders consider further refinements to the protocol to incorporate the latest science as well as social considerations, the DeCesare study is one resource they’ll be looking at.

In order to both reduce and resolve wolf-livestock conflict, DeCesare and his co-authors recommend wildlife managers maintain an equal focus on “preventative efforts to reduce the propensity for conflicts in places where they are less common and reactive efforts to reduce the severity or number of conflicts in places where they are more common”. As mentioned above, their results also “uphold the use of targeted lethal removals to reduce recurrent depredations” {DeCesare et al., p. 721} and conclude that “targeted removal but not public harvest, significantly reduced the recurrent presence of depredations” {DeCesare et al., Abstract, p. 711}. We’ll dive deeper into that second point shortly.

What causes conflict in the first place?

In addition to statistically analyzing conflict data and providing management recommendations, DeCesare and his co-authors also provide insights on variables behind these conflicts. The study assessed two metrics to help explain the annual variation in depredations throughout the state, whether any depredations occurred within a Game Management Unit at all, and the level of depredations in each unit. In other words, the authors asked, “Are statewide depredation levels better explained by the occurrence of depredations, even single depredations, or the average number of depredations in Game Management Units from year to year?” They found the answer to be that both variables correlate with and influence statewide depredation numbers, leading them to investigate what factors affect both depredation occurrences and levels within Game Management Units.

Some of their findings are intuitive: such as that higher densities of wolves and livestock, and the level of overlap between them, both increase the chance of a single occurrence of a depredation and the overall number of depredations in an area. In the northeastern corner of Washington we’ve seen this occur: areas with increased overlap and a high-density of wolves and cattle have more depredation incidents and higher depredation levels; triggering strong non-lethal deterrence efforts as well as the lethal removal of wolves to resolve chronic conflicts.

Another relatively intuitive finding is that higher levels of forested lands are positively correlated with increasing wolf-livestock conflict. There are large areas in northeastern Washington that are either National Forest or commercially-owned forest land with interspersed valleys where ranches and crops occur. Just outside of towns are “twenties”, or areas with 20-acre ranchettes, where people raise cattle, sheep, goats, or horses but not on a commercial scale. As you move out from towns and populated areas like the city of Colville, forested land increases as does the interspersion of agricultural land and grazing allotments, and wildlife becomes more common. Also, predictably, as you get further from human-occupied areas, depredations caused by wolves are more prevalent.

The authors also speak to the fact that livestock depredations occur more frequently in late summer, which is the general time frame when the majority of depredations occur in northeast Washington.

One interesting finding of the study is that wolf-livestock conflict can be predictable in that it recurs in areas where prior conflicts have taken place {DeCesare et al., p. 719}. The occurrence of previous depredations was the single strongest explanatory variable that predicted future depredations. This has been the rule in the Kettle River Mountain Range and other areas in northeast Washington where we have wolf pack territories that have had repeated wolf-cattle conflict for years, with heavy losses of cattle and controversial wolf removal.

Another controversy brewing in Washington is the effect that the available level of deer, elk and other native wolf prey has on cattle depredation levels. This study found no conclusive relationship between native prey densities and the occurrence or number of wolf-livestock conflicts.

In other literature, native prey densities have been either positively (also this study from Italy) or negatively (also this study from Finland) correlated with wolf-livestock conflict. A positive correlation may indicate abundant native prey herds that overlap with cattle, drawing wolf activity into cattle grazing areas where incidental, random cattle depredations occur. A negative correlation between native prey density and the occurrence or number of wolf-livestock conflicts may indicate that native prey herds are deficient, and wolves increasingly turn to other sources of prey, such as domestic cattle.

The discussion of cattle as potential prey leads to a crucial question addressed by the study. Do cattle depredations occur randomly when wolves happen upon grazing cattle (perhaps by being drawn to areas with high native prey densities) or do wolves learn to prey upon cattle over time, causing recurring depredations in high risk areas? It appears the answer is both. Given that both the occurrence of individual depredations and the level of cattle in a given area are correlated with statewide depredation levels, then both random depredations and more chronic depredations explain the statewide depredation total over the years examined in the study {DeCesare et al., p. 719}.

Wolf hunting does not reduce wolf-livestock conflicts

The effects of regulated public hunting of wolves as big game after recovery goals are met is obviously a complicated social issue, but this study did not find it to be a strong variable in explaining or preventing wolf-livestock conflict.

The authors “found no evidence that removing wolves through public harvest affected the year-to-year presence or absence of livestock depredations by wolves” {DeCesare et al., p. 720}. Reduced wolf densities across the landscape resulting from general hunting seasons do not affect whether depredations on livestock will occur, but if they do occur in a given area, the effect on the number of depredations that may occur is small. The authors conclude that in areas where cattle depredations are occurring, less than one in ten will be prevented by the presence of a public hunt.

On the other hand, targeted removal of wolves conducted by government agencies can have an effect on the probability of recurring depredations in subsequent years. Precise removal of the offending animals may decrease the probability of depredations recurring even further {DeCesare et al., p. 721}. The study did not take into account, but acknowledged, the broad ethical and social issues surrounding wolf hunting and lethal removal of wolves.

Where do we go from here?

The takeaway messages from this study are complicated, and science concerning ecological topics is never as precise as the hard sciences such as chemistry or physics. The results of social science must be considered as well—society and politics have a large impact on wildlife conservation and management, particularly given our increasingly human-dominated environments.

Nonetheless, we can say a few things:

• The science does not support general public wolf hunting as a solution for stopping or even reducing cattle depredations in areas where wolves and livestock overlap.
• Wolf-livestock conflict can be predictable in that it often recurs in areas where prior conflicts have taken place. Conflicts also predictably happen more frequently in forested areas further from towns and cities, and in areas where there is greater density and overlap of wolves and livestock.
• The current body of science does not support the conclusion that lethal removal of wolves by wildlife agencies increases future conflict.
• Targeted lethal removal can effectively stop chronic depredations on livestock, at least for a few years given the propensity for conflict to reoccur in a given area. This underscores the importance of using proactive non-lethal conflict deterrence methods (such as range riders) to keep losses of wolves and livestock to a minimum, and validates the use of lethal removal as a tool for resolving persistent conflicts.

These results should also give us pause to consider what to do when neither non-lethal deterrents as currently implemented, nor lethal removal, are successful at ending cycles of conflict, as has recently been the case in northeast Washington’s Kettle Range.

In a future blog, we will describe Low-Stress Livestock Handling and other techniques that ranchers in parts of Montana are applying to greatly reduce depredations, even in places where they were once common. Their success provides hope that places where wolf-livestock conflicts have frequently occurred can become areas with much fewer losses of both cattle and wolves.

As with all issues, there are times for prevention and reaction, and for reflection on the latest research and how to incorporate it into policy. Washington continues to have a science-based Wolf Conservation & Management Plan, and the Wolf Advisory Group is working to bring relevant research to bear in developing sound policy and building common-ground between wolf advocates, hunters, ranchers, farmers, recreationists and other wildlife stakeholders.

Our goal has always been to make Washington the state where wolf recovery works—for wolves, other native wildlife and local communities. Science is a vital tool for progress toward that goal.

 

read jay’s last blog on understanding wolf behavior—for their safety and yours. or Learn more about WOLVES IN WASHINGTON, our WORK FOR COEXISTENCE, or our RANGE RIDER PILOT PROJECT.