Potential Impact of Wolf Predation in the Greater Yellowstone Area
Discussion Paper by Ed Bangs - U.S. Fish and Wildlife Wolf Recovery Coordinator


In response to inquiries about speculation that elk herds have been severely impacted by wolf predation, the Wyoming Game and Fish Department looked at all six herd units that surround Yellowstone and Grand Teton National Parks in Wyoming. The Department estimates winter elk population in 2000-2001 was 34,255 individual elk which is over the Wyoming State elk management objectives for every elk herd unit. The Fish and Wildlife Service National Elk Refuge reports the Jackson Hole elk herd numbers (11,029 elk) have been over the Wyoming state and Federal objectives since 1987. The Refuge also reports that recent elk cow/calf ratios have been lower (mid to upper 20s per 100 cows) than they were in the early 1980s but it has not been determined that wolf predation is responsible. There has been a prolonged drought and herds not exposed to wolf predation have also witnessed similar decreases in cow/calf ratios. Both the Refuge and State have been attempting to reduce elk numbers around the parks in Wyoming for the past 5 years through the use of liberal elk hunting seasons.

The Wyoming Game and Fish Department has not made any changes to hunter harvest of elk because of wolf depredation. The Department reports that two herd units, one north of Dubois and another north of Cody, have seen a recent decrease in cow/calf ratios, but they are not sure predation is the cause of that decline since Wyoming has been suffering from an extreme drought. The Wyoming Game and Fish Department states it will look at elk numbers and the potential effect of wolf predation more closely in the next 6 months as they prepare their State wolf management plan. At this time elk herds in Wyoming are still over the Department's objectives and the Department is continuing to use liberal hunter harvest to reduce elk numbers.

For the past three winters, the Service, USDA Forest Service, and Wyoming Game and Fish Department has been conducting an ongoing study of wolf predation on elk at three state elk winter feed-grounds in the Gros Ventre drainage, near Jackson, Wyoming. At this point in the study, wolf predation seems to have had little measurable effect on that segment of the elk population south of Yellowstone National Park or on the State's ability to feed and vaccinate wintering elk. While there is evidence that wolves caused elk to move from one Gros Ventre feed ground to another, elk were obtaining supplemental winter feed and wolf kill rates on elk were within expected levels. We acknowledge there is speculation and expressed public concern about wolf predation, however, at this time there is no scientific information to suggest that elk populations have declined or been significantly impacted by wolf predation in Wyoming.

Data from Yellowstone National Park show over 90 percent of the ungulates killed by wolves in the Greater Yellowstone Area are elk, but all but one of the elk herds surrounding Yellowstone National Park, including those in Montana, are still at or above the State of Montana's management objectives. Winter hunting of cow elk is used by the states bordering Yellowstone National Park to reduce elk populations. Wolf predation, like any other cause of mortality, can accelerate elk population declines or slow population increases but the general trend of herd growth is most often determined by a combination of other factors, primarily habitat condition, weather, and human hunting of adult females. Wolf predation can impact ungulate populations and the impact of wolves on elk or other ungulate populations is a legitimate concern of the Service, state fish and game agencies and sportsmen. Consequently, the Service has helped initiate and fund an extensive cooperative university-led research on wolves and ungulates since the 1980's so that discussions about these concerns and any possible solutions can be based on scientific data rather than individual speculation and rumor.

While there is a great deal of speculation and anecdotal observations about elk movements in relation to wolves, an ongoing Montana State University study of a hunted elk population and wolves just west of Yellowstone National Park stated "Elk recruitment early in winter was already at approximately half of the recruitment during winter 2000-01. But did not change significantly because of wolf off-take...", "Mule deer recruitment did decline over the course of the winter. Wolf off-take was a factor in this decline but was not the sole cause", and "We found no indications of an effect of wolves on ungulate distribtuion. group size, or spacing..." Likewise research on the northern range elk population along the Montana and Wyoming indicated that the average elk population level during the past 20 some years was about 13,000 elk and last winter's count was about 12,000 elk but has fluctuated between 9,000 and 19,000. While the number of calves per 100 cows in 2002 was the lowest on record in over 20 years, the prolonged drought is suspected as the major contributor to that decline, although wolves and other predators undoubtably had some impact. Ongoing long term cooperative research efforts by the National Park Service, Forest Service, Montana Department of Fish, Wildlife and Parks and various universities will be able to clarify the potential affect of wolf predation on elk, but at this time the purported drastic effects claimed by some have not been documented by scientific inquiry.

In the Environmental Impact Statement completed at the direction of Congress prior to wolf reintroduction, the Service predicted that wolf predation might eventually cause declines in some elk herds by 5 to 30 percent. At this time, we have not seen any measurable effect to elk herd populations that has been caused directly by wolf predation. The EIS estimated that 100 adult wolves would kill the equivalent of about 1,200 adult cow elk annually. Based on that estimate, the current wolf population of just over 200 wolves maybe killing the equivalent of over 2,400 ungulates annually in the Greater Yellowstone Area. The nonessential experimental population rule allows wolves to be moved from areas where wolf predation is having a significant negative effect on ungulate populations. To date no significant effects on overall ungulate herd levels has been documented, and consequently, no wolves have been moved to reduce predation pressure. That provision in the experimental rule was specifically written and included in the rule-making to address the concerns of hunters and the states should wolf predation begin to significantly impact ungulate populations. The Service will not hesitate to relocate wolves should the need to reduce wolf predation on specific native elk herds arise.

Wolf predation also has not had a significant impact on the agriculture industry. Since wolves were first reintroduced to Yellowstone National Park in 1995 there have been a total of 41 cattle, 256 sheep, and 23 dogs confirmed killed by wolves in the entire Greater Yellowstone area which includes areas in Montana, Idaho, and Wyoming. Prior to wolf reintroduction livestock producers in the Greater Yellowstone Area estimated they were already losing 8,340 cattle and 12,993 sheep annually, mostly from causes other than predation. In Montana, Idaho, and Wyoming typically less than 3 percent of all cattle deaths are typically caused by predators. Sheep losses to predators are higher with nearly one third being attributed to predators. Normally between 60 and 70 percent of all predation losses of sheep and most calf losses are caused by coyotes feeding on newborn livestock. Livestock losses caused by wolves represent a small fraction of the total loss caused by predators, which in itself is a fraction of overall livestock losses. In 2001 wolf predation attributed about 1 percent of the total cattle losses caused by predators and wolf predation attributed 0.4 percent of total sheep losses caused by predators. This means that wolves caused the death of approximately 3 of every 10,000 cattle and 134 of every 10,000 sheep that died from all causes last year in the three states.

While the numbers of wolf predations is insignificant to the livestock industry, we recognize that wolf depredation can be very emotional issue and one that can significantly affect individual livestock producers. The experimental rules allow private landowners many options to help reduce the potential for conflict with wolves. In addition, the Service and USDA Wildlife Services treat wolf depredations seriously and address them aggressively. As of December 2001, in the Greater Yellowstone area, our agencies moved wolves 42 times and killed 34 wolves specifically to reduce conflicts with livestock. Even though a private group compensates for livestock and guard and herding animals that are killed by wolves, we know that other losses occur but are never documented. Wolf-caused conflicts are infrequent compared to other issues effecting livestock survival but the Service addresses each of them as a very serious issue.

The wolf population in Montana, Idaho, and Wyoming will almost certainly achieve the recovery goal of maintaining 30 breeding pairs that are distributed throughout Montana, Idaho, and Wyoming for three successive years ending in December 2002. By law two things must happen before wolves can be removed from the list of endangered or threatened species. First, the recovery goals must be met. Second, there must be legal protections in place so that if the Endangered Species Act (Act) protections were removed, wolves would not again become endangered or threatened. In 1997, the Governors of Montana, Idaho, and Wyoming signed a Memorandum of Understanding agreeing to prepare State plans to assist in the timely delisting of the wolf population once it is recovered. Currently the State of Idaho has a state wolf management plan, Montana's State plan should be completed this fall, and the State of Wyoming is initiating the process of developing a state management plan. The Service has provided all three states with funding to aid in the preparation of their wolf management plans. The Service intends to propose delisting the wolf as soon as legally possible, which means when both the recovery goal have been met and all three states have completed wolf management plans. The Service and the states of Montana, Idaho, and Wyoming have recently signed a cooperative agreement to jointly prepare a delisting package to assure a smooth transition to state management once the wolf population has recovered and state wolf management strategies are completed.