Abstract
Gray wolves (Canis lupus) were nearly eradicated from the 48 conterminous states in the United States by the 1930s, largely to protect livestock producers from the threat of depredation (Young and Goldman 1944; Lopez 1978; McIntyre 1995). However, 4 decades later, in 1974, wolves were granted protection through the United States Endangered Species Act (16 U.S.C. 1531–1544, 87 Stat. 884), and due to successful reintroduction efforts and natural expansion, the species was reestablished in the northern Rocky Mountains (United States Fish and Wildlife Service et al. 2012, 2014). With the return of wolves, threats to livestock (primarily sheep, Ovis aries, and cattle, Bos taurus) again have become a source of conflict, and as a result wildlife agency managers often kill wolves that prey on livestock (Fritts et al. 1992; Mech et al. 2000; Bangs et al. 2006). However, killing depredating wolves without addressing the underlying causes of depredation only temporarily eliminates depredation attacks on livestock (Fritts et al. 1992; Gehring et al. 2003; Musiani et al. 2005; Harper et al. 2008; Bradley et al. 2015). For example, Bradley et al. (2015) found that recurring depredations were typically made by the next pack to occupy the vacant territory within 2 years, yet, in the Northern Rockies region, costs for investigations into livestock depredation, lethal control, and compensation for livestock losses exceeded $1.5 million in 2010 alone (Bradley et al. 2015).
Research indicates there is broader public support for nonlethal methods of predator control than for lethal methods (Arthur 1981; Reiter et al. 1999; Bruskotter et al. 2009; Holsman et al. 2014; Slagle et al., this issue). For example, in the state of Washington, recent surveys on public attitudes indicate growing opposition to lethal control of wild predators to prevent livestock losses (Duda et al. 2008). Public attitudes help shape public policy and, as a consequence, the nature of wildlife management programs. However, when surveyed, many livestock producers who had experienced livestock losses to wolves expressed skepticism concerning the anticipated effectiveness of nonlethal methods and the costs to implement them, whereas others expressed uncertainty regarding which methods were appropriate to use and when to use them (Stone 2009). Even established researchers of wolf and livestock management have mostly dismissed large-scale nonlethal predator deterrents as a viable alternative to traditional lethal control measures because they claim that nonlethal methods do not provide “an adequate or overall solution to this problem” and have “little or no long term value” in predator management efforts (Shelton 2004:3–4).
The willingness of livestock managers to adopt nonlethal techniques often relies on proof of their efficacy (Baker et al. 2008), which requires research aimed at determining their effectiveness across a variety of situations. Employing these measures for a small-scale farm or ranch is often feasible and inexpensive, and several specific methods have been studied at this level (Breck et al. 2002; Musiani et al. 2003; Gehring et al. 2010). However, most livestock killed by wolves in the northern Rocky Mountains of the United States are part of large, open-range grazing operations covering 4,000–40,000 ha or more. The question then becomes not just whether nonlethal deterrents can work but whether they are feasible in large landscapes. Some wolf scientists have cautioned that “all means of protecting livestock from wolves over large areas are largely ineffective and expensive” (Mech et al. 2003:336) yet also acknowledge that most methods remain untested (Harper et al. 2008). Others have dismissed nonlethal methods as too costly, impractical, and limited in their effectiveness due to wolves habituating to deterrent stimuli (Smallidge et al. 2008).
To date, there have been few landscape-scale trials of nonlethal deterrents in overlapping wolf and livestock range, and none that involved thousands of sheep in rugged national forests. Because wolves kill far more sheep than other types of livestock in the northern Rockies of the United States, including in Idaho (United States Fish and Wildlife Service et al. 2016), our goal was to determine if we could proactively and adaptively use nonlethal tools and techniques to significantly reduce losses of sheep to wolves while reducing lethal control of wolves across a large, rugged, and primarily forested landscape. Our case study compared the rate of sheep loss to wolves in a Protected Area (PA) and a Nonprotected Area (NPA) over 7 years. Details of our methods are given below, but critical here is that the PA and NPA were comparable in that both were on national forest lands, in adjacent areas, and occupied by wolves and both had a history of sheep losses due to wolf depredation. Furthermore, the sheep we monitored on the PA and NPA all belonged to several of the same 4 producers who participated in this project, and some of the same wolves from established packs ranged in both the PA and NPA. We emphasize that our goal was not to evaluate any single tool or method using a standard research design but rather to evaluate the holistic strategy of increasing the presence of humans, more diligence in handling of sheep (animal husbandry), and using a variety of nonlethal techniques in a proactive and adaptive fashion based primarily on wolf-monitoring information, grazing conditions, terrain, time of day, available resources, and accessibility.
Background
Wolves were reintroduced into Idaho in 1995 and 1996 as part of the northern Rockies wolf recovery efforts. Since that time, more than 2,400 wolves have been killed across the region in response to reported depredations involving more than 6,000 sheep and cattle (United States Fish and Wildlife Service et al. 2016). In the northern Rockies, significantly more sheep (4,514 confirmed) than cattle (2,274 confirmed) have been killed by wolves since 1987, when the 1st confirmed wolf depredations on livestock occurred (United States Fish and Wildlife Service et al. 2016). Approximately 200,000–220,000 sheep graze annually in Idaho, with estimated average annual losses of 20,000–30,000 from all mortality causes other than intentional slaughter for market (Idaho Sheep Loss Report 2013). Predator depredations account for 30–40% of all sheep mortality as estimated and reported by sheep producers (United States Department of Agriculture – National Agricultural Statistics Service 2010), with wolves accounting for ≤ 4.1% of total losses statewide in 2012, the most recent data available for sheep mortality loss in Idaho. While coyote (Canis latrans) depredation is the main cause of sheep losses in the northern Rockies, accounting for > 66% of depredations (United States Department of Agriculture – National Agricultural Statistics Service 2013), wolf depredation is more controversial and results in state-sanctioned efforts to reduce wolf numbers to address conflicts (Russell 2015). Nearly 64% of Idaho consists of federally owned or administered forests and other rangelands, almost half of which is leased to private individuals or corporations for rangeland grazing (Rimbey et al. 2014). According to the United States Department of Agriculture’s (USDA) Wildlife Services Idaho Depredation Field Investigation Reports from 1995 to 2010, more sheep were killed by wolves on national forest lands (which are typically more remote and rugged) than on privately owned lands in Idaho.
Materials and Methods
Regional study area.
Our demonstration project was conducted in one of the largest sheep-grazing sectors in the Idaho wolf range (S. Boyd, Executive Director, Idaho Woolgrowers Association, pers. comm.). Domestic sheep and wolf packs share the same range each year from mid-June through early October on the Sawtooth National Forest, federally managed public lands that cover 854,052 ha in the states of Idaho (96%) and Utah (4%). This region includes sagebrush steppe, spruce-fir forests, and alpine tundra, among other vegetation types. The elevation ranges from 1,784 to 3,660 m, and the terrain is largely mountainous, unpopulated, and rugged. There are few maintained access roads in the more remote areas. The region is interspersed with lower-lying areas of concentrated human use and permanent settlement. Native mule deer (Odocoileus hemionus), elk (Cervus elaphus), and moose (Alces alces) are present, among many other wildlife species, and game hunting is regulated by the state wildlife agency (Idaho Department of Fish and Game and Nez Perce Tribe 2014). Idaho Fish and Game reported a minimum of 6 documented packs of wolves in the Southern Mountains wolf management zone in 2007, 7 in 2008, 7 in 2009, 6 in 2010, 7 in 2011, 11 in 2012, 9 in 2013, and 8 in 2014 (Idaho Department of Fish and Game and Nez Perce Tribe 2008, 2009, 2010, 2011, 2012, 2013, 2014). Recreational use of the national forest (hunting, hiking, camping, skiing, and snowmobiling) is popular among local residents and tourists year round. Sheep traditionally are grazed in large bands attended by 1 or more shepherds, herding dogs, and livestock guardian dogs (LGDs). Bands are generally either “ewe–lamb” bands or “dry” bands. “Ewe–lamb” bands consist of about 850–950 ewes plus their lambs, usually totaling > 2,000 animals per band. “Dry” bands consist of a few hundred ewes early in the season, but later, after their lambs have been shipped, can grow to as many as 2,000 when older ewe bands and young replacement ewe bands are combined. Idaho range operators primarily employ Peruvian sheepherders to manage bands in the field. These bands slowly graze from lower to higher elevations in the spring and summer months after the native forage has become green. This seasonal cycle, known as transhumance migration, is an ancient pastoral tradition that has been practiced in areas around the world since sheep were first domesticated approximately 10,000 years ago. Sheep ranchers participating in the Demonstration Project have sheep bands that typically graze across a distance of more than 200 km each season.
Sheep grazing.
Although there are several farm flock operators in the vicinity of the study area that each manage up to a few hundred sheep in pastures, we were principally concerned with large-scale “range operators”, producers who graze thousands of sheep across a vast landscape. Range operators graze lands with complex surface ownership, including their own deeded properties and public lands managed by various state and federal agencies. These range operators typically release (turn out) ewes and their lambs on the Snake River Plain in early April at an elevation of approximately 1,219 m, then travel slowly north through sagebrush steppe into mid-elevation country ranging from 1,524 to 2,438 m in May that offers greater topographic relief and is dissected by riparian corridors. In June, sheep bands enter the PA when they move into higher, more mountainous country ranging from 1,981 to 2,896 m in 1 or more national forests and where wolf packs establish their range. Bands of ewes and lambs are herded down from the high mountains in July or August to corrals in the valleys below where the lambs are weaned and shipped. The resulting “dry” bands then return to high elevation forest allotments for several weeks before the migration back to lower elevations begins in early- or mid-autumn. Rams typically are added to the ewe bands in August for breeding purposes. The bands are slowly herded to the vicinity of lambing sheds, located on the operator’s deeded property, or to lambing range on private or public lands in sagebrush steppe on the Snake River Plain, home ranch, or farm. Shed-lambing for most project participants occurs from January to March. Turnout onto desert allotments occurs in early April, beginning the annual cycle anew. Following these spatiotemporal schedules, sheep bands passed through allotments (for which the operator held grazing permits or trailing rights) during the summer grazing season on public lands. Most bands were accompanied by a sheepherder and both herding and guardian dogs by day (Fig. 1), and by guardian dogs and sheepherders in the area at night. Sheepherders are the most experienced in day-to-day band management and are responsible for protecting the sheep from predators, keeping them watered and grazing, and managing their herding dogs, LGDs, horses, and equipment. Sheepherders also have the most direct influence on sheep and predator management in the field, and their ability to implement nonlethal methods on the ground in challenging terrain is critical to the project.