Lion vs Sheep

For some, keeping a constant eye on game cameras and venturing deep into the backcountry is a break from their everyday lives. For Jeff and Vicki Davis, it is their lives.

The Sierra Nevada mountains are known to people for many reasons. The rugged, majestic crags of the high-country draw thousands of visitors throughout all seasons; spring and summer through hikers seeking the Pacific Crest Trail, John Muir Trail and countless trails in between, and ice climbers and backcountry winter enthusiasts in the winter. What many of these people don’t know and indeed never see is the battle playing out between the one of the oldest species of bighorn sheep and one of California’s newest “protected” species. When factoring in severe summer droughts followed by equally severe winters, the battle is looking increasingly bleak for the sheep.

Since the 1990s, both lion and sheep populations have experienced ebbs and flows. Today, witnessing either species is much more common, albeit usually under unfavorable circumstances. When adding in the factor of well-intentioned but politically misguided state and federal agencies, the fate of the Sierra Nevada bighorn sheep species has edged closer to falling off the very precipices they inhabit. Currently, three players are jockeying for position in a delicate balance of ecosystem synchronicity, and it will be anyone’s guess how the final cards will lie in a game that has been played many times before, but somehow the rules seem to again have been forgotten.

"the fate of the Sierra Nevada bighorn sheep species has edged closer to falling off the very precipices they inhabit."

Photo courtesy of California Department of Fish & Wildlife

The People

Jeff and Vicki Davis are the few remaining amongst a dying breed. Jeff, currently a Federal wildlife contractor, and Vicki, a CA state scientific aid, began trapping at young ages; Vicki bought her first car with trapping money and Jeff his first house. The two have been working in the Sierra’s for decades and when community members of the Owens Valley were issued depredation permits (which in the past was more common than now), Jeff and Vicki received the first call. Jeff was instrumental in the US Department of Agriculture Animal and Plant Health Inspection Service, Wildlife Service (USDA APHIS WS) Sierra Nevada bighorn sheep (SNBS) recovery effort from 1999 to 2013 (after a three-year hiatus, the contract was continued and is currently active) when data collection on mountain lions began in order to develop appropriate actions to protect SNBS. With tremendous help from a well-oiled team of dogs and mules, their work with lions and sheep continues.

The dogs, usually an average of five, are hounds specially bred to detect scent in the difficult dry ground of the Sierra’s. Each has a specialized job and plays a particular role when treeing a lion or pushing it into a rockpile, where it can be tranquilized and collared. They are not impervious to the danger of lions and over the years some have been killed in their pursuits. The mules, having better endurance and agility than a horse are more adept at getting in and out of lion country and are equally important. Although highly intelligent they tend to kick at dogs, which makes finding the right one for this particular job tricky. Jeff choreographs the dance of hounds, mules, and lions against the background of an extremely rugged landscape.

In the past, the hounds were the primary means of finding lions, but the utilization of cage traps has risen to the point where both methods are now used about equally.  Technological advances have benefited the process greatly, and the team can incorporate data into the tracking, using game cameras and GPS clusters from collared lions which they’ve placed over the years. When a mortality signal is observed (often of the sheep, but sometimes a lion) either they or one of the many biologists working on the project hike or ride into the location, no matter how difficult to access, to verify the kill. If the kill is verified the process for removing the lion responsible, if one can be identified, begins. Lately, the process has entailed waiting 1-2 weeks to receive permission to relocate the lion, then upon receiving permission determining the lion’s current location. Depending on the location either the hounds or a cage trap will be used and eventually the lion will be tranquilized and packed out to be transported to Southern California and released on state land. Every single mortality signal is investigated whether it be by Jeff or biologists involved in the SNBS monitoring and recovery effort. Time spent not verifying kills is focused on game cameras and tracks to identify lions without collars and subsequently collar them. Their work through the decades has resulted in very detailed and well-maintained data on kills, territorial movement, and insight into what lions prey on which includes beaver, coyote, owl, sheep, deer, and dogs in the Sierra’s, and wild horses and birds inhabiting Mono Lake in Mono County.

The Sheep

On precipice, crag, and ledge a scrappy band of ruminants cling to survival, much like their sticky hooves cling to slick granite faces. With short, stocky bodies, a white rump and rams displaying the distinctive horns curved outward and down, the SNBS are well adapted to their high elevation home range. Today’s sheep are descendants of the ancient Siberian Snow Sheep, which crossed the Bering Land Bridge during the Pleistocene era nearly one million years ago. Since that time, the sheep have broken into three main subspecies; the Rocky Mountain bighorn, Desert bighorn, and Sierra Nevada bighorn. The SNBS have survived three ice ages, harsh winters, record breaking droughts and a deadly pneumonia spread by domestic sheep beginning in the 1800s. The North-South gradient of the Sierra Nevada’s provides a diverse habitat which has sustained the Sierra Nevada Bighorn for thousands of years, ranging from elevations of 12,000 feet to the lower lying winter habitat range in the foothills. Molecular genetic analysis suggests that SNBS diverged from the Desert Bighorn around 300,000 years ago and are now found only in their namesake mountains, with herds ranging from Olancha Peak in the South to Twin Lakes in the North. Ewes can live up to 20 years, while rams typically have a lifespan of around 10 years. Despite their resiliency, sheep numbers began to decline noticeably, reaching a low of around 100 individual sheep in 1995. In 1999 Sierra Nevada Bighorn Sheep were listed as a Federal endangered subspecies. A recovery plan written in 2007 by the U.S. Fish and Wildlife Service stated that with optimal herd growth, the sheep could be potentially downlisted in 10 years and delisted within another 10 years, with the cost over 20 years estimated at $21,730,000.

Photo courtesy of California Department of Fish & Wildlife

Thanks in large part to the work of dedicated scientists, biologists, and tracking experts, the SNBS experienced a rebound and almost reached threshold population numbers to be downgraded from an endangered to threatened species. This effort was largely supported by the successful Langley herd located around Mt. Whitney, which supplied ewes to the Baxter and Olancha herds to repopulate and bolster genetic diversity. The population growth slowed and took a major hit in 2016 when mountain lions decimated the Langley herd, bringing the number of ewes from approximately 45 down to ten or eleven. Since that winter, the SNBS has been struggling to regain their numbers. The sheep have just recently begun to return to their winter range where the 2016 kill off happened, as ewes are likely wary of returning to a previous high predation area. When forced to winter at higher elevations where conditions are brutal and food is scarce, ewes are unable to raise as many lambs to maturity as they would otherwise be able with winter access to the foothills. In the past several months herds sensitive to winter death have been hit hard, facing both starvation and increased avalanche activity due to the record snowpack in the high country. Between November and March 2023 the SNBS suffered an extremely high mortality rate of approximately 100 individuals, about half the entire population, with lions contributing to about 40% of the deaths.

The Lions

The Sierra Nevada mountain lion population has experienced a 300% increase since 2006, primarily due to the 3-4x increase in resident females observed through monitoring. Females are now observed raising a litter of three kittens to maturity, whereas in years past it was typical to raise only one. The mountain lion conservation program was enacted in 2016, the same year the Langley herd lost the majority of its ewes. Until very recently, that was the last time period in which a depredation permit was issued resulting in the death of two lions, while five were left to remain in the area.

Photo courtesy of California Department of Fish & Wildlife

Lions will favor different prey dependent on their location. Because of the variation in sheep and deer numbers along the eastern Sierra Nevada, and thus a variation in lion numbers throughout the winter ranges, maintenance of lion population levels requires a unique approach throughout each of the three recovery zones.

The Conflict

Proposition 117 - the Wildlife Protection Act, was passed in California in 1990 and was to serve as the first safety net for lions. Under the WPA, mountain lions were a specifically protected mammal and all authority for CDFG to remove mountain lions for the sake of protecting sheep was rescinded. Soon after, CA State Legislature requested a recovery program for the sheep, and simultaneously passed AB 560, which altered the WPA and modified the State Game Code to allow the removal of mountain lions that were perceived to be a threat to the sheep. In 1999 the SNBS were listed as endangered species, and it was in the Spring of that same year that APHIS WS were brought in to aid the recovery effort. WS quickly concluded the lack of lion management played a large role in the diminishing populations of the SNBS. Methods to alleviate negative effects of mountain lion predation was a key factor written into the recovery plan for SNBS, but it was cautioned that management of predation should be carried out in such a way that would maintain the viability of the mountain lion population.

In the 20 years that WS worked on the contract, which is currently active after a three-year hiatus, there were 66 confirmed lion kills of sheep. Data collected via the deployment of GPS collars on sheep and lions was used to determine which lions were preying on sheep in winter ranges. By investigating clusters of GPS locations, parties involved were able to identify SNBS kills that would not otherwise have been found and confirmed.

That count likely under-represents the actual numbers, due to the very specific criteria that have to be met for the agency to designate a mortality as the result of a lion. Twenty-two lions were removed in a time period which lion predation was highest, unsurprisingly, in herd units that overlap with the greatest concentrations of wintering deer. It has been 6 years since the passage of the lion conservation act, within which there is no authority to restrict depredation permits. Despite this, the relocation of lions, even those which prey almost exclusively on pets and sheep, is the current advocated method, though it is difficult to positively identify where the advocating stems from. Private citizens seeking a depredation permit need both an adeptness for jumping through the hoops of bureaucratic policy and the means to navigate a very strict set of rules and regulations to successfully obtain permission and then take a lion with a permit. Once a permit is granted, the holder must adhere to restrictions such as beginning to track a lion only within a mile from a kill site when using dogs, and prohibited pursuit of a track beyond 10 miles from the kill.

Recovery efforts have shown to be less effective when focused lion management is not adequate and timely. The Langley herd, and more recently the Mt. Baxter herd, are unfortunate examples of how quickly habituated lions can begin to affect SNBH herd population and habitat usage to the detriment of recovery efforts. Inadequate management adds years to achieving recovery goals, and each year comes at the expense of taxpayers. It is not illegal to take a lion when using the correct channels, (yet valid requests are increasingly restricted or denied) and the lion population is proving itself to be healthy, thriving, and increasing. In cases where lions are documented sheep killers/repeat offenders and prey exclusively on a federally listed endangered species, it would stand to reason that the opposition, wherever it may stem from, to remove abundant and habituated lions with depredation permits may arise from social and political influence rather than scientific and anecdotal evidence. Governor Gavin Newsom’s late father, William Newsom, a state appeals court judge and member of Earthjustice’s Board of Trustees, helped establish the national nonprofit Mountain Lion Foundation, who’s vision “requires humans to respect and trust, not fear, lions in proximity.” In 2019 the MLF, along with the Center for Biological Diversity, petitioned to have lions in the “evolutionary significant unit” of Southern and the Central Coast of California listed as a candidate Endangered species. Lions are currently relocated out of the Sierra Nevada range to Southern California, which helps to enhance genetic diversity and bolster the population of SoCal lions. If this listing goes through, the population supply up north would be even more strictly regulated and create more limitations and restrictions for those trying to protect the sheep, not to mention other favorable prey species such as deer. Mule deer populations face challenging conditions as it is without the survival threat that would result from increased lion predation.

Lions and Sheep and…Bears?

Though there has not yet been formal legislation brought forward to outlaw depredation permits altogether, the current situation with the lions is reminiscent of the attempts made the past two years to ban bear hunting. Common sense has prevailed for the present and the bear ban has failed to be passed into law, which is good news for the sheep. If there were an increase in the bear population due to a ban on hunting, there would likely be a corresponding decline in prey populations such as sheep and deer. Since bear habitat is known to overlap with lion and sheep habitat, as bears proliferate lions are then forced to kill more prey, including sheep, due to kleptoparasitism.

Decades of effort has gone into ensuring the viability of both the lion and sheep populations. Biologists, field workers, experts, and policy makers have worked very hard to ensure each species has had representation in public discourse and policy. There is no easy answer, but there are hard lessons that have been learned which shouldn’t be ignored, and there are options which make sense despite not being politically palatable to some. There is also very concrete data which should be used to educate the public to the danger of lions once they become habituated to a particular prey. Co-existing with wildlife is a process we must continuously work to perfect, though it can’t be perfected if we’re unwilling to separate emotion from natural biological processes. It is still possible for the SNBS to recover and for both species to thrive, but in order for decades of hard work to count for something we must understand our role and carry out the responsibilities the role bestows upon us.

Photo courtesy of California Department of Fish & Wildlife

Learn more about Sierra Nevada bighorn sheep.