“Under the aegis of wildlife management, the oxymoron that is now a fact of life for most North American creatures, spins unbounded tinkering, with further tinkering made necessary by past tinkering, effects of causes, effects of causes — a “cascade of consequences” precipitated by human intervention, well intended though it may be.” —Ellen Meloy
San Andres ewe 067 was languishing on a rocky hillside, chewing on tufts of grass when she heard the far-off noise of a chopper. She hated helicopters. She’d already been netted and captured once. That was when she was four years old. The biologists collared, tested and treated her for scabies, a disease that was killing her sheep compadres. During the capture she broke her leg. Although her leg mended, she hadn’t forgotten the noise associated with the trauma. Spotting the helicopter in the distance, she darted uphill into a covey of rocks. The helicopter passed without seeing her.
Before the arrival of the market hunters killing sheep to feed railroad workers and miners, before settlers trailed thousands of sheep into Texas and New Mexico, this eighty-five-mile rib of northward trending rock called the San Andres Mountains was prime habitat for desert bighorn sheep. Biologists describe it as a metapopulation: sheep that travel from one range to another, following fluctuations in weather patterns and forage. The home range of ewe 067, probably held the largest population of desert bighorns in the southern Chihuahuan desert of New Mexico. Unhindered by human interference, sheep connected north through the a desert gap into the Oscura Mountains and southward into the Organ Mountains. With the arrival of livestock that brought disease, overgrazing, and unregulated hunting, the sheep died off. By the 1940s only a small remnant bighorn population lived here.
To save the desert bighorns, the San Andres National Wildlife Refuge was created in1941. Only thirty-three sheep remained, mostly in the southern half of the range. White Sands Missile Range was created in 1945, encompassing the Refuge within 3500 square miles. Seven days later, the first atomic bomb exploded on the northern edge of the military testing site. In a fortuitous quirk of isolation, the Refuge was now surrounded by a huge tract of land, with no public visitation or livestock. The bighorns flourished. The military never used the ground, just the air space, and the sheep eventually habituated to the screeching sounds of jets and missile launches.
By the mid-1960s the herd grew to over 200 sheep. Yet living on an island has its limitations, even with those high levels of protections from human interference. Island populations are subject to genetic drift, disease outbreaks, forage decline and weather changes. Within the next ten years, by 1979 the herd crashed to around eighty animals and kept declining from there. By the time ewe 067 was born in 1989, only about 35 bighorns comprised her herd. The culprit of the crash was determined to be a scabies-mite infestation, its origin a mystery, but the main suspect of transmission was domestic goats and sheep. Scabies causes incessant itching, hair loss, ear drum damage, loss of hearing and upset equilibrium. The scabies left the sheep vulnerable to contagious ecthyma, a viral disease that causes scabby lesions on the mouth and can lead to blindness, lameness, impaired feeding and starvation. This disease complex, if it didn’t kill a sheep outright, predisposes them to death by other causes such as predation, bacterial infections, falls from precipices.
Now in the winter of 1996, seven year old ewe 067 ran for cover from the helicopter. Meanwhile, two other choppers were also surveying the Refuge. In 15 hours of survey time, not one sheep was observed. The following year the concerted effort was repeated, but this time 067 was on a naked bluff. She was captured, collared and treated for scabies. San Andres ewe 067, the lone remaining native desert bighorn in the Chihuahuan desert, now became known nationwide as “the last ewe.”
067 was born on an isolated protected perch with a wide view. Her mother probably sought out rugged terrain for protection from lions, eagles and coyotes. As the ewe dropped her newborn, an intensive study on mountain lions was taking place within her home range. From 1986 through 1996, Kenneth Logan and Linda Sweanor collared, followed, and documented mountain lions in the Refuge. Bighorn sheep had been listed by the state of New Mexico as endangered in 1980, so although their focus was mountain lions, they agreed to include sheep predation monitoring as well. During the years of the study, the mule deer thrived, so lion kills were mostly opportunistic and compensatory. Of forty-three collared sheep during their ten year tenure, twenty-six died, ten from lion kills. Yet after the study was completed, the mule deer population crashed, and mountain lions were hunting farther and wider for food. With the added predation, along with a small, weakened diseased population, all the sheep disappeared.
All but our last ewe. Ewe 067 watched sheep around her drop, get eaten by lions, or fall off cliffs while she found safe areas to forage. For two years 067 lived alone. For a herd animal, she must have become extra vigilant. Ewes in particular like to live high, combing for good escape habitat, a survival instinct honed to protect their lambs. Sheep have excellent vision. Even at ten years of age, hers must have been highly acute.
Ewe 067 never had much luck with humans. Now easily located with a telemetry collar, during her third capture in 1999 she was placed in a paddock by a guzzler for a week. Bashing her horns against the enclosure, she broke one off.
Possibly 067’s luck with humans was about to change. New Mexico Game and Fish was beginning a new bighorn sheep transplant program. The Refuge with its historical evidence of a large herd of sheep was on its radar to be next. Yet the scabies transmission was scaring them. How was it communicated—did it stay in the soil? Was it through direct contact? A test was devised to see if the Refuge was safe. The NMDGF brought in six “Sentinel” rams in 1999 from Red Rock Wildlife Refuge, a 1,250-acre fenced enclosure in southwest New Mexico where they were raising bighorn sheep for seed stock. The rams were sprinkled on various ranges, used as canary-in-the-coal-mine sheep. They waited two years to see if they died. When all the Sentinels lived, additional transplants were brought in from Red Rock, along with sheep from the Kofa National Wildlife Refuge in Arizona. Between 2001 and 2005, fifty more sheep were brought in from Kofa along with a few more from Red Rock.
Three years after her capture in the paddock, 067 was spotted with a lamb. One of the Sentinel rams had found her. At thirteen, this feisty survivor had birthed again. She beat scabies, lions, capture, and the terrible fate of aloneness for a herd animal dependent on others.
______________________
“Hintza, come!” I’m keeping my ten-month-old golden retriever close. We’re walking dry washes in the southern New Mexico Chihuahuan desert, looking for mule deer, and I just spotted some javelinas on a nearby scrubby slope. Javelinas don’t like dogs and have been known to kill them. Really, Lindsay Smythe, my hiking partner, is doing most of the work. I’m just tagging along, holding my recorder out, navigating around creosote bushes and rocky terrain trying to keep up and corral the pup. Smythe is the San Andres Wildlife Refuge manager, here helping her friend and fellow lead biologist Ron Thompson on this four-day project. Smythe points out what javelina scat looks like. “Kind of like cattle droppings.” It’s everywhere now that I recognize it. Seeing Hintza, the javelinas deposit some fresh scat to confirm.
I was invited to spend a few days on Ted Turner’s Armendaris Ranch with a small team of biologists as they completed an annual deer survey. The Armendaris, a desert property bordering the Rio Grande by Elephant Butte Reservoir, is over 350 acres of untouched land Turner has reserved for wildlife. It’s impressive and vast private land that stretches across the desert basin east to the San Andres, encompassing the Jornada del Muerto, a name given to the basin by the Spanish for its waterless expanse. The Fra Cristobal mountains hug the reservoir and western edge of the basin. They’re a small range, not terribly high, but their classic crags and high mesas are good sheep habitat, though it’s debatable whether they ever held sheep historically. Looking east, the San Andres appear far in the distance, a long wall of mountains. To the south, much closer, lie the less formidable Caballo mountains, shrouded in clouds suspended above the desert floor.
I’m actually here at the invitation of Ron Thompson, big cat biologist. These days Thompson mainly spends his time on jaguars in Mexico as president of the Primero Conservation nonprofit. But he still continues his contract work for the Turner Endangered Species Fund. He helped restore these bighorn sheep and continues research here on adaptive mountain lion management strategies, his most recent being water. It was through his work collaring lions on the Kofa that he met Smythe.
Deer, being the primary lion food, it’s important to keep tabs on how they are doing with an annual study. Deer health bodes well for sheep longevity. The summer of 2020 was especially hard on all wildlife. The monsoons never arrived. Thompson tells me forage on the ranch is in poor shape.
“The habitat is private land and so the ranch manager is responsible for maintaining healthy habitat. It’s not healthy now. We’re in a drought and the main browse component is way overused. I’m telling him your plants are dying. And the deer are declining because of the competition.”
Thompson points me to a nearby hillside where a series of lines demarcate the slope.
“That’s from desert sheep going back and forth. That used to be all grass. It’s been denuded. All been eaten and the sheep aren’t there anymore. Those are the visual impacts I’ve seen in twenty years of being here. But you can’t just come here, look at the mountain, and say, where are the sheep. They’re here and they continue to have an impact.”
Thompson says the deer fawn recruitment is down 10%. That’s why he’s brought this small team to comb, section by section, the Fra Cristobal range. Today, Smythe and I observe one buck, one set of coyote tracks, and several dozen javelina. The sheep are higher up so we don’t expect to see them on this route. Smythe tells me the lower area of the mountain is poor deer country so she’s not surprised at our limited success.
Smythe is the perfect person to discuss sheep and lions with. She’s been the sole biologist and manager of the Refuge for two years. Before that she worked at Kofa National Wildlife Refuge in Arizona, and at the Desert National Wildlife Refuge (DNWR) near Las Vegas, another sheep refuge surrounded by Nellis Airforce base. Kofa is the main supplier of desert bighorn transplants for Arizona with currently over 900 sheep. The DNWR has 900 sheep.
Kofa National Wildlife Refuge had a precipitous drop in their sheep population in the early 2000s, from over 800 animals to 400. This was before any awareness of Mycoplasma ovipneumoniae. Since Kofa was providing the majority of the sheep transplants throughout Arizona, alarm bells went off. Meanwhile, for years Kofa had been developing more and more artificial water sources specifically for sheep. In fact, the increase was phenomenal. Arizona had 750 managed waters in 1997 for wildlife. By 2019, the state was managing over 3,000. It was through trail cameras set at water developments in the Kofa that managers noticed an increase of mountain lions.
“In that portion of the state, southwestern Arizona, it had very low to no mountain lions historically. A mountain lion might come through, be seen, but it wasn’t a regular occurrence.” Amber Munig, big game program management supervisor for Arizona Game and Fish tells me.
“And we had relatively no mountain lion harvests in that portion of the state for decades. We started to see mountain lions in there, and at one point we had over 14 mountain lions within the Kofa complex itself.”
Arizona Game and Fish sprang into action. Sensitive to public opinion, the Agency created a mountain lion predation management plan. They collared sheep and every mountain lion they could snare. The policy said that if a mountain lion killed two sheep within a six-month period, that lion was removed. If it only killed one, it was left alone, or if it was two outside of the six months, then it went free.
“We had this very strict approach for dealing with mountain lions killing bighorn sheep.” Munig says.
Smythe’s employment from 2005 through 2011 at the Kofa coincided with the sheep drop. She helped push for control limits in their management plan. The idea was the plan would target any lions that showed a clear affinity for killing sheep.
“My opinion is that a lot of the declines (at Kofa) attributed to predation—the real root cause was disease. For a long time we weren’t testing for it at all. When I was at Kofa we had six mountain lions collared, and there were definitely some males that killed a lot of sheep. There was one that killed six sheep within the span of a few months. But the problem is every time you had a mountain lion kill sheep, it was killed. No one has ever left mountain lions collared long enough to really understand the interaction very well. Everybody starts panicking, and that’s what happened in our lion study at Kofa.”
Smythe explains that “the intent was to kill offending lions that had really learned how to target bighorn sheep. But it turned out that all the lions met that criteria very quickly and so they ended up killing all of them.” It’s the rare mountain lion that actually shows a clear preference for one prey or another. Usually, it’s an opportunistic kill while hunting for their preferred prey, deer. In Logan and Sweanor’s study only one lion in ten years demonstrated a clear affinity for sheep. He was removed.
Kofa’s predation management plan area was vast. The borders were delineated at highway 35 to the east, i-10 to the north, i-8 as the southern boundary, and west to the California border. The argument was “you can’t just kill lions in the mountain range because lions migrate in from other places.” So dispersers were killed too. Because it takes ten to fifteen years for a herd to rebound from a disease epidemic, it might have eventually cycled out of the infection on its own. It may have happened faster with lion removal, but, as Smythe reiterates, “the problem is they never do research. Everybody starts to panic and the lions always end up losing.”
The Plan did have a shut off valve. When the population reached 800, mountain lion killing would end. In 2019 that target population was reached, with over 900 animals in the Kofa, thus ending lion culling, a good fifteen years since the plan’s inception. The AZGF is still monitoring the collared lions for data purposes, but there is no longer removal of lions.
As we circle around an enormous obstacle of prickly pear cactus, Smythe argues that if every lion is killed in a treatment area, “they have no way of knowing if that’s what caused the rebound or not.”
Smythe reminds me that in 2002, twenty sheep were imported into San Andres from the Kofa herd, and another thirty in 2005.
“We know the Kofa decline was caused by disease because when they transplanted the bighorns from Kofa to San Andres, they all came down with Mycoplasma. When we tested them, we strain-typed it, and it’s the same strain. It is the Kofa strain that killed my sheep. All these declines that we’ve had were more than likely disease. Predation may have compounded that.”
Lions, like wolves, are good at sensing the weak and sick in a herd. Compromised animals are easier prey than healthy. An entire herd of sick animals may be like an open market for a lion.
Smythe feels the models for sheep management may be in the San Andres and Desert National Wildlife Refuge. The DNWR has never had lion management, yet they’ve also had deep disease dips along with rebounds. The San Andres did have a period of state lion controls when the animals were listed as state endangered and reintroduced into the Refuge in the 2000s. An environmental assessment was done and offending lions were to be removed. Over a ten year period around thirty lions were culled. But that plan sunsetted and there hasn’t been any active lion removal since. With the last visual aerial count at 170 animals, the Refuge population is doing fine, probably around carrying capacity.
Smythe’s recount of no testing going on during the Kofa decline is accurate. Arizona came particularly late into the disease monitoring game, probably starting only eight years ago. Yet during the early 2000s this was the situation throughout the West. Sheep biologists had been chasing sheep diseases for decades, but the science wasn’t there yet. Everything was cultured, which is unreliable for identifying and differentiating finicky pathogens.
“We were clueless,” Mike Cox of Nevada Department of Wildlife told me. “We didn’t want to be clueless but we didn’t have the science behind it. We didn’t have any money. Nobody cared. There’re no huge grants working on bighorns. We were blind of what was really causing the issue, just a lot of ideas and theories…It was a big circle-jerk for decades.”
In 2009, more than 2,000 bighorn died throughout the Western states.
“No one understood what was going on. People were thinking it was sunspots,” Cox told me, joking to emphasize how blindsided sheep biologists were.
Finally, a breakthrough occurred in the lab. Thomas Besser, a clinical veterinarian pathologist from Washington State University along with a few others, were able to isolate and identify the ringleader of sheep bacteria, Mycoplasma ovipneumoniae. Although there are several other bacteria living dormant in sheep, with their defense mechanisms intact, they can fight those off. But Mycoplasma destroys those immunities.
All this was happening sight unseen in the Kofa sheep die-off in the early 2000s. Now, in retrospect, game agencies can look back and see the real culprit.
Amber Munig pieced it out for me. “What we believe happened is that we had a disease episode that went through the Kofas which affected lamb recruitment and probably an all age class die-off. At the same time, we were seeing some expansion of mountain lions, some from south and some from east. We don’t know exactly why. Our deer and javelina populations were relatively stable at that time.”
“We had predation increasing, something we hadn’t had in the past for this population, occurring when the population was depressed. With our predation management and time allowing animals to clear any pathogens that were holding on within the population, it allowed for that population to recover. I think it was a combination of time and our very focused effort to not allow predation to keep suppressing that population.”
Yet the question still remains as to why the lion population in the Kofa complex increased from almost zero to fourteen animals. Ron Thompson has thoughts on the answer. Along with several other researchers, Thompson conducted a simple, yet elegant long-term study placing camera traps at water catchments spanning all three southwest deserts—Mohave, Sonoran, and Chihuahuan—including traps in the Kofa. Using data collected over years, the study revealed bighorn sheep using water catchments at limited times of the year, specifically the driest, hottest season. In the Sonoran Desert, where the Kofa traps were located, 85% of all desert bighorn sheep visits occurred during May through August. Bighorns have been evolutionarily adapted to get their water from their food. In the winter, they can kick barrel cacti over and chew the pulp. Predators on the other hand, need year-round water sources. Thompson found “desert bighorn sheep concentrated their visits to water within 4-5 summer months across all 3 deserts. Mountain lions visited water year-round in the Chihuahuan and Mojave deserts, and generally year-round in the Sonoran.”
The research concluded that “managed waters allow populations of desert bighorn sheep to inhabit areas they previously had not. Indeed, this outcome forms justification of managing waters for desert bighorn sheep. It follows that managed waters could enable mountain lions to inhabit locations they previously had not…”
Thompson reminds me to “keep this association in mind”—the increase in the number of photos of lions at water developments in the Kofa. “That,” meaning the lion numbers increase he says, “was suspected as the smoking gun cause for the decline.”
Day two of the mule deer survey I’m out on my own with Hintza. I suppose the researchers feel I’ve gotten the hang of walking and looking for deer. I’m combing a long wide wash that runs through a deep ravine. Two others are hiking the high ridges above. I’m assigned to not only look for deer, but scout for lion tracks. Before I set out, Thompson checked a trail camera located on a water source pinch point here. No lions had come by.
Although it hasn’t rained for weeks, maybe months, a tiny spring emerges through the rough rocks to fill a sandy hole. Hintza gets to quench his thirst. I see javelina tracks everywhere along the sandy bottoms. They resemble small versions of deer tracks set closer together in stride. A few deer tracks but none in the flesh appear. A large lizard suns itself on the hot rocks.
The canyon is stark and beautiful, with gleaming bare stone along the base, sparse desert plants as the hillsides rise steeply above. I’m a plantofile, though unfamiliar with New Mexico, I don’t know many of these plants. I pause to admire a Dasylirion as it is unfurling. Sometimes mistaken for a yucca but they are unrelated. I know it from my days as a landscape designer in Northern California.
At one point I spot Thompson’s son who is assisting with the study. A small speck walking along the high rims, sky lining like a bighorn sheep. The canyon opens and ends at a water development with a rough dirt road leading to it. My assignment is to keep walking up the road and connect to another dirt road where we’ll all meet. As I’ve heard so much about water catchments during my time in the southwest, I spend time studying how this one works.
Unfortunately, for the bighorn, the story does not end with water developments, predator controls, or the recent uncovering of Mycoplasma as their vulnerability to respiratory infection. The beat goes on and we just do not know how to stop it.
Thompson told me over last night’s dinner how he has applied the data from his research. The idea was to allow sheep and deer to drink, but not lions. Sheep and deer have narrow faces, lions have round faces. Those face measurements are known to any researcher. But how long is a lion’s tongue? A key question for a cat that can lap through bars. Since Thompson spends lots of time capturing and collaring lions, it was just one additional measurement. The design he came up with was a trough with pipe laid vertically just wide enough for a lean sheep nose, and water depth just below a lion’s tongue reach. Water for thirsty deer and sheep, yet a deterrent for lions in waterless country. If water isn’t available, lions and other predators will have to search far and wide, leaving the sheep, who are less water-dependent, alone.
That predators kill prey is the simplest of biological equivalents, known to any high-schooler. But the intricate dance of nature is a puzzle that humans have difficulty teasing out even absent our interference. Yet nature has been so tinkered with, trampled on, and altered by humans, that when one adds our own unintended consequences to the fluidity of natural factors like climate, habitat, and disease, sorting out cause becomes a veritable soup. To save an animal from extinction, we now find it necessary to trade wildness for rescue interventions.
_____________
There’s so much more to this story. Stay tuned for Part III
Filed under: New ideas | Tagged: Bighorn Sheep, Cougars, Kofa National Wildlife Refuge, Pumas, San Andres National Wildlife Refuge | Leave a comment »
Leslie Patten Books: Wild Places, Sacred Spaces 