Desert tortoise troubles blamed on ravens, other large birds

Desert tortoise troubles blamed on ravens, other large birds

Harry Pappas remembers the jaw-dropping sight that proved predators were putting a dent in wild desert tortoise populations.“Two wildlife biologists from California walked in,” he said, recalling a citizens panel meeting in Las Vegas in the 1980s. “They had a couple Hefty trash bags — the big, 45-gallon size — and they were full of shells from baby tortoises, pecked to death by ravens.”

Looking back after 30 years of state, federal and local governments grappling with desert tortoise issues in Southern Nevada, Pappas said a case can be made that the long-lived reptile might not have been as threatened by human activities, such as development and livestock grazing, as biologists once thought. The numbers didn’t add up, and the real culprits, he perceived, were ravens along with magpies and large birds of prey.

In retrospect, Pappas believes what transpired over those decades until the closure this month of the Desert Tortoise Conservation Center — the so-called “tortoise gulag” where thousands were held in pens and many supposedly sick ones were humanely killed by lethal injection — was a power play by federal agencies to further restrict access to public lands they control, which is the vast majority of acreage in the state. The demise of the tortoise was the vehicle the agencies used to carry out their plan, he said in recent interviews and emails to the Review-Journal.

“Knowing what I do about the Forest Service, BLM, Park Service, U.S. Fish & Wildlife Service … they are consistently doing studies on virtually anything that moves on so-called ‘their land,’ ” he wrote in a Dec. 15 email. “They are consistently studying and monitoring everything from (gnats) to butterflies to polar bears. Virtually anything and everything that walks, crawls, swims or flies on ‘their’ land either has been studied, is being studied or is gonna be studied.”


Pappas had been appointed by Rep. Barbara Vucanovich, R-Nev., in the mid-1980s to represent outdoor sporting interests on the Bureau of Land Management Citizen Advisory Council to provide input on public lands issues affecting Southern Nevada.

This was a few years before the desert tortoise became a federally protected species in 1989 and long before the conservation center was built south of Las Vegas in the 1990s to hold hordes of the reptiles taken from lands targeted for development in the Las Vegas Valley. Thousands of others that had been abandoned as backyard pets also were brought there.

Before some of the last adult tortoises from the conservation center were released into the wild in October at a translocation site 40 miles southwest of Las Vegas, as many as 1,400 had been kept in captivity in 2013.

Driven by the U.S. Fish & Wildlife Service’s finding in 1990 that Mojave range tortoises were threatened but not endangered, as had been declared in the emergency listing, Clark County administrators established a citizens committee to find consensus-based solutions for protecting tortoise habitat in parts of Southern Nevada. This enabled the service to allow tortoises to be “taken,” or collected and taken to the center or a designated sanctuary, or put up for adoption, or simply killed by bulldozers clearing land for urban growth.

From that, a second citizens committee evolved to find ways to protect habitat for many species, not just the tortoise.

Pappas served on both committees until he found out that “truckloads” of tortoises were showing up at the Desert Conservation Center, and it was overflowing to the point that many, particularly those that showed signs of a respiratory disease, were being euthanized.

He wondered if the tortoise was as threatened as biologists had portrayed. If it was nearing its demise, then why wasn’t there more focus on dealing with the raven predator issue? Every time he would bring it up at meetings, he said it would get little attention and the facilitator would quickly move on to the next agenda item.

It seemed to him that the committee didn’t want to let the facts get in the way of their objective: to get beyond the Endangered Species Act mandates so that urban sprawl could continue. “So the questions keep coming back,” Pappas wrote. “Why the cover-up? … Why wasn’t tortoise impact data concerning the enormous predation by the ravens divulged to the committees and the public? Why was it given insignificant concern and only passing mention?” he asked. “How could the Vegas valley with its massive human impact now, all of a sudden, be producing so many tortoises?”

Biologists said hatchlings and young tortoises in the Mojave range that spans parts of California, Nevada, Utah and Arizona were being gobbled up by predators, primarily ravens, but also by other large birds and animals such as rattlesnakes, foxes, coyotes, even feral dogs. The damaged shells in the bags, however, had been collected from beneath ravens’ nests and areas where they roost.


One biologist in 1983 “had found 136 dead bodies or carcasses of juvenile desert tortoises with evidence of raven predation at the base of fence posts on the perimeter of the Desert Tortoise Natural Area” in California, according to a 100-page study from 2008 that considered ways to deal with problem ravens by trapping them, shooting them, even poisoning them. “Within a 4-year period, 250 juvenile desert tortoise carcasses were located beneath one raven nest in the west Mojave Desert,” the report states.

Human impacts from litter, creation of landfills and water developments in rural desert areas had allowed raven numbers to increase almost unchecked while fences and transmission lines provided perches for their attacks on wild tortoises and on sage grouse nests in Northern and central Nevada. Biologists estimate raven populations have increased 300 percent nationwide in the past 40 years and possibly as much as 600 percent in Nevada.

For that reason, even though ravens are protected by the Migratory Bird Treaty Act of 1918, Nevada holds a U.S. Fish & Wildlife Service permit to kill up to 2,000 ravens per year. In 2012, the state legally killed all but three allowed under the permit.

Because tortoises don’t reproduce until they reach sexual maturity at 12 to 20 years old, it would only be a matter of time, biologists figured, until the rapidly increasing raven population would annihilate young tortoise generations, leaving only those that would die off during their average adult lifespan, which is 25 to 35 years. Some, however, can live in the wild as long as 50 to 70 years. Last week, Mike Senn, U.S. Fish & Wildlife supervisor for Southern Nevada, said biologists believe there are hundreds of thousands of tortoises thriving in the four-state Mojave range. “It’s somewhere around 650,000,” he said.

But the relatively high number of tortoises can be deceptive, considering they are spread over such a large area. If there is only one tortoise per square mile, for example, a breeding adult might have to crawl a relatively long distance just to find a mate. But unlike some other federally protected species such as the Devil’s Hole pupfish, which can be more accurately counted in its small confines, desert tortoises are more difficult to find and count because they are scattered over a wide swath of the Southwest and spend much of their lives in burrows underground. Nevertheless, Senn said raven predation of desert tortoises has been well-known for decades. It varies on a site-by-site basis. “It’s a known threat. Whether it’s more important or less important, that’s going to vary greatly across the landscape,” Senn said. He said respiratory disease was a big factor for listing the desert tortoise for protection “but predation was well known.” “When we write a biological opinion, we include the potential for predators and include a raven management strategy,” said Senn, who has been a federal wildlife biologist in Southern Nevada for 2½ years.

Pappas, however, is convinced that the government’s strategy for treating the downward trend of desert tortoises as a federally protected species missed the mark, particularly when it came to euthanizing tortoises or releasing them into the wild. “Why did they say to the committee when asked, ‘Why don’t (you) release the overflow into the great outdoors?’ They hesitantly, sheepishly, quietly uttered that the great outdoors/wilderness was at ‘carrying capacity.’ Carrying capacity? Did I hear that right? They’re kidding aren’t they?” Pappas wrote.