It's 20,000 years ago, the Pleistocene Epoch. A desert tortoise emerges from its burrow in shrinking swamplands around Tule Springs and ambles down to a pond to drink. Off in the distance, Columbian mammoths are foraging, their curved, 16-foot-long tusks waving ominously. A dire wolf, made famous in Game of Thrones but smaller in real life, suddenly pounces on the tortoise from behind, its massive jaws crushing the shell in a single bite.
Mojave desert tortoises (Gopherus agassizii) are the state reptile of both Nevada and California. They have remained essentially unchanged for three to five million years, says wildlife biologist Kristin Berry of the U.S. Geological Survey (USGS). Their turtle ancestors date back to the late Triassic Period, some 220 million years ago, and tortoises diverged from them about 55 million years ago. In their long evolutionary history, turtles and tortoises have survived mass extinctions, the last ice age, and, most recently, desertification of the American Southwest, all by exploiting remarkable adaptations such as recycling precious water stored in their bladder. The late expert Glenn Rogers of the Nuwuvi (Shivwits Band of Southern Paiutes) in southwestern Utah called them “warriors,” because they are such fierce survivors.
Yet in the last century, especially the last 50 years, the number of Mojave desert tortoises has dwindled by a sobering 90 percent. Consequently, they are now deemed “critically endangered” by the International Union for Conservation of Nature (IUCN) and “threatened” by the U.S. Fish and Wildlife Service (USFWS). In December 2002, the General Accounting Office reported that the federal government has spent more than $100 million on desert tortoise recovery since it was listed in 1980. The exact investment is unknown.
Nonetheless, their losses are accelerating, and the desert tortoise appears to be quickly spiraling to extinction after millions of years on the planet. How has it come to this? What is being done about it? And why should we care?
The balance tips
Present day, in the Mojave Desert. Scooter has spent more than 90 percent of her life in the deep, desert burrow that she excavated beneath a large creosote bush with her powerful forelegs and claws, allowing her to escape the scorching heat of the summer, the freezing air in the winter, and predators. She permits other tortoises, kangaroo rats, rabbits, and birds to share it with her — every animal but the Gila monster that made relentless attempts to eat her eggs before she drove it off. Her life is about to change dramatically.
Desert tortoises can live 80-100 years in captivity, but in today’s environment, females in the wild are lucky if they survive long enough to become sexually mature at 15-21 years old.
Most of the direct causes for tortoise death are human in origin (anthropogenic) and lead to degradation, fragmentation, or complete loss of habitat: renewable energy projects, transportation and utility corridors, mining, livestock grazing, military activities, urban and agricultural development, vehicle recreation, roads, arson, and campfires. Then there are attacks on the tortoises themselves: poaching, disease, predation, even death from gunshot wounds and deliberate vehicular collisions. Predators such as coyotes, badgers, rodents, and eagles have been ecologically balanced with tortoises for centuries. But since the 1970s, that balance has tipped in favor of ravens and coyotes.
The indirect causes of tortoise decline from starvation and dehydration can be traced to climate change with increased periods of drought, record-high temperatures, and fires caused by lightning strikes. Invasive plant species without nutritional value quickly seed in after fires and habitat disturbance on construction sites, only to become tinderboxes for subsequent fires. For an animal with low mobility and a limited home range such as the tortoise, it all combines to create a perfect storm for rapid extinction.
The desert tortoise has been called a keystone species because it plays a pivotal role in providing burrows for other animals — rodents such as kangaroo rats, lizards (even those Gila monsters), snakes, burrowing owls, rabbits, other tortoises. Nature’s network of relationships is more complex, wondrous, and delicate than we can comprehend. Much remains invisible to the naked eye, such as the organisms in the desert crust that bind the soil, which in turn provides nutrition for plants that harbor and feed wildlife.
Removing one species makes another domino fall, then another; bulldozing thousands of acres for a solar project causes an immediate chain reaction, in a few days wiping out vast biological, interconnected communities that have evolved over millions of years and can take centuries to recover.
“The desert tortoise and the pupfish (another endangered species) may not seem like consequential things,” says Patrick Donnelly, Great Basin director of the Center for Biological Diversity. “But together they are what make life on Earth possible. If we let these species go extinct one by one, we are truly jeopardizing our own existence.”
In Aesop’s fable, the tortoise reached the finish line first while the haughty hare napped, but in this present race, developers won’t sleep. They’re heeding both federal mandates for expanding renewable sources of energy and the constant demand for more housing and commerce in the desert Southwest.
Fortunately for Scooter’s kind, many government and grassroots groups are working to save them and their habitat — 20-plus scientists and agency officials talked to Desert Companion for this story. While their ingenuity and passion are clear, so are the challenges they face.
Here comes the sun
Scooter never got the memo, the eviction notice. She hears human voices above her burrow, followed by the sound of shovels striking the centuries-old biocrust, teeming with living organisms. The blades come down only inches from Scooter’s shell as the soil around her flies in all directions. She retreats farther into her shell.
The Mojave Desert stretches over 20 million acres from southeast California and southern Nevada to northwest Arizona and southwest Utah, and receives almost twice as many sunlight hours as the rest of the country. So, it’s no surprise that developers have targeted it for renewable energy sources — chiefly solar but also wind, hydroelectric, geothermal, and biomass. Solar thermal power plants (so-called “farms”) first sprang up in the 1980s.
Open since 2014, the Ivanpah Solar Electric Generating System near Primm, is the world’s largest concentrating power facility, according to the Department of Energy. BrightSource Energy spent $2.2 billion building its three blazing 459-foot solar towers, familiar landmarks to I-15 travelers between Las Vegas and L.A. In compliance with the Endangered Species Act, which took effect in 1973, BrightSource spent more than $56 million to translocate the sizable tortoise population on the site and install 50 miles of tortoise-exclusion fencing. (Birds are not so lucky. In September 2016, federal biologists reported that about 6,000 birds die annually while chasing insects through the area, from either collisions with mirrors or immolation in temperatures as high as 1000°F.)
According to Nevada’s 2022 Status of Energy Report, the state has 45 operational solar sites, almost all of them photovoltaic (PV) power stations, rather than solar thermal like Ivanpah. Arrays of PV cells, more bird-friendly, produce direct current electricity, which is then converted on-site to alternating current for electricity grids. Nevada has more than tripled its renewable energy production since 2011 and is aiming for 50 percent of its total energy coming from renewables by 2030.
Other states with regions of the Mojave Desert have similar ambitions. California has set targets of 60 percent by 2030 and 100 percent by 2045. In collaboration with Rocky Mountain Power, 23 Utah communities, including Salt Lake City, have a goal of net-100 percent renewable energy by 2030. Arizona’s three largest utility companies are working toward 90-100 percent renewables by 2050. With the 2020 Energy Act and President Joe Biden’s 2021 Executive Order Tackling the Climate Crisis, the Bureau of Land Management, or BLM, plans to accelerate the permitting process to streamline renewable energy development and meet the target of 25 gigawatts of solar, wind, and geothermal energy production on public lands by 2025.
Responding to written questions, staff from the BLM Southern Nevada District told Desert Companion through spokesperson Kirsten Cannon that there are currently 33 pending applications for utility-scale solar projects and four applications for wind energy exploration. At the same time, however, Nevada’s Public Utilities Commission (PUC) website lists 101 applications for solar and wind projects, not counting separate applications for generation-intertie (“gen-tie”) lines that connect solar projects to substations on the electrical grid. The BLM had no explanation for the threefold discrepancy other than to say that “the BLM doesn’t manage the Nevada Public Utilities website.”
In any case, almost half of the proposals are in tortoise habitat in Clark and Nye Counties. Aiming to minimize and mitigate the inevitable environmental impacts to wildlife and habitats, the BLM does communicate with other agencies and Tribal governments. It also solicits comments (but not questions) about proposed solar projects at public scopings. Armed rangers from the Department of the Interior are routinely present at these events, an unsettling sign of the superheated emotions that can bubble up during such meetings.
Voices in Opposition
In June, the BLM held three scopings — two in-person and one virtual — for the Bonanza Solar Project, proposed five miles west of Indian Springs. As designed, it would cover 2,500 acres between U.S. Route 95 and a utility corridor to the south. Ironwood Consulting estimated 50 adult and juvenile tortoises on the site in January 2022, but judging from the number of active burrows they reported there, that is probably an underestimate. Consultants estimated 53 for the 3,000-acre Yellow Pine Solar Project southeast of Pahrump in Clark County, but there turned out to be three times that number, says Kevin Emmerich. He and Laura Cunningham founded Basin and Range Watch in 2008 as an informal volunteer group with a science-based approach to conserving the Mojave Desert and educating people on the federal public lands development process.
“Kevin and Laura fill a vital role in the nonprofit ecosystems that work on desert issues,” Donnelly says.
Emmerich, a biologist and former National Park Service Ranger, and Cunningham, a paleontologist and former U.S. Fish and Wildlife Service (USFWS) and U.S. Geological Survey employee, have always had an abiding love for nature and natural history. They’ve been active proponents of placing solar arrays on rooftops, parking lots, along highways, and land already stripped for mines, rather than in undisturbed desert.
Donnelly agrees with them wholeheartedly, as do other conservationists. Kenneth Nussear, a University of Nevada, Reno, geology professor and longtime tortoise researcher, suggests solar panels could be placed along I-15 in Nevada and California instead of undisturbed desert habitats. Ed LaRue of the Desert Tortoise Council submitted extensive comments on the proposed Bonanza Solar Project, among them a mention of L.A.’s successful Feed-in Tariff program, which enables owners of large buildings with rooftop solar panels to sell the power generated back to utilities for distribution into the power grid. “This approach puts the generation of electricity where the demand is greatest, in populated areas,” he says, thereby lowering costs and reducing greenhouse gas emissions during construction.
When asked what they thought of such alternatives to developing undisturbed desert habitat, the BLM succinctly replied that it does not fall within their jurisdiction. Local and state governments have yet to take up the issue, putting the onus on private and commercial interests.
Professor Rebecca Hernandez and her colleagues at UC Davis have pinpointed several large commercial and aircraft assembly plants, such as the Boeing Everett Factory and Lockheed Martin, that would be ideal sites for solar panels. Her team has calculated that panels atop Lockheed buildings alone, equivalent to 400 acres, could produce 55 megawatts of solar energy. USGS research ecologist Todd Esque asks why Walmarts and Costcos couldn’t have covered parking lots (with rooftop solar). “We’d be the happiest people in the world if we didn’t have to get into a car that is 150 degrees every day,” he adds.
“The idea of using rooftop surfaces for siting our power plants is logical. It makes sense, especially when we think about meeting our goals for climate-change mitigation,” Hernandez says. More importantly she adds, it would protect important ecosystems, such as deserts.
Moving Day
Gloved hands lift Scooter from the excavation and place her in a crate. She travels with 10 other tortoises across a fenced road and miles from the future solar energy facility site. She wonders what is happening and sees little from the safety of her shell.
Beginning in the early 1880s, people captured tortoises for pets and food, a practice that intensified in the 1930s and 1940s. They collected not only desert tortoises, but also non-native species, such as the Russian tortoise. The USGS’s Berry says this resulted in a genetic “cesspool” that gave rise to an upper respiratory tract disease called mycoplasmosis, caused by the bacterium Mycoplasma agassizii. Owners surrendered hundreds of sick tortoises with runny noses to local humane societies, which passed them on to fish and wildlife departments in California, Nevada, and Utah in the 1960s and 1970s.
“The state agencies then released them throughout the Mojave Desert close to interstates or paved highways, often a mile or two off the road. There was no thought or concern for conservation,” Berry says. Quite the contrary. Such releases spread the fatal respiratory disease throughout the western Mojave Desert, killing thousands of tortoises, adding to the ensuing, inevitable roadkills.
Here in Nevada, some of the first documented releases of captive tortoises occurred in 1973, with hundreds more in the late 1970s and early 1980s. The rate slowly diminished after the National Environmental Policy Act (NEPA) of 1970 and Endangered Species Act of 1973. Under the latter, the Mojave Desert tortoise was not federally listed as a threatened species until 1990. The Endangered Species Act required developers to move desert tortoises out of harm’s way and adhere to project-specific translocation plans developed in coordination with the USFWS. Such plans entail huge expenses for health assessments, fencing, building road underpasses, and monitoring.
Translocation is the most commonly used method to mitigate habitat disturbance from human activity. Yet there have been several failures in the past, notably one associated with the expansion of the U.S. Army National Training Center at Fort Irwin in California in 2008. Outfitted with radio-transmitters on their carapace (the upper part of the shell), 158 adult tortoises were transported to four study sites at various distances from the origin. At the end of the experiment more than 10 years later, 28 were found alive, 104 were dead, and 24 were missing. Two had even returned to the training center.
“Adults have great fidelity to their home sites,” Berry says. “In certain habitats, they appear to use local cues (roads, rocks) and may use the skyline of topography.” Numerous scientific studies have also shown that sea turtles, migratory birds, and salmon can follow Earth’s magnetic fields to navigate back to the origin of a displacement — called geomagnetic imprinting — and tortoises might be similarly equipped with magnetoreception. More research is needed to discover how they can find their way home.
As military bases have enlarged their training grounds, tortoises must be moved elsewhere. According to the USFWS’s Five-Year Review of the Mojave Desert Tortoise, 650 adults had to be translocated at Fort Irwin in 2012 from an area of 18,197 acres. Another planned expansion requires their removal from 62,045 acres. Both these translocations have been assigned to 100,000 acres of non-federal land. In 2017, the Department of the Navy needed to extend the training ground of the Marine Corps Air Ground Combat Center at Twentynine Palms, California, so it transferred 1,000 desert tortoises to the Johnson Valley Off-highway Vehicle Recreation Area. To compensate for the loss of habitat, the Navy instituted several conservation initiatives, including tortoise-exclusion fencing and predator monitoring in the new location.
Closer to home, Olivia Curtis and Anna Johnson, natural resource managers of the 99th Civil Engineer Squadron, survey Nellis Air Force Base, Small Arms Range, and the Nevada Test and Training Range every spring and fall — including 800,000 acres of desert tortoise habitat. They record presence of tortoises (living or dead), burrows, tracks, and scat, helped by 16 biologists from the Colorado State University Center for Environmental Management of Military Lands. They also interact with the BLM, USFWS, USGS, Nevada Department of Wildlife, Desert National Wildlife Refuge, and 17 Tribes.
According to Curtis, the current tortoise population density in the area is only 13 per square mile. “The persistent drought is really taking a toll,” she says. If they find a large population, they recommend that the Air Force not develop in that area or, if it does, add fences to keep tortoises out. Translocations are rarely needed, Johnson says, but when they are, they do not exceed a distance of 100 feet.
A more current, long-term translocation study spanning 10 years was done by the Geological Survey’s Esque and colleagues, who used blood samples, radio-telemetry, and GPS recorders to learn how constrictions in habitat affected the movements and genetics of desert tortoises. They were surprised to find that one male at one site was dominant in producing progeny. Robert Fleischer of the Smithsonian’s National Zoo and Conservation Biology Institute found the same phenomenon along the southern boundary of the training center at Fort Irwin. Resident females preferred to mate with prior residents rather than translocated males, and resident males outcompete “newbie” males for access to females during the breeding season. So, even if translocations might seem successful in the short term, they could lead to less genetic variation and fitness in the long term. Still, they “are one of the few remaining options for re-establishing lost populations and reconnecting fragmented ones,” says Tracey Tuberville of the University of Georgia’s Savannah River Ecology Laboratory.
The fact is, little is known about the long-term success of translocations, because they involve studies of 10 years or more, straining finances and staffing. “We really don’t know what kinds of habitats are suitable for tortoises,” Berry says. “There are differences between translocating juveniles or small tortoises and translocating (large) adults. And there are vast differences between a long-distance translocation and a short-distance one, like outside a fence.”
Roads to ruin
The car stops moving. Those same gloved hands lift Scooter from the crate and set her down in unfamiliar territory. Some minutes later, after the humans depart, she pokes her head out and looks around. Her first priority is to return to her home range to protect her eggs from that Gila monster. She trudges back and forth along the fence in triple-digit temperatures, pushing against it here and there, trying to find or make an opening to cross the road again. The searing heat radiating from the road raises her body temperature to dangerous levels.
Roads, transportation corridors, and transmission corridors, which are associated with renewable energy developments and military facilities, exert both direct and indirect impacts on tortoises and other wildlife. When tortoises cross a road, they often remain on it in colder weather to warm their bodies. They view approaching vehicles as a threat and, rather than pull themselves off the pavement, withdraw into their shells. Drivers may swerve to avoid them but more often than not see them too late or even crush them intentionally. They may also stop to let the tortoises pass, move them off the road, or illegally collect them.
Paved roads and highways facilitate poaching, predation, and the spread of invasive plant species. Pollutants released from the asphalt as gases and/or run-off contain oil, metals, and rust, contaminate the soil, and are absorbed by plant roots. Tortoises are next in the food chain. Plant diversity is often greater along roadsides where water collects, which encourages burrowing and foraging and often leads to vehicular fatalities. Off-road traffic collapses burrows and raises dust that causes erosion and kills surrounding vegetation.
All these factors fragment the habitat and alter tortoises’ movements, contributing to a loss of connectivity and gene flow, which could result in localized extinction. “If you go to the west Mojave Desert — Apple Valley, Victorville — you’ll still see tracts of undeveloped desert because the area is so fragmented, the connectivity is so cut off, it’s so inundated with invasive weeds, and there are so many ravens that you don’t find tortoises,” Emmerich says. “That’s really the future scenario of Nevada.”
Esque and his colleagues have studied the genetics of the desert tortoise over a 10-year period. “The Ivanpah Valley is where several valleys come together. It is considered one of the key areas for the connectivity of the species,” he says. Running through it and the Mojave National Preserve, crossing from Nevada to California, is the Union Pacific railroad, visible from I-15. “We can see a statistically significant difference in the genetics of the tortoises on one side or the other due to their separation by the railroad,” Esque says.
On a grander scale, gene flow is limited between the Mojave desert tortoise on the west side of the lower Colorado River and the Sonoran desert tortoise (Gopherus morafkai) on the east side, although the former occurs in a handful of populations east of the river along with hybrids between the two species.
Culverts, underpasses, and overpasses offer safe passage across roads for tortoises. That’s the intent, anyway. Cunningham recalls a project on U.S. Route 95 in Clark County, where the developer installed culverts and placed large boulders (rip-rap) in them to stop flash-flooding. The USFWS later inspected the culverts and found dead tortoises wedged between the boulders. The developer was forced to pour in gravel to smooth out the boulder surfaces and allow unimpeded transit.
All these threats help to explain public outcries over proposed roadways and transmission lines, such as the proposed Greenlink North and West Lines that would span more than 700 miles from Las Vegas to Reno and allow for future development of solar, wind, and geothermal projects. The Greenlink West Line would run along a line just inside the boundary of the Tule Springs Fossil Beds National Monument bordering the 95, but the effects would be felt much farther into the national park. Conserve South Utah and several other nonprofit organizations have filed a lawsuit and lobbied the U.S. Congress and the Department of the Interior to prevent construction of the four-lane, 4.5-mile Northern Corridor Highway through Red Cliffs Desert Reserve and National Conservation Area in Washington County, Utah; it supports one of the last high-density populations of the desert tortoise and 20 other endangered, threatened, or sensitive species.
Barrier fencing, consisting of galvanized wire mesh, has been highly effective in preventing tortoise deaths on the roads and highways, at least in the short term. There are thousands of miles of road with tortoise-exclusion fences in Arizona, California, Nevada, and Utah. In Nevada, fencing was installed along about 1,660 kilometers of roads through 2011, but only 43 kilometers since then, according to the USFWS Desert Tortoise Recovery Office.
The Tortoise Group, headed by executive director Sarah Mortimer, sponsors a volunteer force called Road Warriors. These citizen scientists monitor roads for tortoise mortality and look for breaches in fences in specific areas assigned by USFWS and the Nevada Department of Transportation. Fencing has clearly prevented vehicle-wildlife collisions, they say, but unless culverts and other crossings are used, it can also fragment populations, which can be more detrimental than road mortality in the long term.
Starvation diet
Scooter looks along the road for her favorite native plants to eat — Mojave lupine, desert dandelion, dwarf milkvetch, dune primrose — but in this summer drought finds only invasive, non-native grasses, such as red brome and Sahara mustard, that have no nutritional value and lead to water loss and starvation if there’s nothing else to complement them. This is just not her day.
In solar farm construction, the next step after removal of endangered wildlife is bulldozing (“blading”) topsoil, biocrusts, and plant life over large tracts. As of 2021, the BLM set 0.1-1.0 percent limits on new surface disturbance in tortoise conservation areas, but only in California; it is 0.1 percent in the Ivanpah Valley. There are still no such limits in Arizona, Nevada, or Utah according to the BLM, but it notes that it’s working on a revised Solar Programmatic Environmental Impact Statement for 2023 that will update substantial exclusion areas and design features to protect desert tortoises and critical habitat throughout their range. It has also required two utility-scale solar energy projects to retain topography, vegetation, and soils within development areas, which scientists are evaluating to gain insight for future projects.
The most obvious thing eliminated during blading is tortoise food — but there’s also history at stake. Creosote communities can reach thousands of years old. One plant named King Clone in the Mojave Desert goes back about 11,700 years. Joshua trees are sometimes well over a century old. These plants and others, such as catclaw acacia and Mojave yucca, shelter tortoise burrows and provide shade and nutrients to tortoises’ favorite edibles, mostly forbs (non-grass herbaceous plants). In the absence of these, tortoises will eat grasses and Opuntia cacti, such as beavertail and prickly pear.
When developers bulldoze flora, the average time for the full re-establishment of perennial plants is 76 years, says Scott Abella of UNLV’s School of Life Sciences. Various studies estimate that it would take 335 years for a site’s flora to be restored to an undisturbed state.
An almost immediate effect after disturbance, whether by commercial development, fires, or drought, is the appearance of invasive grasses such as red brome and cheatgrass, and Mediterranean grass from Europe and Asia. Some other plants are just as problematic. A single Sahara mustard plant, originally from Africa and the Middle East, can disperse thousands of seeds, which germinate even in drought conditions. All these outcompete native species for nutrients and water.
Even worse, they’re highly flammable and often the first to set seed after fires, so they set in motion a grass/fire cycle, wiping out whole ecosystems over time. Apart from directly causing tortoise mortality by fire, the loss of nutrition and water leads to a slow death by starvation and dehydration. This is especially common among juvenile tortoises, further reducing the breeding population.
The latest USFWS Recovery Plan for the Mojave Population of the Desert Tortoise encompasses several management actions, among them restoring native perennials with nursery-grown plants (“outplanting”) and seeding; improving forage quality and quantity by removing invasive species, and limiting livestock and feral burro grazing; and restoring or conserving soil health by salvaging the upper layer from disturbed sites and then reapplying it, as well as avoiding or remediating soils contaminated with toxins such as mercury and arsenic. Spraying herbicides is an effective control of invasive plants, but “the BLM does not have the manpower to deal with the red brome outbreak, especially in places where there have been numerous fires,” Cunningham says. Instead, land managers themselves are the ones who spray herbicides, or they hire a licensed herbicide applicator, according to the USFWS’s Kristina Drake. Nellis plans to treat more than 6,000 acres of cheatgrass across part of its range to reduce fires caused by lightning strikes.
Abella, his students, and staff at UNLV established eight restoration sites in the Nevada Mojave Desert and set up monitoring at another 18 sites on public lands where the land management agencies conducted restoration activities, such as outplanting nursery-grown, native desert plants. Most of these efforts began in 2006 and initiated a long-term research and monitoring effort. The bet-hedging approaches of applying a mixture of treatments to restore the habitat itself in ways favorable for plants are showing some of the best success, Abella says. Phased plantings and seedings across multiple years to spread out risk also has potential.
Endgame
At twilight, Scooter still has not found shelter and is too dehydrated to dig her own burrow. As she struggles down a wash toward some boulders to spend the night, her motion catches the eye of a hungry coyote. It races toward her, feet barely touching the ground … When day breaks, ravens flock in to scavenge the carcass.
Desert tortoises suffer no shortage of predators in the modern world: coyotes, domestic dogs, kit foxes, badgers, bobcats and mountain lions, eagles and hawks, burrowing owls, ravens, fire ants, and, yes, humans. Some of these also eat tortoise eggs, as do Gila monsters, snakes, skunks, and rodents. By far, though, the most common predators in the Mojave Desert today are coyotes and ravens.
Coyotes’ chief prey are rabbits and rodents such as the kangaroo rat and pocket mouse, but during droughts they will feed opportunistically on tortoises, including those that are disoriented at translocation release sites. Adult female tortoises, juveniles, and hatchlings are particularly vulnerable because they are smaller than adult males, and their shells are therefore easier for coyotes to grasp in their jaws and break. Predation of both genders is higher close to sites of human activity such as fast-food restaurants in desert towns, where there is an ample supply of discarded hamburgers, fries, and water to “subsidize” predators.
Common ravens are intelligent, social, curious, and prolific, making them at least as dangerous to tortoises as coyotes, if not more so. Bill Boarman, formerly with the USGS and now chief scientist at Hardshell Labs, Inc., notes that ravens have been here at least since the late 1800s but in much lower numbers. The population began to increase in the 1960s in the northeast Mojave Desert, and lately in the western Mojave around Barstow, California. Asked how many there are today, he ballparks the number in the tens of thousands, 17 times what they were 40 years ago, primarily because they have been supported by waste, landfills, and artificial water sources. Favored nesting sites are utility poles and billboards.
As the desert has been developed, ravens and coyotes have followed, attracted by easily available food sources in uncovered trash. Empty clamshell takeout boxes can attract ravens within 10 seconds of being dropped on the ground. And ravens are now responsible for 70 percent of juvenile tortoise deaths. Famous tortoise researcher A. Peter Woodman visited a single raven nest in the Mojave Desert over the course of four years and found more than 250 carcasses of juvenile tortoises beneath it in that time span.
What’s being done to stop or reduce this? Boarman and his colleague at Hardshell Labs, Tim Shields, jointly won the USFWS 2002 Theodore Roosevelt Genius Prize for promoting nonlethal human-wildlife conflict, specifically for creating a no-fly zone for nuisance birds. They discovered that ravens are very sensitive to laser light, and whole flocks immediately scatter when exposed to it.
Boarman and Shields created other technological tools such as the Techno-Tort, a booby trap that also frightens ravens. Above ground is a lifelike, 3-D-printed tortoise shell. “I have fooled tortoise biologists with these things,” Shields says. It’s attached to a canister filled with methyl anthranilate, an artificial grape flavoring, and buried below ground level. When a raven touches the shell, it’s sprayed with the solution and immediately flies off. Both the Techno-Tort and lasers are methods of training ravens to avoid tortoises. Researchers have observed a significant reduction in attack rates where the Techno-Tort was deployed.
A third plan of attack is remote egg-oiling in nests, now in wide use in desert tortoise habitats. Application of a thin layer of oil to a bird egg causes the embryo to die — simple in concept, but how to deliver it high up in nests on highway billboards and cell towers? Hardshell developed its Remote Fluid Application System, which is a Go-Pro camera mounted on a telescoping pole that enables coating and monitoring eggs 20-30 feet above the ground. Three utility companies in California currently allow Hardshell Labs to treat raven eggs on transmission towers and distribution poles. Drones can also deliver the oil to nests higher than 30 feet, such as on cliffs and rock faces. Boarman and Shields are working on crowd-sourcing nest locations to expand coverage across the Mojave Desert. It’s “kind of a bizarre version of an Easter egg hunt,” Shields says.
Hope on the horizon
On eviction day, conservation biologists had removed eight eggs from Scooter’s home burrow and carried them off to a laboratory for hatching. Over a year or more, they provided nutritious food and lots of water to the juveniles for rapid growth before releasing them into safe habitats. Scooter’s progeny live on to dig their burrows, feed, mate, and do their best to survive in their rapidly disappearing world.
Headstarting is a conservation technique to raise young, endangered birds, reptiles, and mammals in captivity until they are able to survive in their natural habitats. The goal for desert tortoises is to accelerate growth of hatchlings to make them less vulnerable to predation, specifically to increase their size and harden their shell. Although this won’t guarantee survival if we don’t also correct habitat fragmentation and degradation, and manage subsidized predators, it certainly increases the odds.
Professor Brian Todd in the Department of Wildlife, Fish, and Conservation Biology at the University of California, Davis, has conducted several experiments in headstarting with colleagues including the University of Georgia’s Tuberville and Kurt Buhlmann. After only two years of being raised both indoors and outdoors, juvenile tortoises can grow as large as six- to eight-year-old wild tortoises; within seven months they have reached the size of wild five- or six-year-olds.
Todd and Tuberville help to supervise the Ivanpah Desert Tortoise Research Facility, built 12 years ago in the Mojave National Preserve by Chevron. Staff take X-rays of female tortoises; those with eggs are kept in burrows in protected enclosures for nesting and then returned to their home range afterward. Hatchlings are reared indoors for six to 12 months and fed a diet of chopped chard, dandelion and mustard greens, and tortoise meal supplemented with calcium five times a week. Just as important, they are given unlimited water because their smaller bladders cannot store very much of it at one time; during drought many juveniles in the wild die from desiccation. After indoor rearing, they are moved into outdoor, predator-proof enclosures with native plants and burrows for another six to 12 months before release into the Preserve with a radio-transmitter attached to their carapace so that their movements can be tracked for several years. “We prioritize the (release) sites where we know we can picture the future of those species that we care about,” Tuberville says.
Military bases in the Mojave Desert have collaborated with the USGS, USFWS, and universities in headstarting, fencing, field surveys, predator-control, and/or translocations (sometimes requiring land purchases as mitigation). One of the first and most successful headstart programs began in 2002 at Edwards Air Force Base in California. In 2016, the San Diego Zoo Wildlife Alliance (SDZWA) partnered with Edwards to begin a program there, following procedures similar to Ivanpah’s. Before 2022, hatchlings were raised in predator-proof, outdoor pens at Edwards. They are now transported to the Living Desert Zoo and Garden’s conservation unit in Palm Desert, California, curated by Luis Ramirez, where they’re raised indoors for six months and fed a super-diet. After that, they’re returned to outdoor pens at Edwards. The project there is supported by USFWS with additional funding from the National Science Foundation and the Paul G. Allen Family Foundation (of Microsoft fame).
This fall, 70 tortoises hatched in 2022 were released, and the hatch rate is 89 percent, says Melissa Merrick, SDZWA’s associate director of recovery ecology. The alliance also has a program in predator-avoidance training for young tortoises using 3-D-printed tortoise decoys supplied by Hard Shell Labs.
Meanwhile, the Marine Corps Air Ground Combat Center at Twentynine Palms instituted a headstart project in 2006 at its Tortoise Research and Captive Rearing Site, created in partnership with UCLA. Biologists attach radio-transmitters to tortoises at release for monitoring, followed by population surveys and behavioral observations across the entire tortoise population there. Since its inception, there has been almost 96 percent annual survivorship on site.
A little respect
With the rapid influx of new residents from across the nation to the Southwest, there’s a never-ending need to educate newcomers on the ancient, fragile desert environment, including the desert tortoise. Several organizations take on this daunting task.
One is the Desert Research Institute with campuses in Las Vegas and Reno. Among the many programs it offers is a research immersion program, open to first- and second-year students at Nevada’s state and community colleges and supervised by Meghan Collins. Every fall since 2021, students who may not even be planning a career in science can apply to work one full day or two half-days a week on specific projects in different disciplines, mentored by staff members. This year, Tiffany Pereira, DRI associate research scientist, supervised two students, Akosua Fosu and Amelia Porter. They worked at Tule Springs Fossil Beds National Monument surveying 20 plots for signs of desert tortoises such as tracks, scat, burrows, and tortoises themselves. Their data will be useful in assessing the environmental impact of the proposed Greenlink West Transmission Line through Tule Springs. What they’ve learned about tortoises and science in general made such an impact that one of them wants to pursue veterinary science as a career.
In addition to monitoring roads and fences, the Tortoise Group functions as a broker for rehoming tortoises so they’re not irresponsibly released into the wild. The group gives talks in schools on request, sponsors symposia, and offers after-school and internship programs at the college level. With local veterinarians, it helps to organize free health clinics with microchipping. Volunteers are always needed.
Most Las Vegas residents have heard of Mojave Max. Clark County manages the Desert Tortoise Conservation Program that hosts the annual Mojave Max Emergence Contest, in which elementary school students guess the day, hour, and minute when the celebrity tortoise will emerge from his Springs Preserve burrow after brumation (the reptilian/amphibian version of mammalian hibernation). To help their prediction, kids research desert temperatures and tortoise habits. The winner and his/her teacher each win a laptop computer, and classmates get free T-shirts.
Another nonprofit advocacy group, Desert Tortoise Council, sponsors an annual symposium with a wide range of educational sessions. The next one is scheduled at South Point Hotel and Casino in February. The Council also offers introductory, advanced, and health assessment training courses for desert tortoise biologists. And besides their relocation and study efforts, military facilities hold annual environmental education programs for personnel. Edwards, Fort Irwin, and Nellis officials described a variety of community outreach programs they lead, from signage to school programs.
The take-home messages of these programs are all the same: Dispose of trash in covered containers. Do not touch, harass, collect, kill, feed, or move desert tortoises unless they are in imminent danger; federal penalties for violations are fines of up to $50,000 and/or a year in jail. Do not release them into the wild. Report poaching. Spread the word in schools. Remain on roads and trails, and obey the speed limit and signage for tortoises. Look under your car and around the tires before you leave a desert habitat because tortoises seek shade. Get involved at the local level. Write letters, and take photographs of infractions, fence damage, and roadkills; all are powerful tools. Volunteer in tortoise conservation organizations.
“It all comes down to care and respect,” LaRue says. “It’s a hard thing to teach people if they don’t already have it.”
But these committed educators will keep trying, for the sake of Scooter’s progeny — as well as their own.