Desert Tortoise Paternity Assignments Highlight Unexpected Shortcomings of Common Conservation Strategy - Herp Digest

New Smithsonian Study Reveals Reduced Effectiveness of Translocation on Vulnerable North American Species

From Smithsonian's National Zoo & Conservation Biology Institute’s

Newsroom, May. 24, 2017

Four years after conservationists relocated 570 desert tortoises (Gopherus agassizii) in California from a threatened habitat to a new nearby location, the tortoises outwardly appeared to have acclimated successfully to the change. Genetic paternity testing of 92 hatchlings by Smithsonian Conservation Biology Institute (SCBI) geneticists, however, has revealed that the translocated males are failing in one key way—they are reproducing at a much, much lower rate than resident males. The findings suggest that for some species, translocation may not be as effective a tool to rescue populations at risk, or bolster genetic diversity and health, as previously thought.

“The fact that none of the hatchlings we tested were sired by a translocated male tortoise is both unexpected and alarming,” said Kevin Mulder, a graduate student in SCBI’s Center for Conservation Genomics and lead author of the study, which was published in Biological Conservation May 23. “Based on measures such as survival and health, the translocated males seem to be doing fine, but when looking at their ability to reproduce they strongly underperform compared to the local males. Although we can only speculate on why this is happening, it is clear that the translocation itself is having a larger impact on the males than meets the human eye.”

 

Translocation is a common conservation strategy used to increase gene flow between populations and to move animals out of harm’s way in the case of habitat loss. In 2008, SCBI field collaborators worked with the U.S. Army National Training Center at Fort Irwin in the Mojave Desert to move 184 female tortoises, 293 males and 93 juveniles out of the way of the expanding base and into nearby desert habitat that already had tortoises. They put radio transmitters on both the translocated tortoises and a smaller group of the resident tortoises to track the effects of combining the two populations. This study is the first to use genetic methods to look at whether males of a translocated population are successfully reproducing and integrating their genes into a resident group.

“It’s much easier through observation to tell which females are successfully reproducing, but only by genetic assignment are we able to get a real handle on the reproductive success of the males,” said Robert Fleischer, head of SCBI’s Center for Conservation Genomics and senior author on the study. “These findings have important implications for the use of translocation as a mitigation tool for the desert tortoise and perhaps for other endangered species. It highlights the important role of genetic tools in conservation, which we suggest should be considered any time conservationists are doing a translocation.”

Unlike the males, the female translocated tortoises reproduced successfully at the same rate as the resident females. According to the paper’s authors, there may be a few reasons that the translocated male tortoises are failing to reproduce. They might have had to expend too much energy on adjusting to the new environment, resulting in reduced vigor that makes them less appealing to female residents. Or resident males may be competitively excluding the new males from mating, although there is considerable overlap of home ranges.

In addition to confirming why translocated males are not breeding, the researchers hope to repeat this study in the future to determine if there has been any breeding improvement. In the meantime, conservationists can use the results to consider the best options for managing translocated desert tortoises, including the possibility of relocating only females or breeding sets of tortoises before moving them.

The desert tortoise is a federally threatened species and listed as vulnerable by the International Union for Conservation of Nature's Red List of Threatened Species. They range throughout the Mojave and Sonoran deserts of the Southwestern United States, north and west of the Colorado River. Their numbers have declined substantially since the 1950s as the result of continued habitat loss and predation.

The paper’s other authors are Andrew Walde, Walde Research and Environmental Consulting; William Boarman, Conservation Science and Consultation; A. Peter Woodman, Kiva Biological Consulting; and Emily Latch, University of Wisconsin-Milwaukee.

SCBI plays a leading role in the Smithsonian’s global efforts to save species from extinction and train future generations of conservationists. SCBI spearheads research programs at its headquarters in Front Royal, Va., the Smithsonian’s National Zoo in Washington, D.C., and at field research stations and training sites worldwide. SCBI scientists tackle some of today’s most complex conservation challenges by applying and sharing what they learn about animal behavior and reproduction, ecology, genetics, migration and conservation sustainability.

An 'evolutionary gamble' may be killing Joshua Tree's mother desert tortoises – via Herp Digest

by Louis Sahagun, LATimes, 5/24/17 

Wildlife biologists say an alarming number of female desert tortoise carcasses found earlier this year just outside the southern edge of Joshua Tree National Park may be the result of mothers fighting extinction by exhausting their water and energy to lay eggs, even under stress.

U.S. Geological Survey biologist Jeffrey Lovich, who has monitored tortoises in and around the park for two decades, said the potentially lethal response to prolonged drought may become more common throughout the Southern California desert as temperatures rise and forage diminishes.

“This is still a hypothesis,” Lovich said on Monday, “but I believe these tortoises died after continuing to lay clutches of four eggs the size of ping pong balls year after year, using up vital resources they need to survive.”

“It was an evolutionary gamble,” he said. “If it pays off, their genetic information will be passed on to a new generation of hatchlings in conditions more suitable for survival of the species.”

A research team led by Lovich was surveying a study area of several square miles on the northern flanks of the Orocopia Mountains when it discovered the remains of 14 female and three male tortoises, and 15 live animals, most of them males.

Judging from the deterioration of the carcasses and chalkiness of the bones, Lovich concluded the animals perished over the last five to 10 years, a period including five consecutive years of drought regarded as the most severe in recorded history.

The find has stepped up concerns over the fate of tortoises within the nearly 800,000-acre national park, which recent rains made into a showcase of habitat, lush with plants and flowers for the lumbering reptiles to fatten up on.

But vast swaths of terrain carpeted with daisies can only do so much, biologists say, in the face of longer droughts and climate change.

Despite its name, scruffy body armor and status as a symbol of the desert conservation movement, the tortoise is not well adapted to arid landscapes. It evolved thousands of years ago, when the region was cooler and dominated by lakes and marshes fringed with Joshua trees and junipers, Lovich said.

Over the past three decades, the park’s tortoise population has plummeted from roughly 30,000 to an all-time low of about 3,000, Michael Vamstad, a wildlife ecologist at the park, said.

A federal analysis determined that a viable population of tortoises must maintain an average minimum density of about 10 adults per square mile. The average density within the park today is about nine adults per square mile, Vamstad said.

“We’re at a point now where we expect tortoises to disappear in certain areas because there aren’t enough of them around to find a mate,” he said. “But we believe there will also be pockets with the right combinations of air temperature, moisture and forage to sustain tortoises for years to come.

Over the past century, desert tortoises have been decimated by habitat loss, trampling by cows and sheep, shootings, vehicle strikes, disease, collecting, relocation efforts on military bases and predation by ravens, coyotes and dogs.

Now their deadliest foe is climate change, which is upsetting the delicate balance of life and death conditions for the species in an otherwise intensely managed expanse of habitat within a national park.

“The recent five-year drought is a window into the future of what climate change may look like across the Southwestern United States,” Cameron Barrows, a UC Riverside ecologist who specializes in the park’s wildlife, said. “In certain study plots where we found lots of tortoises even two years ago, we didn’t find any this year.”

Improving the odds of survival for tortoises hasn’t been easy at a time when record numbers of tourists are straining park roads, campsites and services, officials said. The park had 2.5 million visitors in 2016, twice the number seen five years ago, officials said.

In the midst of a spectacular wildflower bloom in March that attracted both hungry tortoises and a crush of camera-toting tourists, three tortoises were struck and killed by cars in a single week.

Officials are considering roadside fencing, which is effective in reducing mortalities of tortoises and other reptiles. It is also controversial, however, because it is expensive to install and maintain, fragments habitat and is an eyesore on federal lands set aside for their natural beauty.

“Climate change has no regard for traffic signs, speed limits, roadside barriers or national park boundaries,” said Debra Hughson, a research biologist at the Mojave National Preserve, about 50 miles northwest of the park.

It’s not all bad news.

Under a hot morning sun on a recent weekday, park biologist Kristen Lalumiere followed telemetry pings across a desolate arroyo edged with cholla cactus to a radio-collared female desert tortoise the size of a volleyball emerging from a burrow to bask in the sunshine, dine on flowers and, perhaps, find a mate.

Lalumiere peered inside, then smiled and said, “You’re looking good, girl -- clear eyes, clean nose and flower stains all over your mouth.”

Adding a hopeful dose of anthropomorphism, she said, “Single female seeks relationship with strong male willing to fight to protect her. Must enjoy flowers, long slow walks and cuddling up in desert caves.”

The tortoise biologists dubbed “Salsa Verde” stared back at her, then retreated into her burrow.

In a nearby burrow, a male tortoise known as “Scuter” was taking a siesta.

Whether or not they produce a new generation of tortoises will not be known for 15 to 20 years because that is how long it takes hatchlings to reach maturity, even in the best of times.

To Save Desert Tortoises, Make Conservation a Real-Life Video Game - Traditional techniques weren’t working for the raven-ravaged reptile. So researchers got creative – via Herp Digest

By Sam Schipani, smithsonian.com 5/16/17  

JOSHUA TREE, CA — Tim Shields holds a baby desert tortoise shell up to the sun, peering through it like a kaleidoscope. He’s carrying a container filled with these empty carapaces, perforated with coin-sized holes and picked clean of life.

Over the four decades Shields has been a wildlife biologist with the Bureau of Land Management and U.S. Geological Survey, he has watched the tortoise population in the Mojave Desert steeply decline. Where once he saw dozens of baby tortoises over the span of a season, now he can go days without spotting a single one. What he does find are these empty shells—sometimes dozens in a single nest, scattered around like discarded pistachio shells.

We’re standing in a picnic area in Joshua Tree Park, and Shields is showing me these hollowed-out shells to illustrate the damage. It’s easy to see how an animal could peck right through this thin casing: “It’s about as thick as a fingernail,” Shields points out. Desert tortoise shells don’t harden into a tank-like defense until the reptile is about 5 or 6 years old. Until then, hatchlings are walking gummy snacks for one of the most intelligent, adaptive and hungry desert predators: ravens.

Even before ravens, the tortoise was in trouble—and its fate has long been tied up with the history of humans. As people moved into the Mojave, the tortoise was faced with challenges its evolution could not have foreseen: off-road vehicle use, the illegal pet trade and pandemic-level respiratory disease. By 1984, biologists estimated a 90 percent population decline in desert tortoise population over the last century, thanks largely to habitat destruction. Today, an estimated 100,000 tortoises remain in the American Southwest.

According to Kristin Berry, a research scientist with the U.S. Geological Survey's Western Ecological Research Center who has been monitoring desert tortoises since the 1970s, these reptiles are an umbrella species. In other words, they require such specific conditions to survive that they are one of the best indicators of the health of the Mojave Desert ecosystem.

“It’s the proverbial canary in the mine,” adds Ron Berger, chairman and CEO of the nonprofit Desert Tortoise Conservancy and president of the nonprofit Desert Tortoise Preserve Committee. “If we can’t help this animal that can go without food or drink for years, then what are we doing to this planet?”

Humans are also culpable in aiding and abetting the tortoise’s primary threat, those pesky ravens. Over the past half century, these predatory birds have been proliferating as new sources of once-limited food and water resources become available in the form of human-made landfills, road kill, dumpsters, sewage ponds and golf courses. In direct contrast to the falling tortoise numbers, estimates place the raven population as increasing by 700 percent since 1960.

Shields remembers a pivotal moment in 2011, when he could not spot a single juvenile tortoise roaming out in the field. Instead, the only one he saw was struggling in the beak of a raven. “That moment hit me really hard,” he says. He decided that the current conservation model—monitoring tortoises, restoring their habitats and relocating them to preserves—wasn’t working. Something more innovative needed to be done.

Desert tortoises have roamed the Southwest for millions of years, adapting as the shallow inland sea transformed into the dry landscape it is today. These reptiles are crucial to their desert ecosystems. While creating their burrows, they till soil nutrients for plant life and inadvertently create hiding spots for lizards and ground squirrels. Gila monsters and coyotes eat their eggs for breakfast; roadrunners and snakes snack on juvenile tortoises; badgers and golden eagles feast on adults.

They're also a bit of a celebrity around these parts. Ironically, the same pet trade that contributed to their decline may have also contributed to the species’ iconic status: Shields wagers that the generation of Southern Californians who grew up with sweet pet tortoises have developed a nostalgic fondness for the species. As the California state reptile, they’ve cemented their position as poster-children for conservation in the desert.

In 2014, Shields founded the investor-funded company Hardshell Labs to develop a series of high-tech defense methods for protecting this beloved reptile. He hopes to use these techniques to enact a process called active ecological intervention, creating safe zones for baby tortoises throughout the desert where they can reach maturity at 15 to 20 years old and breed until, someday, the populations reach a sustainable level.

One of those methods is scattering 3D printed baby tortoises decoys, which emit irritants derived from grape juice concentrate (farmers use this chemical compound to keep birds from congregating on agricultural fields and commercial centers). Another is laser guns—TALI TR3 Counter-Piracy lasers, to be precise. These forearm-sized guns, mounted with aiming scopes that were originally used as a form of non-lethal defense for ships in the western Indian Ocean, fire a 532 nanometer green light, to which ravens’ eyes are especially sensitive.

Ravens have such sharp vision that even in the daylight, the 3-watt beam looks as solid as a pole waving in their faces. The lasers can be mounted on a rover known the Guardian Angel rover, or shot by skilled humans. Shields will aim for the ravens’ heads to get closer to their sensitive eyes if they are being persistent, but shooting within a meter’s range is usually enough to spook them.

“We once cleared a pistachio field [of ravens] in three days,” Shields says of his technological arsenal. 

Perhaps the most crucial part of these technologies is that they are non-lethal. Ravens are federally protected: Though they’re native to the desert, the birds, their nests and their eggs all fall under the Migratory Bird Treaty Act. And while organizations like the Coalition for a Balanced Environment argue that the boom of raven populations warrants their removal from the list in order to enhance raven management practices, many recognize their importance to the ecosystem.

Shields is among them. Even if he finds shooting near the birds with the lasers “intensely satisfying,” he doesn’t want to risk angering those who love and appreciate these birds by supporting more deadly technologies. “We’re not going to get rid of the charm of ravens, and there are people who are as charmed as ravens as I am by tortoises,” he admits. “We better acknowledge that if we’re going to find a solution.”

Instead, his technologies work with the raven’s intelligence in mind, frustrating the birds but not hurting them. Ravens are incredibly adaptive, so no single line of defense alone will work. Biologists will stake out in the desert scrub and shoot the lasers to keep the ravens on their toes. It is a skill that takes training —and time—to develop.

Now, Hardshell Labs is hoping to turn that challenge into a benefit. They’re aiming to roboticize their technologies and turn them into a sort of video game. The team hopes to tap into flow theory, the obsessiveness on solving the problem that makes gaming so addictive, in order to draw players into the game of protecting the desert tortoise.

“Environmentalism does not sell,” explains Michael Austin, Co-Founder of Hardshell Labs and Shields’s childhood friend. “What plays for people is fun and joy.”

It’s especially hard to get people to care about conservation way out in the deserts. When compared to lush biomes like rainforests, the desert has long persisted in the popular imagination as remote, barren and inhabitable, Austin says. Historically, “desert” is synonymous with “wasteland.” “The coral reefs have better PR,” he laughs.

In actuality, the desert is a place teeming with life. Because of its elevation and unique geology, the Mojave Desert especially is a  unique eco-region, with 80 to 90 percent endemic plants and species found nowhere else in the world. It is also one of the most imperiled areas of the West, with over 100 of its over 2,500 species considered threatened. 

Shields’ ultimate vision for Hardshell Labs is to turn armchair activists into real-time conservationists, by allowing users to remotely control techno-tortoises, lasers, and rovers online. They have already tested an early version of the game with Raven Repel, an augmented reality app in the vein of Pokémon Go. One day, he says, players from around the world will work in teams, using different tools to engage in ecological management like predation reduction, behavioral observation, fostering the spread of native plants, and preventing invasive species. 

Several bird species, including the endangered sage grouse, also suffer from the ever-increasing hordes of ravens preying on their eggs. The same principles used for the decoy tortoises could be used to 3D print realistic eggs equipped with repellant, Shields says. Beyond ravens, other invasive species—the Indo-Pacific lionfish in the Caribbean, pythons in the Everglades, the Asiatic carp in the Great Lakes—could be captured by submarines controlled remotely by players. Players could even monitor video feeds over the elephant and rhinoceros habitats to spot illegal poachers.

The irony of defending nature digitally does not escape Shields. “Tortoises are so wired in to their immediate environment,” he muses. “In contrast, our species is catastrophically alienated on every level from our life support system.”

But he also recognizes the potential. A 14-year-old kid in a wheelchair could be a valued tortoise biologist, he says; a prisoner could reconnect with the world through positive contribution to the cause. In Shields’s view, denying that we are a screen culture now is delusional, so conservationists might as well make the most of it and use modern-day tools like crowdsourcing and virtual reality to leverage positive change.

“My long, long term goal is to get people to fall in love with the planet through the screen, and then realize the limitations of the screen, and then get out themselves and do it,” he says. “This is my game, and I am having so bloody much fun.”