The Desert Tortoise Conservancy
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The Desert Tortoise Conservancy is a proud member of the Coalition for a Balanced Environment (CBE), and is proud to be a Life Member of the California Turtle and Tortoise Club (CTTC), The Desert Tortoise Council (DTC), and the Desert Tortoise Preserve Committee (DTPC).
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Scientists Use 3D-Printed Shells to Ward Off Ravens and Aim to Save Desert Tortoises
In a video captured last year in Victorville, a raven can be seen pecking at a shell on the desert floor. With scrub brush and electric transmission towers in the background, three other ravens stand nearby and watch with curiosity. Without warning the shell hisses, emitting a spray that sends the birds flying.
Did the desert tortoise learn a new defense mechanism to fend off one of its biggest predators? Not quite.
But one company is hoping their invention will make ravens think twice before daring to mess with what they think is a defenseless reptile.
The booby-trapped shell was a Techno-tortoise, a 3D-printed model designed to look like a baby desert tortoise that was developed by Hardshell Labs, a company founded by Tim Shields. Shields, a wildlife biologist with more than 35 years experience, said he was inspired to start his company eight years ago after seeing firsthand the decline of the slow-moving species.
Though the desert tortoise in the Mojave has been protected as a federally threatened species since 1990, scientists found in 2014 their numbers in the western Mojave Desert had dropped roughly 50% from those counted 10 years earlier.
Other studies estimate tortoise populations have collapsed as much as 90% since the 1980s. As a contract field biologist for the Bureau of Land Management, Shields would spend upwards of three months living and studying in desert tortoise habitat, never seeing another human being. In the early days, he’d see plenty of tortoises. That pattern changed as the years progressed.
“More and more, the track of my career has been from going from days that were absolutely packed with interactions with tortoises to now, a tortoise encounter being a rare event,” he said in a 2015 video.
Killer ravens
Scientists note several factors as contributing to the decline: Urban development destroying tortoise habitat, invasive plant species, disease, off-road racing and vehicle strikes. For Shields, one factor stuck out above the rest as potentially solvable. “There’s a lot of threats to tortoises, but raven predation seemed to be the one we could do something about,” he said in an interview Friday.
In contrast to the tortoises, common ravens flourish in the west. Once an uncommon bird to see in the western Mojave Desert, populations of the black bird rose 795% from 1968 to 2014, according to the Breeding Bird Survey.
Increased human presence in the region drove this explosion. With more people living in the desert, ravens can scavenge trash and roadkill, nest on electrical towers and dip their beaks in man-made sources of water.
They also use their beaks to poke holes and kill young tortoises. The reptiles are essentially defenseless to the attacks during the first decade or more of their lives because their shells aren’t as strong.
Scientists have found kill sites with dozens to hundreds of shells scattered beneath raven nests.
To save his beloved creatures, Shields said he had to switch from being a tortoise biologist to a raven biologist.
Since its inception in 2014, the main focus of Hardshell Labs is to invent technologies to prevent damage from birds.
Shields’ team developed a system of using drones to oil raven eggs in nests that could be 20 to 100 feet off the ground. The oil prevents the eggs from hatching while the raven parents remain unaware and continue nesting.
The first models of the Techno-tortoise, on the other hand, started off as just a simple lure to attract the birds.
Inspired by Styrofoam tortoise models in the 1990s created by Bill Boarman, Hardshell’s lead scientist, Shields and his colleagues collaborated with the software company Autodesk to create something more lifelike using 3D-printing. The initial decoy shells were used to calculate and understand the threat of ravens by measuring the rate of attacks.
Hardshell Labs deployed a wide spread of the rubes in 2018 and 2019 and sold about 1,000 to the U.S. Fish and Wildlife Service, Fast Company reported. Later models were installed with sensors that would trigger a blast of bird repellent when fiddled with.
Five counter attacking shells were placed in the field along with cameras for the first time in spring 2021. One spot the Hardshell team picked was a popular roost in northern Victorville where Shields said 6,500 ravens have been recorded. The results were exciting. Footage from one test showed an innocuous-looking shell scaring an aptly-named treachery, or group, of at least more than a dozen ravens into the air.
“So we know the device works. It does the first thing it needs to do which is scare the bejesus out of ravens,” Shields said. “Now we have to figure out, OK, if you get that effect does that reduce raven predation on tortoises. That’s a much harder question to answer.”
The biologist and others who use the shells hope the birds — which are considered one of the most intelligent animals on Earth — will learn and teach their brood to stay away from tortoises. Shields said he plans to test another 10 spraying shells in the field this year. In the meantime, plans are being proposed to make the Techno-tortoise robotically mobile to even better deceive the ravens and keep them guessing. It's all an effort to save a reptile that Shields said he has an endearment toward.
“Tortoises just gave me a great life and I just want to keep them on the planet,” he said. “Earth would be a lot more boring without tortoises.”
Did the desert tortoise learn a new defense mechanism to fend off one of its biggest predators? Not quite.
But one company is hoping their invention will make ravens think twice before daring to mess with what they think is a defenseless reptile.
The booby-trapped shell was a Techno-tortoise, a 3D-printed model designed to look like a baby desert tortoise that was developed by Hardshell Labs, a company founded by Tim Shields. Shields, a wildlife biologist with more than 35 years experience, said he was inspired to start his company eight years ago after seeing firsthand the decline of the slow-moving species.
Though the desert tortoise in the Mojave has been protected as a federally threatened species since 1990, scientists found in 2014 their numbers in the western Mojave Desert had dropped roughly 50% from those counted 10 years earlier.
Other studies estimate tortoise populations have collapsed as much as 90% since the 1980s. As a contract field biologist for the Bureau of Land Management, Shields would spend upwards of three months living and studying in desert tortoise habitat, never seeing another human being. In the early days, he’d see plenty of tortoises. That pattern changed as the years progressed.
“More and more, the track of my career has been from going from days that were absolutely packed with interactions with tortoises to now, a tortoise encounter being a rare event,” he said in a 2015 video.
Killer ravens
Scientists note several factors as contributing to the decline: Urban development destroying tortoise habitat, invasive plant species, disease, off-road racing and vehicle strikes. For Shields, one factor stuck out above the rest as potentially solvable. “There’s a lot of threats to tortoises, but raven predation seemed to be the one we could do something about,” he said in an interview Friday.
In contrast to the tortoises, common ravens flourish in the west. Once an uncommon bird to see in the western Mojave Desert, populations of the black bird rose 795% from 1968 to 2014, according to the Breeding Bird Survey.
Increased human presence in the region drove this explosion. With more people living in the desert, ravens can scavenge trash and roadkill, nest on electrical towers and dip their beaks in man-made sources of water.
They also use their beaks to poke holes and kill young tortoises. The reptiles are essentially defenseless to the attacks during the first decade or more of their lives because their shells aren’t as strong.
Scientists have found kill sites with dozens to hundreds of shells scattered beneath raven nests.
To save his beloved creatures, Shields said he had to switch from being a tortoise biologist to a raven biologist.
Since its inception in 2014, the main focus of Hardshell Labs is to invent technologies to prevent damage from birds.
Shields’ team developed a system of using drones to oil raven eggs in nests that could be 20 to 100 feet off the ground. The oil prevents the eggs from hatching while the raven parents remain unaware and continue nesting.
The first models of the Techno-tortoise, on the other hand, started off as just a simple lure to attract the birds.
Inspired by Styrofoam tortoise models in the 1990s created by Bill Boarman, Hardshell’s lead scientist, Shields and his colleagues collaborated with the software company Autodesk to create something more lifelike using 3D-printing. The initial decoy shells were used to calculate and understand the threat of ravens by measuring the rate of attacks.
Hardshell Labs deployed a wide spread of the rubes in 2018 and 2019 and sold about 1,000 to the U.S. Fish and Wildlife Service, Fast Company reported. Later models were installed with sensors that would trigger a blast of bird repellent when fiddled with.
Five counter attacking shells were placed in the field along with cameras for the first time in spring 2021. One spot the Hardshell team picked was a popular roost in northern Victorville where Shields said 6,500 ravens have been recorded. The results were exciting. Footage from one test showed an innocuous-looking shell scaring an aptly-named treachery, or group, of at least more than a dozen ravens into the air.
“So we know the device works. It does the first thing it needs to do which is scare the bejesus out of ravens,” Shields said. “Now we have to figure out, OK, if you get that effect does that reduce raven predation on tortoises. That’s a much harder question to answer.”
The biologist and others who use the shells hope the birds — which are considered one of the most intelligent animals on Earth — will learn and teach their brood to stay away from tortoises. Shields said he plans to test another 10 spraying shells in the field this year. In the meantime, plans are being proposed to make the Techno-tortoise robotically mobile to even better deceive the ravens and keep them guessing. It's all an effort to save a reptile that Shields said he has an endearment toward.
“Tortoises just gave me a great life and I just want to keep them on the planet,” he said. “Earth would be a lot more boring without tortoises.”
Consider this:You are only about an inch high and very slow moving. You do have a hard outer shell, which is helpful at keeping some predators from eating you. Still, many predators think of you as a crunchy-on-the-outside, juicy-on-the-inside treat. What's more, you live in a harsh desert environment, and are fortunate if you get a few drinks of water each year. You may have guessed by now that you are a desert tortoise. Getting "inside a tortoise's shell" to understand its perspective on the world is a large part of what we do to try to better conserve this species.
By Ron Swaisgood, Ph.D., Melissa Merrick, Ph.D., and /Tali Hammond, Ph.D. |
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Desert Tortoise Upgraded to Critically Endangered on IUCN Red List
The IUCN Red List upgraded the desert tortoise to critically endangered. To see this, go to the IUCN Red list website: (https://www.iucnredlist.org) and type in Gopherus agassizii. View the report below.
https://documentcloud.adobe.com/link/track?uri=urn:aaid:scds:US:1f5c6856-7cec-4b16-818f-5f51c5b56d28
https://documentcloud.adobe.com/link/track?uri=urn:aaid:scds:US:1f5c6856-7cec-4b16-818f-5f51c5b56d28
The Heat is On: Desert Tortoises and Survival
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I am pleased to report to our supporters that I signed the petition described in the following article, last March, in my capacity as President of The Desert Tortoise Preserve Committee, joining our friends at Defenders of Wildlife as well as at The Desert Tortoise Council, which we submitted to the California Fish and Game Commission.
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To Save Desert Tortoises, Make Conservation
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The Common Raven Boom in the Rugged West Isn't Necessarily a Good Thing.The raven population has ballooned over past decades, upsetting ecosystems and endangering wildlife. To check the ravenous birds, conservationists are cleaning up trash and shooting lasers...
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Tortoise in Peril.Desert tortoises are a threatened species. Habitat destruction, diseases and other factors have reduced their numbers by up to 90 percent.
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The Desert's Canary: A Narrative Examination
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Pacific Southwest Region External Affairs
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The tortoise and the desertThe desert tortoise, the state reptile for California and Nevada, likes to spend its time burrowing in holes near mountain slopes. In the summer months, temperatures can easily reach a blistering 120°F in the Mojave Desert. Seeking shelter from the heat, tortoises burrow in the ground or seek refuge in the shade of shrubs. In the winter, temperatures can reach below freezing, and tortoises snuggle into burrows once again to stay warm and conserve energy when less food is available. Other species also rely upon the desert tortoise and its burrowing skills for shelter to escape the harsh climate.
In the spring and fall, desert tortoises can be found roaming the 25,000-square-mile Mojave Desert, looking for mates and the food and water needed for survival. Native forbs that only sprout during a narrow window in the spring provide most of their food. They rely on water stored in their bladders to prevent dehydration. This water storage allows them to go without a drink for a year. Finally, the tortoise’s exterior shell offers protection from predators. Adaptations like these allow desert tortoises to live up to 70 years in the wild. So, why has the population in the Mojave Desert dropped 90 percent in some areas since the 1980s? |
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Threats to the desert tortoiseDesert tortoises are dying at alarming rates, primarily due to invasive species of grass, especially red brome and cheatgrass (Bromus rubens and Bromus tectorum). Foreign to the Mojave Desert, these grasses are not as nutritious to tortoises as their normal forage.
“The red brome in particular has these very spiky awns on the seedheads and those get lodged inside the tortoises’ mouths,” says Roy Averill-Murray, desert tortoise recovery coordinator for the U.S. Fish and Wildlife Service. “The tortoises will eat them especially if they don't have a lot of other choices. [Their mouths] could become infected and then they can have difficulty eating anything else and it could cause severe health issues.” Research by U.S. Geological Survey scientists showed that juvenile tortoises that had to rely on red brome as forage grew less and declined in health compared to juveniles that had native plants to eat. |
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To make matters worse, the invasive grass dries quickly as spring temperatures warm and the grass forms dense undergrowth that burns easily by lightning strikes or cigarette embers. Many tortoises caught on the surface during a fire are killed, while those in burrows also may succumb to smoke inhalation. Wildfires are increasing in the Mojave Desert over the past two decades as a result of the invasion. More than 400,000 acres of tortoise habitat burned in 2005 alone.
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