Ravens prey on juvenile desert tortoises.
Illustration by Emily Lankiewicz / Hardshell Labs, Inc. / William I. Boarman

On a crisp spring morning in 2016, biologists Tim Shields and Bill Boarman hiked into a remote location of California’s Mojave Desert to place an thought they had to the test. The arid Mojave touches 4 states, though the bulk of it lies in California. It boasts the globe-record higher temperature of 134 degrees Fahrenheit, and a great deal of the sparse terrain is dotted with brush, cacti and, in some locations, Joshua trees. Bighorn sheep, coyotes, jack rabbits, rattlesnakes and scorpions traverse the landscape. Water is scarce, particularly at reduce elevations, and several animals have adapted to survive on significantly less than 4 inches of typical annual rainfall. The desert tortoise, for instance, can survive up to a year devoid of fresh water just by consuming plants and reusing water stored in its bladder.

In this intense landscape, Shields and Boarman set up lifelike, 3D-printed replicas of juvenile desert tortoises, dubbed Techno-Torts, and aimed motion-activated cameras at them. The researchers hoped the fake reptiles would lure ravens, which feed on child tortoises. The scientists left, and when they returned to verify the cameras, they discovered the birds had swooped in for the prey but left disappointed. With the footage they captured, the two researchers gathered useful info on how ravens strategy and attack desert tortoises.

Shields, who has more than 35 years of fieldwork below his belt, formed a corporation referred to as Hardshell Labs just a year earlier as a way to create and deploy new wildlife conservation technologies that would assist save the threatened desert tortoise. Considering the fact that then, Shields and his associates have collaborated with the U.S. Fish and Wildlife Service to gather information employing hundreds of Techno-Torts in essential habitat locations.

The outcome was an astonishing new study on the influence of raven predation on tortoises. Performed by Fish and Wildlife biologist Kerry Holcomb, it was published November 2021 and produced readily available on the net a year later in Human-Wildlife Interactions. According to Holcomb, amongst birth and age ten, raven predation diminishes the quantity of juvenile tortoises by around 42 % each and every year if any portion of their core use location is inside roughly 1,600 feet of an active raven nest and the neighborhood raven population consists of about six birds per square mile, a density that is often observed in the western Mojave. That bird count is vastly greater than the quantity of ravens the land could typically help. The animals are bolstered by human meals and water supplies, and nesting in such structures as electrical utility towers and billboards. About a further 15 % of juvenile tortoises die from other causes.

Holcomb explains that, below these circumstances, if four,000 tortoises have been born in a provided year, soon after ten years only one particular of the hatchlings would have survived. According to Holcomb, multiyear research have established that devoid of ravens, 429 hatchlings out of four,000 would have survived in that identical time period. “Tortoises start out to reproduce at about age 13,” says Shields. “Significant losses at an early age due to raven predation are taking a heavy toll on the all round population.”

“When raven eggs hatch, the adults go into overdrive mainly because they have babies to raise,” says Shields. “You have these predatory vacuum cleaners scooping up every thing, and it is not just child tortoises—its lizards, mammals, snakes, insects and the young of other birds. They just go out and start out killing every thing, and if child tortoises are about, they’re genuinely quick to nail.”

Throughout one particular 4-year period in the 1980s, an alarming 250 tortoise shells have been discovered below a single raven nest.

Only a handful of biologists have the practical experience to operate on raven and tortoise interactions, and fieldwork is pricey. Boarman has spent 3 decades studying this issue. “Techno-Torts can sit out there for two to 4 weeks. I’ve even had them out 4 to 5 months,” he says. “We can record a lot of activity more than that time. We would require 200 biologists, each and every operating 12-hour shifts for 60 days, to get related information.”

It is really uncommon for any individual to witness a genuine-time raven attack on a tortoise. “Prior to this we have been carrying out forensic biology,” says Shields. “We have been coming to the scene of the crime and attempting to discern its nature from the remains of actual tortoises.” With Techno-Torts, biologists can study video of ravens for the duration of an actual attack.

“It’s difficult to study juvenile tortoise mortality if you can not uncover them or if they’ve all been eaten,” says Roy Averill-Murray, desert tortoise recovery coordinator for Fish and Wildlife. “Having a proxy with the Techno-Torts is permitting us to measure predation prices relative to the quantity of ravens.”

Shields and his group are researching strategies to use the technologies to modify the behavior of predatory ravens. They are testing “weaponized” Techno-Torts that, when attacked, emit a noxious, nonlethal spray that causes unpleasant sensations in the birds. “If this permits us to trick them into considering that tortoises are yucky and not to be messed with, that would be great,” says Averill-Murray.

Tortoises have lived in the Southwest for 20 million to 30 million years, but they are now in danger of extinction. According to Boarman, tortoise numbers in some locations have dropped by 90 % in the final 40 years.

The portion of the Mojave situated amongst Los Angeles and Las Vegas has been severely impacted. Amongst 1950 and 2020, the population of the Las Vegas metropolitan location grew from 35,000 to practically two.7 million. Nowadays, Riverside County, which cuts by way of the southern portion of the Mojave, is the quickest-increasing county in California. Its population improved about 12 % amongst 2010 to 2021. Loss of habitat, introduction of illness, poaching and improved car strikes have devastated tortoise populations. Climate modify has impacted tortoises as effectively by raising temperatures, lowering rainfall and decreasing edible vegetation. Invasive plants with reduce nutritional worth are crowding out preferred native plants. On top rated of all that, ravens are aggressively hunting juvenile tortoises.

According to Boarman, the quantity of ravens in the Mojave Desert has improved by 1,000 % considering the fact that the 1960s. Throughout the identical period, the birds improved 1,400 % in the Sonoran Desert, which lies southeast of the Mojave and extends into Mexico. In California’s Central Valley, the raise was a whopping 7,600 %, largely mainly because of agricultural activities that help ravens. Whilst raven predation on tortoises is not an concern in the Central Valley, some of these ravens have migrated into the Mojave Desert and feed on tortoises.

With all this in thoughts, a petition has been filed by concerned citizens and scientific organizations asking Fish and Wildlife to raise the tortoise’s status from threatened to endangered. They hope a choice will be produced sooner rather than later. “We’re in a chess match with one particular of the smartest birds on the planet,” says Shields. “They discover, communicate, issue-resolve, play and even use easy tools. They’re genuinely impressive.”

Bolstered by the information obtained employing Techno-Torts, the objective now is to use the birds’ intelligence against them. In a test, Hardshell Labs effectively dissuaded ravens from raiding a California pistachio orchard. The birds really like the extremely nutritious nuts and can swiftly destroy a harvest. Researchers applied drones and lasers to flush ravens from portions of the orchard, denying them a useful meals supply and decreasing crop losses by 95 %. They now want to incorporate artificial intelligence application into completely autonomous lasers that will repeat this achievement. According to Boarman, these revolutionary tactics can be applied to teach ravens to keep away from higher-top quality resource internet sites like landfills, compost facilities and agricultural locations exactly where meals and water are readily readily available. “Without access to subsidies, the existing raven population can not sustain itself anyplace close to the existing level,” says Boarman.

Shields’ corporation is also implementing drones to spray oil on raven eggs. The eggs do not hatch, but the adults continue to care for them, correctly halting reproduction for a year. Researchers hope continued reproductive failure will trigger ravens to abandon their nests and leave the location.

With each other, these new technologies could assist mitigate raven predation on tortoises, but Holcomb is speedy to point out that the objective is not to get rid of ravens. The aim is to humanely supply juvenile tortoises with relief from the existing price of predation although nevertheless preserving a steady, low-density raven population.

In September 2022, the Fish and Wildlife Service announced that the Hardshell Labs group was awarded the Theodore Roosevelt Genius Prize for “promoting nonlethal human-wildlife conflict management.” “It’s a terrific honor,” says Shields. “If we can demonstrate achievement in assisting the desert tortoise, we count on these tactics to be applied a great deal a lot more broadly in conservation. There could be no a lot more satisfying feeling for somebody who loves the tortoise and respects the raven.”





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