The raven population in the western Mojave has increased more than 700% in the last 25 years and threatens to wipe out desert tortoises if nothing is done. In some places, “where there used to be 10 ravens, there are now 15,000,” Allison Fedrick, tortoise outreach and animal care keeper at The Living Desert, said.
In contrast, the number of desert tortoises in the western Mojave has plummeted by more than 90% since 1990. Although the turtles are also hit by cars, wiped out by development and energy operations and felled by disease, ravens were a critical factor. The birds are capable of pecking holes in the shells of tortoises up to 10 years old. One study found the carcasses of 250 juvenile tortoises beneath a single Mojave raven nest over a four-year period.
In response, scientists are experimenting with drones to coat raven eggs with oil so they won’t hatch, The Los Angeles Times reported. Remote egg oiling is primarily used for hard to reach spots, like nests 20 feet high in a tree or 40 feet up a cliff face.
Research biologist Mercy Vaughn and self-described “life-long tortoise biologist” Tim Shields are spearheading the drone project in coordination with the U.S. Fish and Wildlife Service. Over the past two months, their team has oiled 525 raven eggs in 116 nests on public land that is considered critical habitat for desert tortoises.
Shields is also experimenting with other technological strategies in a bid to save the animals he describes on his Hardshell Labs company website as “quiet,” “careful” and “iconic.” One option, known as “techno-tortoises,” emit non-toxic irritants when pecked or bitten as a form of “aversive training” for tortoise-eating birds. Mini remote-control “rovers” also scare away birds and track the tortoises.
Shields said that after decades of studying the tortoises, these creatures’ deaths had profoundly affected him.
“If they were completely wiped out, I would be crushed. It would be hard to take,” he told The Guardian. “It’s already been very hard to take.”