“Slow and steady” helped the tortoise win the race with the hare. But when the tortoise comes up against the raven, that strategy might not work so well.

Altitude makes all the difference. From a high perch — such as a power line — a raven can scan the terrain for baby desert tortoises as they slowly amble across the Mojave Desert. The raven simply swoops down and gobbles them up, one at a time.

They eat baby tortoises like they’re popcorn,” says Conservancy ecologist Sophie Parker.

But isn’t this just survival in the desert? Sort of.

Except the desert is now a human-altered landscape, one where  power lines — built to serve the burgeoning renewable energy development currently occurring in the Mojave Desert — are cropping up all over,  enabling the ravens to much more easily find small prey like baby tortoises.

It’s an unintended — and largely overlooked — consequence of the rapid boom in wind and solar farms in the Mojave Desert.

Energy development is an intensive use of desert land. Conservationists want these developments located in areas where they incur the least ecological damage. But even if the solar or wind farm is located well away from wildlife habitat, it might still have consequences for wildlife like tortoises.

Ravens, along with their relatives the crows and jays, are among the most intelligent of birds. As biologists like Bernd Heinrich have shown in numerous studies, ravens can learn to cooperate and to use new food sources.

Most people don’t think of ravens and crows as predatory. But they’re consummate omnivores. Like Andrew Zimmern of Bizarre Foods fame, they’re not adverse to sampling new and unusual food — whether it’s a discarded box of McDonald’s fries by the roadside or a crunchy tortoise.

Faced with energy development, ravens don’t just survive, they thrive.

Energy towers provide hunting perches. They use them as nests. More people working and living in an area means fast food, overturned garbage cans and pet food left out overnight — a virtual smorgasbord for clever birds.

Ravens are native, but currently they are subsidized by humans,” says Parker. “Development means more ravens. They do quite well with human disturbance.”

Desert tortoises, on the other hand, need relatively intact and undisturbed habitat. Slow and steady doesn’t help adapt to rapid change.

A tortoise’s life resembles a permanent stint in The Hunger Games: They face the usual loss of habitat and danger from off-highway vehicle use and military base expansion. Non-native cheatgrass doesn’t provide sufficient nutrition. Some tortoises carry a contagious respiratory disease. Poachers collect them for the pet trade.

And now come the ravens and other predators that can adapt to people, like coyotes.

“It’s not easy being a tortoise right now,” says Parker. “Some propose controlling ravens, but that carries its own controversy. And it’s really not addressing the cause, only the symptom.”

Conservancy ecologists recognize wind and solar farms to be important sources of renewable energy. They’re using data to help plan where those farms are located. As they analyze sites, they have to take into account other potential impacts — and propose alternatives.

The tortoise can’t outwit the raven on its own. Only sound research — and sound alternatives — can steer energy development in a way that benefits both wildlife and people.

[Image: Desert tortoise licensed under a Creative Commons Attribution-Share Alike 3.0 Unported license. Image source: Tigerhawkvok]

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Comments

  1. Excelent article … amazing … tortoises and sage grouse share a prime predator that is enabled by wind power … this points out one of several reasons the Owyhee County Local Working Group (a mixed group of ranchers, state, federal and county agencies, Air Force, Sportsman, TNC and concerned citizens here in Idaho who work to preserve, enhnace and protect sage grouse and their habitat) … have opposed sighting of power lines and wind power development in sensitive sage grouse habitat.

  2. It’s not just the power lines, but also transportation routes as well. The Raven works the road system and their take of Tortoises declines the further they are from roads.
    It has been noted that beneath many a Raven nest, is a Tortoise graveyard.
    Put a bounty on the Raven and the Tortoise population will expand.
    But then again, the Enviro community takes advantage of keeping endangered species on the brink. It furthers their agenda..

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