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Environment & Science

Can relocation save the endangered Mojave desert tortoise?

A desert tortoise photographed in the Mojave desert.
A desert tortoise photographed in the Mojave desert.

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Before humans moved in to the Mojave desert and began building tract homes and army bases and solar farms, it was the land of the tortoise.

This hearty creature has been a part of the desert landscape for millions of years, before it even was a desert. But over time, humans have been creeping further and further into tortoise habitat and their numbers have been shrinking.

In an effort to save the desert tortoise, conservation groups settled on a simple fix: move them. Over the last decade, hundreds of tortoises have been relocated and there are plans to move thousands more.

Reporter Emily Green writes about some of the problems with this approach in a new piece for High Country News. She joins the show to explain. 

Interview highlights:

On how important tortoises are to the desert ecology:
"They are terribly significant. A lot of animals — burrowing owls, reptiles, all the different kinds of mice you have out in the desert and kangaroo rats — rely on the burrows that the tortoises dig. They have burrows that they hibernate in in the winter. If you walk through the mojave, and see a bush, look at the root of the bush and you'll see a burrow entrance."

When and why did they become listed as endangered:
"There was a population biologist named Christine Berry. She began censusing tortoises and she realized that the numbers were dropping precipitously. And because they're very slow and very long-lived, if the numbers drop below a certain concentration per square mile, they can't find their mates, they can't mate or lay eggs and you have just a total crash.

"In 1984, she published a paper pointing out that the numbers had fallen by 90 percent in the century before and within five years, a pet store disease had ripped through a wild population. Somebody had been dumping pet tortoises and they introduced a pet store disease…the animals were just lying on rocks, kind of feverish, vividly dying.

Is relocation really a good solution?
"It's a $10 term for moving an animal from where it is to where you want it to be so you can build over its habitat. And it's something that the fish and wildlife service has been doing for a long time to other species. They've been airlifting big horn sheep from one part of the Sierra and putting it in another. The problem with doing it to tortoises is that they have very finely tuned homing instincts. They seem to know where they were taken from and they try to get back."

What makes it difficult to track them?
"You have to radio tag them and watch them for a period of years, because with the mammal you might be able to tell whether it was going to live or die within a year. A tortoise can go a year without water. You have this situation where they could appear to live if you only studied for two, three four years but could be dying very slowly."

How have the relocation efforts gone so far:
"There have been lots of different moves. The one that's being monitored very closely had to do with the 2008 expansion of Fort Irwin, [when] they moved hundreds of animals. I wrote about a scientist who studied 150, and five years in, half of those animals were dead. They translocated more than 9,000 tortoises during the big expansion of Las Vegas. Nobody kept track of them.

"I interviewed desert tortoise recovery office coordinator about it and he said, 'Well we haven't really pulled the data yet, but if you go out there, there are a lot of dead tortoises.' It is shocking that this is the de facto conservation technique and it's got such a shocking failure rate."