Biologists in slow and steady race to help North America's largest and rarest tortoise species

The tortoise is just the latest example of a growing effort to find new homes for endangered species as climate change and other threats push them from their historic habitats

While the average lifespan of North America's largest and most rare tortoise species is unknown, biologists have said it could span upward of a century.

So saving the endangered species is a long game — one that got another nudge forward Friday as U.S. wildlife officials finalized an agreement with Ted Turner's Endangered Species Fund that clears the way for the release of more Bolson tortoises on the media mogul's ranch in central New Mexico.

The “safe harbor agreement” will facilitate the release of captive tortoises on the Armendaris Ranch to establish a free-ranging population. U.S. Fish and Wildlife Service Director Martha Williams said the agreement, which offers private landowners protections from regulations, can serve as a model as officials look for more innovative ways to work within the Endangered Species Act.

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Dozens of people gathered for the release Friday of 20 more adult tortoises on the property, which is already home to 23 of them as well as dozens of juvenile ones. With the sun high in the sky and temperatures nearing 90 degrees (32 degrees Celsius), the release was held off until the evening to ensure their well-being.

The tortoises usually spend about 85% of the time in their earthen burrows, which in some cases can be about 21 yards (20 meters) long.

Shawn Sartorius, a field supervisor with the Fish and Wildlife Service, said the results of the breeding and restoration efforts for the slow-reproducing and long-lived animals will not be known in his lifetime.