SAN FRANCISCO (CBS SF) — A once threatened species of turtle is now thriving again in San Francisco.

After a years-long cleanup effort at Mountain Lake, the population of Western Pond Turtles seems to be flourishing.

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It’s spring at San Francisco’s Mountain Lake, time for the birds and the bees. And this year, for the first time in many, the turtles.

Dana Pope with the Presidio Trust said, “The Western Pond Turtle is one of those species that existed centuries ago here in San Francisco. They used to be very common in lakes and ponds. Unfortunately, they pretty much disappeared.”

But now they are back and thriving, like a lot of other long lost animals, some welcome, some not. It’s part of the restoration of this lake which took almost a decade to clean up poison, get rid of species that didn’t belong. And these turtles thriving means it worked.

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“Having all these species work together is a sign of the health, that the lake is healthy and functioning again,” Pope said.

With the reintroduction of the species and the improvement in the lake, it looks like it did a century ago. You could sit there pretend it’s 100 years ago. Except for the cars on Park Presidio Blvd and the golfers at the Presidio Golf Course.

“You just don’t have those species that are emblematic of San Francisco. You just don’t see them anymore,” Pope explained.

The turtles are tracked with a tiny transmitter on their tiny backs. Since their release last summer, it’s believed only 1 of the 55 have died.

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The Presidio is very proud of what has turned out to be a very successful shell game.