Originally posted on the San Francisco Bay Area National Parks Science and Learning Blog
Although no one knows exactly when western pond turtles vanished from Mountain Lake in the Presidio of San Francisco, they are known to have been abundant historically. Now, as part of the ongoing restoration of Mountain Lake, this long-extirpated species is back. On July 18th, 28 western pond turtles reared by the San Francisco Zoo were released into the lake before an audience of more than 70 people. The release follows similar releases of other native species including Pacific chorus frogs and three-spined sticklebacks earlier in the year.
The western pond turtle release is also part of a research effort to determine which of two different release methods is better for the turtles in terms of their stress hormone levels. Half of turtles were brought to Mountain Lake and kept in a protected enclosure for three weeks to acclimate ahead of their release, while the rest were released without an acclimation period. All had their stress hormone levels measured upon their release and are equipped with radio transmitters so they can be relocated and have their hormone levels re-measured in the coming weeks and years. The preliminary results will inform another round of western pond turtle releases at Mountain Lake on September 12th and contribute to knowledge about native species reestablishment efforts in general. Future reestablishment projects at Mountain Lake may include the Pacific newt and the California red-legged frog.