El Jefe Has a Posse
Natives Thrive at Mountain Lake
2018 was good year at Mountain Lake in San Francisco’s Presidio for habitat and native species restoration. Pacific Chorus Frogs and Three Spined Sticklebacks continue to thrive. Presidio biologists released more freshwater mussels and a new species, the endangered San Francisco Fork-tailed Damselfly. And the Western Pond Turtles came back in a big way.
Sticklebacks are adaptable fish, living in both salt and freshwater, from Japan to Norway. So it’s not a big surprise that they’re doing well at Mountain Lake. Likewise, the chorus frogs will be demonstrating their numbers soon, when the rainy season starts. This is the first year for the damselflies, and too early to say how they’ll do.
As for the mussels, the larger ones continue to grow, but the smallest fry introduced this year were eaten, most likely by crayfish and worms. Shellfish play a vital role in environments like Mountain Lake. Filter feeders, the mussels eat tiny animals and algae, literally cleaning the water. As the water becomes clearer, aquatic plants can gather more sunlight. Once the plants and mussels are fully established, harmful algae blooms become less likely. But for now, there aren’t enough mussels to hold their own in Mountain Lake, and Presidio biologists will be introducing more mussels next year.
El Jefe has a posse
But the superstars of the lake, the Western Pond Turtles, defied all expectations. Northern California got thoroughly soaked during the winter of 2016–7 and some turtles were lost in the high waters. Of the 54 turtles released in 2016, only eleven turtles were spotted at once in 2017, suggesting a devastating loss.
But the picture changed in April 2018. On the first day of turtle monitoring for the 2018 season, 20 turtles were spotted basking along the lakeshore. Wherever they’d been the previous year, they reemerged to be counted this spring and summer. One day in September, 29 Western Pond Turtles were spotted at once, eclipsing all expectations after the discouraging results in 2017.
Among the Western Pond turtles, there’s one who lacks the tracking antenna that the original group wear on their shells. And it’s much bigger than its fellow turtles. It’s not clear where it came from, but it is the right species, and has picked up the nickname “El Jefe.”
The lake was healthy enough to be a nursery for a variety of birds. Coots, mallards, pied-billed grebes and red-winged blackbirds all nested alongside the lake. Plenty of bird species were spotted this year, including kingfishers, snowy egrets, great blue and night herons and ruddy ducks. Violet-green and barn swallows patrolled the lake surface during the summer, and double-breasted cormorants took to hanging out on the buoys, diving for (invasive) black bullheads. From the ring of willow and oak trees around the lake emerged even more birds, warblers and nuthatches, buzzing Ana’s and Allen’s hummingbirds and scolding Steller’s Jays.
The harsh bong of reality
So, overall, a positive year for habitat restoration at Mountain Lake. But there is another side to the story. As one biologist puts it, it’s time for a “harsh toke on the bong of reality.” There are still invasive species in Mountain Lake. One is crayfish — there’s no effective way to eliminate them. They’ve been in the lake for decades, and probably always will be. But there are newer arrivals. Among the native turtles, there is a single Red Eared Slider, a notorious invasive species. The slider stands out like the Easterner who steps off the railcar in the Old West, a dope in a striped green & yellow suit among the cowboy Western Pond turtles.
This Red Eared Slider didn’t get to the lake on its own. Neither did the black bullheads. These catfish feed by sucking up everything on the lake bottom and spitting out what they don’t like. They muddy the water and interfere with the native species.
The Presidio provides a drop-box for unwanted pets, and Presidio staff does education year-round to explain why dumping your unwanted aquatic animals in the lake is a Bad Idea. Nevertheless, some humans have released these animals in the lake.
Keeping invasive species at bay while giving the native species a chance to get established is the day-to-day work of habitat restoration. It’s a continual process, requiring constant monitoring of the Presidio habitat. Thanks to the efforts of the Presidio naturalists, interns and volunteers, Mountain Lake is humming with activity. It’s a tiny lake in a big city, but with our help, it’s becoming an oasis for wildlife.
