The California Red-Legged frog
and
the San Francisco Garter Snake
at Mori Point
Delphine Vergara
Bio 28
October 16th and 17th 2010
Crima Pogge
The California Red-legged frog and the San Francisco Garter Snake are both endemic
species of California. Once widespread across the state, both species now have a special status
on the endangered species lists and found only in few locations. The California red-legged frog
was once a big part of California’s culture. It was made famous to the world by Mark Twain in
“The Celebrated Jumping Frog of Calaveras County,” and was a staple protein for the fortyniners (Wild equity institute). Both species could become extinct if we continue to destroy their
natural habitats and don’t implement conservation measures. The history of both species and the
management of the environment at Mori Point, sheds light on their interdependence for survival.
The California Red-Legged Frog
According to the Center for Biological Diversity (CBD), the Red-legged frog, or Rana
draytonii, is its own specie and part of the family of Osmeridae. It is native of western America
and the largest frog of the region. The Red-legged frogs got their name from the color of their
bellies and the underside of their legs; it can either be red or salmon pink, however it is yellow in
young frogs. The back of both adults and youngs, is brownish with speckled spots, more
pronounce in young frogs.
The Red-legged frog, once found from Point Reyes down to Baja California, now have
lost 70% of its range and is only found in 23 counties of California, mostly in Monterey, San
Luis Obispo, and Santa Barbara, but the densest population is found at Mori Point. The frogs
travel at the most two miles away from their breeding ponds during rainy or wet season into the
grassy areas. The overall population has decreased by 90% (CBD).
The frogs live in ponds, creeks, and marshes with no currents, but also need areas of
uplands with lots of vegetation for cover during aestivation or hunting and open grassy areas.
Some frogs will also hibernate in winter. The adult frogs hunt at night and catch their prey with
their sticky tongues. Their diet consists mostly of insects such as the rare San Francisco Forktail
Damselfly (Fimrite), Pacific tree frogs and California mice. However, the young frogs hunt
invertebrates day and night (CBD).
The frogs need still water for breeding. The breeding period is from November thru
April, during the rainy season. The females meet up with the males at breeding locations, mate
on site then move away after laying their eggs. Tadpoles need two week to hatch, and about six
months metamorphose into frogs, and three years to become sexually mature (CBD).
The San Francisco Garter Snake
The Center for Biological Diversity classifies the San Francisco Garter Snake, or
Thamnophis sirtalis tetrataenia, in the family of Colubridae. It is a very colorful snake, with a red
or orange head, a green/yellow back, a red and black stripped side and a blue/turquoise belly. It
can measure up to three foot long.
The San Francisco garter snake’s range is from San Mateo county Lake Merced down to
Santa Cruz. Only six main locations are known to support the snake, however four of these
locations have seen their number of snakes reducing significantly over the years, and it is
believed that only 1000 to 2000 specimens live in the wild today. The snakes do not travel far
from their wetlands, one kilometer at the most to find convenient winter spots (CBD).
The Snakes live in ponds, canals, and marshes with little currents, plants and frogs, but
also need uplands with lots of vegetation for cover and grassy open areas. The San Francisco
garter snakes feed on California red-legged and Pacific tree frogs, western toads, newts and
salamanders, but also on insects such as mosquitoes, or fish (CBD).
The garter snakes mate mainly in the spring and the females bare on average sixteen live
offspring during July and August. They are dormant in the winter, but very active from March to
July, preying on frogs leaving their breeding ponds to move upland (CBD).
Threats and dangers
Both the San Francisco garter snake and the California red-legged frog are in danger of
becoming extinct. Their wetland habitat is diminishing due to urban developments, such as
roads, drainages, reservoirs and recreational constructions, but also agriculture and farming. In
addition, their habitat is contaminated with pesticides used in agriculture, and predatory or
invasive nonnative species. Furthermore, the nonnative bullfrog is a danger for the garter snake,
and global warming has significantly reduced the number of amphibians around the world.
The Endangered Species Act enacted by Congress in 1973 responded to alarming
scientific revelations of the rates of species extinction. Both species are listed under the
Endangered Species Act (Wild Equity Institute). The California red-legged frog entered the list
as a threaten status in 1996 after frog biologist filed a law suit to enlist the species under the Act
(CBD).The San Francisco garter snake entered the California State list in 1967and then added to
the federal list in 1973, as an endangered species (CBD).
Mori Point
Mori Point is part of the National Park Service's Golden Gate National Recreation Area
since 2002 and spreads across 110-acre of headlands. It has suffered many human interactions
from being a smuggling point for Canadian whisky during the prohibition, to an off-road
vehicles park for a motorcycle club (Fimrite). Some developers had submitted construction
projects for the site, such as hotels, casino, or condos and although some projects had been
approved by the Pacifica City council, a dedicated group for the conservation of Mori Point sued
and was able to overturn the decisions. In the late 1990’s when the owner of Mori Point had to
sell, the land was bought at an auction by the Trust for Public Land in 2000 and then transferred
to GGNRA in 2002 (Rademacher).
Since Mori Point belongs to GGNRA, many management decisions have been made in
order to preserve the site. The fact that two endangered species share the Point and depend on
one another for survival has influenced the way the site is being restored. In addition, even
though the San Francisco Forktail Damselfly is not listed on the endangered species list, it is
rare, endemic and an important food source for the California red-legged frog. Since 2002, four
ponds have been created, fenced from dogs and planted with native vegetation (Rademacher).
Almost immediately, frogs were spotted in the ponds, and since 2005, the ponds have become
breeding sites since eggs were spotted in the water. The increase in frog population will in turn
increase the snake’s population (Fimrite)
Works Cited
Peter, Fimrite. "Abused Mori Point leaps back to life." San Francisco Chronicle 26 Apr.
2008. EBSCO. Web. 7 Oct. 2010.
http://search.ebscohost.com/login.aspx?direct=true&db=nfh&AN=31789758&site=ehost-live
Rademacher, Dan. "MORI'S STORY." Bay Nature 2 Sept 2009 MasterFILE Premier.
EBSCO. Web. 7 Oct. 2010.
http://search.ebscohost.com/login.aspx?direct=true&db=f5h&AN=39750316&site=ehost-live
“San Francisco Garter Snake.” Wild Equity Institute. Web, 8 Oct. 2010.
http://wildequity.org/species/23
“California red-legged frog.” Wild equity institute. Web, 8 Oct.2010.
http://wildequity.org/species/22
Center for Biological Diversity. “Reptiles” web 8 Oct. 2010.
http://www.biologicaldiversity.org/species/reptiles/San_Francisco_garter_snake/index.html
Center for Biological Diversity. “Amphibians” web 8 Oct. 2010.
http://www.biologicaldiversity.org/species/amphibians/California_red-legged_frog/index.html