Red Legs, Yellow Legs, Edible Legs, NOT

by Eric Ettlinger

This post is the second in a year-long series celebrating the 40th anniversary of the Endangered Species Act. Read last month’s post here.

Peoples’ interest in frogs can be viewed as something of a leg obsession. The most obvious example is our insatiable appetite for frogs’ legs. During the California Gold Rush, populations of native red-legged frogs (Rana draytonii) were decimated by over-harvesting, leading to the importation of bullfrogs (Rana catesbeiana) from the eastern United States to help satisfy demand. These voracious predators (bullfrogs, not people) quickly spread to anywhere year-round fresh water could be found, and they continue to eat their way through native frog populations to this day.

Our obsession with frogs’ legs is not limited to cuisine, however, and extends to the very names we’ve given them. Here in Marin County we have three native frog species: the northern Pacific treefrog (Pseudacris regilla), the California red-legged frog, and the foothill yellow-legged frog (Rana boylii). We also have California toads (Anaxyrus boreas halophilus), which aren’t technically frogs, and since they don’t fit into this essay’s theme on leg obsessions, they will not be mentioned further.

Of our real frogs, two of the three are named for their legs, which gives the impression that there’s something quite distinctive about those springy appendages. On the contrary, the red and yellow coloration for which these frogs are named is generally confined to the undersides of their legs, which few can see.

Naming these frogs for their legs fails to capture what’s truly fascinating about them. The red-legged frog is most famous for being the central character in Mark Twain’s “The Celebrated Jumping Frog of Calaveras County.” Given such celebrity, wouldn’t a more fitting name be something like “Twain’s jumping frog?”

Female FYLF on cliff at Little Carson Falls. Photo by docent Peter Barto.

Foothill yellow-legged frogs (FYLFs) don’t have a claim to fame but can perform feats like climbing slick bedrock cliffs and clinging to rocks at the bottom of waterfalls. “Clingy frog” is more apropos and interesting, and doesn’t require an acronym.

In recent years both of these frogs have  taken on new, more ominous, labels. California red-legged frogs have been listed as a federally threatened species, and FYLFs are listed as a “species of special concern.” The reasons for their declines include predation by non-native bullfrogs, crayfish, and fish; habitat loss; pesticides; and the modification of river flows. Their plight is a small part of an unfolding global amphibian crisis, which may result in the largest extinction event since the age of dinosaurs. A significant cause of the crisis is the global spread of a deadly Chytrid fungus, although FYLFs appear resistant to Chytrid infection and the role it plays in red-legged frog declines is unknown.

Red-Legged Frog in Lagunitas Creek

In the last decade, a single red-legged frog was seen on the Marin Municipal Water District’s watershed lands. That individual likely dispersed over a ridge from Point Reyes National Seashore, where a relatively large population uses managed stock ponds (artificial ponds for cattle) for breeding.

FYLF populations on MMWD watershed lands appear to include roughly 30 breeding pairs, which breed in only two locations. One of these breeding sites is Little Carson Falls, a popular hiking destination near Pine Mountain. On warm spring days when the falls are flowing, hikers and their dogs have been known to wade in the water and inadvertently dislodge fragile egg masses clinging to the rocks. Fortunately for the frogs, volunteer “Frog Docents” also hike out to the falls, educate visitors about the plight of the frogs, and collect data for the biologists monitoring the population.

Foothill Yellow-Legged Frog at Little Carson Falls. Photo by docent Matthew Sykes.

Now in its sixth year, the Frog Docent Program is looking for volunteers to help conserve these rare frogs. If you’d like to help save this species from possible extinction by becoming a 2013 frog docent,  call our Volunteer Program at (415) 945 -1128 or e-mail volunteerprogram@marinwater.org.