by Marisa Evans
Little Carson Falls is a very romantic place this time of year for the Foothill Yellow-legged Frog (Rana boylii). Native to parts of the Mt. Tamalpais Watershed, the frogs breed and lay their eggs in and around the pools of the waterfalls from March through June.
The Foothill Yellow-legged Frog is both a federal and state species of “special concern,” which means its population is declining. To help stop the decline and restore a healthy population within the watershed, MMWD trains volunteer frog docents to monitor the falls each spring when the eggs and tadpoles are at their most vulnerable.
In April, our 15 frog docents saw an average of seven frogs per shift. Surveys have recorded sightings of a juvenile frog, adult males, gravid females filled with eggs, and pairs in amplexus—part of the mating process in which the male clasps the female with his front legs in order to fertilize her eggs. The first egg mass spotted has been washed away, but on the brighter side two new egg masses have been observed.
In addition to the amorous frogs, docents have spotted salamanders, newts, snakes and mating lizards at the falls. Most importantly, they have engaged with more than 500 visitors so far! Our docents have spent their days educating Cub Scout troops on “frog safety” and cautioning hiking groups from as far as Sacramento that they are entering frog territory. One docent shared a glimpse of an egg mass through a scope with a couple who might otherwise have let their dog sip from the pool where the helpless eggs cling for dear life.
The frogs are small (1.5 – 3.0 inches long), greenish brown, and hard to spot, and the egg masses are no match against hiking boots and dog paws. If you visit the falls, you can help by keeping your distance from the pools, keeping dogs on leashes, and sharing this information with other hikers. Thank you for doing your part to protect this sensitive habitat, and thank you to our docents for being there to engage and educate visitors on behalf of the frogs!