Rearing Pacific Tree Frogs

Rearing Pacific Tree Frogs

It’s been just over a week since I picked up Pacific tree frog (Pseudacris regillaeggs and tadpoles from Charlotte Hill at Visitacion Valley Middle School on the edge of San Francisco’s McLaren Park. Charlotte’s organization Kids in Parks has been working with students to build frog ponds in the school’s vegetable garden, and the frogs have been breeding with increasing numbers.

The tadpoles I collected are now in a sunny, south facing window in a small fishtank complete with lots of aquatic swimmers and algae on which the tadpoles feed. I distributed 50 of them so far to colleagues including a preschool teacher and the stewards of two backyard ponds, one in Noe Valley and one in the Mission District. The ponds are complete backyard habitats with shallow water that warms in the sun, dense aquatic and edge vegetation, and rocks, and logs to protect the frogs from raccoons, herons and other predators. Our goal is to keep these ponds seeded with new tadpoles until these become successful breeding spots in their own rite, which may take a few years.

Life cycle of the Pacific tree frog
In San Francisco, the frogs breed in seasonal ponds filled by rain. These vernal pools last only as long as the water remains, during which time, the eggs hatch, the tadpoles fed on algae and vegetation that falls into the pond, and in in about two to five months, they emerge as full-grown frogs. Before emergence, the tadpoles change their diet. From wikipedia: “During the final stages of transformation when the tadpoles have [four] limbs and a tail, they stop feeding for a short time while their mouths widen and their digestive system adjusts from herbivorous to carnivorous.” During the rest of the Mediterranean dry season, the frogs live in vegetation, and under logs and stones eating small insects. In winter, with the first heavy rains, breeding and egg-laying begins again. Males with vocal sacs noisily attract mates, they breed, then females find ponds and lay clusters of eggs attached to aquatic vegetation.

Pacific free frogs have a wide distribution in the western states from Baja to British Columbia. More from wikipedia: “They are found upland in ponds, streams, lakes and sometimes even further away from water: their habitat includes a wide variety of climate and vegetation from sea level to high altitudes. The Pacific tree frog makes its home in riparian habitat as well as woodlands, grassland, chaparral, pasture land, and even urban areas including back yard ponds.”

In San Francisco, the remaining natural habitat for this frog is relegated to Lake Merced and a very small population along the Caltrain tracks on the eastern slope of Potrero Hill. Email Jim McKissock if you’re interested in the frog’s habitat and lifecycle. Jim and volunteers work every Tuesday in Brisbane, just south of San Francisco, to restore a breeding population along a slow-moving creek that was once an old railroad throughway.

If you’re interested in stewarding a Pacific tree frog pond in your own backyard, I am very happy to help, email me for more details. These frogs provide many benefits for you, your family and the ecosystem. Take a trip back in time to middle school biology class and feel awe as you watch them grow, or better yet, share this remarkable metamorphosis with your kids. When the frogs are adults, they will keep the mosquito and fly population down in your garden, and a few will undoubtedly become food for the other creatures that frequent your space. Also, the winter mating song of the male Pacific tree frog is like none other, and you can experience a bit of country in the City.