The Interesting and Common Pacific Chorus Frog

With these wonderful summer rains, I have been seeing an abundance of juvenile Pacific Chorus frogs, or treefrogs as they are called. Everywhere I walk in Little Lake Valley, I must watch where I step because they are hopping through the tall grass and the edges of the creeks and wet meadows. Sometimes I am surprised to find one high up on a Cow Parsnip plant or in an Ash tree looking out at the world.

The Pacific Chorus frog, Pseudacris regilla, is the most widespread and common amphibian on the west coast of North America. Their range extends from British Columbia down to Baja California and from the Pacific Ocean to Nevada and Montana. They live in a variety of habitats, from deserts to redwood forests and from sea level to over ten thousand feet in elevation.

There are two important identifying characteristics that are important to look for and will tell you if you are indeed looking at a Pacific Chorus frog and not some other species. Look for a dark stripe that starts just before the nostril, goes through the eye, and extends down past the tympanum, the ear opening that is covered by a thin circular membrane. The second important characteristic that all Pacific Chorus frogs have are large, rounded toes that are adhesive, allowing them to climb straight up and over smooth surfaces. These amazing toes are the subject of many research papers because of their biomimetic potential. This means that they are being studied for their adhesive properties under wet conditions. As humans we are always trying to learn from nature how to solve complex problems. Biologically inspired design or adaptation from nature, biomimicry, is a very exciting and popular scientific field of study. Chorus frog toes have pads with grooves that secrete mucus that forms a thin layer allowing them to adhere to smooth, dry, rough, and wet surfaces. This mucus also allows them to keep their toepads clean and functional through a self-cleaning and flushing action that removes contaminants that get trapped in the mucus.

Climbing is an important and significant advantage for animals since it makes them inaccessible to non-climbing or non-flying predators and gives them more cover options. It may be a factor in Pacific Chorus frogs having maintained good populations when other amphibians have not.

There is a variety of skin colors and patterns found among the Pacific Chorus frogs. Typically, they are green or brown but here in Little Lake Valley and in other places you can find frogs that are bright gold colored, bronze, lime and dark green, grey, and even a few with reddish coloration. In my research I found out that some of these frogs have the ability to change their color from brown to green which may help them camouflage in different environments. There are still many questions about why there are a variety of color morphs and if it affects their mating or thermoregulation.

Pacific Chorus frog is a good name because during the breeding season, which can be prolonged by cool weather, as it has this year, the males get together and sing all night long in a loud chorus that can be deafening. This begins in Willits during the warmer rainy evenings in December and can go into summer (as they are this year). There are hundreds of chorus frogs in Little Lake Valley, especially on the north end that becomes inundated and stays wet even into late June.

The female chorus frogs are generally larger than the males and have smooth white throats while the males have rough dark throats. The name Pseudacris comes from the Greek Pseudes, which means false, and acris, which means locust. During breeding season, the male chorus frog vocalizations sound like loud locusts. When singing in unison, the raucous ‘kreck-ek’ sounds like a swarm of insects.

There is research that has shown that females may prefer males that call more frequently than other males. (Whitney and Krebs 1975 Nature). The females lay between 500 and 1,250 eggs every year in multiple small clusters, each containing 1 to 100 eggs. The clear gelatinous clusters can be found in many waters such as roadside puddles, streams, ponds, and even in bird baths.

Adult Chorus frogs eat a wide variety of invertebrates, especially ones that fly. During the tadpole phase they are suspension feeders, filtering out and eating algae, bacteria, protozoa, and even organic and inorganic debris in the water.

Chorus frog predators include giant water bugs (during the tadpole stage), snakes, raccoons, and many species of birds including ducks, bitterns, herons, Red-tailed hawks, and American Kestrels.

Even a small creature like the Pacific Chorus Frog is a fascinating and important part of our complex ecosystem in Little Lake Valley.