Pacific Treefrog

Pacific treefrogs (Pseudacris regilla) are amphibians. Derived from the Greek “amphi”  and “bios” meaning “both” and “life” respectively, amphibians inhabit water early in their lives and then change to a form that can live on land.

Pacific treefrogs are small, usually under 2 inches in length with females larger than males. They inhabit a variety of habitats near water at altitudes as high as 10,000 or more feet in British Columbia, the Pacific States, Idaho and Nevada.

Pacific treefrogs can be green, tan, brown or blackish with pale or whitish bellies. They have a black eye stripe and sometimes there are dark markings on their backs. A dark triangle is often present between the eyes. Males may have a black throat patch, particularly visible during the breeding season. Large suction pads at the tips of their toes give Pacific treefrogs the ability to climb vertical surfaces. However, despite their common name and suction pads, these treefrogs are rarely found high above the ground. There is limited webbing between the long toes.

In the spring male Pacific treefrogs sing loudly at night or on cloudy rainy days while perched on vegetation near water. Females lay eggs in “patches” of several to nearly 90 that float on the surface of water in thin films. The eggs may also be laid on or under leafy vegetation in the water. Within 3 weeks the eggs hatch into tadpoles (polliwogs), round-bellied, long-tailed larvae. The tadpoles are vegetarian and feed on algae, diatoms and bacteria in the water as well as pollen floating on the water surface. After about 2 to 2 1/2 months the tadpoles transform (metamorphsis) into adults that live on land and require live insect food which they locate by vision. During the final stages of metamorphosis, when the tadpoles have four legs and still retain a tail, they stop eating while their mouths widen and their digestive systems adjust from vegetarian to carnivore.

There is much confusion about Pacific treefrog color. There appear to be green morphs and brown morphs. Some say that these amphibians can change color or appear lighter or darker over hours or longer depending on their environment. Others say Pacific treefrog color changes, including shifting from patterned to pure colors, are due to the brightness of ambient light or season of the year (winter is generally cloudy and darker while summer is sunnier and brighter) not the environment or habitat. The response to light is due to contraction of melanophores (pigment cells) in the skin. In brighter situations the melanophores contract making the treefrogs appear brighter while when the light is muted the pigment cells open exposing the color.

Confusion also exists concerning the scientific classification of Pacific treefrogs. Prior to 1986 P regilla was known as Hyla regilla. Recently these treefrogs were separated into three distinct species that seem to have different ranges and are very difficult to visually distinguish. I will follow the lead of many and simply continue to refer to all three species as P regilla or the Pacific treefrog.

Also commonly called Pacific chorus frogs, these Pacific treefrogs were photographed on BLM land near Howard Prairie Reservoir (Jackson County OR).

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3 Responses to Pacific Treefrog

  1. Lin Erickson says:

    They are prolific around our house…I even heard one recently (though our temps have been very cold).

  2. Jim G. says:

    It will always be Hyla regilla in my brain. One was a great pet in college.

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