The film editor reviews the scene for the ninth time: soft rain falls, a couple embraces passionately on the porch of an antebellum mansion, the warm, heavy southern air envelops them, heat lightening flickers in the distance. The mood is nearly perfect; but something is missing something that the editor cannot put his finger on. What is it? WHAT IS IT? “FROGS” he shouts, “Frogs! We need croaking frogs!” The director agrees that frogs are just what the scene requires and he sends the sound technician scurrying to the tape library for frog sounds.

And so once again our hero, the Pacific tree frog, is called into action. The vocalizations of this amphibian are the most common frog sound heard in the background of movies. Whether the movie takes place in Britain, New Guinea, Texas or the Serengetti, if it’s a Hollywood set it gets the local frog. Not coincidentally this is the most common frog in southern California and throughout the far west. So, even though frog sounds vary around the world, for the sake of expediency this frog is the star of the night.

The scientific name, Hyla regilla, means “the little king of the woods” and I would add that they are also the king of the fields. Right now we hear loud and wonderful evening choruses. Wherever there is standing water roadside ditches, farm ponds, and even outdoor hottubs; there are uncountable numbers of males singing, each trying to attract a mute female. Imagine her dilemma: she must choose one mate out of thousands based on his singing ability alone. This is cutthroat (frogthroat?) competition.

Though easily heard, this diminutive amphibian is difficult to see. It is distinguished by its small size; adults average 1 1/2 inches from nose to rear. And while we call it “treefrog,” it is usually found hidden in the grass. It has the ability to climb anything including trees and glass. An extra joint in its toes gives it great dexterity and the ability to adhere to slick surfaces.

Pacific treefrogs range in color from brown to green with every shade betwixt and have the phenomenal ability to change those colors completely within ten minutes. They use special pigment containing cells on the surface of the skin called chromatophores to achieve this remarkable feat. But regardless of its color phase each frog has a brown stripe running from the shoulder through the eye to the tip of the nose which helps even the novice amphibiophile identify the critter.

In addition to the loud (some say obnoxious) rapidly, repeated kreck eks, olive throats and roughened toes distinguish males from females. Also females are on the average slightly larger than males. They mate in quiet waters, with the male using his roughened toes to clasp the slippery female from the back. Just after he discharges a cloud of sperm she sheds her eggs and attaches them to submerged vegetation. Eggs and sperm unite externally. The frogs may repeat this ritual several times. The entire act takes 8 to 40 hours or more!

Tadpoles develop and hatch in a relatively short time. They are primarily vegetarians or scavengers that breathe with gills. After a period of growth, they transform: their hind legs appear, their digestive tract shortens to a more suitable size for an insect diet, lungs replace their disappearing gills, and their tail is gradually recycled into other body parts. Soon a little (7/8 inch) treefrog hops from water onto the land.

The Pacific tree frog ranges all the way from British Columbia to Baja California and east to Montana. It lives from sea level to 11,000 feet and is found in a wide range of habitats. It is the most widely distributed of any amphibian in the west.

So the next time you are watching old reruns of MASH and see Major Houlihan and Frank trysting in the “Korean” spring evening, remember our very own treefrog serenades them.



Posted on

August 22, 2009