When the rains finally arrived this year, a frog chorus began to rise up from the meadows and ponds around the valley. Now, in some places it is so loud you can hear it from inside a moving car. There is almost no way to miss it if you are walking by. I have been fortunate enough to be able to walk next to a wetland meadow on a few evenings over the last week. As if perfectly designed to tease someone who is curious, the sound always stops just as I get close enough to discover what might be making it. It starts up again just when I am safely past. Not to be daunted, I walked back in wading boots in daylight, right into the wetland ponds, and of course, there was no sign of a frog to identify.

A little research and some inquiry turned up information that lifts the veil on these elusive animals. The song was the call of the Pacific Tree Frog, another of the interesting and often overlooked members of the natural world here.

The Pacific Tree Frog, Hyla regilla, is a member of the order of amphibians known as Salientia, the frogs and toads. The treefrog family, Hylidae, has about 600 known species, 26 of which are found in the US. Tree frogs have special adaptations that allow them to be good walkers and climbers, and not great jumpers. Their toes are enlarged to include sticky pads and special joints that allow the pads to stay flat against a climbing surface. Once more contrary, the Pacific Tree Frog actually spends most of its life on the ground or in low vegetation near water and is a fair jumper. Fairly small (less than two inches), it has the ability to change its skin shade in a just minutes, allowing it to blend in readily to its surroundings.

An individual begins its life in a mass of about 25 eggs laid in shallow water, and hatches as a legless tadpole after three to five weeks. The tadpole grows rapidly. As it nears adult size, it develops legs and lungs and prepares to make the remarkable transition from an aquatic to a terrestrial, or earth dwelling, animal. Some speculate that this development reflects the changes that the ancestors of this frog made as they adapted to life on land, thus mirroring the evolution of most land animals, and now making in a few days the transition that took millions of years for animal life to make.

As humans, we tend to view the value of an animal in terms of direct benefits that it provides to us. We see the tree frog in terms of the pests it eats that otherwise affect us. What we may miss in this view is the less obvious and often more significant role that the animal plays in supporting the rest of life. Our tree frogs eat numerous organisms, including beetles, flies, spiders, ants, leafhoppers, and isopods that inhabit wetland areas. They excrete material that is incorporated by numerous other animals, plants, bacteria and fungi into the wetland around them. Merely by living, it passes material on to nature in a new form that is vital to some other organism. This is why it is so important to protect species and their habitats that contain countless organisms we can't see. As material and energy is passed around, all organisms are linked to support the vast process that is life, including our human lives. This process is ongoing and so far represents billions of years of work as life has evolved to become our world.

Like most amphibians, the Pacific Tree Frog is thin-skinned, and therefore more vulnerable than most animals to the effects of stress in its environment. Most amphibians, including the red-legged frog here in our valley, are under acute stress--from habitat loss, chemical toxins including acid rain, and ultraviolet damage from ozone depletion. Many species are in serious decline or are in danger of extinction. Apparently, the Pacific Tree Frog has one interesting advantage. It produces a large amount of a special enzyme called "photolyase", which helps repair damage caused to DNA, something that happens with more frequency as ultraviolet light increases. Species like the Cascades Frog and Western Toad also lay eggs in shallow water exposed to sunlight, and do not produce high levels of photolyase. Their eggs do not survive nearly as well. Even so, like most wetland animals, there are far fewer tree frogs here now than a few years ago because suitable wetland habitat is disappearing.

One of the more interesting aspects of these frogs is their vocal behavior. Males sing to claim territory and to attract females. A Pacific Tree Frog male typically sings a single note chirp when not courting actively, or perhaps when trying to let females know he is there. He will switch to a high pitched two note "ribbit" when he thinks a possible mate is near. Males may sing in turn, as two or three males create a round started by a "bout leader". A male will give a different call when his territory is challenged as a warning that he will combat intruders. All of this can go on for months each evening. As hundreds and even thousands of voices from the wetlands join together, the chorus can be deafening. These sounds of our Pacific Tree Frog are actually famous around the world, used commonly by Hollywood as the preferred sound effect for outdoor movie scenes.