The Pacific Tree Frog is a very common species of chorus frog, with a range from the West Coast of the United States to British Columbia in Canada. Living anywhere from sea level up to over 11,000 feet. They live in many types of habitats and reproduce in aquatic settings.
They can reach up to about 5 cm long from snout to urostyle. The males are often smaller than the females and have a dark patch of skin on their throat. This dark patch is the vocal sac which stretches out when a male is calling. These frogs can have highly variable color on their bodies. They can be anywhere from gray, brown, tan or bright green and can even change between them. They are usually a pale or white color on their bellies. They have many variations of markings on their back and sides that are usually dark and spotty. The one identifiable mark is a dark stripe that goes over the eye from the nose to the shoulder. Their skin is covered in small bumps. They have long legs compared to their bodies and they tend to be slender. Their toes are long and are only very slightly webbed. On the end of each toe, there is a round sticky pad that is used for climbing and sticking to surfaces.
The evolutionary history of these frogs is a very interesting one that has recently been changed to better suit tree frogs. Amphibians themselves are thought to have descended from the lobe finned bony fishes. These fishes had an ossified skeleton and emerged from the water as they developed limb girdles and terrestrial characteristics such as lungs and a neck. It is hard to figure out an exact frog lineage because of the lack of fossil record. The habitat in which these animals lived was moist and decay was quick, which was not helpful in preserving biological clues.
The genus appeared just after the dinosaurs went extinct. They originated in South America and expanded to the north into Mexico and eventually into North America. There was then a rise in sea level and the connection between the northern and southern populations was gone. They have been separate ever since and have become genetically distinct from one another.
One of the most interesting features of these frogs is their ability to change color from brown to green. Previously, it was thought that there were two different fixed colors that an adult tree frog could be. Now it has been found that some of them are actually able to change between the two. They can also change from lighter to darker. These color changing morphs are triggered not by color change in their environment, but a change in background brightness. This type of environmental change would be caused by seasonal fluctuation, and has been shown to be a very useful cryptic survival feature for these frogs.
Pacific tree frogs are most common on the pacific coast of California. They are also found eastward to Montana and Nevada. They love water, but they can also be found upland from ponds, streams, lakes. Their habitat consists of a wide variety of climate and vegetation from sea level to high altitudes. The tree frog makes its home in riparian habitat as well as woodlands, grassland, chaparral, pasture land, and urban areas including back yard ponds.
The Pacific Tree Frog begins mating in early winter to early spring. Since these frogs are so widespread geographically, it is thought that their breeding season is determined by local conditions. When it is time, the males migrate to the water. They all call at the same time very loudly. This lures the females to the water and they mate. The females lay their eggs in clumps of 10-90 and usually put them on and under vegetation and leaf litter in the pond. Females usually lay their eggs in shallow, calm water that has little action around it. If they are not eaten, embryos will hatch into tadpoles within one to three weeks.
The tadpoles feed on periphyton, filamentous algae, diatoms and pollen in and on the surface of the water. They feed using a beak like structure that helps scrape vegetation off surfaces and suction. Metamorphosis follows about two to two and a half months later. Prior to transformation, they stop feeding for a short time while their mouth is transformed from herbivorous to carnivorous. Then the tiny baby frogs emerge from the pond measuring as little as one centimetre. They hunt using their sticky pads to climb on vegetation and other surfaces. Much of their diet consists of spiders, beetles, flies, ants and other insects. They mature very quickly and are likely able to mate in the next season after metamorphosis. Predators include snakes, raccoons, herons, egrets, and other small mammals and reptiles. The tree frog is mostly nocturnal, but can be spotted during the day. It spends a lot of time hiding under rotten logs, rocks, long grasses and leaf litter.
These frogs are the most common frogs on the west coast of North America. Although the Pacific Tree Frog remains abundant and most populations of tree frogs appear healthy, there is some evidence of declines. The cause has not been fully understood, but pollution, the introduction of exotic species and habitat loss are very high on the list of factors. Some ways to stop amphibian declines are by respecting and protecting amphibian habitat as well as supporting laws and legislation that help to do this. Another important way is to help limit pollutants that will end up in amphibian habitat, usually from agriculture and urban run off, by boycotting companies who are heavy pesticide users and by not pouring chemicals or pollutants down storm drains or in amphibian habitat.