Pacific tree frog

Appearance

The Pacific tree frog grows up to 2 in from snout to urostyle. The males are usually smaller than the females and have a dark patch on their throats. The dark patch is the vocal sac, which stretches out when the male is calling.

Pacific tree frogs can be a number of different colors, including green, tan, reddish, gray, brown, cream, and black, but most are a shade of green or brown, with pale or white bellies. They have a variety of dark and spotty markings on their backs and sides and can be identified by a black or dark brown eye stripe that stretches from the nose, across the eye, and back to the shoulder.

They can change color seasonally to better match their environments. 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 only very slightly webbed. On the end of each toe is a round, sticky toe pad or disk used for climbing and sticking to surfaces.

Distribution

Pacific tree frogs are common on the Pacific coast of Oregon and Washington, but they are found from extreme northern California to British Columbia.

A small population also exists in a pond on Revillagigedo Island near Ketchikan, Alaska, having been intentionally introduced there in the 1960s.

Status

These frogs are the most common frogs on the West Coast of North America. Although Pacific tree frogs remain abundant, some other species found in the same areas, such as California red-legged frogs, are declining. Most populations of tree frogs appear healthy, and they have no concern or conservation status.

Behavior

For the most part, Pacific tree frogs are nocturnal, but they have been spotted during the day. These frogs spend a lot of time hiding under rotten logs, rocks, long grasses, and leaf litter, where they are very difficult to see unless they move.

When they hunt, their toe pads allow them to climb on vegetation and other surfaces where they are to ambush their prey. Much of their diets consists of spiders, beetles, flies, ants, and other insects and arthropods; they can and do eat insects that are almost as large as they are, and will expand their bodies slightly to accommodate these meals.

Pacific tree frogs mature quickly, and are usually mate the season after metamorphosis. Predators include snakes, raccoons, herons, egrets, and other small mammals and reptiles.

When they sense potential food nearby, they commonly twitch a toe to attract it within easy reach of their tongues. They can live up to 9 years in captivity.

They produce several call types. These include the males' advertisement call, commonly described as “ribbit” or “crek-ek”, as well as an encounter trill call.

The cre-ek call can be quite loud and can thus be heard from very far away. Males also produce a “dry land call”, a long cre-ee-ee-eeek, that can be heard anytime in the year except during the coldest and driest periods. Pacific tree frogs are the most commonly heard frogs along much of the West Coast of the United States.

Habitat

They are found upland in ponds, streams, lakes and sometimes even further away from water; their habitat includes a wide variety of climate and vegetation from sea level to high altitudes. The Pacific tree frog makes its home in riparian habitat, as well as woodlands, grassland, chaparral, pasture land, and even urban areas including back yard ponds.

Reproduction

The Pacific tree frog begins mating in early winter to early spring. Since these frogs are so widespread geographically, their breeding season is thought to be determined by local conditions.

When it is time, the males migrate to the water. They then make a call at the same time, calling "ooh-yeeh" or ribbiting 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 survive, embryos will hatch into tadpoles within one to three weeks.

The tadpoles feed on periphyton, filamentous algae, diatoms, and pollen in or on the surface of the water. They feed using suction, and a beak-like structure that helps scrape vegetation off surfaces.

Metamorphosis usually follows about two to two and a half months later, but experience raising these tadpoles shows that some may delay metamorphosis, changing up to five months after hatching. The survival rate of these delayed metamorphs is lower, and the evolutionary utility of this delayed metamorphosis is uncertain. It may be related to the prevalence of fire in their natural ecosystem.

During the final stages of transformation when the tadpoles have four limbs and a tail, they stop feeding for a short time while their mouths widen and their digestive systems adjust from herbivorous to carnivorous.

Predators

Eggs of the Pacific tree frog may be consumed by the rough-skinned newt and other amphibians.

Evolution

The evolutionary history of these frogs is a very interesting one that is still being debated. Amphibians are thought to have descended from the lobe-finned bony fishes. These fishes had ossified skeletons and emerged from the water as they developed limbs, girdles, and terrestrial characteristics such as lungs and necks.

The exact frog lineage is difficult to determine because of the lack of fossil records. The habitat in which these animals lived was moist and decay was quick. This was not helpful in preserving biological clues. The family Hylidae is somewhat recent, appearing around 50 million years ago.

The genus "Hyla" then appeared just after the dinosaurs went extinct. This genus originated in South America and expanded to the north into Mexico and eventually into North America. Then the sea level rose 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.

For this reason, the genus "Hyla" has been split into three separate genera: "Aris", "Limnaoedus", and "Pseudacris," which has caused" "the current confusion. Although the Pacific tree frog has carried the scientific name of "Hyla regilla" for many years, the most current consensus among scientists is that their name should actually be "Pseudacris regilla". This is still not agreed upon completely.