Pacific Treefrog

Contents:
 
Links:
Taxon, Status, and Ranks Habitat Photos
General Description State Status Comments
Identification Tips Inventory & Research Needs Key Features
Phenology Threats & Mgmt Concerns
Range References Distribution Map

Taxon, Status, and Rank

Species Pseudacris (= Hyla) regilla     (Baird and Girard, 1852)
Family Hylidae
(Tree Frogs)
Status None
State Rank S5
Global Rank G5

General Description

This small frog has a somewhat flattened body, narrow waist, long legs, relatively smooth skin and a pointed snout. Adults are usually less than 5.0 cm (2 in.) snout-vent length. Females attain larger sizes than males. Tips of the fingers and toes have sticky broadened circular discs called “toe-pads” that adhere well to smooth surfaces. The dorsal body color is typically green or brown, but can also be shades of gray, red, copper, or some combination of all these colors. A conspicuous dark mask extends from the tip of the nose through the nostril, eye, and tympanum to the shoulder. Frequently, two or three stripes run down the back and a “Y” shaped marking exists on the head between the eyes. These markings may be discontinuous, appearing more like spots or blotches or may be subtle or absent. Other dark blotches or markings may be present on the sides of the body and limbs. The ventral surfaces are mostly white, often with yellow to yellow-orange coloration on the legs and sides of the belly; mature males also have darkly pigmented throats with a translucent yellow wash and wrinkly skin. Newly metamorphosed Pacific Treefrogs look similar to adults.

The tadpole has eyes on the margins of the head and a tail fin with a high arch that starts mid-way along the back and is rounded at the tip. The overall coloration is brown or olive usually with black speckling (but not inky black spots). The underside is white with metallic iridescence. Tadpoles grow to about 50 mm total length before metamorphosis. Newly metamorphosed Pacific Treefrogs range in size from approximately 12 to 18 mm snout-vent length.

The eggs are laid in small loose packets of around 9 to 70 eggs. The egg packets are approximately 20-40 mm in diameter. Individual eggs, when fully expanded, are small with the ovum and gel together measuring less than 7 mm in diameter. Egg packets are typically attached to a brace, often vegetation; less frequently, they are laid directly on the sediments.

Voice: Males produce a variety of calls in the breeding chorus including a two-part advertisement call, “rib-it” or “crek-ek,” an enhanced male attraction call, and a trilled encounter call. The choruses are audible from great distances. Outside the breeding season, males produce a one-part dry land call. These calls are produced throughout the year except during the driest and coldest periods. Pacific Treefrogs are the most commonly heard frogs in Washington.

See Photos Page.

Identification Tips

The Pacific Treefrog is easily distinguished from all other Washington frogs by the circular discs at the tips of the fingers and toes. Pacific Treefrog tadpoles are the only tadpoles in Washington that, when viewed from above, have eyes located on the margins of the head. The eyes, especially in large tadpoles, stick out from the outline of the head.

Eggs of the Great Basin Spadefoot are arranged somewhat like a bunch of grapes with each egg being loosely attached to the next instead of being contained within a single small cohesive packet like that of the Pacific Treefrog. Eggs of Long-toed Salamanders, when fully expanded, are larger and somewhat darker on the pigmented (upper) side with individual eggs, including ovum and gel, measuring 10 mm or greater in diameter. See Key Features Page.

Phenology

Warm winter rains appear to trigger migrations to the breeding ponds. Males arrive first. Chorusing takes place at night during the early part of the season and may continue during the day at the peak of the breeding season. Calling will cease if nighttime temperatures fall below 5ºC (41ºF). Calling may take place for several weeks before egg laying actually starts. Most egg laying starts in mid-February at lower elevations in western Washington and in April at lower elevations in eastern Washington. Breeding is later at higher elevations. Breeding at most sites is prolonged, up to 3-4 months. Eggs hatch in 3-5 weeks. Larval development typically takes 1 1/2 to 2 1/2 months to complete. The juveniles grow quickly and some are able to reproduce the spring following metamorphosis. Overwintering behavior has not been studied in Washington. At low elevations on the west side of the Cascades, males call sporadically during the winter when temperatures are above 8-10ºC (46-50ºF), implying that they remain active throughout the winter.

Range

The Pacific Treefrog is the most widespread and common frog species in Washington and occurs in all ecoregions. See Distribution Map.

For information on the complete range of this species, see NatureServe Explorer.

Habitat and Habits

Pacific Treefrogs are able to utilize a wide variety of habitats and persist even within urban and disturbed areas, where pockets of undeveloped habitat exist. In the Columbia Basin, their distribution is limited to areas with water. This species was not detected during an extensive herpetological inventory conducted at the Hanford Site in1996 and 1998. This is the driest area of the state and may exceed the species’ tolerance limits. Pacific Treefrogs are able to use almost any type of still or slow-flowing water for breeding including wetlands, ponds, lakes, still water edges of rivers, slow flowing springs, irrigation ditches, road ditches, seasonally flooded pools and puddles, deep tire ruts, children’s wading pools and spring boxes. Survival in seasonal water bodies can be precarious; water may dry up before tadpoles can complete metamorphosis. This species is prolific and the tadpoles are usually the most common amphibian larvae at any breeding site.

Transformed treefrogs are terrestrial but need to be in moist microhabitats or near water. Terrestrial habitats include wet and dry forests, prairies, alpine areas, and both shrubland and grassland communities. Contrary to strict interpretation of their common name, they tend to be found on the ground or in shrubs. Much activity is nocturnal, especially at low elevations, but it is not unusual to find them out during the day.

State Status Comments

The Pacific Treefrog is the most common frog species in Washington and can persist in a variety of habitats including developed and disturbed areas. While local declines have been reported from selected extensively urbanized areas, no major declining trends have been noted in Washington.

Inventory and Research Needs

None at this time.

Threats and Management Concerns

Larvae may not persist in the presence of introduced warmwater fish. Pollution and chemical contaminants may cause declines or localized extinctions in affected areas.

Populations with malformations, especially in the form of extra limbs, have been found in Washington. Frogs that breed in ponds with high levels of nutrients from fertilizers, cattle or other sources, may be at higher risk for developing malformations. Current research indicates that a trematode parasite in the genus Ribeiroia often causes these deformities. A suggested reason for the apparent increase in the number of anurans found with deformities is that eutrophication causes a predator-mediated shift in snail species composition toward the snail Planorbella spp., the exclusive first intermediate host of the parasite Ribeiroia ordatrae.

References

Corkran and Thoms 1996, Davison 1995, Hallock (1998), Johnson and Chase (2004), Johnson and Lunde (1999), Nussbaum et al. 1983, Stebbins 1951, Stebbins 2003


Personal communications: M. Hayes, P. Johnson, J. Lewis




Hallock, L.A. and McAllister, K.R. 2005. Pacific Treefrog. Washington Herp Atlas. http://www1.dnr.wa.gov/nhp/refdesk/herp/

Last updated: February 2005


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