Pseudacris regillaNorthern Pacific Treefrog(Also: Pacific Treefrog)

Geographic Range

Pacific treefrogs (Pseudacris regilla) are common throughout North America, west of the Rocky Mountains. Their geographic range extends from southern British Columbia, Canada, south through Washington, Oregon, and California, to Baja California, Mexico. Their eastern-most portion of their geographic range extends into Nevada, Idaho, and Montana. Pacific treefrogs also have been reported in deserts of southern California, where they are thought to have been introduced. (Elliott, et al., 2009; Ripplinger and Wagner, 2004)


Pacific treefrogs occur in a variety of habitats, including mesic and xeric forests, high altitude mountains, and desert steppe. Most commonly, they occur in moist environments, especially in low vegetation near water. Typically, they are found near lakes, ponds, rivers and streams. They can also be found in residential areas. Outside of breeding season, they often are seen near large, which is thought to provide shelter from predators. Pacific treefrogs are tolerant of rapid changes in weather and varying climatic conditions. Populations extend across a broad elevational range, from sea level to nearly 3500 m; however, most populations occur around 914 m above seal level. (Jameson, 1966; Ripplinger and Wagner, 2004; Stebbins, 2003)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams
  • Range elevation
    0 to 3500 m
    0.00 to 11482.94 ft
  • Average elevation
    914 m
    2998.69 ft

Physical Description

Pacific treefrogs are a small, slender frogs with large toe pads. They have smooth skin that varies in color from light-brown to bright-green. Pacific tree frogs with red or brown backs also have been reported, but are thought to be rare. This species typically has darker markings on its body, including stripes on its dorsal surface and sides of its heads, which vary in intensity and in some individuals may be nearly absent. A dark triangular marking between the eyes is also common. Generally, a line of broken spots extends down the ventral surface to the groin area. The legs, arms, and feet are generally darker than the rest of the body. Within their natural range, Pacific treefrogs are the only frogs with padded toes and dark markings. Pacific treefrogs can change their body color depending on environmental conditions and need for camouflage to avoid predation. Recent research suggests that P. regilla changes color seasonally to match the presence or lack of green foliage. Color variation has also been associated changes in mean temperature. At high temperatures, these frogs often turn a shade of yellow. Under cooler temperatures, they return to their more typical darker colors. Males often are slightly different in color than females. Their upper body can be a dark gray olive color and may have a brown band extending through the eye and a yellow stripe along the upper lip. Females may be similar to males in color, but with little to no yellow stripe on the groin. During breeding season, it is easier to distinguish males from females by their different colored throats. Females have a smooth white throat while males have a dark brown or yellow throat with wrinkled skin. (Awbrey, 1978; Bernard, 2005; Brattstrom and Warren, 1955; Holman, 2003; Morey, 1990; Stebbins, 1951; Stebbins, 2003; Wente and Phillips, 2005; Wright and Wright, 1949)

Adult body size in Pacific treefrogs ranges from 2.5 to 4.8 cm. Mature females tend to be larger than males, which is not uncommon for anurans. Body mass of newly hatched tadpoles is, on average, 0.24. After 30 days, weight increases to between 0.35 and 0.45 g, which is more typical of adult Pacific treefrogs. (Sparling and Fellers, 2009; Stebbins, 1951; Stebbins, 2003; Wright and Wright, 1949)

Pacific treefrogs, Sierran treefrogs, and Californian treefrogs were once considered a single species and referred to as Baja treefrogs (Pseudacris hypochondriaca). These species were later reclassified primarily due to differences in geographic ranges. These three species look very similar, except for the bumpy skin of the Sierran and Californian treefrogs. (Elliott, et al., 2009; Nussbaum, et al., 1983; Stebbins, 2003)

  • Sexual Dimorphism
  • female larger
  • sexes colored or patterned differently
  • Average mass
    0.35 g
    0.01 oz
  • Range length
    2.5 to 4.8 cm
    0.98 to 1.89 in


Breeding season for P. regilla extends from January to mid-May. During this time, females lay eggs which are brown and yellow. Males externally fertilize the eggs, which are usually laid in gently moving water, in clutches of 5 to 70 eggs, and must be kept moist. (Jameson, 1956; Wright and Wright, 1949)

Pacific treefrog tadpoles are of medium size, typically about 46.6 mm long, and brown in color. Tadpole tails are not flagellated. Pacific tree frogs show rapid growth during the first summer after hatching. Tadpoles undergo metamorphosis between 50 and 80 days of age. During the metamorphosis, individuals typically measure between 12 and 15 mm long. Within two months of metamorphosis, individuals approximately double in length. Newly metamorphosed frogs leave the breeding area and seek habitats similar to that of an adult frog. Pacific treefrogs reach sexual maturity quickly and participate in the first mating chorus following their hatching. (Jameson, 1956)


Breeding occurs seasonally for Pacific tree frogs and typically occurs from winter to spring. This species is polygynous. During the breeding season, males often are found near small bodies of waters, particularly ponds, where they begin to sing. Females are attracted to males based on their calls and their different colored throats. Females prefer males that initiate calling. Once attracted, females move towards males. Males continue calling for several minutes, followed by several minutes of silence. Males continues this pattern until females are in their immediate vicinity. (Dickerson, 1906; Whitney and Krebs, 1975)

Pseudacris regilla attracts mates using a choral song. Males call to females as loudly as possible and produce a croak so loud that they sound as though they are produced by multiple males. These sounds can be heard by numerous females. Once a female approaches, the male stops singing and attempts amplexus, a pseudocopulation act during which the male grasps the female with hist forelegs. Breeding takes place at night, near shallow water, typically after rainfall. Mating season usually extends from December to May, although some variation occurs. Altitude often affects the length of the breeding season. (Dickerson, 1906; Grinnell and Storer, 1924; Schaub and Larsen, Jr, 1978)

Male Pacific tree frogs are occasionally aggressive during breeding season. They produce a warning call if another male approaches too closely. If the intruding male does not leave the area, the two frogs may fight until one departs. In addition, while attracting females, males can extend vocal pouches on their lower jaw, which helps in calling females. The act of copulation takes place in water. They are oviparous, and once the female enters the water, the male grasps her and helps to thrust out the eggs as he fertilizes them. Eggs are laid in small ponds or puddles. Typical broods range from 5 to 70 eggs. A jelly-like substance is left with the eggs to maintain moisture. Eggs remain in shallow water, often near twigs or leaves. Once reproduction is complete, both the male and female leave the water. Eggs hatch in three to four weeks, and within three to seven days, offspring develop into tadpoles. Development time varies with the temperature of the environment. Once they emerge from the egg, offspring use the jelly-like substance carried with the egg to sustain them for the first two to three days. Tadpoles then swim to shallow waters and ingest nearly any edible food item. When tadpoles reach three months of age, they metamorphose into froglets. This typically occurs between July and September.Research shows that as water temperature increases, development time decreases. In general, Pacific treefrogs reach sexual maturity in 1 to 2 years. (Awbrey, 1978; Brenowitz and Rose, 1999; Dickerson, 1906; Goin, et al., 1978; Noble, 1931; Nussbaum, et al., 1983; Oliver, 1955; Pickwell, 1931; Pickwell, 1947; Schaub and Larsen, Jr, 1978)

  • Breeding interval
    Pseudacris regilla breeds once per year.
  • Breeding season
    Pseudacris regilla breeds from January to May.
  • Range number of offspring
    5 to 70
  • Average time to hatching
    3.5 weeks
  • Average age at sexual or reproductive maturity (female)
    1 to 2 years
  • Average age at sexual or reproductive maturity (male)
    1 to 2 years

Once females lay eggs in the water, both males and females abandon the eggs. There is no parental investment. (Goin, et al., 1978; Nussbaum, et al., 1983)

  • Parental Investment
  • no parental involvement


Little is known about the lifespan of Pacific treefrogs, either in the wild or in captivity. There is record of a captive Pacific treefrog that lived for 9 years. Other chorus frogs in the genus Pseudacris have an average lifespan of approximately 5 years in the wild. Closely related mountain chorus frogs P. brachyphona live for approximately 7 years in the wild. (Blaustein, et al., 2001; Green, 1938)

  • Range lifespan
    Status: captivity
    9 (high) years


Pacific treefrogs are social, especially during mating season. Like other chorus frogs, Pacific treefrogs use calls to attract potential mates. Males avoid call overlapping, which helps to maximize each male's chances of mating. This pattern of call recognition suggests advanced social interactions. Pacific treefrogs remain dormant when temperatures are below 10 C. Above this temperature, they emerge from their dormant state and search for water. They prefer warm water and will not breed in or occupy areas near cool water. It has been reported that Pacific treefrogs are unable to call when their body temperature falls below 9.8 C or rises above 20 C. In addition, they do not lay eggs when water temperatures are below 12 C or above 15 C. Temperature also effects body coloration. At high temperatures, green and brown frogs turn a shade of yellow. Upon cooling, the frogs return to their typical coloration. (Awbrey, 1978; Brattstrom and Warren, 1955; Brenowitz and Rose, 1999; Jameson, 1956; Morey, 1990; Wright and Wright, 1949)

Pacific treefrogs show relatively unique behaviors when chorusing. They stop calling if they see an intruder, and then begin calling again after a few minutes. Chorusing continues unless the intruder moves again. On the other hand, vibrations, loud noises, and thrown objects do not interrupt chorusing. During the breeding season, males are territorial. They often produce warning calls to warn rival males to leave the area. If the intruding male does not leave, the two typically fight until one leaves the area. Because females are not attracted to encounter calls, these interactions may reduce mating success for males. (Awbrey, 1978; Brattstrom and Warren, 1955; Brenowitz and Rose, 1999; Jameson, 1956; Morey, 1990; Wright and Wright, 1949)

  • Average territory size
    75 cm^2

Home Range

Limited information exists regarding the home range of Pseudacris regilla; however, it most often inhabits areas ranging from 60 to 300 m away from a suitable breeding areas. (Brattstrom and Warren, 1955; Morey, 1990)

Communication and Perception

Pacific treefrogs have a very rapid call that has been described as a “kreck-ek” noise. The rapid call is called the chorus note; this serves to bring individuals in the area together for breeding. Pacific treefrogs also have an encounter call that warns other males not to get too close during mating season. This differs from their normal call, which is lower pitched and longer. Research has shown that males avoid overlapping calls in order to increase each male’s chance to attract a mate. Typically, up to three males can call without overlapping, if timing is well synchronized. Pacific treefrogs have well developed senses of sight, smell, and hearing. Hearing is particularly well-developed, as these frogs must be able to call to each other during mating season. (Awbrey, 1978; Brenowitz and Rose, 1999; Wright and Wright, 1949)

Food Habits

As tadpoles, Pacific treefrongs consume a variety of aquatic invertebrates and detritus. They mostly feed on algae, bacteria, and floating vegetative debris. Adults primarily consume terrestrial invertebrates, with only 4.8% of their diet coming from aquatic sources. Adults usually feed at night on invertebrate species, often consuming great quantities of flying insects. During breeding season, adults may feed during the day. Adults capture insects by extending their tongues. The tongue is coated by a sticky secretion that traps the insect, along with any debris or dirt near the insect. Food items are typically swallowed whole. (Hothem, et al., 2009; Wright and Wright, 1949)

  • Animal Foods
  • insects
  • terrestrial non-insect arthropods
  • Plant Foods
  • algae


Garter snakes are known predators of Pacific treefrogs. Other predators include other species of frogs, raccoons, Virginia opossums, fish, and birds. Their primary defense against predators is to remain motionless, though this technique is only effective if the frog matches its environment very well. They also tend to hide in areas of tall grass or jump into water when threatened. The primary predator of Pacific treefrog tadpoles is mosquitofish. Research has shown that even when presented with mosquito larva, mosquitofish often prefer treefrog tadpoles. Other predators on tadpoles include numerous species of fish and some aquatic invertebrates. (Awbrey, 1978; Brattstrom and Warren, 1955; Goodsell and Kats, 1999; Morey, 1990; Wente and Phillips, 2005)

The best defense of Pacific treefrogs against predation is their camouflage. The coloration of their dorsal surface varies from shades of brown to shades of green. They tend to stay in habitats that have coloring similar to their bodies. Recent studies have shown that Pacific treefrogs can vary their coloring based on the presence or absence of green foliage. In addition, during spring and summer, when green foliage is abundant, these frogs tend to be greenish in color; in fall and winter, they tend to be shades of brown. (Awbrey, 1978; Brattstrom and Warren, 1955; Goodsell and Kats, 1999; Morey, 1990; Wente and Phillips, 2005)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Pacific treefrogs are insectivorous and may help control a number of insect pest species throught their geographic range. In addition, a number of different species depend on Pacific treefrogs as their primary prey. There is no information on the potential parasites of this species. (Goodsell and Kats, 1999; Watkins, 1996)

Economic Importance for Humans: Positive

As an insectivore, Pseudacris regilla likely helps control insect pest species throughout their geographic range. (Bernard, 2005)

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

There are no known adverse effects of Pseudacris regilla on humans.

Conservation Status

Pacific treefrogs are classified as a species of least concern on the IUCN's Red List of Threatened Species. They have a broad geographic range and are the most common frog in the United States, west of the Rocky Mountains. The greatest current threat to Pacific treefrogs appears to be increased predation from non-native mosquitofish; however, this threat does not occur throughout the entirety of the Pacific treefrogs geographic range. (Wright and Wright, 1949)


Michelle Ferguson (author), Radford University, Samantha Mullins (author), Radford University, Christine Small (editor), Radford University, John Berini (editor), Animal Diversity Web Staff.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map


uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.


an animal that mainly eats meat


Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.


to jointly display, usually with sounds, at the same time as two or more other individuals of the same or different species


used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.


having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.


particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).


animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body


union of egg and spermatozoan


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


mainly lives in water that is not salty.


An animal that eats mainly plants or parts of plants.


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.


the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.


An animal that eats mainly insects or spiders.


referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


marshes are wetland areas often dominated by grasses and reeds.


A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.


having the capacity to move from one place to another.


specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.


active during the night


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


having more than one female as a mate at one time


"many forms." A species is polymorphic if its individuals can be divided into two or more easily recognized groups, based on structure, color, or other similar characteristics. The term only applies when the distinct groups can be found in the same area; graded or clinal variation throughout the range of a species (e.g. a north-to-south decrease in size) is not polymorphism. Polymorphic characteristics may be inherited because the differences have a genetic basis, or they may be the result of environmental influences. We do not consider sexual differences (i.e. sexual dimorphism), seasonal changes (e.g. change in fur color), or age-related changes to be polymorphic. Polymorphism in a local population can be an adaptation to prevent density-dependent predation, where predators preferentially prey on the most common morph.


specialized for leaping or bounding locomotion; jumps or hops.

seasonal breeding

breeding is confined to a particular season


remains in the same area


reproduction that includes combining the genetic contribution of two individuals, a male and a female


associates with others of its species; forms social groups.


living in residential areas on the outskirts of large cities or towns.


a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.


A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.


uses sight to communicate


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