Animal Diversity Web

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)

• Biogeographic Regions
• nearctic
  • introduced
  • native

Habi­tat

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)

• Habitat Regions
• temperate
• terrestrial
• freshwater

• Terrestrial Biomes
• savanna or grassland
• chaparral
• forest

• Aquatic Biomes
• lakes and ponds
• rivers and streams

• Wetlands
• marsh
• swamp
• bog

• Other Habitat Features
• suburban

• 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)

• Other Physical Features
• ectothermic
• heterothermic
• bilateral symmetry
• polymorphic

• 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

De­vel­op­ment

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)

• Development - Life Cycle
• metamorphosis

Re­pro­duc­tion

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)

• Mating System
• polygynous

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)

• Key Reproductive Features
• iteroparous
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• fertilization
  • external
• oviparous

• 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

Lifes­pan/Longevity

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

Be­hav­ior

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)

• Key Behaviors
• terricolous
• saltatorial
• natatorial
• nocturnal
• motile
• sedentary
• hibernation
• social
• colonial

• 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)

• Communication Channels
• visual
• tactile
• acoustic

• Other Communication Modes
• choruses

• Perception Channels
• visual
• acoustic

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)

• Primary Diet
• carnivore
  • insectivore
• herbivore
  • algivore

• Animal Foods
• insects
• terrestrial non-insect arthropods

• Plant Foods
• algae

• Other Foods
• detritus
• microbes

Pre­da­tion

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

• Known Predators

  • garter snakes (Thamnophis elegans)
  • mosquitofish (Gambusia affinis)

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)

• IUCN Red List

  Least Concern
  More information

• IUCN Red List

  Least Concern
  More information

• US Federal List

  No special status

• CITES

  No special status

• State of Michigan List

  No special status

Con­trib­u­tors

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

Ref­er­ences

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Bernard, M. 2005. "Nat­ural His­tory of the Pa­cific Cho­rus Frog Pseudacris regilla" (On-line). Ac­cessed April 03, 2011 at http://​www.​mister-toad.​com/​PacificTreeFrog.​html.

Blaustein, A., L. Belden, D. Olson, D. Green, T. Root, J. Kiesecker. 2001. Am­phib­ian breed­ing and cli­mate change. Con­ser­va­tion Bi­ol­ogy, 15/16: 1804-1809.

Brattstrom, B., J. War­ren. 1955. Ob­ser­va­tions on the ecol­ogy and be­hav­ior of the Pa­cific treefrog, Hyla regilla. Copeia, 1955/3: 181-191.

Brenowitz, E., G. Rose. 1999. Fe­male choice and plas­tic­ity of male call­ing be­hav­iour in the Pa­cific treefrog. An­i­mal Be­hav­ior, 57/6: 1337-1342.

Dick­er­son, M. 1906. The Frog Book. New York: Dou­ble­day, Page and Com­pany.

El­liott, L., C. Ger­hardt, C. David­son. 2009. The Frogs and Toads of North Amer­ica. Ith­ica, New York: Na­ture­Sound Stu­dio.

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Good­sell, J., L. Kats. 1999. Ef­fect of in­tro­duced mos­qui­tofish on Pa­cific treefrogs and the role of al­ter­na­tive prey. Con­ser­va­tion Bi­ol­ogy, 13/4: 921-924.

Green, N. 1938. The Breed­ing Habits of Pseudacris Brachy­phona (Cope) with a De­scrip­tion of the Eggs and Tad­pole. Copeia, 1938/2: 79-82.

Grin­nell, J., T. Storer. 1924. An­i­mal Life in the Yosemite. Berke­ley, CA: Uni­ver­sity of Berke­ley Press.

Hol­man, J. 2003. Fos­sil Frogs and Toads of North Amer­ica. Bloom­ing­ton, IN: In­di­ana Uni­ver­sity Press.

Hothem, R., A. Meck­stroth, K. Weg­ner, M. Jen­nings, J. Crayon. 2009. Diets of three species of Anu­rans from the Cache Creek Wa­ter­shed, Cal­i­for­nia, USA. Jour­nal of Her­petol­ogy, 43/2: 275-283.

Jame­son, D. 1956. Growth, dis­per­sal and sur­vival of the Pa­cific tree frog. Copeia, 1956/1: 25-29.

Jame­son, D. 1966. Rate of weight loss of tree frogs at var­i­ous tem­per­a­tures and hu­midi­ties. Ecol­ogy, 47/4: 605-613.

Morey, S. 1990. Mi­cro­hab­i­tat se­lec­tion and pre­da­tion in the Pa­cific treefrog, Pseudacris regilla. Jour­nal of Her­petol­ogy, 24/3: 292-296.

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Nuss­baum, R., B. Edu­mund, R. Storm. 1983. Am­phib­ians and Rep­tiles of the Pa­cific North­west. Idaho: The Uni­ver­sity Press of Idaho.

Oliver, J. 1955. The Nat­ural His­tory of North Amer­i­can Am­phib­ians and Rep­tiles. Prince­ton, NJ: D. Van Nos­trand Com­pany, Inc..

Pick­well, G. 1947. Am­phib­ians and Rep­tiles of the Pa­cific States. Stan­ford, CA: Stan­ford Uni­ver­sity Press.

Pick­well, G. 1931. West­ern Na­ture Study: Frogs, Toads, Sala­man­ders. San Jose, CA: San Jose State Col­lege Press.

Rip­plinger, J., R. Wag­ner. 2004. Phy­lo­geog­ra­phy of north­ern pop­u­la­tions of the Pa­cific treefrog, Pseudacris regilla. North­west­ern Nat­u­ral­ist, 85/3: 118-125.

Schaub, D., J. Larsen, Jr. 1978. The re­pro­duc­tive ecol­ogy of the Pa­cific treefrog (Hyla regilla). Her­peto­log­ica, 34/4: 409-416.

Spar­ling, D., G. Fellers. 2009. Tox­i­c­ity of two in­sec­ti­cides to Cal­i­for­nia, USA, anu­rans and its rel­e­vance to de­clin­ing am­phib­ian pop­u­la­tions. En­vi­ron­men­tal Tox­i­col­ogy and Chem­istry, 28/8: 1696-1703.

Steb­bins, R. 2003. A Field Guide to West­ern Rep­tiles and Am­phib­ians. Sin­ga­pore: Houghton Mif­flin Com­pany.

Steb­bins, R. 1951. Am­phib­ians of west­ern North Amer­ica. Lon­don, Eng­land: Cam­bridge Uni­ver­sity Press.

Watkins, T. 1996. Preda­tor-me­di­ated se­lec­tion on burst swim­ming per­for­mance in tad­poles of the Pa­cific tree frog, Pseudacris regilla. Phys­i­o­log­i­cal Zo­ol­ogy, 69/1: 154-167.

Wente, W., J. Phillips. 2005. Sea­sonal color change in a pop­u­la­tion of Pa­cific treefrogs (Pseudacris regilla). Jour­nal of Her­petol­ogy, 39/1: 161-165.

Whit­ney, C., J. Krebs. 1975. Mate se­lec­tion in Pa­cific tree frogs. Na­ture, 255: 325-326.

Wright, A., A. Wright. 1949. Hand­book of frogs and toads of the United States and Canada. Ithaca, New York: Com­stock Pub­lish­ing Com­pany.