Animal Diversity Web

Ge­o­graphic Range

Both gray treefrog species, Hyla ver­si­color and Hyla chrysoscelis, in­habit a wide range from south­ern On­tario and Maine, west­ward to cen­tral Texas, north­west to Man­i­toba, and north­ern Florida. An iso­lated colony is also noted in New Brunswick. The two species ap­pear phys­i­cally iden­ti­cal, and con­se­quently more stud­ies are nec­es­sary to de­lin­eate where the species over­lap. (Collins and Co­nant, 1998)

Gen­er­ally, the east­ern gray treefrog (H. ver­si­color) is mostly found to the north and north­east of the range. How­ever, the gray treefrog species are ex­tremely vari­able in their dis­tri­b­u­tion pat­tern. For in­stance, the east­ern gray treefrog is com­mon in the east­ern Great Lakes re­gion, in­clud­ing south­ern Michi­gan; how­ever, both species: H. ver­si­color and H. chrysoscelis share the same breed­ing ponds in Wis­con­sin and north­ern Michi­gan. (Hard­ing, 1997)

• Biogeographic Regions
• nearctic
  • native

Habi­tat

East­ern gray Treefrogs in­habit all el­e­va­tions of wooded areas near tem­po­rary and per­ma­nent wa­ters in such di­verse sur­round­ings such as swamps, ponds, lakes, old fields, thickly wooded sub­ur­ban neigh­bor­hoods, farm wood­lots, and mixed or de­cid­u­ous forests. Dur­ing the sum­mer months, they are most often found in damp rot­ten logs or hol­low trees. In win­ter, gray treefrogs hi­ber­nate on land under woody de­bris such as logs, roots and leaf lit­ter. (Hard­ing, 1997)

• Habitat Regions
• temperate
• terrestrial
• freshwater

• Terrestrial Biomes
• forest

• Aquatic Biomes
• lakes and ponds
• temporary pools

• Wetlands
• swamp

• Other Habitat Features
• suburban
• agricultural
• riparian

Phys­i­cal De­scrip­tion

The east­ern gray treefrog mea­sures 1.25 to 2 inches (3-5cm) in length. The record length is 2.25 in. (6 cm). There is no sex­ual di­mor­phism. The dor­sal sur­face of the gray treefrog species is rough and lightly sprin­kled with warts,more than most frogs but less than the av­er­age toad. The large toepads pro­duce mu­cous to ad­here to smooth bark or man-made struc­tures near light sources, and are char­ac­ter­is­tic of the fam­ily Hyl­i­dae. The col­ors of a gray treefrog vary with the col­ors of its back­ground and en­vi­ron­men­tal fac­tors such as sea­son and hu­mid­ity, but shades of gray are most com­mon with black blotches on the back. Vari­a­tions of brown, green, and pearl-gray col­ors have been noted. Green col­ors are more promi­nent dur­ing the breed­ing sea­son and in year­ling frogs. Usu­ally, there is a white mark be­neath the eye. The ven­tral skin on the hind legs, in the groin re­gion, may ap­pear or­ange to golden yel­low with black speck­les and the belly is white.

If the col­oration is in ques­tion, place the treefrog in a box, allow it to sit qui­etly, and later re-ex­am­ine the spec­i­men. The year­ling frogs are about half the size of the older H. ver­si­color pop­u­la­tion, but re­tain the same char­ac­ter­is­tics. Gray treefrogs con­tinue to grow each year until they achieve the phys­i­cal limit of the species. (Collins and Co­nant, 1998; Hard­ing, 1997)

Both gray treefrog species pos­sess the same lar­val traits, but H. ver­si­color was used to ex­em­plify the tad­pole stage in Co­nant and Collins' "A Field Guide to Rep­tiles and Am­phib­ians of East Cen­tral North Amer­ica". The tad­poles are small, but col­or­ful, 1.25 in. to 1.5 in. (3.2 cm. to 3.8 cm.) long. The tip of the tail is well-de­fined with a 5 mm nar­row tip. The oral disc is com­prised of 2 upper labial tooth rows and 3 lower, ser­rated jaws, and an over­hang­ing upper jaw. The in­testi­nal coil is also vis­i­ble. The back­ground color is light green to yel­low. The tallest sec­tion of the tail fin is the mid­dle and heavy black dots are scat­tered along the mar­gin on a red or or­ange back­ground across the tail. (Collins and Co­nant, 1998; Hard­ing, 1997)

• Other Physical Features
• ectothermic
• heterothermic
• bilateral symmetry

• Sexual Dimorphism
• sexes alike

• Average mass

  7.175 g

  0.25 oz

  AnAge

• Range length

  3 to 5 cm

  1.18 to 1.97 in

• Average basal metabolic rate

  0.00433 W

  AnAge

De­vel­op­ment

Tad­poles of the east­ern gray treefrogs meta­mor­pho­size into froglets in six to eight weeks. The young frogs are ap­prox­i­mately 0.6 in. (1.5 cm) snout to vent length. The lar­val and adult rate of growth is de­pen­dent on the avail­abil­ity of food and stress of preda­tors. The sex de­ter­im­i­na­tion of am­phib­ians is ge­netic. How­ever, if lar­vae are treated with es­tro­gen, then hor­monal sex reveral is pos­si­ble after meta­mor­pho­sis. Hyla ver­si­color fol­low the XX/XY pat­tern of het­eroga­mety. (Hard­ing, 1997; Skelly, 1992; Wal­lace, et al., 1999)

• Development - Life Cycle
• metamorphosis

Re­pro­duc­tion

The breed­ing cho­ruses of gray treefrogs begin in late April to early May after the evening air tem­per­a­ture rises above 15°C, which varies through­out the range. These frogs end their hi­ber­na­tion in the early months of spring, but do not have the en­ergy re­serves to call, yet. Warm, cloudy nights, from dusk to mid­night, pro­duce the most in­tense cho­ruses. How­ever, in­ter­ludes of cold weather may tem­porar­ily end the male gray treefrog calls. Gen­er­ally, the breed­ing cho­rus lasts for sev­eral weeks. Some­times, the breed­ing calls are con­tin­ued into late June or early July, de­pend­ing on local tem­per­a­tures and un­usual weather phe­nom­ena. (Hard­ing, 1997)

Fe­male choice dom­i­nates the mat­ing scheme of gray treefrogs, since the fe­male ap­proaches the male with the most pro­longed and fre­quent calls. If the male de­tects a nearby fe­male he will also fur­ther en­tice her with a “courtship call” that is longer and more em­phatic than the usual ad­ver­tise­ment call. Suc­cess­ful call­ing re­sults in am­plexus as the fe­male de­posits eggs which are ex­ter­nally fer­til­ized by the male. Al­most im­me­di­ately, the large egg mass breaks into small, loose egg clus­ters of 10 to 40 eggs at­tach to plants or other struc­tures within the pond. De­pend­ing on the water tem­per­a­ture, the tad­poles hatch in three to seven days. Both gray treefrog sp. do not hy­bridize due to a mat­ing bar­rier, the dif­fer­ent pulse rate and pitch be­tween the two calls. (Hard­ing, 1997; Haus­fater, et al., 1990)

• Mating System
• polygynous

East­ern gray treefrogs em­ploy their unique call from the safety of veg­e­ta­tion next to the shal­low breed­ing sites, prefer­ably in tree branches that over­hang the water. The males ag­gres­sively de­fend and use their voice to out­line their ter­ri­to­ries with ex­tended calls. Satel­lite males, often in their first breed­ing sea­son or oth­er­wise dis­ad­van­taged, do not call to save en­ergy. In­stead, they lie in wait near a call­ing male and in­ter­cept the fe­male by claim­ing the caller’s po­si­tion after he moves away. The fe­male only vis­its the breed­ing site to lay her eggs. Dur­ing the last weeks of the breed­ing sea­son, oc­ca­sional calls may still be heard as the males slowly re­treat from the shore­line and dis­ap­pear into the fo­liage. Rare calls may still be heard in the trees in late sum­mer or fall, yet they are un­re­lated to mat­ing, and occur more often dur­ing rain show­ers. Call­ing males are often at­tacked by preda­tors, and this re­sults in a fe­male-bi­ased pop­u­la­tion. (Du­ell­man and Trueb, 1986; Hard­ing, 1997; Steb­bins and Cohen, 1995)

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

• Breeding interval

  Treefrogs breed once yearly.

• Breeding season

  Late April to May or until the temperature rises above 15°C

• Range number of offspring

  1,000 to 2,000

• Range time to hatching

  3 to 7 days

• Average age at sexual or reproductive maturity (female)

  2 years

• Average age at sexual or reproductive maturity (female)
  Sex: female

  912 days

  AnAge

• Range age at sexual or reproductive maturity (male)

  1 to 2 years

Fe­male gray treefrogs in­vest in their off­spring by pro­vid­ing yolk to the eggs, and choos­ing ponds that are rel­a­tively free of preda­tors (they es­pe­cially try to avoid fish). Males do not in­vest in the off­spring, and fe­male in­vest­ment ends when she lays her eggs. (Hard­ing, 1997; Skelly, 1992)

• Parental Investment
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth

Lifes­pan/Longevity

One cap­tive gray treefrog lived for over seven years in cap­tiv­ity. Un­fo­tu­nately, it was not dis­tin­guished as H. chrysoscelis or H. ver­si­color. The po­ten­tial lifes­pan in cap­tiv­ity and the wild is un­known. It is likely that few gray treefrogs die of old age, preda­tors, dis­ease and cli­mac­tic ex­tremes are more likely causes of death. (Hard­ing, 1997)

• Range lifespan
  Status: captivity

  7 (high) years

• Average lifespan
  Status: captivity

  7 years

  AnAge

Be­hav­ior

Male east­ern gray treefrogs are ter­ri­to­r­ial dur­ing the breed­ing sea­son. Dur­ing the rest of the year, males and fe­males are tol­er­ant of the pres­ence of con­specifics of sim­i­lar size. How­ever, they are op­por­tunis­tic can­ni­bals, and may eat other gray treefrogs if they are small enough to catch and swal­low. (Du­ell­man and Trueb, 1986)

As a mem­ber of the genus Hyla, east­ern gray treefrogs pos­sess ad­vanced toe pads to ad­here more strongly to ver­ti­cal sur­faces of glass, metal, and pri­mar­ily tree bark. A very low angle be­tween the toe pads and sub­strate with a com­bi­na­tion of mu­cous glands and sur­face mois­ture cre­ate sur­face ten­sion to sup­port the body mass. The toe tips are able to be flex­i­ble and grip more firmly due to small bone or car­ti­lage be­tween two ter­mi­nal toe bones that sup­port the toe pad. These spe­cial­ized ad­he­sion abil­i­ties would not exist if a de­ter­gent were ap­plied to the pad; how­ever, the ad­he­sion would re­turn with the re­moval of the de­ter­gent. Climb­ing abil­ity is an im­por­tant adap­tive trait of this species and it is cen­tral to their sur­vival. (Steb­bins and Cohen, 1995)

When gray treefrogs hi­ber­nate, they ap­pear rigid, and have a high freez­ing tol­er­ance due to glyc­erol in their blood. Dur­ing hi­ber­na­tion, 80% of the body freezes and the eye be­comes opaque as breath­ing and heart­beat are tem­porar­ily sus­pended. Their high tol­er­ance for freez­ing tem­per­a­tures en­abled the gray treefrogs to ex­pand their ter­ri­tory north­ward and to­wards higher el­e­va­tions. (Du­ell­man and Trueb, 1986; Du­ell­man and Trueb, 1986)

• Key Behaviors
• arboreal
• scansorial
• saltatorial
• nocturnal
• crepuscular
• motile
• sedentary
• hibernation
• solitary
• territorial

Home Range

The home range of the east­ern gray treefrog varies widely de­pend­ing on the suit­abil­ity of the habi­tat and the avail­able food sup­ply. Due to their small size, sev­eral frogs may in­habit one tree if there is a suf­fi­cient food sup­ply. (Hard­ing, 1997)

Com­mu­ni­ca­tion and Per­cep­tion

The male's ad­ver­tise­ment call is the main trait to dis­tin­guish the east­ern gray treefrog (H. ver­si­color) from Cope's gray treefrog (H. chrysoscelis). In gen­eral, the sound is com­prised of a res­o­nant mu­si­cal trill. The east­ern gray treefrog has a slower trill than Cope’s, which is faster and higher pitched. An in­crease in air tem­per­a­ture raises the rate of the trill and tape record­ings may be nec­es­sary for pos­i­tive iden­ti­fi­ca­tion, es­pe­cially if only a sin­gle species is pre­sent. (Collins and Co­nant, 1998)

In com­par­i­son to other frog species in the range, the gray treefrogs calls are shorter, only 0.5 to 3 sec­onds, yet sim­i­lar to the call of the Amer­i­can toad (Anaxyrus amer­i­canus). (Hard­ing, 1997)

In the lar­val state, Hyla ver­si­color uses chemore­cep­tion as its pri­mary method of com­mu­ni­ca­tion and de­fense against preda­tors. Preda­tory fish and sala­man­der lar­vae are de­tected via chemore­cep­tion. In­jured tad­poles also re­lease an "alarm sub­stance" to warn their con­specifics. (Du­ell­man and Trueb, 1986)

Adult gray treefrogs are very sen­si­tive to ground vi­bra­tions and pos­sess ex­cel­lent hear­ing. Yet, dur­ing hi­ber­na­tion they are un­re­spon­sive to most ex­ter­nal stim­uli. (Du­ell­man and Trueb, 1986)

• Communication Channels
• visual
• acoustic
• chemical

• Other Communication Modes
• choruses

• Perception Channels
• visual
• tactile
• acoustic
• vibrations
• chemical

Food Habits

As tad­poles, east­ern gray treefrogs begin life by graz­ing on algae and de­tri­tus in their pond. (Hard­ing, 1997)

After meta­mor­pho­sis, H. ver­si­color prey upon most types of in­sects and their lar­vae. Mites, spi­ders, plant lice, har­vest­men, and snails are also eaten. Gray treefrogs mostly hunt in­sects in the un­der­story of wooded areas in small trees and shrubs, where they may rely upon their cam­ou­flage with less risk of pre­da­tion. How­ever, like most frogs, H. ver­si­color is op­por­tu­ni­tis­tic and may also eat smaller frogs, in­clud­ing other tree frogs. (Collins and Co­nant, 1998)

• Primary Diet
• carnivore
  • insectivore
• herbivore
  • algivore

• Animal Foods
• amphibians
• insects
• terrestrial non-insect arthropods
• mollusks
• terrestrial worms

• Plant Foods
• algae

• Other Foods
• detritus

Pre­da­tion

Many as­sorted species of birds, snakes, other frogs, and small mam­mals eat gray treefrogs. These frogs are ar­bo­real to avoid preda­tors, and ex­ploit new food re­sources. They also avoid the at­ten­tion of preda­tors by call­ing after dusk and being most ac­tive in the evening and night. They use cryp­tic col­oration and rarely leave the trees until the breed­ing sea­son. Their skin is able to as­sume most nat­ural col­ors in which it comes into con­tact.

Larger frogs, such as the bull­frog (Litho­bates cates­beianus) and green frog (Litho­bates clami­tans clami­tans, have been ob­served to con­sume gray treefrogs by stalk­ing call­ing males. In the water, giant wa­ter­bugs (Be­lostom­ati­dae) also at­tack Cope's gray treefrog. (Collins and Co­nant, 1998; Hard­ing, 1997)

In the lar­val state, gray treefrogs are sub­ject to pre­da­tion by fish and larger am­phib­ian lar­vae, such as the tiger sala­man­der (Am­bystomma tigrinum). When aquatic preda­tors are abun­dant, gray treefrog tad­poles re­duce their ac­tiv­ity and feed­ing. They grow more slowly, and meta­mor­phose at a smaller size. (Skelly, 1992)

• Anti-predator Adaptations
• cryptic

• Known Predators

  • Bullfrog (Lithobates catesbeianus)
  • Green frog (Lithobates clamitans clamitans)
  • Giant waterbugs (Belostomatidae)
  • Larval tiger salamanders (Ambystoma tigrinum)
  • shrews (Soricidae)
  • birds (Aves)
  • small mammals
  • snakes (Serpentes)

Ecosys­tem Roles

East­ern gray treefrogs can play a crit­i­cal role in the food­web of their ecosys­tems. As tad­poles they may graze enough algae to change the com­mu­nity of algal species in their ponds. Later, local pest pop­u­la­tions of mos­quito, gnats, and flies are re­duced in the ter­ri­tory of a sin­gle gray treefrog. In turn, Cope's gray treefrogs are the prey of larger frogs, car­niv­o­rous birds, and small mam­mals. H. ver­si­color are a sig­nif­i­cant link to sup­port the sur­vival of other an­i­mals in the ecosys­tem. (Hard­ing, 1997)

Like just about all an­i­mals, this species is host to par­a­sitic species. Among oth­ers, Poly­toma nearcticum is a flat­worm that lives in the gills of tad­poles and the blad­der of adults. Ne­ma­todes in the genus Strongy­loides are found in the di­ges­tive sys­tems of these frogs.

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

Peo­ple ben­e­fit from the sub­stan­tial amount of in­sect pests that are eaten by H. ver­si­color. The spring breed­ing cho­rus also pro­vides evening en­ter­tain­ment to re-af­firm our con­nec­tion with na­ture. We also use the pres­ence of east­ern gray treefrogs as a sci­en­tific tool to in­di­cate the over­all bio­di­ver­sity and the level of con­t­a­m­i­nants in a re­gion. Over­all, the east­ern gray treefrog plays an im­por­tant role in the eco­log­i­cal bal­ance of wooded farm­lands and res­i­den­tial areas and con­tributes to our own well-be­ing. (Hard­ing, 1997)

• Positive Impacts
• controls pest population

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

There are no known ad­verse ef­fects of Hyla ver­si­color on hu­mans. (Hard­ing, 1997)

Con­ser­va­tion Sta­tus

Hyla ver­si­color is not cur­rently clas­si­fied as en­dan­gered or of spe­cial con­cern. How­ever, habi­tat de­struc­tion and human pol­lu­tants are con­tribut­ing to the over­all de­cline of am­phib­ians, in­clud­ing frog and toad species. Pub­lic sup­port of habi­tat areas in state parks, na­ture re­serves, and pri­vate prop­erty con­tin­ues to pro­mote the sur­vival of am­phib­ian species. On­go­ing sci­en­tific re­search also im­proves our un­der­stand­ing of this dy­namic species. (Hard­ing, 1997)

• 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

Other Com­ments

Cope's gray treefrog (H. chrysoscelis) and the East­ern gray treefrog (H. ver­si­color) are a unique ex­am­ple of spe­ci­a­tion in ac­tion. The two species have very sim­i­lar genes, and ap­pear iden­ti­cal; how­ever, the east­ern gray treefrog pos­sesses a sec­ond chro­mo­some set, twice the num­ber of chro­mo­somes as Cope's gray treefrog. Cope's (H. chrysoscelis) is called a diploid, and the east­ern (H. ver­si­color) is called a tetraploid. The only re­li­able ways to dis­tin­guish be­tween the species are by the calls of the males or by mi­cro­scopic ex­am­i­na­tion of their chro­mo­somes. (Collins and Co­nant, 1998)

H. ver­si­color is thought to have evolved from H. chrysoscelis when an extra chro­mo­so­mal set was passed to sev­eral sur­viv­ing egg masses some­time early in the Pleis­tocene epoch, com­monly known as the "Ice Age." At this time, pop­u­la­tions of H. chrysoscelis were iso­lated by in­ter­ven­ing areas of ex­treme low tem­po­er­a­tures. By the time the cli­mate warmed and the glac­i­ers re­treated, the two pop­u­la­tions had evolved in dif­fer­ent di­rec­tions, and though they now occur to­gether, they no longer in­ter­breed and are dif­fer­ent species. (Ger­hardt, et al., 1994; Hard­ing, 1997)

The west­ern fox snake (Pan­therophis vulpi­nus) and east­ern fox snake (Pan­therophis gloydi) of the Great Lakes Basin in North Amer­ica are an­other ex­am­ple of this pat­tern of spe­ci­a­tion. The habi­tats and prey vary greatly be­tween these two species, yet ex­cept for min­i­mal vari­a­tion of their scale pat­terns they al­most ap­pear iden­ti­cal. (Hard­ing, 1997)

Con­trib­u­tors

George Ham­mond (ed­i­tor), An­i­mal Di­ver­sity Web.

Lee A. Mueller (au­thor), Michi­gan State Uni­ver­sity, James Hard­ing (ed­i­tor, in­struc­tor), Michi­gan State Uni­ver­sity.

Ref­er­ences

Collins, J., R. Co­nant. 1998. A Field Guide to Rep­tiles and Am­phib­ians of East Cen­tral North Amer­ica. 3rd edi­tion, ex­panded. New York: Houghton Mif­flin Co.

Du­ell­man, W., L. Trueb. 1986. Bi­ol­ogy of Am­phib­ians. New York: Mc­Graw-Hill Book Com­pany.

Ger­hardt, H., M. Ptacek, R. Sage. 1994. Spe­ci­a­tion By Poly­poidy in Treefrogs: Mul­ti­ple Ori­gins of the Tetraploid, Hyla ver­si­color. Evo­lu­tion, 48: 898-908.

Hard­ing, . 1997. Am­phib­ians and Rep­tiles of the Great Lakes Re­gion. Ann Arbor, Michi­gan: Uni­ver­sity of Michi­gan Press.

Haus­fater, G., C. Ger­hardt, G. Klump. 1990. Par­a­sites and mate choice in gray treefrogs, Hyla ver­si­color. Amer­i­can Zo­ol­ogy, 30: 299-331.

Skelly, D. 1992. Field Ev­i­dence for a Cost of Be­hav­ioral An­tipreda­tor Re­sponse in a Lar­val Am­phib­ian. Ecol­ogy, 73/2: 704-708.

Steb­bins, R., N. Cohen. 1995. A Nat­ural His­tory of Am­phib­ians. Prince­ton, New Jer­sey: Prince­ton Uni­ver­sity Press.

Wal­lace, H., B. Bad­away, B. Wal­lace. 1999. Am­phib­ian sex de­ter­mi­na­tion and sex re­ver­sal. Cel­lu­lar and Mol­e­c­u­lar Life Sci­ences, 55/6-7: 901-909.