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.
Range lifespan
Status: captivity: 7 (high) years.
Average lifespan
Status: captivity: 7 years.
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.
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.
Known Predators:
Anti-predator Adaptations: cryptic
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.
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.
Range length: 3 to 5 cm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: sexes alike
Average mass: 7.175 g.
Average basal metabolic rate: 0.00433 W.
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.
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.
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.
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.
Habitat Regions: temperate ; terrestrial ; freshwater
Terrestrial Biomes: forest
Aquatic Biomes: lakes and ponds; temporary pools
Wetlands: swamp
Other Habitat Features: suburban ; agricultural ; riparian
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.
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.
Biogeographic Regions: nearctic (Native )
As tadpoles, eastern gray treefrogs begin life by grazing on algae and detritus in their pond.
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.
Animal Foods: amphibians; insects; terrestrial non-insect arthropods; mollusks; terrestrial worms
Plant Foods: algae
Other Foods: detritus
Primary Diet: carnivore (Insectivore ); herbivore (Algivore)
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.
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.
Commensal/Parasitic Species:
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.
Positive Impacts: controls pest population
There are no known adverse effects of Hyla versicolor on humans.
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.
Development - Life Cycle: metamorphosis
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.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
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.
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). The spring peeper (Pseudacris crucifer) also uses a similar call, but several ‘peeps’ can be heard before and after the trill.
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.
Adult gray treefrogs are very sensitive to ground vibrations and possess excellent hearing. Yet, during hibernation they are unresponsive to most external stimuli.
Communication Channels: visual ; acoustic ; chemical
Other Communication Modes: choruses
Perception Channels: visual ; tactile ; acoustic ; vibrations ; chemical
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.
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.
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.
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.
Range age at sexual or reproductive maturity (male): 1 to 2 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (External ); oviparous
Average age at sexual or reproductive maturity (female)
Sex: female: 912 days.
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.
Parental Investment: pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth
The gray treefrog (Dryophytes versicolor) is a species of small arboreal holarctic tree frog native to much of the eastern United States and southeastern Canada.[2]
It is sometimes referred to as the eastern gray treefrog, northern gray treefrog,[3] common gray treefrog, or tetraploid gray treefrog to distinguish it from its more southern, genetically disparate relative, Cope's gray treefrog.
As the scientific name implies, gray treefrogs are variable in color. This ability to vary their color provides them with the ability to camouflage themselves from gray to green or brown, depending on the environment around them. H. versicolor can change from nearly black to nearly white. They change color at a slower rate than a chameleon. A unique aspect of the appearance of gray treefrogs is that its legs feature a dark band-like pattern which then contrast sharply with the black-marked bright yellow or orange under the sides of its legs and arms. Dead gray treefrogs and ones in unnatural surroundings are predominantly gray. The female does not call however, the male does call. Female gray treefrogs are usually larger than their male counterparts. They are relatively small compared to other North American frog species, typically attaining no more than 1.5 to 2 in (3.8 to 5.1 cm) in length. Their skin has a lumpy texture to it, giving them a warty appearance.
This species is virtually indistinguishable from Cope's gray treefrog, the only readily noticeable difference being that Cope's Gray treefrog has a shorter, faster call. This varies depending on the temperature, however, as the call rates of both gray treefrogs are temperature dependent. At lower temperatures, Cope's gray treefrog can have a call rate approximating that of the gray treefrog.[4] This difference in calling can be heard, but it is best quantified by counting the number of pulses per second in their whistled trills. At usual temperatures, the gray treefrog has a pulse rate of 16 to 34 pulses per second, while Cope's gray treefrog has a pulse rate of 34 to 60 pulses per second. Even though there is potential for overlap, because of the temperature dependence of the pulse frequency the two species are easily distinguished where they occur together. At a given temperature, the pulse frequency for the gray treefrog is approximately 1/2 that of Cope's gray treefrog.[5]
The gray treefrog also has 48 chromosomes (4n), and is sometimes referred to as the tetraploid gray treefrog in scientific literature. Cope's gray treefrog, or diploid gray treefrog, retained its 2n (24) original chromosome count. Hybridization between these species results in early mortality of many larvae, but some individuals survive to adulthood, but these individuals suffer from reduced fertility.[6]
Both of these similar species have bright-yellow patches on their hind legs, which distinguishes them from other treefrogs, such as the bird-voiced tree frog.[7] The bright patches are normally only visible while the frog is jumping. Both species of gray treefrogs are slightly sexually dimorphic. Males have black or gray throats, while the throats of the females are lighter.[8]
Tadpoles have rounded bodies (as opposed to the more elongated bodies of stream species) with high, wide tails that can be colored red if predators are in the system.[9] Metamorphosis can occur as quickly as two months with optimal conditions. During metamorphosis, the new froglets will almost always turn green for a day or two before changing to the more common gray. Young frogs will also sometimes maintain a light green color, only turning gray or darker green once adulthood is reached.
Gray treefrogs inhabit a wide geographic range, and can be found in most of the eastern half of the United States and as far west as central Texas and Oklahoma. They also range into Canada in the provinces of Quebec,[10] Ontario, and Manitoba, with an isolated population in New Brunswick.
The gray treefrog is capable of surviving freezing of its internal body fluids to temperatures as low as −8 °C (18 °F).[11]
The gray treefrog is most common in forested areas, as it is highly arboreal. Its calls are often heard in rural residential areas of the East Coast and the Midwest. It prefers to breed in semipermanent woodland ponds without fish, but it also lays eggs in swamps, vernal pools, man-made fountains and water gardens, and even in rainwater-filled swimming pool covers.
Male gray treefrogs rarely have large choruses, as they are mostly solitary animals, but might vocalize competitively at the height of breeding periods. Gray treefrogs have been observed to congregate around windows and porch lights to eat insects that are attracted to the light. Insect larvae, mites, spiders, plant lice, harvestmen and snails also contribute towards the diet of the gray treefrog.[12] Some populations have a diet high in ants and beetles.[13] However, like most frogs, D. versicolor is opportunitistic and may also eat smaller frogs, including other treefrogs.[12] During the day they often rest on horizontal tree branches or leaves out in the open. Gray treefrogs have also been observed to lay out in the direct sun. Gray tree frogs are less prone to overheating and desiccation than other amphibians and rely on their superb camouflage to hide them from predators.
Research on anuran communication reveals that groups of male frog chorus attract female frogs to mate. The relative success of these male frogs, including H. versicolor males, at attracting females depends on how their advertisement call is able to lead females to their calling space. As male density increases, a male’s advertisement call is confused with the other calls. This confusion leads to the inability of females to accurately locate the origin of the call. The lowest intensity of a neighbor's call that a male frog is tolerant of is known as the aggressive threshold. When this threshold is reached, a male frog will use a different call known as an aggressive call to initiate male-male conflict or intolerance.[14]
Aggressive calls are usually much shorter in length and have lower frequencies than advertisement calls. Aggressive calls specifically in H. versicolor males also do not show much variation in amplitude throughout the call, unlike advertisement calls which contain many pulses. This is very unique to the H. versicolor species since most species with graded aggressive calls have advertisement and aggressive calls with very similar structures. They are similar in that they both have two peak frequencies, but the aggressive call peak frequencies are usually lower.[15][16]
Since females do not prefer call overlap between males in a close range of each other, this can cause a change in call-timing as well as a change in the characteristics of the calls these males produce.[17][18] When there are other male frogs calling, H. versicolor males will adjust the timing of their calls; however, this is done in a much less strict fashion than most frog species. Compared to other species, H. versicolor does not exhibit selective attention. Selective attention is the phenomenon observed in many chorusing male frog species to change the timing of their calls to reduce overlap based on their loudest one or two neighboring male competitors, while ignoring the timing of other calls farther away.[19] Instead, H. versicolor males will avoid call overlap when paired with only one other male, but will not actively avoid overlap with adjacent frogs in a group nearly as much as other frog species do.[19] In response to increased competition, males can change the timing of their calls, but also change the characteristics of their calls. As surrounding competition increases, males will increase the length of their advertisement calls, but produce those calls less often since each call requires more energy to produce. But call amplitude and call frequency do not change as the amount of surrounding competition changes.[18]
When males get closer and there is infiltration of each others territories, there are increased chances of aggressive encounters. This results in males engaging in conflict with one another through aggressive calls. The timing of these aggressive calls changes as distance from the intended recipient varies.[17]
Conflict between two H. versicolor males will begin with trading advertisement calls between each other. Even though advertisement calls are primarily used to attract females, they still play a role in male-male interactions. Rarely the conflict escalates from this point and transitions into the exchange of aggressive calls and only in few cases will conflict result in physical contact.[15][16]
Unlike most species, H. versicolor females do not prefer leading calls, but do prefer leading pulses if there is call overlap between male calls. Overall, females prefer the lack of call overlap. However, increasing the distance between males producing overlapping calls may reduce the cost that usually causes females to not choose those potential mates. The distance between the males allows the female to distinguish calls opposed to overlapping calls produced from very close points that make two individual males harder to distinguish by sound. This means that H. versicolor males are not as forced to make specific timed-call responses and initiations to increase mate attractiveness compared to other chorus anurans and insects. Instead, H. versicolor males can allow call-timing to be more dependent on other things, like the social environment and male competition.[17]
H. versicolor females are not usually attracted to aggressive calls no matter the range of aggressive frequency it is produced in, but may occasionally still be attracted to aggressive calls. Females also exhibit no preference within the range of advertisement call frequencies, they generally prefer advertisement calls over aggressive ones. There is a range in the advertisement and aggressive call frequencies because H. versicolor males are capable of producing certain frequencies based on their size and properties of their vocal structures.[15][16]
Females are more attracted to longer male calls, which is also supported by their preference for advertisement calls over any aggressive call.[18] Aggressive calls from nearby males don’t reduce the attractiveness of advertisement calls from a given other male.[20]
Male frogs will change their vocalizations when female frogs move closer to them. They do this in order to increase the likelihood that their advertisement call is received by a female over the other noise and vocalizations that could obscure it. H. versicolor males specifically do this by increasing the length of their calls to several lengths of a normal advertisement call.[19] Males will also lengthen the duration of their calls when they see a female or sense them through touch. Females will initiate the mating position by touching the male frog resulting in the male frog vocalizing one or two especially long calls, known as courting calls.[18]
H. versicolor males are known to follow a similar pattern that is seen in other species termed graded aggressive calling. Compared to aggressive calls, H. versicolor male aggressive calls are a lower frequency than advertisement calls. However, they decrease the frequency of their aggressive calls as the aggressiveness with another male rises. This gradient in frequencies allows their calls to efficiently balance energy costs of calling and when intense calling is necessary during male-male conflict. The energetic cost of producing vocalizations increases if there is any shift from a male’s individual natural frequency. That being said, there is more of an energetic cost for low frequency and frequency decreasing calls than higher frequency ones, so this could be an explanation for why these types of calls are usually reserved for the most intense conflict.[15][16]
Graded aggressive calling and a lower need to avoid call overlap allows H. versicolor males to have more freedom in the types of calls they produce. More freedom in call-timing also allows H. versicolor males to use advertisement call-overlap to signal the beginning of rising levels of aggressiveness between two males. Increasing overlapping calls can also be a response to an increase in the level of male competition or might simply be because call overlap increases as males communicate with each other for a longer period of time. For the same reason why males respond with call overlap in areas with the most acoustic competition, males in high density call choruses also produce the highest levels of overlapping calls with male frogs closest to them.[17]
Male aggressive calling not only is affected by mating and their need to defend their calling space but is also affected by social communication with other aggressive males.[21] The social environment can change as male callers move around and as females arrive to assess their potential mates producing different levels of perceived male competition heard by H. versicolor males.[17] In particular, the social environment surrounding a male responding to an intruder will affect the intensity of the responding aggressive calls produced. This idea of a social environment affecting aggressive call output arose in this frog species from research that examined the relationship between aggressive call intensity in environments with an intruder versus and environment with other surrounding male competitors. With that being said, the effect of the social environment is more complex and requires further research.[21] There are effects of other male competition on a male’s advertisement call timing in the gray tree frog. As males get closer to another males calling space, they become more aggravated by another male infiltrating their calling space. This results in males engaging in conflict with one another through aggressive calls and the timing of these calls changes when the intended recipient is within close range.[17]
Dryophytes versicolor is known to be largely intersterile with D. chrysoscelis but there may be a limited amount of interfertility in sympatry. When D. versicolor is sympatric with D. chrysoscelis, females more strongly weight a species-specific cue (call rate) than a more general cue (call duration) when choosing mates.[22] This appears to be an example of reproductive character displacement to keep the species separate. In addition, to enforce speciation there may be unknown mechanisms of reinforcement deployed between these species and further research may be fruitful.[23]
Dryophytes versicolor and Dryophytes chrysoscelis call next to each other ponds resulting in interference of their vocalizations because their calls are so similar acoustically. In response to male advertisement calls, D. versicolor male answers with the same level of aggressiveness to males of the same species and to D. chrysoscelis males producing the initial call. D. versicolor male interactions with D. chrysoscelis males increase in aggressive intensity more quickly than with male interactions with their own species. Once the aggression levels intensified between these species, the weaker frog was more likely to retreat from the winner. In general, D. versicolor males initiate physical attacks during intense vocal conflict between the two species more often than D. chrysoscelis.
In previous studies, D. versicolor mate attractiveness decreases when there is call overlap with D. chrysoscelis. The H. versicolor mate attractiveness decreases even more so than D. chrysoscelis when there is call overlap, which can explain why the D. versicolor male tends to initiate aggressive physical contact more often: the D. versicolor has more to lose from the call overlap continuing to take place. While the advertisement calls of D. versicolor and D. chrysoscelis are distinguishable, the aggressive calls between these two species are similar.[24]
In arboreal forest habitat, north-eastern US The gray treefrog (Dryophytes versicolor) is a species of small arboreal holarctic tree frog native to much of the eastern United States and southeastern Canada.
It is sometimes referred to as the eastern gray treefrog, northern gray treefrog, common gray treefrog, or tetraploid gray treefrog to distinguish it from its more southern, genetically disparate relative, Cope's gray treefrog.
