American green tree frog | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Amphibia |
Order: | Anura |
Family: | Hylidae |
Genus: | Dryophytes |
Species: | D. cinereus |
Binomial name | |
Dryophytes cinereus (Schneider, 1799) | |
Approximate range | |
Synonyms | |
The American green tree frog (Dryophytes cinereus or Hyla cinerea) is a common arboreal species of New World tree frog belonging to the family Hylidae. This nocturnal insectivore is moderately sized and has a bright green to reddish-brown coloration. [2] Commonly found in the central and southeastern United States, the frog lives in open canopy forests with permanent water sources and abundant vegetation. [3] [4] The American green tree frog is strictly aquatic during the hibernating and mating seasons. [5] When defending its territory, the frog either emits aggressive call signals or resolves to grapple with intruders, seldom leading to injury or death. [6] To avoid predation, the frog will leap into the water or jump into the treetops. [7]
Female green tree frogs are larger than males. Pairs breed through amplexus. [4] Males emit low frequency advertisement calls to attract females. [8] During mating competition, males will eavesdrop on neighboring rivals and either adjust their signal timing or remain silent to intercept call signals and mate with approaching females. [8] [9] Androgens energize males to vocalize. [6]
The American green tree frog is moderately sized. It has long legs, a streamlined and slender build, and smooth skin. The American green tree frog ranges from 3.2 to 6.4 centimetres (1+1⁄4 to 2+1⁄2 in) in length. For perspective on the growth of juveniles, recently metamorphosed "young-of-the-year" were found to be about 20.6 mm. [10]
Their dorsum can range in color from the more common bright green to reddish-brown. Such a range in coloration may result in the frog being mistaken for other species. [2] [11] Some evidence suggests that green tree frogs can exhibit a color change in response to their background and/or temperature. [12]
The dorsum is peppered with small golden spots, and the frogs have a white to cream coloration on their ventral side. American green tree frogs also contain white prominent lateral stripes.
They are normally ectothermic and heterothermic. [4]
The American green tree frog weighs on average 3.76g with a range between 2.15g and 5.11g. Female frogs are usually larger than males. Larger males tend to have an upper hand in attracting females than smaller males either through increased physical strength in duels or more pronounced call signals during mating competition. [8]
The American green tree frog is found in the central and southeastern United States with a geographic range from the Eastern Shore of Maryland to southeast Florida with populations as far west as central Texas and as far north as Delaware and southern New Jersey, though the size of its distribution may be larger or vary seasonally. They are indigenous to the coastal plains of North Carolina, South Carolina, Georgia, and all of Florida. [13] The American green tree frog is considered monotypic, but clinal variation has been observed from Florida north along the Atlantic coastal plain. This may be attributed to the result of strong selection and/or drift. [4]
American green tree frogs prefer to live in open canopy forests with a permanent water source and filled with plentiful vegetation. The species is found in both natural and settled environments, often being sighted in backyards with ponds, in garages or garden structures. The species commonly resides in cypress ponds, water lily prairies, and marshes. They are often found perched on twigs, low branches, and grasses. [3]
A growing number of American green tree frogs have experienced severe habitat loss primarily due to urbanization and destructive wildfires that can destroy forest canopy cover. Since most amphibians have narrow habitat tolerances and migration constraints, American green tree frogs urgently need alternative shelters for survival as forest canopies recover. In a study from Central Texas, scientists have tried to combat wildfire habitat loss by creating artificial shelters using PVC pipes. [3] Wetlands that the American green tree frogs occupy for breeding have had an increase in salinity and an increase in pesticide concentration in recent years due to urbanization. This has proven to have a negative effect on sperm mobility and has reduced reproductive success [14]
One study finds that there are at least 31 tree frog species of the genus Hyla (or Dryophytes) in North America, Central America, and Eurasia. Examples include both the H. gratiosa and H. walkeri. While many tree frogs reside in the New World, a notable number of frogs inhabit the Eurasia continent and display unique biogeographic patterns based on an analysis of nuclear and mitochondrial DNA sequences. [15]
American green tree frogs will defend their mate calling sites against foreign rivals and invaders using aggressive interactions. Such behaviors include a combination of aggressive call signals and wrestling from males. [6]
American green tree frogs are insectivores, primarily consuming flies, mosquitoes, grasshoppers, cockroaches, spiders, beetles, and other small insects such as crickets and ants. [16] One study suggested frogs select prey not by their size, but according to their activity levels, with the most active prey being the most frequently eaten. The same study showed "nearly 90% of Hyla cinerea prey were actively pursued", with the other 10% being "insects walking or close enough to be snatched up by the frog's tongue". [4] Another study showed that it is not uncommon for American green tree frogs to ingest plant material. [17]
Because the species is small and easily frightened, they often do not do well with frequent handling. Some specimens do seem to tolerate it occasionally, so handling frequency should be determined on an individual basis. The American green tree frog tends to be nocturnal, so they will be most active once the lights are off. Males call most of the year, especially after being misted in their tank. [18]
Most American green tree frog females breed once per year, but some have multiple clutches in a single mating season. In a Florida population, "advertisement calls of males were documented between March and September and pairs in amplexus were observed between April and August". The average number of eggs in a single clutch was observed to be about 400 for this specific population. In a population in Florida where conditions were better, clutch size averaged over 1,200. [19] Eggs take between 4 and 14 days to hatch, with an average of five days. According to the Animal Diversity Web at the University of Michigan Museum of Zoology, "Female size was positively correlated with clutch size, but after the initial clutch, the number of eggs nearly always decreased". [4]
Tadpoles are green with a yellow or white stripe extending from each nostril to the eye and may have mottled tail fins. [20] American green tree frogs show only the parental investment of mating and egg-laying. [4]
Breeding is known to be strongly influenced by day length, temperature, and precipitation. While the influence of these factors with respect to breeding is not well understood, it is well documented, as the frogs generally breed following rainfall and males call more frequently as temperature and day length increase. The green tree frog is the only species in the hyla genus in the southeastern U.S. that commonly breeds around predatory fish habitats. [21] Some evidence demonstrates that the length of the breeding season is correlated with latitude; seasonal length decreases as latitude increases due to temperature limitations. [4]
To attract mates, the male American green tree frog uses a distinctive advertisement call which is noticeably different from its release or warning calls.[ citation needed ] This is important for reproductive isolation in areas where different species share breeding areas. [22] Once a mate has been attracted, the pair begins amplexus in which the male frog grasps onto the female to initiate fertilization. The species is polygynous, with the male generally seeking to mate with as many females as it can attract. [4] Eggs are attached to substrates such as emergent vegetation, and unlike other frog species, these egg masses are typically laid in permanent bodies of water rather than vernal pools. [23]
When male frogs aggregate, choruses will form and establish a cacophony of numerous unique advertisement calls. Consequently, male individuals experience intraspecific mating competition and often encounter immense pressure to produce unique call signals that are both attractive and audible to the limited number of available females. Such challenges are further complicated by the rapid fluctuation of males within a chorus, the potential risk of increased exposure to predators, and sexual selection of specific call signals through female choice. [24]
These factors give rise to a social plasticity in the calling behavior of the American green tree frog. In order to maintain competition, male individuals will either modify their signal features, such as the temporal and spectral properties of calls or their signal timing, to reduce signal interference with other neighboring males. Temporal and spectral properties include call duration and call frequency. Changes in signal timing include initiation of advertisement calls during different times of the night. It has been found that male green tree frogs will more often alter their signal timing to attract females due to physiological constraints in the frog's call production mechanism and female choice against increased call duration and period in favor of precise call timing. Modifying signal behavior towards every frog within a chorus is extremely costly and inefficient. However, forcing male individuals to engage in selective attention of advertisement calls from only a few of their closest rivals. [24]
Some male American green tree frogs will not emit or alter their advertisement calls and instead choose to remain silent. Labeled as 'satellites', these frogs will wait to intercept the signals of nearby calling males and mate with approaching sexually active females through amplexus. Such sexual parasitism and call avoidance occur mainly to conserve the frog's energy and avoid predation during mate competition. [9]
Androgens are used for energy during call signal production. As a satellite male green tree frog engages in non-calling mating behavior, androgen quantities are found to decrease to lower levels compared to calling behavior, suggesting a causal relationship between sex hormones and mate calling tactics. [6]
In order to help decide whether to engage in satellite non-calling behavior, male green tree frogs will eavesdrop on other nearby male competitors and adjust their mating responses based on the qualities of their call signals. If given with the choice, females prefer large males with advertisement calls of lower frequencies. Other notable features include the latency to call and male focal size. When eavesdropping male competitors with low call frequencies, large male green tree frogs are found to reduce their latency to call and raise call rates. Small males in contrast will only reduce their latency to call in response to competitors with average call frequencies. [8]
American green tree frogs are also able to undergo interspecific mating competition. In southern Florida, the Cuban tree frog (Osteopilus septentrionalis) is an invasive species that has a similar call to the American green tree frog with respect to timing and pitch. A study found that their calls compete acoustically with each other due to their similarity which limits communication space. In order to compete with the Cuban tree frog, American green tree frogs modified their calls to be shorter, louder, and more frequent so that potential mates would have a better chance of detecting the call. [25] [26]
As a tadpole, the American green tree frog is easily predated by sunfish, bass, and dragonflies, including both aeshnidae and libellulidae odonate naiads. The species is especially vulnerable to predation when living in temporary ponds compared to permanent waters. To combat predation, green tree frog tadpoles may increase hiding behavior while in water to avoid capture. [7] [27]
The American green tree frog is also prone to a few parasites, including nematodes, protozoans, and trematodes. [28]
Contrary to most amphibians, the American green tree frog is not easily susceptible to the Batrachochytrium dendrobatidis (Bd) pathogen and the disease chytridiomycosis. Reasons explaining why are relatively unknown, but one study hypothesizes that variances in climate, frog immunity, and frog habitat are potential factors. [29]
When a male frog engages in vocalization either for aggression or mate attraction, androgen energy stores are used and become depleted. Interestingly, glucocorticoids, such as corticosterones, also appear to change during calling behavior. According to the Energetics-Hormone Vocalization model, glucocorticoid levels in males will rise as androgen levels decrease following vocalization. When observing hormonal levels in both calling and satellite non-calling males, reduced androgen levels and elevated glucocorticoid levels are found among satellite non-calling males compared to calling males. These observations suggest a possible mechanism dictating vocalization and the alternation between calling and non-calling behavior in the green tree frog. Further study is required however on the relationship between glucocorticoids and male vocalization to consider causality. [6]
The causality of vocalization by androgens is also limited by the American green tree frog's social environment. According to one study, androgens themselves were not sufficient to initiate call signals in male frogs when in the presence of social stimuli such as other frog choruses. This suggests that androgens on their own may provide males with enough motivation to call, but they may also require additional social context to produce various call signals during situations such as mating. [30]
American green tree frogs are popular pets because of their small size, appearance, and the undemanding conditions needed to take care of them. Unlike many amphibians, they do not require artificial heating unless household temperatures drop below 21 °C (70 °F). They need a large (at least ten-gallon) terrarium and do best with a substrate that will hold some humidity, such as commercial shredded bark or coconut husk bedding, or untreated topsoil on the floor of the terrarium. Tree frogs are arboreal, so the height of the tank is more important than the length. A variety of things for climbing, such as plants or branches, should be in the habitat. A shallow water dish should be included. Captive frogs should not be handled more than necessary; when necessary, clean gloves should be worn. [31]
The American green tree frog became the state amphibian of Louisiana in 1997 [32] and of Georgia in 2005. [33] [34]
American green tree frogs can also be used as bioindicators for aquatic contamination. Synthetic compounds such as polychlorinated biphenyls are found in many pesticides and pollute the green tree frog's aquatic habitats. Because the frog's skin is thin and permeable, synthetic compounds absorb easily upon contact, making the species a viable variable to measure contamination. [35]
Hylidae is a wide-ranging family of frogs commonly referred to as "tree frogs and their allies". However, the hylids include a diversity of frog species, many of which do not live in trees, but are terrestrial or semiaquatic.
The Cuban tree frog is a large species of tree frog that is native to Cuba, the Bahamas, and the Cayman Islands; but has become invasive in several other places around the Americas. Its wide diet and ability to thrive in urban areas has made it a highly invasive species with established colonies in places such as Florida, the Hawaiian island of Oahu, and the Caribbean Islands. These tree frogs can vary in size from 2 to 5.5 inches in length. Due to their large size, Cuban tree frogs can eat a wide variety of things, particularly native tree frogs, and their removal has shown to result in an increase in the amount of native tree frogs in an area. The tadpoles of Cuban tree frogs also heavily compete with native frog tadpoles, which can cause negative effects in body mass, size at metamorphosis, and growth rates for the native tadpoles.
Hyla is a genus of frogs in the tree frog family Hylidae. As traditionally defined, it was a wastebasket genus with more than 300 species found in Europe, Asia, Africa, and across the Americas. After a major revision of the family, most of these have been moved to other genera so that Hyla now only contains 17 extant (living) species from Europe, northern Africa and Asia. The earliest known fossil member of this genus is †Hyla swanstoni from the Eocene of Saskatchewan, Canada, but its designation to Hyla happened before the major revision, meaning that its position needs confirmation.
Agalychnis callidryas, commonly known as the red-eyed tree frog or red-eyed leaf frog, is a species of frog in the subfamily Phyllomedusinae. It is one of the most recognizable frogs. It is native to forests from Central America to north-western South America. This species is known for its bright coloration, namely its vibrant green body with blue and yellow stripes on the side. It has a white underside, brightly red and orange colored feet, and is named after its distinctive bright red eyes. One particular and special feature of the frogs coloration is its exceptional high reflectance in the near-infrared.
Spikethumb frogs are a genus (Plectrohyla) of frogs in the family Hylidae found in Central America from southern Mexico through Guatemala and northern El Salvador to central and northern Honduras. A major revision of the Hylidae moved an additional 21 species to this genus from the genus Hyla. The additional species moved to Plectrohyla were identified as the Hyla bistincta group, also called the Plectrohyla bistincta group; a separate group from the initial Plectrohyla guatemalensis group. This phylogenetic classification was later revised by moving the Plectrohyla bistincta group from the genus Plectrohyla into a new genus called Sarcohyla. Meanwhile, the guatemalensis group remained in Plectrohyla. They are called spikethumb because of the spike on their thumbs, which is called a prepollex. The genus name comes from the Greek word plēktron ("spur") and hyla.
Hyla japonica, commonly known as the Japanese tree frog, is a species of anuran native to Japan, China, and Korea. H. japonica is unique in its ability to withstand extreme cold, with some individuals showing cold resistance at temperatures as low as −30 °C for up to 120 days. H. japonica are not currently facing any notable risk of extinction and are classified by the IUCN as a species of "least concern". Notably, H. japonica have been sent to space in a study that explored the effect of microgravity on H. japonica. Hyla japonica is synonymous with Dryophytes japonicus.
The gray treefrog is a species of small arboreal holarctic tree frog native to much of the eastern United States and southeastern Canada.
Cope's gray treefrog is a species of treefrog found in the United States and Canada. It is almost indistinguishable from the gray treefrog, and shares much of its geographic range. Both species are variable in color, mottled gray to gray-green, resembling the bark of trees. These are treefrogs of woodland habitats, though they will sometimes travel into more open areas to reach a breeding pond. The only readily noticeable difference between the two species is the mating call — Cope's has a faster-paced and slightly higher-pitched call than D. versicolor. In addition, D. chrysoscelis is reported to be slightly smaller, more arboreal, and more tolerant of dry conditions than D. versicolor.
The Pine Barrens tree frog is a species of New World tree frog. It is becoming rare due to habitat loss.
The squirrel tree frog is a small species of tree frog found in the southeastern United States, from Texas to Virginia. This is an introduced species in the Bahamas. Squirrel tree frogs are small frogs, about 1.5 inches in length as adults. There are several color variations, but most commonly they are green and look very much like the American green tree frog. They can also be varying shades of yellow or brown, sometimes with white or brown blotching.
Dryophytes gratiosus, commonly known as the barking tree frog, is a species of tree frog endemic to the south-eastern United States. Formerly known as Hyla gratiosa.
Dendropsophus ebraccatus, also known as the hourglass treefrog, referring to the golden-brown hourglass shape seen surrounded by skin yellow on its back. Their underbellies are yellow. Their arms and lower legs usually display bold patterns while their upper legs or thighs are light yellow giving them the appearance of wearing no pants. The species name "ebraccata" translates to "without trousers" in Latin.
The pine woods tree frog is a species of frog in the family Hylidae, endemic to the southeastern United States.
The Italian tree frog is a species of frog in the family Hylidae, found in Italy, Slovenia, Switzerland, and possibly San Marino. Its natural habitats are temperate forests, rivers, intermittent rivers, freshwater marshes, intermittent freshwater marshes, arable land, and urban areas. It is threatened by habitat loss.
Rosenberg's treefrog, also known as Rosenberg's gladiator frog or Rosenberg's gladiator treefrog, is a species of frog in the family of tree frogs (Hylidae) and genus of gladiator frogs (Boana) found in Costa Rica, Panama, Colombia, Trinidad and Tobago and north-western Ecuador. Its scientific name is a testimony to Mr. W. F. H. Rosenberg who collected the type series, and its common name refers to the aggressiveness of males of the species.
The Panama cross-banded tree frog or pug-nosed tree frog is a species of frog in the family Hylidae found in the humid Pacific lowlands of southwestern Costa Rica to eastern Panama and in the Caribbean lowlands of Panama and northern Colombia. Males of the species utilize synchronous calling to hide their position from predators. Females create basins during amplexus and deposit fertilized eggs onto the surface of the water.
A tree frog is any species of frog that spends a major portion of its lifespan in trees, known as an arboreal state. Several lineages of frogs among the Neobatrachia suborder have given rise to treefrogs, although they are not closely related to each other.
Ecnomiohyla rabborum, commonly known as Rabbs' fringe-limbed treefrog, is a possibly extinct species of frog in the family Hylidae. They were relatively large frogs that inhabited the forest canopies of central Panama. Like other members of the genus Ecnomiohyla, they were capable of gliding by spreading their enormous and fully webbed hands and feet during descent. The males of the species were highly territorial and would guard water-filled tree holes used for breeding. They were also the ones responsible for guarding and caring for the young, including providing food. They were the only known species of frog where the tadpoles derived nutrition by feeding on the skin cells of their fathers.
Sexual selection in amphibians involves sexual selection processes in amphibians, including frogs, salamanders and newts. Prolonged breeders, the majority of frog species, have breeding seasons at regular intervals where male-male competition occurs with males arriving at the waters edge first in large number and producing a wide range of vocalizations, with variations in depth of calls the speed of calls and other complex behaviours to attract mates. The fittest males will have the deepest croaks and the best territories, with females making their mate choices at least partly based on the males depth of croaking. This has led to sexual dimorphism, with females being larger than males in 90% of species, males in 10% and males fighting for groups of females.
Dryophytes suweonensis, the Suweon treefrog or Suwon treefrog, is a species of frog in the family Hylidae endemic to the Korean Peninsula probably from the Imjin River to the Mangyeong River, south of Iksan. Its distribution and population have been assessed to be below 800 individuals and the status of the species has been updated as Endangered by the IUCN. The natural habitat of the species has been generally transformed into rice fields and it is threatened by habitat loss.