Hyla cinereaGreen Treefrog

Geographic Range

Hyla cinerea is commonly found in the central to southeastern United States. Its geographic range stretches from Virginia's eastern shore to the southeast tip of Florida and as far west as central Texas. Green treefrogs can be found as far north as Maryland and Delaware. Despite being considered monotypic, clinal variation of Hyla cinerea has been observed from Florida north along the Atlantic Coastal Plain as a possible result of strong selection and/or drift. (Mitchell and Reay, 1999; Aresco, 1996; Mitchell and Reay, 1999)

Habitat

Green treefrogs are frequently found in small ponds, large lakes, marshes, and streams. They prefer habitats with plentiful floating vegetation, grasses, and cattails. One study suggested that, in an artificial hardwood forest setting, the abundance of Hyla cinerea is related to the openness of the forest canopy. The study noted that 88% of 331 individuals were found in areas of the forest where the canopy was open. The presence of green treefrogs in the open canopy areas was interpreted as a method for finding prey, which concentrate in sunny areas with dense ground vegetation. (Horn, et al., 2004; Martof, et al., 1980)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams

Physical Description

Green treefrogs are long-legged and smooth-skinned treefrogs. Most individuals have a bright yellow-green dorsum, but individuals that are reddish-brown to green are also common. Their dorsum frequently has small golden spots which overlay the green color. Ventrally, they are white to cream and have a similarly-colored prominent lateral stripe on each side. Total length ranges from 34 to 62 mm, females tend to be larger than males. (Pham, et al., 2007; Martof, et al., 1980)

  • Sexual Dimorphism
  • female larger
  • Range length
    32 to 64 mm
    1.26 to 2.52 in

Development

Green treefrogs develop similarly to other anuran species. Eggs hatch at about 5 days post-fertilization. The first tadpole stage occurs directly after hatching. During this stage, tadpoles are very small and feed on the remainder of their yolk. Several days after hatching external gills become functional and they begin to graze on microscopic vegetation. Soon after external gills become functional they begin to disappear as the operculum develops and covers over them. Three weeks after hatching external gills have disappeared and internal gills become the primary mode of respiration. Eight to ten weeks after hatching, the front and rear legs begin development. Tadpoles also transition to a carnivorous diet at this point. In the final weeks of development the front and rear legs become fully functional and the tail starts to shorten. At this time green treefrogs are ready to leave the water and venture onto land. (Linzey, 2001)

Reproduction

Breeding is strongly influenced by day length, temperature, and precipitation. These relative influence of these factors is not well understood, but these frogs generally breed following rainfall. Males tend to call more frequently as temperature and day length increases. To attract mates, males use a distinct advertisement call which is noticeably different than release or warning calls. Once the male has attracted an appropriate mate they begin amplexus, with the male tightly grasping onto the female to bring their cloacal openings close together for fertilization. Males generally try to mate with as many females as they can attract. (Linzey, 2001; Saenz, et al., 2006)

Average clutch size in a Florida population of green treefrogs was observed to be approximately 400 eggs. Although many females may only lay a single clutch in a season, some have been known to lay multiple clutches. Female size was positively correlated with clutch size, but after the initial clutch the number of eggs nearly always decreased. In the Florida population, advertisement calls of males were documented between March and September and pairs in amplexus were observed between April and August. There is some evidence to suggest that breeding season length is correlated with latitude; breeding season length decreases as latitude increases because of temperature limitations. (Gunzburger, 2005)

  • Breeding interval
    Most females breed once yearly, although some have several clutches during the breeding season.
  • Breeding season
    Breeding occurs from March to September.
  • Average number of offspring
    400
  • Range time to hatching
    4 to 14 days
  • Average time to hatching
    5 days

There is no parental investment beyond the efforts of mating and egg-laying.

  • Parental Investment
  • no parental involvement
  • pre-fertilization
    • provisioning
    • protecting
      • female

Lifespan/Longevity

Lifespans in the wild are unknown, but captives can live 6 years with proper care. (PETCO Animal Supplies, Inc., 2004)

  • Typical lifespan
    Status: captivity
    6 (high) years

Behavior

Green treefrogs are mobile and can be found in large groups during the breeding season, especially during peak times. They make small scale movements between foraging and breeding areas seasonally. Besides their mating calls, alarm and rain calls are important aspects of social behavior. During most of the year green treefrogs are solitary. They are most active when the weather is moist. (Linzey, 2001)

Home Range

No information was available on green treefrog home ranges.

Communication and Perception

Green treefrogs use a variety of calls to communicate. Males attract females through a specific mating call. Alarm calls are used to broadcast that there is an immediate threat or predator around. There is also a noticeably different rain call, which is vocalized when frogs sense that there will soon be rain. Green treefrogs have well developed hearing and can sense vibrations through the ground. The parietal organ, located on the top of the head between the eyes, has been implicated in compass orientation and thermoregulation. (Linzey, 2001)

Food Habits

Green treefrogs are insectivores that commonly consume flies, mosquitoes, and other small insects. Freed (1980) suggested that prey were not selected by size, but according to their activity; the most active prey were the most frequently eaten. According to Freed, nearly 90% of Hyla cinerea prey were actively pursued, the other 10% were insects walking or close enough to be snatched up by the frog's tongue. (Freed, 1980)

  • Animal Foods
  • insects

Predation

Adult green treefrogs are subject to predation by a wide variety of organisms. Snakes, birds, large fish, and even other frogs may prey on Hyla cinerea. Green treefrogs are one of the only species in the genus Hyla in the southeastern United States that typically breeds in areas with large predatory fish. Tadpoles are at even more risk than adults because they have few defensive mechanisms and are easily caught. Predatory aquatic insects such as giant water bugs (Belastomatidae) frequently feed on tadpoles in their early stages as well as smaller fish such as pumpkinseed sunfish (Lepomis gibbosus) and bluegill sunfish (Lepomis macrochirus). Green treefrog adults are exceptionally good at hiding on grasses and other vegetation. When they tuck in their legs and close their eyes they blend in with the color of leaves. (Gunsburger, 2005; Gunsburger, 2005; Gunzburger, 2005)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Although green treefrogs are not considered a keystone species, they play a vital role ecosystems they inhabit. They are prey to large predatory fish, snakes, and their other predators and green treefrog adults consume large quantities of insects.

Green treefrog parasites in a Florida population include the nematode Cosmocercella haberi (23% of individuals), a protozoan in the genus Opalina (47% of individuals), a trematode Clinostomum attenuatum (2% of frogs), and a nematode in the genus Rhabdias (5%). Another study found that Agamascaris enopla is an internal nemaode parasite. (Creel, et al., 2000; Freed, 1980)

Commensal/Parasitic Species
  • Cosmocercella haberi
  • Opalina
  • Clinostomum attenuatum
  • Rhabdias
  • Agamascaris enopla

Economic Importance for Humans: Positive

Green treefrogs and other anurans impact populations of mosquitoes and other small insects through predation. They can also be bioindicators of aquatic contamination, including contamination by many synthetic compounds used in pesticides, herbicides, and medications. For example, polychlorinated biphenyls (PCBs) have a high affinity for fat and are easily introduced through the digestive system. PCBs continue to accumulate with repeated exposure and should increase with organisms that have more fat. The thin, permeable skin of anurans puts them at a higher risk because compounds are so easily absorbed. Tadpoles and metamorphs are considered to be good indicators of PCB accumulation in sediment because they are usually in more direct contact with contaminated sediment. Adults are considered to be general indicators of contaminated areas but not specific conditions. (DeGarady and Halbrook, 2006)

  • Positive Impacts
  • research and education
  • controls pest population

Economic Importance for Humans: Negative

These treefrogs have no known negative economic impacts.

Conservation Status

Green treefrogs are common throughout their geographic range. Populations are relatively large and stable at this time. Although, like all frog species, they are reliant on aquatic habitats that are frequently destroyed by human activities. They are listed as a species of Least Concern on the IUCN list. (Linzey, 2001)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Matthew Nichols (author), Radford University, Karen Francl (editor, instructor), Radford University.

Glossary

Nearctic

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

World Map

acoustic

uses sound to communicate

bilateral symmetry

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

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

cryptic

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

ectothermic

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

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

forest

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

freshwater

mainly lives in water that is not salty.

heterothermic

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

insectivore

An animal that eats mainly insects or spiders.

iteroparous

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

marsh

marshes are wetland areas often dominated by grasses and reeds.

metamorphosis

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

motile

having the capacity to move from one place to another.

native range

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

oviparous

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

polygynous

having more than one female as a mate at one time

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

saltatorial

specialized for leaping or bounding locomotion; jumps or hops.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

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

solitary

lives alone

swamp

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

tactile

uses touch to communicate

temperate

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

terrestrial

Living on the ground.

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

References

Aresco, M. 1996. Geographic Variation in the Morphology and Lateral Stripe of the Green Treefrog (Hyla cinerea) in the Southeastern United States. American Midland Naturalist, 135/2: 293-298.

Creel, T., C. Foster, D. Forrester. 2000. Parasites of the Green treefrog, Hyla cinerea, from Orange lake, Alachua county, Florida, U.S.A.. Comparative parasitology, 67/2: 255-258.

DeGarady, C., R. Halbrook. 2006. Using Anurans as Bioindicators of PCB Contaminated Streams. Journal of Herpetology, 40/1: 127-130.

Freed, A. 1980. Prey Selection and Feeding Behavior of the Green Tree Frog (Hyla cinerea). Ecology, 61/3: 461-465.

Gunsburger, M. 2005. Differential Predation on Tadpoles Influences the Potential Effects of Hybridization between Hyla cinerea and Hyla gratiosa. Journal of Herpetology, 39/4: 682-687.

Gunzburger, M. 2005. Reprodcutive Ecology of the Green Treefrog (Hyla cinerea) in Northwester Florida. American Midland Naturalist, 155: 321-328.

Halliday, T. 1986. The Encylopedia of Reptile and Amphibians. New York, NY: Facts on File.

Horn, S., J. Hanula, M. Ulyshen. 2004. Abundance of Green Tree Frogs and Insects in Artificial Canopy Gaps in a Bottomland Hardwood Forest. American Midland Naturalist, 153: 321-326.

Linzey, D. 2001. Vertebrate Biology. New York, NY: Mcgraw-Hill.

Martof, B., W. Palmer, J. Bailey, J. Harrison III. 1980. Amphibians and Reptiles of the Carolinas and Virginia. Greensboro, NC: University of North Carolina Press.

Mitchell, J., K. Reay. 1999. Atlas of Amphibians & Reptiles in Virginia. Richmond, VA: Virginia Department of Game and Inland Fisheries.

PETCO Animal Supplies, Inc., 2004. "Green treefrog care sheet" (On-line). Accessed December 08, 2007 at http://www.petco.com/caresheets/amphibians/Treefrog_Green.pdf.

Pham, L., S. Boudreaux, S. Karhbet, B. Price, A. Ackleh, J. Carter, N. Pal. 2007. Population Estimates of Hyla cinerea (Schneider) (Green Tree Frog) in an Urban Environment. Southeastern Naturalist, 6/2: 203-216.

Saenz, D., L. Fitzgerald, K. Baum, R. Conner. 2006. Abiotic Correlates of Anuran Calling Phenology: The Importance of Rain, Temperature, and Season. Herpretological Monographs, 20: 64-82.

Walton, A. 1933. The Nematoda as Parasites of Amphibia. The Journal of Parasitology, 20/1: 1-32.