Lithobates virgatipesCarpenter Frog

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Geographic Range

Carpenter frogs are found in the Atlantic coastal plain of North America, from the Pine Barrens of New Jersey to the Okefenokee Swamp region of southern Georgia and northernmost Florida. Their range extends farther inland in southern North Carolina and in South Carolina. (Conana, 1975; Hammerson, 2004; White and White, 2002)

Habitat

Carpenter frogs live in a variety of habitats which contain still or slow moving water and an abundance of aquatic vegetation. They can be found in Delmarva bays, sphagnum bogs, flooded cranberry bogs, artificial lakes, and pine barren ponds. They prosper in wetlands with acidity levels exceeding the threshold for other members of the genus Rana. In areas where pig frogs (Lithobates grylio) are present carpenter frogs may be present in lower abundance. In northern Florida carpenter frogs can be found in cypress dome and gum swamps, the only area they are found in that state. It is said that carpenter frogs are found in waterways that are tea or coffee colored, where they can easily be camouflaged. Carpenter frogs are often seen completely out of water but never at a large distance from water. They depend on aquatic vegetation in shallow waters for protection and breeding. ("Conservation Plans for Biotic Regions in Florida Containing Multiple Rare or Declining Wildlife Taxa", 2003; Alden and Cassie, 1999; Conana, 1975; Gosner and Black, 1957; Hammerson, 2004; Reshetiloff, 1994; White and White, 2002)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams
  • temporary pools
  • coastal

Physical Description

Carpenter frogs are medium sized frogs ranging from 4.1 to 6.6 cm (1.6 to 2.6 inches). They have a brown head, body and legs. Male carpenter frogs have a narrower head than females. There are four distinct yellowish or golden brown stripes that run down the back and sides of these frogs. Two of the stripes run closer to the centerline of the body, while the second two are more lateral. Carpenter frogs are unique in that they have no dorsolateral folds and the webbing of their feet does not reach the longest toe. The underside is cream to yellow in color with dark mottling that is present in no particular pattern. Mottling patterns are often black. A light line is present on their upper lip. Carpenter frogs have paired throat pouches which are spherical when inflated. (Behler and King, 1979; White and White, 2002)

Carpenter frog tadpoles are large, growing up to 9 cm in length. Like their adult counterparts they are brown, with a white speckled underbody. The tail has dark stripes formed from prominent lines of dark spots which run longitudinally through the musculature. The spots will most often fuse to form dark stripes. (White and White, 2002)

Carpenter frogs can be confused with northern green frogs (Lithobates clamitans clamitans), young American bullfrogs (Lithobates catesbeianus), dark southern leopard frogs (Lithobates sphenocephalus sphenocephalus) and young pig frogs (Lithobates grylio). Northern green frogs and young American bullfrogs lack the yellowish or golden brown stripes present on carpenter frogs. Dark southern leopard frogs have a light spot in the middle of their tympanum, which carpenter frogs lack. Southern leopard frogs lack two of the four stripes present on carpenter frogs. Young pig frogs have pale dorsolateral stripes which sometimes may be unseen at first glance. Their toes are webbed almost to their tips, which is not the case in carpenter frogs. (Conana, 1975; White and White, 2002)

  • Sexual Dimorphism
  • sexes shaped differently
  • Range length
    4.1 to 6.6 cm
    1.61 to 2.60 in

Development

Carpenter frog eggs will hatch approximately one week after laying, depending on water temperature. Tadpoles will live in that state for roughly one year, growing up to 9 cm. They spend the winter in breeding ponds. Between August and September of the following year carpenter frog tadpoles will metamorphose into juveniles. (White and White, 2002; White and White, 2002)

Reproduction

When breeding season begins male carpenter frogs establish and defend their territories through calls. They select territories in shallow wetlands that consist of both still waters and submerged shrubs. The number of calling sites present in a wetland are directly related to the amount of submerged vegetation present that is suitable for laying eggs. (Given, 1988; White and White, 2002)

Through the use of aggressive vocalizations, consisting of three different calls, upright posting displays, and combat practices, male carpenter frogs mark their territory and try to attract the attention of females. Combat practices involve males wrestling for brief periods of time. During the wrestling match the males will interlock their front legs in an amplexus like embrace. This is done by attempting to mount each other. Simultaneously males may make aggressive calls that are growl-like. These activities are used to help draw attention from females. (White and White, 2002)

If females are interested in the male based upon his physical display or calls she will approach the male and sometimes communicate with the male with a chirp like call. This chirp like call is not always noticed in male and female carpenter frog interactions. This particular behavior is more common and unique among Delmarva frog populations. Following male and female interaction, mating may occur. (White and White, 2002)

Carpenter frogs typically mate and lay their eggs between April and July. Female carpenter frogs will deposit a globular mass consisting of up to 600 eggs. The oblong mass is attached to submerged aquatic vegetation within the male’s territory. Egg masses are not attached to vegetation at a depth greater than 30 cm. Each mass ranges from 75 to 100 mm in diameter. Carpenter frog eggs and embryos have the same level of tolerance to acidic water as do adults. Gosner and Black (1957) demonstrated that at a pH of 3.8 or lower resulted in abnormal development. The same results were found when salinity levels were between 0.15 to 0.30 grams per 100 cc. (Gosner and Black, 1957; Livezey and Wright, 1947; White and White, 2002)

Females may lay several egg masses throughout a breeding season. Given (1987) demonstrated that males called on 95% of the nights. As a result, he concluded that males almost continuously call and engage in mating activities throughout the breeding season. Findings also show that calling efforts by smaller males are lower than those of larger males. Smaller males tend to grow more during breeding season. (Given, 1987; Given, 1988)

  • Breeding interval
    Male carpenter frogs call 95% of the nights during breeding season, with females laying eggs 2 to 3 times.
  • Breeding season
    Carpenter frogs breed between April and August.
  • Range number of offspring
    200 to 600
  • Average time to hatching
    1 weeks
  • Average age at sexual or reproductive maturity (male)
    1 years

Specific information pertaining to parental care in carpenter frogs has not been documented. However, most species in the genus Rana invest little in parental care after having laid and fertilized eggs.

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

Lifespan/Longevity

The longest lifespan documented in captivity was 6 years and 2 months. Wild lifespans carpenter frogs have not been documented. (Snider and Bowler, 1992)

  • Range lifespan
    Status: captivity
    6.17 (high) years
  • Average lifespan
    Status: captivity
    6.2 years
    AnAge

Behavior

Carpenter frogs are described as a secretive species. They are often difficult to see or capture due to their natural camouflage and shy behavior. When frightened they quickly dart away underwater and raise their head after a very brief period to reevaluate the situation and surroundings. They will usually only have their head exposed during these times.

Carpenter frogs are nocturnal animals. They aggregate in large numbers in suitable habitat. (Conana, 1975; White and White, 2002)

Home Range

Carpenter frogs are found near wetlands throughout the year. While they are most often seen completely out of water they are never far from a water source. (Conana, 1975; White and White, 2002)

Communication and Perception

Carpenter frogs were assigned their common name based upon their hammering call. When carpenter frogs are calling in a chorus it is often described as sounding like a crew of workmen hammering. When an individual carpenter frog is calling it is described as sounding like two carpenters hammering nails one fraction of a second after each other. While most people have said that the call is “pu-tunk, pu-tunk, pu-tunk.” Males are capable of emitting the call ten times in succession. (Alden and Cassie, 1999; Behler and King, 1979; Conana, 1975; Given, 1987)

Given (1987) demonstrated that carpenter frogs have five other less identifiable calls. Three of which are for aggressive purposes, one release call used when males accidentally grab each other, and one chirp call used by females for courtship. Given (1999) also found that when males call in aggressive situations, they will follow those calls with an advertisement call for attracting females. When they appear to still in be in aggressive situations following the initial call they will adjust their advertisement call to a more aggressive sounding call while still including the necessary components to attract females. (Given, 1987; Given, 1999)

Carpenter frogs also communicate with each other through their breeding practices. Males communicate with the females by displaying their upright posture and combating with other males. (White and White, 2002)

Food Habits

Carpenter frogs forage on the ground and in vegetation for small insects and other small invertebrates. (Conana, 1975; White and White, 2002)

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

Predation

While there is little published information pertaining to natural predators of carpenter frogs, some research suggests that water snakes (Nerodia) eat carpenter frogs. Zampella and Bunnell (2000) suggest that the presence of American bullfrogs (Lithobates catesbeianus) negatively affects carpenter frog populations. When pig frogs (Lithobates grylio) are present there has also been a noticeable absence or decline in carpenter frog populations. Carpenter frogs are well camouflaged in their natural habitats. (Conana, 1975; Zampella and Bunnell, 2000)

  • Anti-predator Adaptations
  • cryptic
  • Known Predators

Ecosystem Roles

Carpenter frogs co-occur with green frogs (Lithobates clamitans clamitans), southern leopard frogs (Lithobates sphenocephalus sphenocephalus), and Pine Barren treefrogs (Hyla andersonii). (Conana, 1975; Gosner and Black, 1957; White and White, 2002; Zampella and Bunnell, 2000)

Economic Importance for Humans: Positive

Like most frogs, carpenter frogs consume insects that may be considered a nuisance.

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

There are no known adverse effects of carpenter frogs on humans.

Conservation Status

According to the 2006 ICUN Redlist, carpenter frogs are of Least Concern. Conservation status varies locally in the United States. In New Jersey, Delaware, and some areas of Virginia they are protected, while in Maryland and other areas of Virginia they are listed as a species of special concern. ("An Introduction to Mid-Atlantic Seasonal Pools", 2005; Hammerson, 2004; Hammerson, 2006)

Knowing that carpenter frogs thrive in acidic waters it is thought that the neutralization of wetland areas in the Delmarva region may be the cause of their decline in that region. As wetlands become less acidic a larger variety of frogs can inhabit the area including more aggressive species such as northern green frogs (Lithobates clamitans clamitans). Historically populations of carpenter frogs have been found in Kent and Sussex County in Delaware, and Queen Anne’s, Talbot, Caroline, Dorchester, Wicomico, and Worcester counties in Maryland. In the 1990s the carpenter frog population in Talbot County was found to be severely decreased as a possible result of habitat degradation. (Given, 1999; White and White, 2002)

Areas farther south like Georgia the Carpenter Frog is considered common. However it does have a limited range. Considering that the Carpenter Frog requires wetland areas with large amounts of submerged vegetation for breeding, human disturbances to such environments have and will continue to impact the species. ("Conservation Plans for Biotic Regions in Florida Containing Multiple Rare or Declining Wildlife Taxa", 2003)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Danielle Morrow (author), Environmental Concern, Inc., Sarah Toman (editor, instructor), Environmental Concern, Inc..

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.

bog

a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

choruses

to jointly display, usually with sounds, at the same time as two or more other individuals of the same or different species

coastal

the nearshore aquatic habitats near a coast, or shoreline.

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

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.

natatorial

specialized for swimming

native range

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

nocturnal

active during the night

oviparous

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

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

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).

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

visual

uses sight to communicate

References

USGS Patuxent Wildlife Center. An Introduction to Mid-Atlantic Seasonal Pools. 2005.

Florida Fish and Wildlife Conservation Commission. Conservation Plans for Biotic Regions in Florida Containing Multiple Rare or Declining Wildlife Taxa. 2003.

Alden, P., B. Cassie. 1999. National Audubon Society Field Guide to the Mid-Atlantic States. New York: Chanticleer Press.

Behler, J., W. King. 1979. National Audubon Society Field Guide to North American Reptiles and Amphibians. Random House Inc.

Conana, R. 1975. The Peterson Field Guide Series: A Field Guide to Reptiles and Amphibians of Eastern and Central North America. Boston: Houghton Mifflin Company.

Given, M. 1999. Distribution records of Rana virgatipes and associated anuran species along Maryland's Eastern Shore. Herpetological Review, 30: 144-146.

Given, M. 1988. Growth rate and the cost of calling activity in male carpenter frogs, Rana virgatipes. Behavioral Ecology and Sociobiology, 22: 153-160.

Given, M. 1987. and acoustic interactions of the carpenter frog, Rana virgatipes. Herpetologica, 43: 467–481.

Gosner, K., I. Black. 1957. The effects of acidity on the development and hatching of New Jersey frogs. Ecology, 38: 256–262.

Hammerson, G. 2006. "NatureServe Explorer" (On-line). Accessed March 20, 2007 at http://www.natureserve.org/explorer/servlet/NatureServe?searchName=Rana+vir gatipes.

Hammerson, G. 2004. "The IUCN Red List of Threatened Species" (On-line). Accessed March 20, 2007 at http://www.iucnredlist.org/search/details.php/58747/summ.

Livezey, R., A. Wright. 1947. A synoptic key to the salientian eggs of the United States. American Midland Naturalist, 37: 179–222.

Reshetiloff, K. 1994. Seranades from the Woods. Alliance for the Chesapeake Bay Bay Journal, March: N/A. Accessed May 20, 2007 at http://www.bayjournal.com/article.cfm?article=154.

Snider, A., K. Bowler. 1992. Longevity of reptiles and amphibians in North American Collections. St. Louis: Society for the Study of Amphibians and Reptiles.

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

White, J., A. White. 2002. Amphibians and Reptiles of Delmarva. Tidewater Publishers with Delaware Nature Society.

Zampella, R., J. Bunnell. 2000. The distribution of anurans in two river systems of a Coastal Plain watershed. Journal of Herpetology, 34: 210–221.