Lithobates clamitans or Rana clamitans, commonly known as the green frog, is a species of frog native to eastern North America. The two subspecies are the bronze frog and the northern green frog.
These frogs, as described by their name, typically have varying degrees of green heads. These frogs display significant acts of territoriality, with males being the primary actors. Male green frogs use this technique against other male frogs in addition to other intruders that might have interest in nearing their territory. Territoriality also plays a role in mating, as females favor males who are strong in this field and exhibit strong mating calls. Male green frogs use four different types of breeding calls to attract potential female mates. Predators of the eggs of green frogs include beetles, water bugs, and water scorpions. Adult frogs are typically threatened by several types of birds.
Taxonomy Lithobates clamitans is a member of the true frog family Ranidae and genus Lithobates. Litho- meaning stone, a rock climber. Originally classified in the genus Rana until systematic revision, features of the genus are true frogs with slim waist and wrinkled skin, found across much of Eurasia and North America.
Subspecies The two recognized subspecies of L. clamitans are: Lithobates clamitans clamitans – bronze frog Lithobates clamitans melanota – northern green frog
Description This species is a mid-sized true frog. Adult green frogs range from in body length (snout to vent, excluding the hind legs). The typical body weight of this species is from .GREEN FROG. Rana clamitans melanota . uri.edu The sexes are sexually dimorphic in a few ways: mature females are typically larger than males, the male tympanum is twice the diameter of the eye, whereas in females, the tympanum diameter is about the same as that of the eye, and males have bright yellow throats. The dorsolateral ridges, prominent, seam-like skin folds that run down the sides of the back, distinguish the green frog from the bullfrog, which entirely lacks them.
Green frogs usually have green heads while the body is brown, gray, or dark green. The green head can be more or less prominent on certain individuals, with some frogs only having green on the side of their heads while other frogs are green all the way down their back. The belly is white with black mottling. Male green frogs in breeding condition have yellow throats. Green frogs are darker colored on colder days to help absorb heat. Green frogs can sometimes be blue due to a genetic mutation known as axanthism that prevents the frog from producing yellow pigments (yellow and blue pigments together make the color green).
Green frog tadpoles are olive green and iridescent creamy-white below. Metamorphosis can occur within the same breeding season or tadpoles may overwinter to metamorphose the next summer.
Habitat and distribution Green frogs are associated with bodies of water and have been found in a variety of habitats, living at the margins of shallow freshwater ponds, road-side ditches, lakes, swamps, and streams, and of vernal pools and other temporary bodies of water though less so than other frogs. They maintain small home ranges around these water sources and spend about a third of their time foraging for resources (especially in regions of abundant leaf litter and dense vegetation), returning to the water for refuge. Their habitat has also been impacted by human interaction via the development of roads, buildings, and other infrastructure and agriculture which involves the destruction of their habitat. However, if there is abundant and quality habitat nearby, green frogs have the capability to flee from deforestation and are also somewhat tolerant of said destruction. When attempting to flee from the destruction of their habitat, Green frogs tend to move primarily among three distinct types of aquatic habitats: ephemeral wetland, stream, and swamp. Additionally, green frogs select for increased soil moisture, fine woody debris, and fewer trees with water cover being the most important factor emphasizing the fact that they tend to inhabit areas near water and with open environments in order to survive.
The green frog is a widespread species native to North America, mainly occurring throughout eastern North America from the St. Lawrence River Valley in southeastern Canada to Northern Florida and Eastern Texas.
Habitat loss Due to increasing destruction of their habitat, deforestation, climate change, diseases, and chemical contaminants, amphibian population decline and extinctions may be as high as 211 times the background extinction rate. Both water and air temperatures play a major role in timing and rates of breeding, larval development, time-to-metamorphosis, size-at-metamorphosis, growth, and physiological parameters. There is experimental data present that details how organisms are more sensitive to contaminants when there is variation in temperature, which explains how chemical contamination can greatly impact the development of these frogs. Chloride in particular affects the development of the Green Frog. Vast exposure to chloride can result in many larvae having broken tails, swollen body cavities, a loss of pigment, and behavioral abnormalities. As the temperature increased in the environment, the frogs had lower time-to-mortality and significantly higher hazard when compared to the controls. This shows how temperature directly affects sensitivity to chemicals and thereby the development of the Green Frog by making their habitat more dangerous. According to the Maryland Biological Stream Survey, stormwater ponds which are a main example of a breeding habitat in Maryland can experience chloride concentrations of up to 3250 mg/L, which shows how there are several factors within their habitat affecting the survival rate of these frogs. Various herbicides and pesticides also can harm these frogs due to their permeable skin.
Diet Green frogs will attempt to eat any mouth-sized animal they can capture, including insects, spiders, fish, crayfish, shrimp, other frogs, tadpoles, small snakes, slugs, and snails. Green frogs practice "sit and wait" hunting and therefore eat whatever comes within reach. Tadpoles will eat nearly anything organic, including diatoms, algae, and tiny amounts of small animals such as zooplankton (copepods and cladocerans).
Reproduction
Males become sexually mature at one year, females may mature in either two or three years. Males will establish breeding territories and maintain them throughout the entirety of the breeding period, with the season occurring from spring through summer, with variations depending on location and temperature. There is a strong positive correlation between temperature and detection. During this breeding period, an egg clutch consisting of 1000 to 7000 eggs is laid in surface films about 15–30 cm in diameter and are attached to vegetation in shallow water in order to protect the eggs from predators. Females may sometimes lay two clutches of eggs in a single season, with their size reaching a maximum of 98–105 mm. Females who are ready to mate typically enter into male territories and assumed a low posture to approach resident males very slowly. Once close, the male my clasp the female in amplexus, but if the female is not clasped, she will eventually swim to another territory. Females tend to ignore noncalling males and satellite males were not observed attempting to intercept females approaching calling males. Egg masses are primarily deposited in male territories.
Research shows that wild green frogs, both living in contaminated suburban backyard ponds and also in relatively pristine forested ponds, can switch sexes. This sex reversal appears to be a natural condition but it is currently unknown whether these wild sex-reversed green frogs are able to breed.
After the eggs are deposited, development begins to occur. The typical larval life of green frogs is between 70 and 360 days depending on the time of year in which the eggs were laid. The season of growth in adult frogs (where snout-to-vent measurements increased the most) is primarily between mid-May and mid-September. This mainly correlates with the mean monthly temperature and the amount of time that the temperature is favorable for feeding. Sexual maturity is reached about a year after metamorphosis. However, frogs do not become sexually active until the year after sexual maturity is attained. There is no sexual dimorphism in size in the fully mature frog.
Home range and territoriality Territoriality of male frogs has been studied using experimental pools. Territory defense behaviors included aggressive behaviors such as chases, jump attacks, and wrestling. Male frogs were only observed to be territorial during the breeding seasons. Male green frogs often establish their territories near to shore. Density of cover foliage impacts territory size. In denser areas, males defend smaller territories while in more open areas, territories defended were larger. Many males occupy multiple territories during a breeding season and will visit each site 2 or 3 times. Residency at each sight tends to last one week or less, although one site tends to be favored and occupied for a longer period. Larger body size positively correlates with length of residency period.
Males who do not have their own territory may inhabit the territories of resident males and are referred to as "satellite males." Such satellite males tend to sit with a low posture with only their eyes and tops of their heads exposed above the water. However, in the absence of the resident male, a satellite males may assume the vacant site. However, satellite males who try to force out resident males are usually not successful. In cases where another male ousts a resident male aggressive, the former resident male tends to remain behind as a satellite male. Resident males only tend to get displaced by smaller males if they have become weak and emaciated. At the end of the breeding season, territorial defense terminates.
Behavior Vocalizations To emphasize their territory during breeding season, males advertise their positions with vocalizations and exhibit aggressive behavior including chases and jump attacks. Males have four main vocalizations used to maintain their territories. The first type of call is the advertisement call, which functions to advertise a male's position to other males and to prospective mates. The distinctive call sounds like a plucked loose banjo string, usually given as a single note, but sometimes repeated. The dominant frequency of the advertisement call has been found to be negatively correlated with snout vent length (SVL). Many studies show that aggressive behavior is evoked from other male frogs in response to this call.
The second type of call is similar to the first but is more urgent. This call is used in response to a disturbance in the territory. It is thought to demonstrate dominance because it is often given by the winners of wrestling bouts when chasing the losers out of their territories.
The third type of call is often directed towards others in an agonistic encounter. It is usually the first call produced when a frog's territory has been invaded and while the male approaches the intruder. Consequently, this call antagonizes more aggressive behavior since there were often physical bouts between the intruder and owner of the territory. This is different from the second type of call, because the second call serves as more of a warning call while this call meant that violence would follow.