Although the pig frog has no special status, there is speculation that their population could be declining. This species has been a staple in the frog leg industry and have been hunted at night by air and John boats. The hunters report that the pig frog population seems to be diminished, however it could just be because populations decline in drought years and erupt in wet years (Bartlett 1999).
No special status known.
CITES: no special status
IUCN Red List of Threatened Species: least concern
Development - Life Cycle: metamorphosis
Pig frogs are hunted for human consumption, as a source of frog legs.
The Pig frog is mainly active at night and does most of its feeding at this time. Its primary diet consists of insects and crustaceans (Capula 1989).
Southeastern US, ranging from eastern Texas to south central South Carolina, extending south into peninsular Florida (npwrc 1999)
Biogeographic Regions: nearctic (Native )
Generally, these frogs are distributed in most waterways, such as rivers, streams, lakes, ponds, swamps and marshes (Bartlett 1999). The pig frog inhabits the open centers of cypress ponds, which are an extension to, or separation from the prairies. They prefer ponds with the following vegetation types: waterlilies, hard heads, never wets, wampee, watershield, bladderworts, floating hearts, pickerel weed, saw grass, and maiden cane (Wright 1932).
Aquatic Biomes: lakes and ponds; rivers and streams
The pig frog ranges in length from 3.25 to 5.5 inches. Their appearance is that of a "bullfrog" with a rather narrow and pointed head and fully webbed hind feet. The fourth toe is webbed nearly to its tip. Pig frog coloration is olive to blackish brown with scattered dark spots. Its venter is white or pale yellow with a pattern that is the colors brown, dark gray and black woven into a net on the thighs. The thighs also have a light line or a row of light spots running across their rear. The Pig frog has no dorsalateral ridges (Conant and Collins 1998). In this frog, the tibia is the same length as the femur. Their eyes are greatly elevated and unusually large, with only a narrow space between them. Nostrils are prominent in Lithobates grylio. They have an elevated fold of skin over the ear that runs to the shoulder, and the ear is orange-brown in color with a green center. The middle and posterior back may have four longitudinal bands of bright orange-brown, alternating with bands of olive (Dickerson 1931).
Pig frogs are sexually dimorphic in size and coloration. Males and females have similar growth rates until the snout-vent length reaches about 100mm. After that, the females grow faster and will eventually reach a larger size than the males (Wood 1998). The male's ear is greatly larger than its eye, whereas the female's ear is equal in size to the eye. Perhaps the most distinguishing characteristic is that males have a bright yellow throat (Dickerson 1931).
Mature tadpoles are very colorful. They have a yellow belly with prominent reticulation on brownish black. Their sides have yellow spots that are encircled by a pinkish color. From the throat region to the pectoral region is clear black and across the pectoral region is green. The yellow spots surrounded by pink continue down the tail in various patterns (Wright 1932).
Other Physical Features: ectothermic ; bilateral symmetry
Little appears to be known about the reproduction of Pig frogs. Published observations are based on very few cases.
Immense choruses of Lithobates grylio erupt at night, when the vast majority of the mating occurs. Rainy, overcast or humid overcast weather seems to provide conditions that make for active mating. Breeding season is thought to begin in late May and continue through to August. They breed when the air is humid with temperatures ranging from 63-78 degrees.
The egg laying process is probably similar to that of the bullfrog (Rana catesbeiana) (Wright 1932).
After mating, approximately 10,000 eggs are laid (Bartlett 1999). The eggs are usually attached to pickerel weed stems in the middle of the pond or on the islands of a cypress pond. They can be found amongst saw grass, maiden cane, and wampee. The eggs, which are small and bead-like, are laid in large masses on the surface of the water. The hatching period is 2-3 days. These eggs appear to have no animal predators; their only threat is the receding water (Wright 1932).
Tadpoles are quite large (100mm), with extremely long tails. Although uncertain, Wright speculates that Lithobates grylio may go through metamorphosis after one year. Bartlett (1999) comments that tadpoles in the northern range of this species reportedly take longer than one year to metamorphose whereas those in the southern part of the range develop in less time. After transformation, the young frogs will remain in the same habitat as adults (Wright 1932).
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate)
The pig frog (Lithobates grylio)[2] is a species of aquatic frog found in the Southeastern United States, from South Carolina to Texas. Some sources also refer to it as the lagoon frog or the southern bullfrog.
Pig frogs (Lithobates grylio) are a species of frog that belong to the class Amphibia, the order Anura, the family Ranidae, and the genus Lithobates. They are part of the phylum Chordata, which includes animals with a notochord and a hollow nerve cord. Pig frogs are vertebrates, meaning they have a backbone, and they are tetrapods, meaning they have four limbs. They are adapted to living both on land and in water, and they are commonly found in the southeastern United States. Norwegian-American naturalist Leonhard Stejneger described the pig frog in 1901, and it still bears its original name. The name comes from the calls the frog makes, sounding like a pig grunting.[3]
The pig frog is green or grey-green in color, with brown or black blotching. It has fully webbed feet, a sharply pointed nose, and large tympana (eardrums). The Pig frog is sexually dimorphic in size and coloration, the males also have a larger tympanum than the females. It is easily mistaken for various other species of the genus Lithobates, with which it shares its geographic range, including the American bullfrog (Lithobates catesbeiana). Pig frogs grow to a snout to vent length (SVL) of 85 to 140 millimetres (3+1⁄4 to 5+1⁄2 inches). They are known for their loud, deep snorting sound, reminiscent to the oinking sound of a pig.
Almost entirely aquatic, they are found predominantly on the edges of lakes, or in cypress swamps and marshes that are heavy with vegetation. They are nocturnal. Their pig-like grunts can be heard during the warm months of the year.
Pig frogs are opportunistic feeders and will eat a wide variety of prey, including insects, worms, and small vertebrates. Their primary diet is crawfish, but like most bullfrogs, they will consume almost anything they can swallow, including insects, fish, and other frogs. They are known to feed on beetles, dragonflies, crayfish, and other aquatic invertebrates, and may also occasionally eat fishes and amphibians. They are nocturnal animals and are usually found near water, where they use their strong legs to leap and catch prey. Pig frogs are important members of their ecosystem, helping to control the populations of the insects and other small animals that they eat. They play a vital role in maintaining the balance of their wetland habitats. The percentage of Pig frogs' prey items varies throughout the year, most likely due to the availability of resources.[4]
They breed from April to August, laying their eggs in large surface films, usually over vegetation. The eggs hatch in several days, and the tadpoles may take a year to transform into adult frogs. Pig frogs are sexually dimorphic, with males and females having similar growth rates until the snout-vent length reaches about 100mm, at which point females grow faster and eventually reach a larger size than males. Due to their larger size as adults, females tend to have higher survivability rates than males. Therefore, they are likely to be more abundant in the wild.[5] Males have a bright yellow throat, which is a distinctive characteristic that helps to distinguish them from females. During the breeding season, males produce a low grunting sound to attract females and establish their territory. This species gets its common name from the call males use, which sounds somewhat like a pig's grunt. Fertilization is external, with males releasing sperm over the eggs as they are laid. Eggs are laid in large masses of up to 10,000 at a time on the surface of the water. [6]
The pig frog holds no particular conservation status and is relatively common in its range. The species has been introduced and established itself in China, Andros Island and New Providence Island in the Bahamas, as well as Puerto Rico.
Pig frogs have been reported to be raised for food by Chinese farmers, along with bullfrogs.[7]
The pig frog (Lithobates grylio) is a species of aquatic frog found in the Southeastern United States, from South Carolina to Texas. Some sources also refer to it as the lagoon frog or the southern bullfrog.
