Amphibians
Pig Frog
Lithobates grylio · also called southern bullfrog, lagoon frog
The pig frog is the big, wary frog that grunts at you from the middle of a Florida marsh and slips underwater before you can find it. It sounds like a farmyard, it almost never comes ashore, and it is the frog behind most of the wild frog legs served in the United States.
Overview
Lithobates grylio lives in the permanent marshes, lakes, and swamps of the southeastern US coastal plain. It is a large frog, 8–16 cm, olive to blackish, with a pointed snout and fully webbed hind feet. It is highly aquatic, floating among vegetation, and it eats mostly crayfish and other animals it can catch.
The grunt
The male’s call is a deep, rolling, pig-like grunt, and a marsh full of them at night sounds like a hog pen. That call, and the pointed snout and full webbing, separate it from the blunter-faced bullfrog and the ridge-backed green frog.
The frog-leg frog
The pig frog is the main species harvested for frog legs in the US, taken at night from airboats across the Florida marshes.
Status
Least Concern and abundant, using canals and reservoirs as well as natural wetlands, with the harvest regulated by season and size.
Pig Frog: common questions
Does the pig frog really sound like a pig?
Enough that early settlers named it after one. The male's call is a short, deep, throaty grunt, repeated in a slow series, and when many males call together across a marsh at night the sound is a rolling chorus of low grunts that carries well over the water and is genuinely reminiscent of pigs in a lot. It is quite different from the American bullfrog's deep, drawn-out "jug-o-rum" and from the green frog's single banjo-string twang, so on a summer night in the southeastern wetlands the three large frogs can be told apart by ear.
Are the frog legs I ate at a restaurant from pig frogs?
Possibly. Frog legs sold in the United States come from three main sources — farmed frogs imported from Asia, wild-caught frogs imported from Asia and elsewhere, and wild frogs harvested domestically, and of the domestic wild harvest the pig frog is the leading species, taken almost entirely from Florida's marshes. American bullfrogs are also harvested. Which frog ended up on a particular plate depends on the supplier, and menus rarely say, but if the legs were described as wild and from Florida or the Gulf Coast, they were most likely pig frog.
How is a pig frog different from a bullfrog?
They are close relatives and similar in size and general shape, both large, both lacking the ridges down the back that a green frog has, and both with a big visible eardrum. The pig frog is the more aquatic of the two, spending almost all its time in the water, and it has a noticeably more pointed snout, more extensively webbed hind feet, and yellow with dark bars on the hidden surface of the thighs. The bullfrog has a blunter face, less webbing between the last two toes, and a plainer thigh pattern. The calls are the clearest difference, the pig frog's grunt against the bullfrog's booming three-part note.
Are pig frogs dangerous to have around a pond?
Not to people, but a large pig frog, like a large bullfrog, is a significant predator in a small pond and will eat other frogs, small fish, hatchling turtles, snakes, and anything else it can swallow, including ducklings. Where pig frogs or bullfrogs have been introduced outside their native range, this appetite makes them a threat to native amphibians. Within their natural southeastern range they are simply part of the wetland food web, taken in turn by alligators, herons, otters, and water snakes, and there is no need to remove them.