Amphibians
River Frog
Lithobates heckscheri · also called river frog
The river frog is the big, dark, warty frog you hear rather than see along a southeastern blackwater river at night, giving a deep drawn-out snore from the bank. Catch one and it may go limp in your hand and pretend to be dead.
Overview
Lithobates heckscheri is a large, heavy-bodied frog, 8 to 12 cm long, dark green to blackish with rough, wrinkled skin. It lives along the edges of slow blackwater rivers, streams, and river-swamps in the southeastern US coastal plain, and it eats large invertebrates, other frogs, and small snakes at the water’s edge.
The snore, and the death act
The male’s call is a deep, low snore or growl. A river frog that is caught often goes completely limp and plays dead, sometimes flipping onto its back and lying still for minutes before bolting.
Schooling tadpoles
Its large black tadpoles, which can exceed 10 cm, school together in dense slow-moving aggregations in the shallows.
Status
Least Concern overall but declining in Florida and patchy elsewhere, from wetland alteration and pollution and the loss of the fishless backwaters its tadpoles need.
River Frog: common questions
Why is it called the river frog?
Because, unlike most large North American frogs, it is genuinely associated with moving water. While the bullfrog and the pig frog favour still ponds and lake edges, the river frog is most often found along the banks of slow blackwater rivers and streams, in wooded river-swamps, and around canals and cypress ponds in the coastal plain. It is a strong swimmer and, when disturbed, dives and swims well out into the current or down among submerged roots rather than making short hops along the bank.
Does the river frog really play dead?
Yes, and it is one of the more theatrical examples among frogs. When a river frog is grabbed and cannot escape, it frequently stops struggling entirely, lets its body and limbs go completely limp, and will often stay that way even if turned onto its back and set down, remaining motionless for many seconds to minutes before suddenly coming back to life and leaping away. Death-feigning of this kind can work if a predator responds mainly to movement, or if it relaxes its grip once the prey seems dead, giving the frog an opening.
How do I tell a river frog from a bullfrog or a pig frog?
All three are large, dark, aquatic frogs of the Southeast. The river frog has distinctly rough, wrinkled, warty skin, often looks almost black, has a heavily dark throat with pale spots, and usually shows a light spot at the corner of the jaw. A bullfrog is smoother and greener with a plain or lightly mottled throat and a prominent ridge of skin curving around the eardrum. A pig frog is slimmer, more pointed-nosed, with fully webbed hind feet and a pig-like grunt for a call. The river frog's deep snoring call and its wrinkled skin are the best marks.
Is the river frog endangered?
It is listed as Least Concern overall because it still occurs across a broad area of the southeastern coastal plain, but its status is uneven. In Florida in particular, herpetologists have reported that the river frog has become hard to find at many sites where it was once common, and it is treated as a species of concern in several states. The causes are not firmly established, but the alteration and pollution of coastal-plain wetlands, and the loss of the shallow, fishless river backwaters its large tadpoles depend on, are the leading suspects.