Amphibians
Little Grass Frog
Pseudacris ocularis · also called least chorus frog
The smallest frog in North America is so small, and so quiet, that most people who live within its range have never knowingly seen or heard one. The little grass frog is about the size of a fingernail, and its call is easy to mistake for an insect.
Overview
Pseudacris ocularis lives in the southeastern US coastal plain, in wet grassy meadows, pine savanna, and pond edges. At 11 to 17 millimetres it is the smallest frog on the continent and one of the smallest vertebrates in North America. It is tan to reddish with a dark stripe through the eye and eats tiny invertebrates like springtails and gnats.
A chorus frog on the ground
It belongs to the tree frog group but stays low in grass and sedge rather than climbing, and has only small toe pads.
The insect-like voice
The male’s call is a very high, thin, metallic tinkling, so faint and high-pitched that many people hear a cricket, and some cannot hear it at all. In the warmest parts of its range it breeds in almost any month in shallow rain-filled pools.
Status
Least Concern and often abundant where grassy wetland edges survive, though it needs the same shallow, fish-free wet ground that drainage removes.
Little Grass Frog: common questions
Is the little grass frog really the smallest frog in North America?
Yes. A full-grown adult is about 11 to 17 millimetres long, which is smaller than any other frog or toad on the continent and smaller than most North American insects people would notice. Newly transformed froglets are only a few millimetres. Worldwide there are smaller frogs still, including a New Guinea species that holds the record for the smallest known vertebrate at under 8 millimetres, but within North America nothing else comes close. The size is why the frog is so rarely seen despite being common, since it is easy to overlook a tan speck the size of a grain of rice sitting on a grass blade.
Why does the little grass frog sound like an insect?
Its call is pitched at the very top of the range a small frog can produce, a fast, faint, high tinkling that lacks the low resonance people associate with frog choruses. Combined with how quiet it is, this makes it blend in with the background sizzle of crickets, katydids, and other insects, and field workers learning frog calls often have to be told which sound is the frog. The high pitch is partly a consequence of the animal's tiny size, since a smaller vocal apparatus produces a higher note, and some people with reduced high-frequency hearing genuinely cannot detect the call at all.
Where would I find a little grass frog?
In wet, grassy, open ground in the southeastern coastal plain, close to shallow water. Good places are the sedgy margins of cypress ponds, wet pine savanna and flatwoods, bog edges, damp meadows, and grassy roadside ditches, especially after rain. The frog stays low in the vegetation rather than up on shrubs or trees, and it is usually detected by its call on warm, humid evenings. Actually seeing one means looking very carefully at the grass stems near a calling site, because the frog is tiny, well camouflaged, and quick to hop out of view.
How is it different from a spring peeper or a cricket frog?
All three are small members of the chorus frog and tree frog group, but the little grass frog is much the smallest, at well under 2 centimetres against roughly 2.5 to 3.5 for a spring peeper and a similar size for a cricket frog. A spring peeper has a dark X mark on its back and a clear, piping single-note whistle. A northern or southern cricket frog has warty skin, a triangle mark between the eyes, and a call like two pebbles being clicked together. The little grass frog has smooth skin, a dark line through the eye, no bold back pattern, and the faintest, highest, most insect-like voice of the three.