The back is olive green to light gray. The sides may be marked with lighter spots, blotches or lines. The belly is lighter with light specks and blotches of yellow-green. A young Greater Siren has a light stripe on the sides of the body which is lost as it grows older. The Greater Siren is the largest of the sirens, ranging from 48 - 97 cm (19 - 38 in) in length.
Eggs are laid in late winter and early spring. Larvae hatch approximately two months later. This totally aquatic species is found in a greater variety of habitats than the other sirens, including rivers, streams, swamps, ditches and lakes. This is one of a few species of amphibians known to tolerate brackish water. It is carnivorous and eats crayfish, aquatic insects, worms, snails, and small fish. It hunts at night and spends daylight hours hidden under debris or logs on the botton. Greater Sirens have lived for up to 25 years in captivity. This salamander undergoes aestivation to survive drought. It burrows into the mud bottom of the stream or pond and secretes a cocoon of mucus and shed skin that covers its body and prevents loss of water. All body functions slow down. The siren can survive for several months this way until the drought ends.
The Greater Siren is found throughout the lower Coastal Plain in shallow waters with an abundance of vegetation.
The Greater Siren is uncommon throughout its range, although it may be common in some locations. It does not seem to be threatened at present. The greatest potential dangers are draining habitats and using aquatic herbicides to clear vegetation from waterways.
At first glance, it is very easy to confuse the Greater Siren with an eel or an xxxAmphiumaxxx. Eels are fish; they have fins and no external gills or legs. Amphiumas have four tiny legs and no external gills. Dwarf Sirens have three toes on their front feet. Adult Greater Sirens are larger and more highly marked than Eastern Lesser Sirens, but these two species can be difficult to tell apart.