- Eel-like body.
Relatively large head with small, lidless eyes.
Two reduced limbs anterior to the large external gills.
Three pairs of gill slits.
Finned, vertically compressed tail.
34-38 costal grooves.
- Olive to dark gray or brown dorsum with tiny black spots.
Ventral surface is dark with tiny light-colored spots.
Siren intermedia can reach an adult total length of 37.5-40 cm (15-16 in). The south Texas form can grow much larger, between 50-57.5 cm (20-23 in).
In North America, Siren intermedia is found in the Mississippi Valley east to Alabama and west to Texas.
Nocturnal, Siren intermedia burrows into the silt and debris during the day. It feeds on crawfish, worms, and mollusks. The lesser siren covers its body with a protective mucus to prevent dehydration during dry periods. It makes a clicking sound when approached or surfacing for air, and squirms when captured.
Breeding in Siren intermedia takes place in late winter. Soon after, up to 200 eggs are laid in shallow water.
Siren intermedia prefers warm, shallow waters with vegetative cover, such as those in ponds, ditches, and swamps.
The lesser siren, outside of south Texas, is is not a protected species in Texas and can be legally collected with a hunting license. The population in south Texas is listed as "South Texas Siren (large form), Siren sp. 1" by the Texas Parks and Wildlife Department and is considered a threatened taxon by TPWD and is fully protected by the state.
The one subspecies of Siren intermedia found in Texas, Siren intermedia, is found in the eastern third of the state from the lower Rio Grande Valley northward along the Gulf Coast to Louisiana.