Amphibians
Lesser Siren
Siren intermedia · also called lesser siren
The lesser siren is a salamander that looks like an eel, keeps its feathery baby gills for its whole life, and has just one small pair of front legs and nothing behind. When its pond dries out, it wraps itself in a cocoon of hardened mucus in the mud and waits, sometimes for over a year.
Overview
Lesser sirens live in ponds, ditches, swamps, and marshes with soft muddy bottoms across the southeastern and central US into Mexico. Usually 18–40 cm, eel-like with external gills, tiny forelimbs, and no hind legs, they hunt insect larvae, worms, snails, and small fish.
Gills for life
It never fully metamorphoses, keeping its larval external gills as an adult — a permanently aquatic salamander.
Riding out drought
If the water disappears, it burrows into mud and seals itself in a hardened mucus cocoon, going dormant for months until rain returns.
Status
The lesser siren is Least Concern, widespread and often abundant in suitable still-water habitats.
Lesser Siren: common questions
Is the lesser siren a fish, an eel, or a salamander?
It is a salamander, one of a small group of fully aquatic salamanders in the family Sirenidae that look strikingly eel-like. Its long, slender body, feathery external gills, tiny forelimbs, complete lack of hind limbs, and paddle-shaped tail give it a very un-salamander-like appearance, but it has the skull, skeleton, and overall biology of an amphibian, not a fish. The resemblance to an eel is a case of convergent evolution, since both animals have evolved a long, limbless or nearly limbless body shape suited to moving through vegetation and soft mud in still and slow-moving fresh water.
How does the lesser siren survive its pond drying up?
When water levels fall and its wetland threatens to dry out completely, the lesser siren burrows down into the soft mud and secretes copious mucus from its skin, which dries and hardens into a parchment-like cocoon that encases most of its body, leaving only the mouth exposed for breathing air. In this state, called estivation, its metabolism slows dramatically and it becomes dormant, able to wait out drought conditions in the moist mud for many months, in some cases more than a year, until rain refills the wetland and the siren emerges and resumes activity.
Why does the lesser siren keep its larval gills as an adult?
The lesser siren never undergoes the full metamorphosis that most amphibians do, and instead retains juvenile features, most obviously its bushy external gills, throughout its entire adult life, a developmental pattern called paedomorphosis. Because the siren remains fully aquatic and never needs to live on land, keeping efficient external gills for extracting oxygen from water is more useful to it than developing the lungs and body changes associated with a terrestrial adult stage. It can supplement its gill breathing by gulping air at the surface, which is part of how it copes with the low-oxygen, stagnant water it often lives in.
Does the lesser siren really make sounds?
Yes, which is unusual among salamanders, most of which are essentially silent. The lesser siren produces a series of faint clicking noises, thought to be used in communication with other sirens, particularly during interactions in dense vegetation where visibility is poor, and when picked up or disturbed it can also emit a soft, high-pitched yelping or squealing sound. These vocalisations are quiet and easily missed, but they represent a genuine acoustic signalling ability in an amphibian group that is otherwise not known for making noise.