The greater siren, which is a large, salamander-like amphibian, is the largest of the four siren species. The other three species are the lesser siren, the northern dwarf siren, and the southern dwarf siren. This last species is further divided into two subspecies: the narrow striped dwarf siren and the Everglades dwarf siren. Unlike salamanders, all sirens have only two front legs, lacking back legs. These front legs are also quite weak. Greater sirens have a tail that is flattened sideways and is tall and skinny. This species of siren lives in the southeastern United States and can be found as far north as Virginia, as far south as the southern tip of Florida, and as far west as the southwestern part of Alabama. Their eastern boundary is the Atlantic ocean. Males and females have no easily visible differences in this species.
Greater sirens are rather large and occasionally grow up to 39 inches (1 m) long. The average length of an adult one of these animals, however, is about 30 inches (76 cm). Males and females are normally the same length, but each individual, as in humans, grows to a different size.
There are several distinctions other than size that can help distinguish greater sirens from lesser sirens. One of these is the number of coastal grooves on the side of their body. Coastal grooves are lines in the skin along the side of a salamander’s body in between the arm and the tail. The red arrows in this picture of a spotted salamander point to some of the coastal grooves. Greater sirens have 36 to 40 coastal grooves while lesser sirens have 31 to 35. Lesser sirens also are darker, skinnier, and have more pointed tails. Young greater sirens are striped and have a yellow to red triangle on their snout while young lesser sirens lack both of these markings.
Greater sirens live on the bottom of slow flowing or still bodies of water. Unlike salamanders, all sirens live in the water for their whole life. They keep their gills even as adults so they can breathe underwater. The axolotl also exhibits this trait. Greater sirens are thought to, unlike other amphibians, withstand slightly salty water.
Since greater sirens are nocturnal, they rest in the day and hunt for food at night. Like many amphibians, the greater siren is a predator that eats mostly invertebrates. Crayfish, worms, snails, and insect make up a large part of their diet. The will sometimes eat small fish also if they get the chance. If none of these others can be found, greater sirens can also eat plants or algae. The national zoo feeds these amazing animals earthworms and crayfish two or three times each week. Greater sirens have no teeth and must swallow their food without chewing. (This is not a good idea for humans!)
Although not much is known about the predators of the greater siren, they have been found in the stomachs of American alligators and some snakes. Some of their greatest dangers are the draining of their habitats and people using aquatic herbicide to clear plants from waterways. This last threat harms the sirens as well as their environment.
Greater sirens are great vocalist and can make many noises that they hope will scare away predators. They can make hissing and croaking sounds and even imitate a young duck! If these noises do not work, they can use their strong tail to swim away quickly. If one is caught, it can make a yelping sound that may scare its captor into releasing it. If none of these work, its last resort is delivering a painful bite to its captor in hopes of finally being able to escape. If their home dries up, greater sirens also were created with a way to survive. They will burrow into the mud and make a cocoon of mucus and shed skin around their body. This prevents them from losing too much water. After this all of their body functions slow down. Greater sirens can live in this way for up to two years!
Instead of laying eggs in groups like most other amphibians, greater siren females will lay many eggs one by one on leaves of different plants. A male is thought will follow the female around and fertilize the eggs after they are laid. The eggs also may be already fertilized without the need of the male and scientists are not sure which hypothesis is correct. This procedure normally takes place in the late winter or early spring.
About two months after being laid, the eggs hatch into tadpoles that, despite the large size of the adults, are about the same size as other amphibian tadpoles. The shape of the young’s body does not change much as it matures and the majority of change comes in the size of the animal. At two or three years of age, greater sirens reach maturity and the females start laying eggs. In captivity, these animals have been recorded living for up to 25 years.
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- Smithsonian Handbooks Reptiles and Amphibians. Mark O’Shea and Tim Halliday, Smithsonian Institution, ISBN: 978-0-7566-6009-3
- Animals of the world. Tom Jackson, ISBN: 978-1780191089
- Animal: The Definitive Visual Guide. David Burnie and Don E. Wilson, Smithsonian Institution, ISBN: 978-0-7566-6002-4
- Greater siren: public domain
- Spotted salamander: Ambystoma maculatun
- Mystery animal: GFDL