Natural History: Greater Siren

The Greater Siren (Siren lacertina) is a member of the family Sirenidae and vaguely resembles an eel in its appearance. Some distinguishing characteristics about this species are its external gills, lack of hind limbs or pelvic girdle, flat tails, and lack of eyelids. Unlike sirens, eels have a fin on either side of their neck as well as lack ANY limbs, and Amphiumas have 4 legs. If you get close enough, you can see that each of its forelimbs possesses 4 toes, helping to tell it apart from a Dwarf Siren, which only has three toes. Found along the east coast from Washington, D.C. to Florida and Alabama, we’ve stumbled across this species a few times on class field trips. These amphibians prefer shallow-water environments such as ditches, ponds, rice fields, lakes, etc. I found our latest one inside a trap in a weedy pond. 

Although greater siren coloration ranges from olive to light gray, this one was very dark with faded markings. It did have the lighter greenish flecks along its dorsal area though. Lesser Sirens tend to be light with dark markings whereas Greater Sirens are dark with lighter flecks. One of the things I read in my field guide earlier this year said that they can emit a yelp when captured that sounds similar to the call of the Green Treefrog, but unfortunately the one that we caught was silent. I'll save you time by saying there sadly isn't a video of this sound they make up on YouTube yet. It was remarkably slippery though, escaping out of people’s grasps like a bar of soap thanks to a slimy layer of mucous. This mucous helps prevent desiccation  They can be found foraging at night with a diet consisting of mollusks, small fish, worms, crayfish, and aquatic vegetation as well. During the day, which is when we came across this one, they like to hide under debris and logs. I originally thought that the one we’d caught was huge, but after researching it a bit, I found that they can grow to be around 20-30 inches with the record being 38 inches. Ours was only about 18 inches, meaning it was most likely an adult or late juvenile. If you get close enough to count them, they have about 36-40 costal grooves, whereas Lesser Sirens tend to have only 31-35. 

There hasn’t really been specified a way of telling the males from the females, especially since ours squirmed so much. Also, there is some uncertainty as to their mating habits. It’s believed they fertilize externally, but that’s still unknown. Obligatively paedomorphic, they lay their eggs in late winter and early spring and the larvae hatch about two months later, remaining aquatic for the rest of their lives. When droughts occur, they aestivate, or burrow in the ground to avoid drying out. Greater Sirens are actually my favorite herp that we’ve encountered on our field trips due to their interesting appearance and size. I’m strangely mesmerized when I see them swim, as they lazily paddle with their forelimbs and whip their flat tails back and forth. It’s always tricky trying to snap a picture of one before it slips out of your hands though. They remain a little bit of a mystery for this reason. Ours managed to make a rather hilarious escape attempt into midair. 

http://naturalhistory.uga.edu/~gmnh/gawildlife/index.php?page=speciespages/species_page&key=slacertina