Natural History: Siren lacertina

Class: Lissamphibia

Order: Caudata

Family: Sirenidae (sirens)

Siren lacertina “Greater Siren”

We have seen lots of awesome herptofauna on our field trips this semester, but my favorite field trip was yesterday when we went to the Donnelley Wildlife Management Area. The first part of the trip we went into a cypress swamp area with really squishy mud and deep black water. Many minnow traps had been set the day before in the area. In multiple minnow traps were found 3 Greater Sirens of varying sizes. The pictures show the size variation we saw, and it was especially awesome to find the really big one that was about 20” and a medium sized one at about 15" and the smaller one which was about 7-8.” Which is typical of the species which are described as being 20-30” eel-like with only forelimbs with 4 toes and very apparent external gills. Greater Sirens will be olive to light gray with faint greenish/yellowish specks, which was demonstrated in those that we found. There is no way to externally sex Greater Sirens, and in fact it is still a mystery as to how they reproduce but it is suspected to be external.

One thing that the field guide does not talk about was how slimy the Greater Sirens are!! When handling them mucus would just flow off their skin like alien slime in a corny horror movie. I was surprised that will all the attention and handling that the Greater Sirens did make any of their “yelping” sounds, which they can generate by snapping their jaws and is often described as being like a Green Treefrog call. These Greater Sirens that we caught seemed pretty docile.  

Greater Sirens will lead a completely aquatic lifestyle as obligate paedomorphs. They like shallow, freshwater areas like the cypress swamps at Donnelley or ditches, muddy ponds, lakes, rice fields, or small streams. If these areas dry up, Greater Sirens can estivate by burrowing and will live off their stored fat deposits. Their diet consists of crayfish, worms, mollusks, small fish, and aquatic vegetation. What is really cool about Greater Sirens, other than how cool-looking they are, is that they are only found in the southeastern United States will a range depicted in the map and described as being from Washington DC to southern FL to southern AL.

Greater Sirens can get confused with many other similar species. Many people mistake them for eels, but eels do not have the flaring external gills or the forelimbs. Amphiumas are very similar and this field trip presented the perfect opportunity for demonstration. One of the other minnow traps contained an Amphiuma means and it was clear when the two species were side-by-side how different they really were. Amphiumas will have very small fore and hind limbs and lack external gills. It was also apparent that the smaller of the Greater Sirens that we found was not a Dwarf Siren because they only have 3 toes on each leg and that it was not an Eastern Lesser Siren because it had pronounced light markings on its skin.  

This field trip was so much fun and it was awesome to find the Greater Sirens, as well as see all the cute alligators.