Monday, April 23, 2012

Summer microhabitats of Greater Sirens and Two-toed Amphiumas!

Like some of my other classmates I was intrigued about Sirens and Amphiumas after catching a wide size range of Sirens and only one Amphiuma on our last field trip out to the Donnelly Wildlife Management Area in one of the many swampy parts. I found this article that answered many of my questions: Summer microhabitat use of the Greater Siren (Siren lacertina) and Two-toed Amphiuma (Amphiuma means) in an isolated wetland. 

This article surveyed an area surrounding the Savannah River in Barnwell County, SC...not TOO far from Charleston. :) They surveyed three areas: a Littoral Zone, a Surface Zone, and a Deep Benthic Zone. They divided sampling areas into two arrays: littoral and deep water. The littoral array had the most diverse range of plant vegetation with floating being the most common followed by submersed and logs with vegetation. The deep water array had a homogenous range of plant vegetation with floating and emergent being the most common. They used some pretty nifty catch the Sirens and Amphiumas as well as other vertebrates and invertebrates. Each microhabitat (each zone) was sampled across 300 trap nights (20 consecutive days) from mid-June to the first of July. The Sirens were most abundantly caught overall than the Amphiumas, with the Sirens being mostly caught in the deep benthic zone and the Amphiumas in the littoral zones.

What I found most useful from this article is why the Amphiumas were caught less than the Sirens. Since Amphiumas have a smaller home range than Sirens, who are active foragers whereas Amphiumas are often oppurtunistic foragers, they were caught near the beginning with none caught near the end. Since the traps did not move, the traps were not in any more Amphiumas home ranges. Sirens on the other hand were caught fairly consistently throughout the 300 trap-nights, because they have such larger home rangers than the Amphiumas and were crossing paths with the traps more often. 

The Amphiumas were not only caught less than the Sirens, but were found in a different area. There were two main factors that suggested a reason for this separation. Amphiumas can hide more in the complex structure of the littoral zone, and sneak up on their preferred vertebrate prey (mainly crayfish and fishys...sometimes even snakes!), which were more common in the littoral zone than the benthic zone. Whereas Sirens most likely prefer the homogenous structure of the deep benthic zone, because they are active foragers and can more easily maneuver through that type of habitat in search of their favorite snacks, invertebrates (which were more abundant in the deep benthic zone compared to the littoral zone).

Although this article provided great information for these aquatic salamanders summer microhabitats, further research could most definitely be done in other times of the year during mating, breeding, and drought seasons! So much opportunity for research!

Below are some of the fun pictures I took on our field trip of these fascinating creatures!

Amphiuma means (Two-toed Amphiuma) So menacing, yet so cute!

Siren lacertina (Greater Siren). Note: There are more than one in this picture!

Citation for information from the article: 
Schalk, Christopher M.. Summer microhabitat use of the Greater Siren (Siren lacertina) and Two-toed Amphiuma (Amphiuma means) in an isolated wetland  AMPHIBIA-REPTILIA. Vol. 31 No. 2. 2010 p. 251 - 256.

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