Searching for Aquatic Salamanders

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A close up of a dwarf siren showing the external gills, small front legs, and characteristic striped pattern of this small salamander. – Pierson Hill
A close up of a dwarf siren showing the external gills, small front legs, and characteristic striped pattern of this small salamander. – Pierson Hill

The southeastern U.S. is well known as a region that supports high reptile and amphibian diversity. The total diversity known to occur within this region also continues to grow as new species are described and existing species are split into multiple species. Despite this diversity, most people, even those who spend a lot of time in natural areas, will only get the chance to observe a small fraction of the species that are present within this region. Many reptiles and amphibians are simply not available for observation most of the time because of life history traits. This is especially true for many salamanders that spend long periods of time underground or live in habitats that make them accessible only to those who go looking for them.

On a warm day in late spring, Research Assistant Ben Stegenga and I recently spent an afternoon searching for some salamanders that are seldom encountered. There were three species that we hoped to find at a single wetland site. The Northern Dwarf Siren (Pseudobranchus striatus) is a relatively small (approximately 4–8 inches in total length), fully aquatic salamander. Dwarf sirens are eel-like in appearance (long and slender) and are neotenic, meaning they retain larval characteristics (e.g., external gills) into the adult portion of the life cycle. Like other sirens, dwarf sirens have two small front legs but no back legs. Dwarf sirens are fairly distinct, with a dark dorsal stripe that is bordered by a yellowish or whitish stripe along both sides of the body. This species is restricted to the Coastal Plain and can be found in a variety of freshwater habitats. They are often associated with floating mats of vegetation or submerged herbaceous vegetation, both of which provide places to hide from predators and forage for food. Dwarf sirens can be somewhat abundant in the right habitats but are encountered infrequently and relatively little is known about their ecology.

An adult dwarf siren captured in aquatic vegetation in southeastern Georgia. – Houston Chandler
An adult dwarf siren captured in aquatic vegetation in southeastern Georgia. – Houston Chandler

Our second target species was the Many-lined Salamander (Stereochilus marginatus). These small salamanders (approximately 2–4 inches in total length) inhabit a mix of mucky swamps and other freshwater environments that provide ample vegetation or leaf litter for shelter. Their range stretches from southern Virginia to parts of northern Florida and is restricted completely to the Atlantic Coastal Plain. Many-lined Salamanders are aptly named as they possess several alternating dark and light stripes along each side of the body. Many-lined Salamanders are highly aquatic (more so than most other Plethodontid salamanders) and are rarely observed out of their freshwater environments.

An adult Many-lined Salamander with characteristic striping along the sides. – Kevin Stohlgren
An adult Many-lined Salamander with characteristic striping along the sides. – Kevin Stohlgren
A larval Many-lined Salamander that still has its external gills. – Pierson Hill
A larval Many-lined Salamander that still has its external gills. – Pierson Hill

The third species of salamander that might be encountered on this sampling trip was Holbrook’s Southern Dusky Salamander (Desmognathus auriculatus). This species has been part of a recent wave of species descriptions and taxonomic splits in the genus Desmognathus, with Valentine’s Southern Dusky Salamander (D. valentinei) being split from D. auriculatus in 2017 (Means et al. 2017). Further, taxonomic revisions within this taxon seem likely to occur in the near future. Southern dusky salamanders are fairly nondescript in appearance, possessing a mostly dark brown color and a smattering of black or white specks. Some individuals have a reddish patch on top of the tail and from the corner of the eye to the end of the jaw. Interestingly, the hind legs of southern dusky salamanders are noticeably stouter than their front legs. Shrinking ranges caused by taxonomic splits have heightened conservation concerns for southern dusky salamanders in recent years, and the species is generally believed to be declining across much of its range. However, the challenges associated with finding and effectively sampling for this species make it challenging to draw firm conclusions about the status of many populations. 

Our field site for the afternoon was a small blackwater creek in southeast Georgia. This creek is braided into several small, intertwined channels with adjacent floodplain forest along each side. The site provides ample habitat for aquatic salamanders in the form of leaf packs, abundant mucky leaf litter, thick mats of aquatic vegetation, and downed woody debris that serves as refugia. We walked along the creek, dipnetting through leaf litter and vegetation in search of our target species. It did not take long before we observed our first amphibian, which turned out to be a Lesser Siren (Siren intermedia). Not as exciting as what we were hoping to see!

A small Lesser Siren scooped up from some aquatic vegetation. – Houston Chandler
A small Lesser Siren scooped up from some aquatic vegetation. – Houston Chandler

Some additional dipnetting proved more successful as we eventually caught a pair of dwarf sirens and a handful of Many-lined Salamanders, including several very small juveniles. We also caught a variety of fish and aquatic invertebrates that all use the same types of habitats as these salamanders. The diversity in high-quality aquatic habitats in the southeast is often incredible. The southern dusky salamander evaded us on this trip, and our ability to search for them was somewhat hampered by high water levels that had submerged many of the potential cover objects.

An adult Many-lined Salamander captured in southeastern Georgia. – Houston Chandler
An adult Many-lined Salamander captured in southeastern Georgia. – Houston Chandler

All in all, this was a very successful detour from our normal research projects. As wetland loss and degradation continue across the southeast, it is harder and harder to find high-quality freshwater wetlands that support healthy populations of reptiles and amphibians. These special places are important to conserve for their biodiversity and are a critical component of southeastern United States natural history.

 

Literature Cited

Means, D.B, J.Y. Lamb, and J. Bernardo. 2017. A new species of dusky salamander (Amphibia: Plethodontidae: Desmognathus) from the Eastern Gulf Coastal Plain of the United States and a redescription of D. auriculatus. Zootaxa 4263:467–506.