An Amphibian in the Urban Stream in Austin, Texas, within the popular Barton Springs Pool, lives an animal with one of the smallest known ranges of any vertebrate in North America.%%CITE_1%% The Barton Springs salamander (Eurycea sosorum) is a fully aquatic amphibian that exists only in the outflows of four springs fed by the Edwards Aquifer: Barton Springs Pool, Eliza Springs, Sunken Garden, and Upper Barton Springs.%%CITE_2%%%%CITE_3%% This entire habitat is located inside Zilker Park, a busy urban green space. The salamander requires a constant supply of clean, cool water, with a stable temperature that hovers around 20°C (68°F).%%CITE_4%%
This species is neotenic, meaning it retains its juvenile, gill-breathing features throughout its life and never undergoes metamorphosis to live on land. Adults grow to about 2.5 inches (6.4 cm) in length and have slender, long-limbed bodies. Their coloration varies from purplish-brown to yellowish-cream, with a mottled pattern on their backs. Three prominent, bright red external gills on either side of its head extract oxygen directly from the water, making the animal extremely sensitive to pollutants. Its translucent skin on its underside is sometimes so clear that its stomach contents are visible. First collected in 1946, it was not formally described as a distinct species until 1993.
A Canary in the Coal Mine for Water Quality
The Barton Springs salamander was federally listed as an endangered species on April 30, 1997. Its survival is directly tied to the quality and quantity of water discharged from the Edwards Aquifer. Urban expansion over the aquifer's recharge zone presents the primary threat. Runoff containing pesticides, fertilizers, and sediment from construction can contaminate the springs. Increased water withdrawal from the aquifer to support a growing city also threatens to reduce the flow of the springs, which is essential for the salamander's habitat.
The population experienced a sharp decline between 1970 and 1992, partly due to pool maintenance practices that included using high-pressure hoses and chemicals, which harmed both the salamanders and the aquatic vegetation they rely on for cover and food. Today, the pool is managed under a Habitat Conservation Plan to protect the species. The City of Austin conducts regular cleanings without harsh chemicals and has worked to restore native aquatic plants. A captive breeding program was established at the Austin Nature & Science Center to serve as a safeguard against extinction and to further study the species' biology. The salamander's diet consists of small aquatic invertebrates, with a particular preference for planarian flatworms, but also includes amphipods, snails, and insect larvae.