Article by AB Newsletter contributor Clayton Bradshaw (Texas State University).
I live a few streets from the San Marcos River. Its clear water flows through town, smooth in its current as the egrets and heron fish alongside their children apprentices on the banks. If you stand on a walking bridge in one of our parks, you can look down upon the green grass streaking under the surface as though Monet had forgotten he was painting the Seine. This grass is Texas Wild Rice, and it only grows here.
My nephew thinks that the Texas Wild Rice tickling his feet is a mermaid statue come to life. He has learned to swim at Rio Vista Park, arms crashing into the water with each elementary arm stroke. He knows that the river is clear, clean, and full of wildlife. His innocence does not permit him to see the beautiful fragility of what lies below.
Take the San Marcos Salamander. Near the headwaters of the river, in Spring Lake, this almost mythical nymph (its scientific name, Eurycea nana, draws from nanos, the Greek word for dwarf) slides through the springs, a finned tail propelling it through the blue-green algae. Once there, the salamander will sit still, quiet, waiting on some amphipod or midge fly larvae or aquatic snail to wander by before snapping its head to snag its prey.
San Marcos Salamanders love Spring Lake, preferring the 72-degree flow of water steadily shooting from the Edwards aquifer over any other place on Earth. Only in San Marcos, where they swim in the shallow, alkaline springs carved out from the limestone, do they choose to lay their jelly-covered eggs in standing pools amid the thick mats of vegetation near the source of the river. These eggs incubate for around three weeks before hatching into fish-like larvae.
After hatching, they spend seven to ten days carrying their yolk sack before they absorb into the body of a full-grown salamander anywhere from 3.5 to 9 cm (1.5-3.5 in) long. Their light brown skin with small yellow spots down each side of their back allow them to blend into the reddish-brown vegetation of the river. A pale-yellow ventral surface allows them to avoid detection from their small, crustacean prey that swim below them.
Currently, around 50,000 San Marcos Salamanders live in Spring Lake and the upper portions of the San Marcos River. Another 5,200 live below the surface in the Edwards aquifer itself. These are not lizards that can move inland on their four front toes and five back toes when necessary; their external gills pull oxygen from the water to keep them moving in a way that the mermaids of old have forgotten.
Almost 39 years ago, on July 19th, 1980, Texas Parks and Wildlife declared them a threatened species. US Fish and Wildlife Services soon followed suit. The increased population and urban development of San Marcos meant that more people used water from the springs and aquifer, their home. Increased water usage by humans meant decreased water flow, greater pollution, and silt accumulation.
In addition to the challenges faced by a challenged water supply, invasive species such as the sucker mouth catfish, tilapia, Ramshorn snail, and Melanoides snail challenge the salamanders for food. The salamanders have also faced threats from dams, forestry, and the decrease in water quality as a result of agricultural and residential development. The International Union for the Conservation of Nature (IUCN) placed them on their Red list of Threatened Species in 2004.
The addition of riparian buffer strips and zones have helped limit the impact of human development on the San Marcos Salamander. They have become stable as the result of safe areas that have been created to give them sanctuary. Now, they may lay their eggs and prey upon tiny insects in relative peace and protection.
The San Marcos Salamander represents the ability of fragile species to survive increasing contact with human development. They have co-existed with human in one of the longest-continually inhabited locations of North America. Despite being small and slender, they have swum below our noses and our feet, possibly helping to foster the fable of mermaids in our river. They could easily pass as the young children of local sirens. They are Greek myth in San Martian form, muses of the music scene, nymphs for the artist. They are San Marcos residents and resilient champions of our river.