Diet and Mesohabitat Association of the Threatened San Marcos Salamander (Eurycea Nana)
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The Endangered Species Act was created to aid in the conservation and protection of species under threat of extinction through all or part of their range. Data regarding habitat associations and dietary needs are required for the efficient recovery and maintenance of endangered or threatened species populations. The San Marcos salamander (Eurycea nana) is a spring-associated organism which exhibits a geographic range limited to the headwaters of the San Marcos River in central Texas, USA. The USFWS and the state of Texas currently list the SMS as threatened and its designated critical habitat includes the headwaters (Spring Lake) and the first 50 m of the river. The present study determined mesohabitat associations and the trophic ecology of the San Marcos salamander in its critical habitat. San Marcos salamander habitat associations were determined over a 1-year period and it was determined that San Marcos salamanders are associated with mesohabitats containing cobble and gravel substrates with coverage of Amblystegium and filamentous algae. In addition, these mesohabitats account for about 14% of the area within the designated critical habitat. To examine the trophic ecology of the San Marcos salamander, gut contents were collected from salamanders and invertebrate samples from the lake and river were collected. Dietary analyses suggest that the San Marcos salamanders in Spring Lake and the San Marcos River are generalist predators of aquatic invertebrates and the composition of their diets closely follows temporal changes in the invertebrate community. I conclude that due to the generalist and flexible diet of the San Marcos salamander, conservation and recovery issues related to the diet and food availability is likely to be a less substantial issue than mesohabitat availability and quality. Peter Diaz received his first Bachelor of Science degree from Texas State in Aquatic Biology. After completion he returned to pursue a Masters degree under Dr. Weston Nowlin in Aquatic Resources. At this time he is awaiting the births of his first child, Zoe Elizabeth Diaz.