Literaturdatenbank
Literaturdatenbank |
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Swanson, R. L. (2009). Temporal and spatial trends of the amphibians, reptiles, and mammals of the relict ottine wetlands. Unpublished thesis , Texas State University-San Marcos.
Added by: Sarina Wunderlich (06 Jul 2014 16:17:24 UTC) |
| Resource type: Thesis/Dissertation BibTeX citation key: anon2009y View all bibliographic details  |
Categories: General Keywords: Amphibien - amphibians, Echsen - saurians, Habitat - habitat, Nordamerika - North America, Schildkröten - turtles + tortoises, Schlangen - snakes, Testudinidae, Testudo kleinmanni Creators: Swanson Publisher: Texas State University-San Marcos |
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| Abstract |
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Ecological surveys are a snapshot in time, providing biological inventories and important documentation about ecological communities. If carefully documented these data may be used to estimate population sizes and demographics as well as community parameters such as abundance, species richness and diversity. The results of such surveys assist land managers and agency personnel to formulate conservation protocols and serve as important tools in assessing results from management efforts and temporal changes in community parameters. Herpetofauna and rodents are particularly important because they are easily monitored, locally abundant, and have been used as indicator taxa of ecosystem diversity and health. From January 2008 to June 2009, amphibians, reptiles, and mammals of Palmetto State Park and the Ottine Wetlands of south central Texas were surveyed to produce a current mammalian and herpetofaunal inventory and produce estimates of relative abundance, evenness and diversity. I compared my data to the results of a survey performed in the late 1950s by Gerald Raun, Ph.D. to determine if the composition of this community has changed through time or in relation to land use practices (agriculture vs. preserve/outdoor recreation). Standard survey methods were used equally among sites to sample amphibians, reptiles, and mammals. A total of 862 amphibians and reptiles representing 38 species (9 amphibians, 29 reptiles) were captured or observed. Time-constrained surveys (46.2%), nocturnal road surveys (30.9%), and drift fence arrays (10.1%) produced the highest amount of observations. Direct comparisons suggested noteworthy changes in the relative abundance within the snake assemblage between 1958 and 2008 despite little observed change in estimates of diversity and evenness. These data suggested that community composition of the herpetofauna has changed over the past 50 years resulting in a loss of amphibian richness (loss of five species) and changes to the composition and relative abundance of species within the reptile assemblage. Twenty-nine mammalian species were documented during the study. Differences in rodent evenness estimates approached significance with the private wetlands yielding higher values for species abundance and evenness. surveys assist land managers and agency personnel to formulate conservation protocols and serve as important tools in assessing results from management efforts and temporal changes in community parameters. Herpetofauna and rodents are particularly important because they are easily monitored, locally abundant, and have been used as indicator taxa of ecosystem diversity and health. From January 2008 to June 2009, amphibians, reptiles, and mammals of Palmetto State Park and the Ottine Wetlands of south central Texas were surveyed to produce a current mammalian and herpetofaunal inventory and produce estimates of relative abundance, evenness and diversity. I compared my data to the results of a survey performed in the late 1950s by Gerald Raun, Ph.D. to determine if the composition of this community has changed through time or in relation to land use practices (agriculture vs. preserve/outdoor recreation). Standard survey methods were used equally among sites to sample amphibians, reptiles, and mammals. A total of 862 amphibians and reptiles representing 38 species (9 amphibians, 29 reptiles) were captured or observed. Time-constrained surveys (46.2%), nocturnal road surveys (30.9%), and drift fence arrays (10.1%) produced the highest amount of observations. Direct comparisons suggested noteworthy changes in the relative abundance within the snake assemblage between 1958 and 2008 despite little observed change in estimates of diversity and evenness. These data suggested that community composition of the herpetofauna has changed over the past 50 years resulting in a loss of amphibian richness (loss of five species) and changes to the composition and relative abundance of species within the reptile assemblage. Twenty-nine mammalian species were documented during the study. Differences in rodent evenness estimates approached significance with the private wetlands yielding higher values for species abundance and evenness. I was unable to detect Cagle’s map turtle (Graptemys caglei) at the park lake as recorded by Raun (1958), but I did observe a single individual on the stretch of the San Marcos River within the park boundaries. Raun (1958) reported observing individuals of the genus Kinosternon but was unable to identify to species. I captured four eastern mud turtles (Kinosternon subrubrum) from the park lake and park fishing pond. The Texas river cooter (Pseudemys texana) population has experienced a temporal increase in detection within the park lake and, along with Red-eared slider (Trachemys scripta), constitute the dominant species within the aquatic turtle assemblage. I was unable to detect ornate box turtle (Terrapene ornata) or three-toed box turtle (T. carolina) at any of the study sites. The last known record of Terrapene (T. ornata; Texas Natural History Collection #46160) collected from the area was in the area of Belmont (~15 km west of Ottine). These data coupled with no observations by land owners or park managers for > 30 years, suggest that a possible decline in Terrapene population size has occurred around the area of Ottine over the past 50 years.
Added by: Sarina Wunderlich |