Microgeographic distribution of Amblyomma americanum on the Edwards Plateau /
Aerial photographs and a global positioning system (GPS) were used to develop a small scale map of tick habitat. Carbon dioxide-baited traps were placed on a regular grid over an 8 hectare area approximately once a month for one year. Approximately half the area had undergone a prescribed burn in M...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2000.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=728408781&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Aerial photographs and a global positioning system (GPS) were used to develop a small scale map of tick habitat. Carbon dioxide-baited traps were placed on a regular grid over an 8 hectare area approximately once a month for one year. Approximately half the area had undergone a prescribed burn in March 6 months prior to beginning the trapping. Temperature and relative humidity were measured at the time of trapping. Species, genus, sex and developmental stage of ticks were recorded before releasing the ticks back to the environment. A sub-sample of larvae was retained for identification in the lab. Vegetation was recorded at each of the trapping sites. Aerial photographs were scanned into a computer based geographic information system (GIS). Variables obtained from the aerial photographs were burn or non-burn, area of woody cover, area of bare ground or limestone, disance to woody cover and distance to bare ground. An additional variable, size of mott, was calculated by placing a 1.5 meter buffer around the areas of woody vegetation and merging those that overlapped. Values for each of these variables were extracted for each sampling node and these were entered into a graphical modeling program. Burning did have a significant effect on adult tick numbers one year after the burn took place. Numbers of nymphs were reduced but not as drastically. Results from graphical models were transformed into likelihood ratios which were then applied to the computerized maps. Maps for tick presence in general (both nymphs and adults) were most successful using the mott variable and showed that mottes larger than 2000 square meters are 7.5 times more likely to have ticks than the average for the area. On average, 37% of traps were positive for ticks, 80% of traps were positive in the most heavily infested areas. Variograms were constructed for adult and nymphs using the residuals of the mott models. Adults showed a range of 15-20 meters while residuals from the nymph models did not show any spatial correlation. |
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| Item Description: | Vita. "Major Subject: Veterinary Microbiology". |
| Physical Description: | xi, 75 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 68-74). |