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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Are gopher tortosies (Gopherus polyphemus Daudin) comapatible with cows?

Hentges, Thomas William 02 July 2014 (has links)
Many Gopher Tortoise populations are in steep decline throughout Florida, and various measures have been attempted to curb the trend. One such measure is to relocate tortoises to protected recipient sites on private lands. The majority of private lands in Florida are used for cattle, however, production and the effect of cattle production on tortoises is not known. Here, I tested six parameters of tortoise behavior by monitoring 1403 gopher tortoises released at the Barthle Brothers Ranch, Pasco County Florida, between August 2009 and December 2012. The parameters tested were (1) burrow density, (2) burrow spacing, (3) burrow relocation, (4) body condition, (5) individual growth rate, and (6) recruitment (addition of young to the population). I used telemetry techniques to observe movement and burrow placement as it related to cattle activity and burrow impacts, and collected morphological data to determine changes in body condition and growth. I used burrow surveys and analyzed movement patterns to interpret the propensity for tortoises to place burrows where cattle may or may not congregate. Lastly, I investigated recruitment of juveniles into the population and followed the mortality of resident and relocated tortoises in all treatment plots. I found that burrow density, distance moved when relocating to new burrows, and avoidance of cattle were not distinguishably different within or between the plots. Burrow relocation, however, was more frequent outside the exclosures. The change in body condition did not differ between males and female or resident and relocated individuals. Females within the exclosure did not grow at a rate different than those outside the exclosure although translocated females grew faster than resident females. Densities of non-adult burrows inside the exclosures were not different then densities outside the exclosure. Eleven percent of tortoises relocated to the ranch died during the project. Although we have no evidence that cattle and tortoise cannot successfully coexist, a number of circumstances prevented rigorous testing of our hypotheses, predominately the failure of the silt fence used to enclose the treatment plots. Using a trespass-proof perimeter fence would allow a better assessment of the actual interaction between the cattle and tortoises and may shed new light on the lack of recruitment and the decline of juvenile tortoises relocated to the ranch. Without recruitment of individuals back into a population, or the persistent of reproducing adults within the population, any efforts to curb the downward trend in gopher tortoise numbers by relocating tortoises to actively grazed pasture is futile.
2

Lake Stage Fluctuation Study in West-Central Florida Using Multiple Regression Models

Gao, Jie 10 November 2004 (has links)
Multiple linear regression models were developed to calculate lake fluctuation that occurs between 10 percent, 50 percent, and 90 percent of the time lake surface elevation is exceeded. A total of 48 lakes were selected from Hillsborough, Pasco, Highlands and Polk counties, which were identified as natural lakes through the study the Southwest Florida Water Management District (SWFWMD) conducted in 1999 and 2002 to develop the models. "Natural lake" refers to lakes that were not impacted by ground water pumping. Among these 48 lakes, 22 lakes from Hillsborough and Pasco counties sit in the coastal lowlands area. 26 lakes from Highlands and Polk counties are located in the Upland and Highlands Ridge area. In developing multiple regression models, the 48 lakes were divided into two groups, the same group of lakes that SWFWMD used to develop the Reference Lake Water Regime, the method that is used to set the minimum lake levels in the region. Further, these two groups of data were subdivided into four categories based on their physical characteristics. 22 lakes were divided into surface water flow through lakes (SWF) and surface water drainage lakes (SWD). 26 lakes used their county line as the divider to separate them into Highlands County lakes and Polk County lakes. A total of six sets of multiple regression models were developed to predict the lake stage fluctuation for lakes that have no or limited lake stage data. The Polk County date set provides the best model with R2 at 0.9. However, due to the lack of available information on lake basin characteristics, the models that were developed for Hillsborough and Pasco counties do not provide a good prediction.

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