Literaturdatenbank
Literaturdatenbank |
|
 |
|
Nazdrowicz, N. N. (2003). Population ecology of the eastern box turtle (terrapene carolina carolina) in a fragmented landscape. Unpublished thesis MSC, University of Delaware.
Added by: Admin (14 Aug 2008 20:38:52 UTC) |
| Resource type: Thesis/Dissertation BibTeX citation key: Nazdrowicz2003 View all bibliographic details  |
Categories: General Keywords: Emydidae, Habitat = habitat, Nordamerika = North America, Schildkröten = turtles + tortoises, Terrapene, Terrapene carolina Creators: Nazdrowicz Publisher: University of Delaware |
Views: 4/494
Views index: 8% Popularity index: 2% |
| Abstract |
|
In the mid-Atlantic region, urban sprawl and development have resulted in habitat loss and fragmentation; however, the effect on eastern box turtle (Terrapene carolina carolina) populations remains undetermined. I employed mark-recapture to study box turtle population ecology and investigate the status of box turtle populations in a fragmented landscape. From April 2001 through October 2002, I used 4 study sites with differing degrees of disturbance in northern New Castle County, Delaware, for my research. Two study sites (University of Delaware Woodlot and University of Delaware Webb Farm) were isolated forest fragments; 1 site (Turkey Run) was a young forest fragmented by small fields and was contiguous to adjacent forested and undeveloped habitat; and 1 site (White Clay Creek) was an interior forest. I used data collected by intensive searches, incidental finds, and radio-telemetry to estimate population abundances and densities, sex ratio, age structure, and survival rates at each study site. We captured 268 turtles 892 times. I estimated adult population densities of 0.81-0.93, 2.12-3.69, 2.44-4.56, and 2.76-4.99 turtles/ha at the Woodlot, Webb Farm, Turkey Run, and White Clay Creek study sites, respectively. Sex ratios (male:female) were male biased at the Woodlot (3.00:1.00) and at White Clay Creek (2.07:1.00 females), whereas Webb Farm and Turkey Run had balanced sex ratios. I tested the validity of aging box turtles by counting annuli on the costal scutes of the carapace. I concluded this method was accurate for estimating age of turtles with 1-10 annuli, less accurate for turtles with 11 annuli, and inaccurate for turtles with =12 annuli. Proportion of juveniles in the total population were 0%, 6%, 25%, and 32% at the Woodlot, White Clay Creek, Webb Farm, and Turkey Run, respectively. I estimated an annual survival rate of 0.98 and a seasonal survival rate of 0.99 for Webb Farm, Turkey Run, and White Clay Creek combined because very few deaths were documented. At the Woodlot, I estimated an annual survival rate of 0.83 and seasonal survival rate of 0.94. Causes of most natural mortalities were undetermined, but 3 resulted from exposure to excessive heat or freezing conditions. Mowing and harvesting agricultural fields were the predominant causes of human induced mortalities. The combination of human management practices, isolation, and lack of early successional areas appears to have the most influence on box turtle populations. We found no evidence of population change at Webb Farm, Turkey Run, or White Clay Creek. However, the Woodlot population was declining due to low survival and little recruitment. In order to preserve box turtle populations, I suggest mowing at a height of =15 cm or planting agricultural crops that do not require mowing on areas adjacent to forest habitats whenever possible.
Added by: Admin |