Browsing by Subject "microhabitat"

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Open Access
A Multiscale Investigation of Snake Habitat Relationships and Snake Conservation in Illinois
(2008-02-11) Cagle, Nicolette Lynn Flocca
Snake populations in the North American tallgrass prairie appear to be declining, yet data unavailability impedes the development of enhanced ecological understanding of snake species-habitat relationships and also hinders snake conservation efforts. This study addresses both issues for the snakes of Illinois in two steps. In a two-year mark-recapture study at twenty-two sites within six northern Illinois prairie preserves, I investigated snake species-habitat relationships using habitat variables at three scales: microhabitat (< 100 m), landscape (1 - 10 km), and regional (> 10 km). A total of 120 snakes representing seven species was captured using drift fence arrays associated with funnel traps and sheet metal cover. The low numbers and diversity of snakes captured, when compared to historic evidence, indicate that Illinois snake populations have declined. At the microhabitat scale, non-metric multidimensional scaling and Mantel tests revealed a relationship between snake species composition and elevation. At the landscape-scale, snake species composition varied along an agricultural-urban cover gradient. Classification and regression trees and maximum entropy models (Maxent) were used to identify the scales at which snake species-habitat relationships were strongest. Six of seven regression trees for individual snakes species contained habitat variables at the landscape scale. Important landscape characteristics included patch size, isolation, and land cover, metrics that strongly covary with habitat loss. Microhabitat features only appeared in the regression trees of two species and in three Maxent models. This study indicates that habitat loss has shaped the current distribution of snake species in Illinois's remnant prairies and that snake conservation efforts should emphasize the landscape-scale. Finally, I developed a risk ranking system based on natural and life history characteristics to assess the conservation status of Illinois's 38 snake species. Cluster analysis identified eight groups of snakes, similar in terms of risk factors, with high risk species sharing characteristics such as large body size, long life span, limited habitat breadth, and a high anthropogenic threat ranking. Here, I emphasize the need for basic demographic studies on snakes and suggest that ranking systems be used with population data (when available) and expert opinion to identify snake species of conservation concern in other regions.
Open Access
LEMUR SPECIES-HABITAT RELATIONSHIPS AT MULTIPLE SPATIAL SCALES IN RANOMAFANA NATIONAL PARK, MADAGASCAR
(2018-05-27) Cooper, Caitlyn
Lemur populations are threatened by many factors, but are most impacted by habitat loss, fragmentation, and alteration. Studies have shown that there is a lag time between habitat disturbance and species response. Thus, more data is needed on long-term relationships between forest change and lemur populations to fully understand how anthropogenic disturbances affect lemurs over time. To bridge this data gap, this study evaluates lemur biodiversity and abundance in three levels of forest disturbance (heavily logged, selectively logged, and pristine forest) at multiple spatial scales. This project 1) isolates which specific microhabitat and landscape variables are important for different lemur species 2) evaluates if the habitat is significantly different between the three forest sites, and 3) evaluates if lemur biodiversity is significantly different between recovering and pristine forests. These results will not only help determine species-specific habitat requirements for critically endangered lemurs, but also contribute to previous data sets on recovering forest monitoring.