Browsing by Subject "habitat preference"

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Open Access
Can Movement Speed Predict Habitat Preference? Assessing the Influence of Topography, Village Proximity, and Land Cover on Forest Elephant (Loxodonta cyclotis) Movement and Preferences in Gabon.
(2019-04-24) Kim, Seokmin
Understanding animal habitat preference is crucial for the management of animal populations and planning of protected areas. However, current models for estimating habitat preference require arbitrary estimates of habitat availability, which introduce a level of uncertainty and qualitative inference that could affect model accuracy. To overcome this problem, Dickson et al. (2005) suggested that movement speed could be used as a metric of habitat preference, assuming that movement speed would be negatively related to habitat preference. However, this speed - preference model ignores potential changes in movement related to behavioral shifts or variations in terrain. To assess the generalizability and practicality of the speed-preference model, I examined the hourly movements of 56 GPS collared forest elephants (Loxodonta cyclotis) in Gabon, central Africa between 2015 and 2018 in the context of three relevant environmental covariates (land covers, topography, and village proximity). I analyzed changes in movement speed by attributing a single value for specific environmental characteristics to each movement step and estimated preferences by calculating the density of each individual’s GPS points within the covariate of interest from the individual’s travel range. I then modeled the relationship between speed and preference with a linear mixed model. Speed failed to predict preferences for different land cover types, and relationships between speed and preference for gradients of topography and village proximity changed in both direction and intensity. Therefore, although using speed to predict habitat preference avoids the limitations of other habitat preference models, this method requires further research to assess the complex interactions between speed and environmental covariates for different animal species.
Open Access
Examining the Influence of Genetics on Migration and Habitat Preference in Callinectes sapidus
(2020-04-23) Moran, Megan
The Atlantic blue crab (Callinectes sapidus) is an ecologically and commercially fundamental species. At various life stages, crab migrations are influenced by environmental cues including light, salinity, chemistry, depth change, turbulence, and water flow. Though adult and juvenile blue crabs live in estuaries, the larval stages of all genotypes are mixed and develop in the coastal ocean. The objective of this study is to determine whether blue crab habitat use, and migration patterns are reflected in the mitochondrial cytochrome c oxidase 1 (CO1) gene region. This will be determined by examining resident blue crabs from Carrot Island, NC (29-35 PSU) and Lake Mattamuskeet, NC (0 PSU), and spawning female crabs from Beaufort Inlet, NC (29-34.5 PSU). Carrot Island had a relatively lower haplotype diversity (0.7260 ± .03900) compared to Beaufort Inlet (0.9841 ± .00021) and Lake Mattamuskeet (0.94154 ± .00118). Significant pairwise differences were found between Carrot Island and Beaufort Inlet (Nm = 0.26018, p < 0.001), as well as between Carrot Island and Lake Mattamuskeet (Nm = 0.19482, p < 0.001), indicating a lack of gene flow. Overall, blue crabs from Carrot Island had high, significant genetic differentiation when compared to crabs from both Beaufort Inlet (Fst = 0.11830, p < 0.001) and Lake Mattamuskeet (Fst = 0.09689, p < 0.001). These results support the hypothesis and provide initial evidence that genetics influence habitat preference and migration patterns in blue crabs.
Open Access
Relationships Between Vernal Pool Reptile and Amphibian Species Composition and Spotted Salamander (Ambystoma maculatum) Egg Mass Density in the North Carolina Piedmont
(2023-04-25) Fajardo, Marisa
Spotted salamanders (Ambystoma maculatum) are essential indicators of vernal pool health, yet little research has identified the effects of interspecies interactions on spotted salamander oviposition. In this study, I evaluated the relationships between vernal pool reptile and amphibian species composition and spotted salamander egg mass density within Durham and Orange County. I observed significantly higher egg mass densities in pools with more Salamandrid, Viperid, and Scincid species despite threats of predation. High egg mass densities were also correlated with the presence of early breeding spotted salamanders and more acidic pH levels. Results suggest that spotted salamanders select breeding sites based on environmental conditions, rather than in avoidance of predation or resource competition. These findings are likely influenced by scarcity of optimal breeding habitat within the study area due to history of urbanization and agricultural land use.