Browsing by Subject "Species distributions"
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Item Open Access Conserving Moving Species under Changing Landscapes and Climates(2008-08-04) Loarie, Scott RobbinsTo conserve biodiversity, it is critical to understand the dynamic landscapes and climates through which species move and how the environment influences movement choices. In particular, I am interested in how species respond to human modifications to landscapes and climates. Chapter 1 uses datasets on the spatial and temporal coverage of remotely sensed land cover datasets to examine gaps in the monitoring of environmental priorities. Temporal gaps in Landsat and spatial gaps in commercial high resolution satellites such as QuickBird may hinder land cover change monitoring efforts.
Chapter 2 uses Global Climate Models and museum specimens to projects the impact of climate change on the flora of California, a global biodiversity hotspot. With anticipated climate change, up to 66% may experience >80% reductions in range size within a century. These projections are less severe if plants are able to disperse in time. With no constraints on dispersal, plant centroids move an average of up to 150 km. The projections identify regions where species undergoing severe range reductions may persist. Protecting these potential future refugia and facilitating species dispersal may be essential to maintain biodiversity in the face of climate change.
Chapter 3 analyzes the movements of 73 elephants fitted with GPS collars against 4 remotely sensed datasets spanning a strong rainfall gradient across 7 southern African countries. Movements show strong seasonal and geographic differences across the study area. Two major human interventions, artificial water and fences, distort these movement patterns by increasing dry season ranging patterns and increasing the density of wet season movements.
Chapter 4 uses the datasets described in chapter 3 to explore elephant vegetation preferences. Elephants consistently prefer greener vegetation throughout the year. Vegetation preferences vary seasonally. Elephants prefer less variable vegetation such as forests in the dry season and ephemeral vegetation such as grasslands in the wet season.
Chapter 5 uses telemetry and remotely sensed landcover data to ask how climatic factors - snow cover - and land cover - agriculture and roads - influence pronghorn movements in South Eastern Alberta. Analysis using a Bayesian movement model reveals that each of these features significantly influences pronghorn movement choices.
Item Open Access Ecology of Beaked Whales and Sperm Whales in the Western North Atlantic Ocean: Insights from Passive Acoustic Monitoring(2017) Stanistreet, Joy EliaBeaked whales (family Ziphiidae) and sperm whales (Physeter macrocephalus) are apex marine predators found throughout the world’s deep oceans. These species are challenging to observe, and little is known about fundamental aspects of their ecology, including their spatiotemporal distributions and habitat use. Passive acoustic monitoring (PAM), can be used to detect their echolocation clicks during foraging dives, thereby providing an indication of species presence. My dissertation investigates the distribution, seasonal occurrence, and diel variability in acoustic detections of beaked whales and sperm whales in the western North Atlantic Ocean, using multi-year passive acoustic recordings collected along the continental slope between Florida and Nova Scotia. First, I describe spatiotemporal patterns in detections of beaked whale echolocation clicks from five beaked whale species and one signal type of unknown origin. At least two beaked whale click types were detected at each recording site, and detections occurred year-round, with site-specific variation in relative species occurrence. Notably, Cuvier’s beaked whales (Ziphius cavirostris) were regularly detected in a region where they have not been commonly observed, and potential habitat partitioning among Cuvier’s and Gervais’ (Mesoplodon europaeus) beaked whales was apparent within their overlapping ranges. To examine the potential effects of using duty-cycled recording schedules on the detection of beaked whale clicks, I performed a subsampling experiment, and found that short, frequent listening periods were most effective for assessing daily presence of beaked whales. Furthermore, subsampling at low duty cycles led to consistently greater underestimation of Mesoplodon species than either Cuvier’s beaked whales or northern bottlenose whales (Hyperoodon ampullatus), leading to a potential bias in estimation of relative species occurrence. Next, I examine the occurrence of sperm whale echolocation clicks, which were recorded commonly between southern New England and North Carolina, but infrequently off the coast of Florida. In the northern half of the study region, I observed distinct seasonal patterns in the daily prevalence of sperm whale clicks, with a winter peak in occurrence off Cape Hatteras, North Carolina, followed by an increase later in the spring at sites further north, suggesting a shift in sperm whale concentrations which may relate to enhanced productivity occurring at higher latitudes in the spring. Finally, I explore the variability in daily detection rates of beaked whales and sperm whales in relation to dynamic oceanographic conditions off the Mid-Atlantic coast. Detection rates did not appear to correlate with temporal environmental variability, and persistent habitat features may be more important in predicting the occurrence of these species. Together, my dissertation provides substantial baseline information on the spatiotemporal occurrence of beaked and sperm whales in the western North Atlantic Ocean, highlighting the diversity within this guild of deep-diving odontocetes and demonstrating the use of PAM to provide species-specific insight into their ecology.