Browsing by Subject "Occupancy"

Now showing 1 - 5 of 5
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    California spotted owl population dynamics in the central Sierra Nevada: an assessment using multiple types of data
    (2014-01) Tempel, Douglas John
    The California spotted owl (Strix occidentalis occidentalis) is a focal management species in the Sierra Nevada because it uses late-seral forests for roosting and nesting. Thus, obtaining accurate and precise estimates of population trends is necessary to reliably assess the effects of management actions and habitat change on this species. To demonstrate how this objective can be better met, I used multiple data types from a long-term population study in the central Sierra Nevada, as opposed to the typical approach of using only mark-recapture data. First, I compared population trends estimated from occupancy and mark-recapture data. Occupancy surveys are more cost-effective than mark-recapture studies for monitoring territorial species over large spatial extents. I found that the realized change in territory occupancy from 1993-2010 (&deltat = 0.702, 95% CI 0.552-0.852) closely matched the realized population change estimated from mark-recapture data (&deltat = 0.725, 95% CI 0.445-1.004). This suggested that occupancy can provide reliable inferences on population trends, especially when funds preclude more intensive mark-recapture studies. I recognize, however, that mark-recapture studies provide important demographic information not provided by occupancy studies, which may allow the identification of life-history stages that are limiting a population. Second, I developed an integrated population model (IPM) to obtain estimates of population change for my study population from 1990-2012 because IPMs may improve the precision of parameter estimates. My IPM incorporated count, reproductive, and mark-recapture data. I observed a significant population decline, as evidenced by the geometric mean of the finite rate of population change (&lambdat = 0.969, 95% CRI 0.957-0.980) and the resulting realized population change (proportion of the initial population present in 2012; &delta2012 = 0.501, 95% CRI 0.383-0.641). My IPM provided more precise estimates of realized population change than either the occupancy or mark-recapture analyses, but I did not account for covariance among the demographic rates in my IPM, which may have resulted in "false" precision (i.e., underestimation of the true variance). If covariances are incorporated into the IPM, they have excellent potential as a tool for assessing the status of species of conservation or management concern. My results also suggested that continued monitoring of this population and reconsideration of the California spotted owl's status under the U. S. Endangered Species Act may be warranted.
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    The Distribution of Elephants, Tigers and Tiger Prey in Thailand’s Western Forest Complex
    (2016-12) Jornburom, Pornkamol
    Conservation of large mammals such as Asian elephants (Elephas maximus), tigers (Panthera tigris) and their main prey, gaur (Bos gaurus), banteng (Bos javanicus), and sambar (Cervus unicolor) requires a systematic and statistically rigorous monitoring system that accounts for imperfect detection. Despite conservation efforts, these large mammals are highly threatened and declining across their entire range. In Thailand, large viable populations of these large mammals remain in the Western Forest Complex (WEFCOM), an approximately 19,000 km2 landscape of 17 contiguous protected areas. To determine species distribution and factors that affect distribution patterns, a government/NGO team conducted occupancy surveys throughout the WEFCOM landscape from 2010-1012. I analyzed these data at both a landscape scale (256 km2 for elephants, 64 km2 for tigers and their prey) and a local scale (1 km2). At the landscape scale, I estimated the proportion of sites occupied by each species. At a finer scale, I identified the key variables that influence site-use and developed predictive distribution maps. At both scales, I examined key ecological and anthropogenic factors that help explain distribution and preferred habitat use. Occupancy models revealed that elephant, gaur and sambar avoided villages and elephants, banteng and sambar prefered lower slopes near streams. Gaur, in contrast, preferred steep slopes at higher elevation. I estimated that elephants occupied 82% of the the landscape. Other species occupied much smaller portions of WEFCOM (tigers = 37%, gaur = 48%, sambar 53% and banteng 13%). Tiger occupancy was largely influenced by the three large prey species. Additionally, presence of villages has a consistent negative impact on occupancy and site-use by all these large mammals; therefore, reducing the impact of human activities near villages is the key conservation recommendation from this study. By modeling occupancy while accounting for probability of detection, I established reliable benchmark data on distribution of these endangered species. The results of this study underlined the need for further conservation and management to maintain wildlife distribution and populations in WEFCOM and other sites in Thailand and Southeast Asia.
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    Landscape-scale conservation planning and wildlife monitoring In Southeast Asia
    (2014-09) Cutter, Peter Guild
    Advances in data availability and methodology have greatly expanded the potential for landscape scale monitoring of biodiversity and the use of resulting insights for conservation planning. This collection of papers explores the use of modeling, monitoring, and conservation planning techniques to better facilitate landscape scale conservation in Southeast Asia.Chapter 1 focuses on the use of linear and logistic regression techniques for modeling occurrence patterns of tigers and tiger prey over a large landscape in western Thailand. I discuss the strengths and limitations of using these techniques to inform landscape scale monitoring and planning activities. Chapter 2 explores the potential for sign surveys of a landscape scale predator (tiger) to inform management decisions. I compare presence/absence and count survey frameworks and assess their value in informing landscape level management. A controlled study of tiger sign interpretation provides the much of the basis for the raw data used in this chapter and this study is presented in a detailed appendix. Chapters 3 through 5 focus on a biodiversity gap analysis conducted for Cambodia's protected area system. Chapter 3 provides a detailed account of methods used to map biodiversity surrogates for the country. Chapter 4 reviews the history and current status of Cambodia's protected area system and includes recommendations for revising IUCN category assignments for the system. Chapter 5 is a detailed account of a national level conservation planning exercise in Cambodia and how this process was translated into specific recommendations for improving Cambodia's protected area system.
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    Maintaining Hornbills in the Working Landscape of the Southern Tenasserim Western Forest Complex Corridor in Thailand
    (2014-08) Teampanpong, Jiraporn
    The Southern Tenasserim Western Forest Complex Corridor in Thailand is a key linkage for wildlife between prominent forests in Southeast Asia. However, it has been facing biodiversity loss due to development. To begin to address the consequences of this loss, understanding the ecology of hornbills as key seed dispersers and their ability to maintain healthy forest and restore degraded ones, is required. This dissertation explores the current state of hornbills in the region and factors that influence it, focusing on the human impacts that interrupt ecological efforts to maintain and restore the forest. I found that the quality of forest inside a large protected area in the region is comparable to other high quality habitat for hornbills in Thailand with respect to providing food and breeding sites. In this area, the smaller-sized hornbills selected nests closer to streams, at lower altitudes and in less steep areas, and in smaller sized trees than the bigger hornbills. Additionally, hornbills were able to use forest outside the protected area, but only as temporary feeding sites, because of the low density of potential fruit trees. My study documents larger foraging ranges of the immature Wreathed Hornbill (WH), which move farther from natal nests, than the smaller immature Oriental-pied Hornbill (OPH). Additionally, it reveals that the immature OPH and WH use evergreen forest disproportionately to other forest types and tend to select areas near the edges of evergreen forest. Moreover, the OPH also selects habitats at lower elevations in large forest patches. Location errors that are inherent to VHF radio telemetry may affect the results in studies using this technique. However, the resource selection models in this study were not affected by location errors. I did document that elevation, locations at lower mountainside, slope, and distance from a tracking station are factors that introduce error in calculating distances. Lastly, I developed occupancy and detection probability models for the four sympatric hornbills in the region. Hornbills respond negatively to human disturbance but positively to the availability of fruit trees, the availability of potential nest trees, and the abundance of ripe fig fruits.
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    Seasonal influence on detection probabilities for multiple aquatic invasive species using environmental DNA
    (2023-12-14) Rounds, Christopher; Arnold, Todd W; Chun, Chan Lan; Dumke, Josh; Totsch, Anna; Keppers, Adelle; Edbald, Katarina; García, Samantha M; Larson, Eric R; Nelson, Jenna KR; Hansen, Gretchen JA; round060@umn.edu; Rounds, Christopher; University of Minnesota Fisheries Systems Ecology Lab
    Aquatic invasive species (AIS) are a threat to freshwater ecosystems. Documenting AIS prevalence is critical to effective management and early detection. However, conventional monitoring for AIS is time and resource intensive and is rarely applied at the resolution and scale required for effective management. Monitoring using environmental DNA (eDNA) of AIS has the potential to enable surveillance at a fraction of the cost of conventional methods, but key questions remain related to how eDNA detection probability varies among environments, seasons, and multiple species with different life histories. To quantify spatiotemporal variation in the detection probability of AIS using eDNA sampling, we surveyed 20 lakes with known populations of four aquatic invasive species: Common Carp (Cyprinus carpio), Rusty Crayfish (Faxonius rusticus), Spiny Waterflea (Bythotrephes longimanus), and Zebra Mussels (Dreissena polymorpha). We collected water samples at 10 locations per lake, five times throughout the open water season. Quantitative PCR was used with species-specific assays to determine the presence of species DNA in water samples. Using Bayesian occupancy models, we quantified the effects of lake and site characteristics and sampling season on eDNA detection probability. These results provide critical information for decision makers interested in using eDNA as a multispecies monitoring tool and highlight the importance of sampling when species are in DNA releasing life history stages.