Browsing by Author "Nichols, James D."

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    Ecology and restoration of Sumatran tigers in forest and plantation landscapes
    Sunarto, Sunarto (Virginia Tech, 2011-02-11)
    Tigers (Panthera tigris Linnaeus, 1758) are in danger of extinction. Their populations have declined from ~100,000 to only ~3,000 individuals in a century and their habitat has shrunk to less than 7% of the historic range. Of the five extant tiger subspecies, the Sumatran tiger (Panthera tigris sumatrae Pocock, 1929) is the most seriously threatened. Currently determined as Critically Endangered under IUCN criteria, the Sumatran tiger is likely to become extinct unless effective conservation measures are enacted. Threats to the tiger include habitat destruction, killing due to conflict with humans and livestock, and poaching for illegal wildlife trade. Long-term survival of Sumatran tigers depends largely on the effectiveness of current conservation efforts in every tiger landscape. Successful conservation and management require accurate information on ecology of the species upon which decisions can be based. This study investigated basic ecological aspects of tigers and developed strategies for management and restoration to improve tiger viability in the Central Sumatra landscape. This landscape is comprised of natural forests and plantations managed for timber and agricultural commodities. The first chapter assesses the variation in tiger abundance across forest types in Southern Riau, and over time in Tesso Nilo National Park, all in Central Sumatra. Using camera traps, my team and I systematically sampled five blocks representing three major forest types in the region: peat land, flat lowland, and hilly lowland. I found that tiger abundance varied by forest type and through time. Excluding two sampling blocks where no tigers were photographed, the lowest tiger density was in peat land forest of Kerumutan, and the highest density was in the flat lowland forest of Tesso Nilo. Repeated sampling in the newly established Tesso Nilo National Park documented a trend of increasing tiger density (SE) from 0.90 (0.38) individuals/100 km2 in 2005 to 1.70 (0.66) individuals/100 km2 in 2008. Overall, tiger densities from this study were lower than most previous estimates from other parts of Sumatra. The trend of increasing tiger density in Tesso Nilo, however, suggests that the tiger population could be augmented by protection of habitats that were previously logged and severely disturbed. The second chapter examines the occupancy and habitat-use of the tiger across the major landcover types (natural forest, acacia plantation, oilpalm plantation, rubber plantation, and mixed agriculture). I found that tigers used some plantation areas, although they significantly preferred forests over plantations. In all landcover types, sites with tiger detections had thicker understory cover than sites without tiger detection. Modeling tiger occupancy while recognizing that probability of detection is not always perfect, I found that tiger occupancy covaried positively and significantly with altitude and negatively, but not significantly, with distance-to-forest-cores. Probability of habitat use by tigers covaried positively and significantly with understory cover and altitude, and negatively and significantly with human settlement and landcover rank. The results suggested that with adjustments in plantation management, tigers could use or roam through plantations within the habitat mosaic provided that the plantations had adequate understory cover and low level of human activity. They also could use riparian forests (as corridors) and smaller forest patches (as stepping stones) to travel between the main habitat patches across the forest and plantation landscape. The third chapter investigates the ecological characteristics and possible inter-specific interactions among wild felids, including tigers and smaller cats, based on data collected using systematic camera trapping in combination with information on their natural history. I found that despite overlap in resource needs of the five felid species, each appears adapted to specific environmental conditions allowing coexistence with other felids. The five felid species used statistically different elevations, with the golden cat found to inhabit the highest elevation. Two-species occupancy models showed that only leopard cats were found to co-occur with other felid species more frequently than expected by chance under independence. Species of similar size or eating similar-sized prey generally tended to have low coefficients of temporal activity overlap, suggesting avoidance. Temporal avoidance is likely occurring in three pairs of felids, namely clouded leopards and golden cats, clouded leopards and marbled cats, and marbled cats and leopard cats. Based on the differences in morphological and ecological characteristics, and on patterns of spatial and temporal occurrence, I identified six possible mechanisms by which felids in Central Sumatra maintain coexistence. I discussed the implications of this study for management, focusing on how to balance diversity and abundance of felids. The fourth chapter presents the tiger distribution models as a case study to illustrate the importance of accounting for uncertainty in species distribution mapping. I applied four modeling approaches, differing in how the response variable (tiger presence) is constructed and used in the models. I compared the performance and output of different models based on the relative importance of variables, descriptive statistics of the predictions, cross comparison between models using an error matrix, and validation using tiger presence data collected from independent surveys. All models consistently identified forest area within the grid as one of the most important variables explaining tiger probability of occurrence. Three models identified altitude as another important factor. While the four models were consistent in predicting relatively high probability of tiger occurrence for high elevation forest areas such as Rimbang Baling and Bukit Tigapuluh, they generally had a lower level of agreement in predictions for low elevation areas, particularly the peat land in the northeastern part of the study area. Based on the results of cross evaluation of the predictions among models and validation with the independent data, I considered the occupancy model to be superior to the others. If data collection format permits, I advocate the use of occupancy instead of the other modeling techniques to develop predictive species distribution maps. The last chapter constructs a strategy to restore the tiger population across the ecosystem of Central Sumatra through integration of knowledge on tiger ecology from previous chapters with consideration of the ecological conditions of the landscape in the region. The strategy combines existing knowledge of tiger conservation and regional ecosystem restoration. It recognizes the limitations and challenges of traditional nature protection and considers existing and new opportunities. Emerging opportunities and new mechanisms, such as direct and indirect economic incentives for nature conservation and restoration, are taken into account. These, coupled with increased awareness of the stakeholders, better policies and implementation of good governance, and the willingness and know-how to maintain coexistence with wildlife among the local people, are expected to support and accelerate the recovery of tigers and their ecosystem.
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    The effects of habitat, climate, and Barred Owls on long-term demography of Northern Spotted Owls
    Dugger, Katie M.; Forsman, Eric D.; Franklin, Alan B.; Davis, Raymond J.; White, Gary C.; Schwarz, Carl J.; Burnham, Kenneth P.; Nichols, James D.; Hines, James E.; Yackulic, Charles B.; Doherty, Paul F., Jr.; Bailey, Larissa L.; Clark, Darren A.; Ackers, Steven H.; Andrews, Lawrence S.; Augustine, Ben C.; Biswell, Brian L.; Blakesley, Jennifer; Carlson, Peter C.; Clement, Matthew J.; Diller, Lowell V.; Glenn, Elizabeth M.; Green, Adam; Gremel, Scott A.; Herter, Dale R.; Higley, J. Mark; Hobson, Jeremy; Horn, Rob B.; Huyvaert, Kathryn P.; McCafferty, Christopher; McDonald, Trent; McDonnell, Kevin; Olson, Gail S.; Reid, Janice A.; Rockweit, Jeremy; Ruiz, Viviana; Saenz, Jessica; Sovern, Stan G. (2016-02)
    Estimates of species' vital rates and an understanding of the factors affecting those parameters over time and space can provide crucial information for management and conservation. We used mark-recapture, reproductive output, and territory occupancy data collected during 1985-2013 to evaluate population processes of Northern Spotted Owls (Strix occidentalis caurina) in 11 study areas in Washington, Oregon, and northern California, USA. We estimated apparent survival, fecundity, recruitment, rate of population change, and local extinction and colonization rates, and investigated relationships between these parameters and the amount of suitable habitat, local and regional variation in meteorological conditions, and competition with Barred Owls (Strix varia). Data were analyzed for each area separately and in a meta-analysis of all areas combined, following a strict protocol for data collection, preparation, and analysis. We used mixed effects linear models for analyses of fecundity, Cormack-Jolly-Seber open population models for analyses of apparent annual survival (phi), and a reparameterization of the Jolly-Seber capture-recapture model (i.e. reverse Jolly-Seber; RJS) to estimate annual rates of population change (lambda(RJS)) and recruitment. We also modeled territory occupancy dynamics of Northern Spotted Owls and Barred Owls in each study area using 2-species occupancy models. Estimated mean annual rates of population change (lambda) suggested that Spotted Owl populations declined from 1.2% to 8.4% per year depending on the study area. The weighted mean estimate of lambda for all study areas was 0.962 (+/- 0.019 SE; 95% CI: 0.925-0.999), indicating an estimated range-wide decline of 3.8% per year from 1985 to 2013. Variation in recruitment rates across the range of the Spotted Owl was best explained by an interaction between total winter precipitation and mean minimum winter temperature. Thus, recruitment rates were highest when both total precipitation (29 cm) and minimum winter temperature (-9.5 degrees C) were lowest. Barred Owl presence was associated with increased local extinction rates of Spotted Owl pairs for all 11 study areas. Habitat covariates were related to extinction rates for Spotted Owl pairs in 8 of 11 study areas, and a greater amount of suitable owl habitat was generally associated with decreased extinction rates. We observed negative effects of Barred Owl presence on colonization rates of Spotted Owl pairs in 5 of 11 study areas. The total amount of suitable Spotted Owl habitat was positively associated with colonization rates in 5 areas, and more habitat disturbance was associated with lower colonization rates in 2 areas. We observed strong declines in derived estimates of occupancy in all study areas. Mean fecundity of females was highest for adults (0.309 +/- 0.027 SE), intermediate for 2-yr-olds (0.179 +/- 0.040 SE), and lowest for 1-yr-olds (0.065 +/- 0.022 SE). The presence of Barred Owls and habitat covariates explained little of the temporal variation in fecundity in most study areas. Climate covariates occurred in competitive fecundity models in 8 of 11 study areas, but support for these relationships was generally weak. The fecundity meta-analysis resulted in 6 competitive models, all of which included the additive effects of geographic region and annual time variation. The 2 top-ranked models also weakly supported the additive negative effects of the amount of suitable core area habitat, Barred Owl presence, and the amount of edge habitat on fecundity. We found strong support for a negative effect of Barred Owl presence on apparent survival of Spotted Owls in 10 of 11 study areas, but found few strong effects of habitat on survival at the study area scale. Climate covariates occurred in top or competitive survival models for 10 of 11 study areas, and in most cases the relationships were as predicted; however, there was little consistency among areas regarding the relative importance of specific climate covariates. In contrast, meta-analysis results suggested that Spotted Owl survival was higher across all study areas when the Pacific Decadal Oscillation (PDO) was in a warming phase and the Southern Oscillation Index (SOI) was negative, with a strongly negative SOI indicative of El Nino events. The best model that included the Barred Owl covariate (BO) was ranked 4th and also included the PDO covariate, but the BO effect was strongly negative. Our results indicated that Northern Spotted Owl populations were declining throughout the range of the subspecies and that annual rates of decline were accelerating in many areas. We observed strong evidence that Barred Owls negatively affected Spotted Owl populations, primarily by decreasing apparent survival and increasing local territory extinction rates. However, the amount of suitable owl habitat, local weather, and regional climatic patterns also were related to survival, occupancy (via colonization rate), recruitment, and, to a lesser extent, fecundity, although there was inconsistency in regard to which covariates were important for particular demographic parameters or across study areas. In the study areas where habitat was an important source of variation for Spotted Owl demographics, vital rates were generally positively associated with a greater amount of suitable owl habitat. However, Barred Owl densities may now be high enough across the range of the Northern Spotted Owl that, despite the continued management and conservation of suitable owl habitat on federal lands, the long-term prognosis for the persistence of Northern Spotted Owls may be in question without additional management intervention. Based on our study, the removal of Barred Owls from the Green Diamond Resources (GDR) study area had rapid, positive effects on Northern Spotted Owl survival and the rate of population change, supporting the hypothesis that, along with habitat conservation and management, Barred Owl removal may be able to slow or reverse Northern Spotted Owl population declines on at least a localized scale.
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    Ocelot Density and Home Range in Belize, Central America: Camera-Trapping and Radio Telemetry
    Dillon, Adam (Virginia Tech, 2005-10-10)
    Historically, ocelots (Leopardus pardalis) were hunted in large numbers for their fur, causing declines in population abundance across their range. In recent decades protection measures (e.g. CITES) and decreased public demand for ocelot fur resulted in declines in hunting pressure. Do to their elusive nature there is little known about ocelot population size, structure or general ecology. This lack of information hampers our ability to provide protection for this endangered species. Remote cameras were deployed in 7 grids across the landscape to estimate the density of ocelots in 2 habitat types; the broadleaf rainforest and pine forest of western Belize. Camera trapping combined with mark-recapture statistics resulted in densities of 18.91 - 20.75 ocelots per 100 km2 in the rainforest and 2.31 0 3.81 ocelots per 100 km2 in the pine forest habitat. This study examined the issues of camera spacing and animals with zero distance moved and their effect on density estimation. Increased camera spacing resulted in larger buffer sizes (increasing the effective trap area) and decreased density estimates. Inclusion of zero distance animals decreased buffer sizes and increased density estimates. Regardless of these effects, ocelot density was higher in the broadleaf rainforest than the pine forest. The ocelot density estimates in Belizean forests were lower than those in other portions of their range. The camera trapping technique demonstrated ocelots to be mostly active at night, with peaks of activity after sunset and before sunrise, and to travel low-use roads in the wet season and high-use roads in the dry season. Radio telemetry was used in this study to estimate the home range size and density of ocelots in the broadleaf rainforest of western Belize. Six collared ocelots (3 male, 3 female) were collared and tracked from September 2003 - August 2004. Male ocelots had an average home range size of 33.01 km2 (95% fixed kernel) and 29.00 km2 (100% MCP), and female ocelots had an average home range size of 21.05 km2 (95% fixed kernel) and 29.58 km2 (100% MCP). Most ocelots had larger home ranges in the dry season than the wet season. Ocelots showed a large amount of same sex home range overlap; with male-male overlap averaging 25% (100% MCP) and female-female overlap averaging 16% (100% MCP). Ocelot density determined using radio telemetry was 7.79 - 10.91 ocelots per 100 km2. The radio telemetry ocelot densities were lower and their home ranges larger in the Belizean broadleaf rainforests than those in other portions of their range. The camera trapping and radio telemetry techniques were compared against one another and combined in order to test which technique may be more successful in studying certain aspects of feline behavior. Activity budgets and density estimates determined from camera trapping were superior to radio telemetry, whereas camera trapping home ranges showed higher variation and lower resolution than radio telemetry. However, home range estimates determined from camera trapping captured long distance movements, a larger percent of territory overlap, and displayed potential for estimating an animal's core use area. When radio telemetry data were used to create a buffer around camera traps based on the average radius of an ocelots' home range size, the resulting density estimates were smaller than those determined using the current camera trapping methodology. This study provided much needed baseline information on ocelot abundance, home range size, activity patterns, and trail use. While sample sizes were small, this study had the largest number of ocelots captured in Central America to date. Although camera trapping is already a useful tool in felid research, this study highlights the importance of further standardization of the camera trapping methodology, increasing its potential for monitoring and conservation across habitats and study sites.
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    Spatial ecology and demography of eastern coyotes (Canis latrans) in western Virginia
    Morin, Dana Janine (Virginia Tech, 2015-07-29)
    Coyote (Canis latrans) range expansion in the Central Appalachian Mountains has stimulated interest in ecology of this predator and potential impacts to prey populations. This is particularly true in the Ridge and Valley Region in western Virginia where white-tailed deer (Odocoileus virginianus) populations are restricted by low nutritional carrying capacity and are subject to two other predators, bobcats (Lynx rufus) and American black bears (Ursus americanus), in addition to an active hunter community. I address two primary objectives of the Virginia Appalachian Coyote Study: to investigate 1) spatial ecology and 2) population dynamics of coyote populations in Bath and Rockingham counties. I deployed 21 GPS satellite collars on 19 coyotes over 32 months. I estimated home range size (mean = 13.46 km², range = 1.23 km² - 38.24 km²) across months using biased-random bridges and second-order habitat selection at four scales using eigenanalysis of selection ratios. I developed a metric to classify social status of individuals as either resident or transient based on stability of home range centers over time. I found evidence for class substructure for selection of territories where adult residents had a higher probability of mortality in high productivity/high risk habitats, compared to subadults and transients that were restricted to less productive habitats. I collected scat samples over five scat surveys across 2.5 years and extracted fecal DNA to identify individual coyotes in a mark-recapture framework. I estimated coyote densities in Bath (5.53 – 9.04 coyotes/100 km²) and Rockingham Counties (2.41 – 8.53 coyotes/100 km²) using a spatial capture-recapture model. Six-month apparent survival was lower in Bath County (ΦBath = 0.442, 0.259 – 0.643; ΦRockingham = 0.863, 0.269 – 0.991). The Bath County population demonstrated persistence despite high mortality and the Rockingham population demonstrated boundedness with recruitment inverse of changes in density. Findings at both sites suggest density-dependence, and tests of territoriality, presence of transients, and territory turnover demonstrate a capacity for immediate local immigration in response to high mortality in Bath County. I suggest that landscape-level habitat management may be a viable strategy to reduce potential conflicts with coyotes in the region.