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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

Assessment of human impact on the genetic diversity of tropical forest taxa

Jumpa, Salisa January 2015 (has links)
Biodiversity in Southeast Asia has been decreasing as a result of human activities. The findings of the Millennium Ecosystem Assessment, reported in 2005, demonstrated that environmental change, such as deforestation, has resulted in recent major loss of biodiversity at the species level and increased rates of extinction; however, it is unknown whether a similar deficit has occurred at the level of genetic diversity within species. This study aims to understand how the past has shaped the current pattern of genetic diversity, the impact of recent forest loss on genetic diversity and how this information can be used to develop effective conservation strategy. To achieve this aim, microsatellites were developed by sequencing genomic libraries and from comparisons of database sequences. The utility of these markers for population genetics studies has been tested and confirmed for the three main study taxa and across a broad range of other squirrel species. These microsatellites and mitochondrial sequence data (cytochrome b gene) were utilized to determine the genetic diversity and population structure of three squirrel taxa with varying degrees of forest dependency on Thailand’s tropical forests. The most forest dependent taxon is Phayre’s flying squirrel (Hylopetes phayrei). The second taxon is the moderately forest-dependent tree squirrel, the Grey-bellied squirrel (Callosciurus caniceps). The third, and least forest dependent taxon, is the Indochinese ground squirrel, Menetes berdmorei. Our data revealed far more biodiversity in these taxa than previously recognized; there were three genetically distinct lineages in H. phayrei and M. berdmorei and two lineages in C. caniceps. This demonstrates that biodiversity in this region has been underestimated. In the two most forest dependent taxa lineage divergence dated to the Pleistocene indicating that this biodiversity was generated by isolation in allopatric forest refugia during the cool, dry periods of the Pleistocene. In H. phayrei, the most forest-dependent taxon, at least two of the lineages were distinct species occurring sympatrically in Thailand on the border with Myanmar. This taxon supported the biogeographical hypothesis developed in forest dependent mosquitoes of allopatric isolation in northwest and northeastern Pleistocene refugia. Callosciurus caniceps had evidence of a southern refugium in peninsular Thailand or Malaysia. The lower levels of structuring in the least forest dependent taxon M. berdmorei suggest a limited impact of Pleistocene environmental change. All three taxa had eastern lineages which may have been due to Pleistocene forest fragmentation in some of the species. These eastern populations typically had lower levels of microsatellite and mtDNA genetic diversity. This is likely due to the recent loss of genetic diversity as in recent decades these forests have been highly fragmented and reduced in size due to human activity. Our finding that the northern Thai-Myanmar border region is a suture zone in highly dependent forest species and has high within lineage/species diversity makes this region a priority for conservation. The distinct genetic lineages in the east and south should also be managed as separate conservation units. Further efforts are required to assess the impact of loss of genetic diversity in Thailand’s fragmented forests and how this may be remedied.
62

The Trophic and Spatial Ecology of the Southern Flying Squirrel (Glaucomys Volans) and Non-Lethal Deterrent Methods

Meyer, Robert Timothy 04 May 2018 (has links)
Southern flying squirrels (SFS; Glaucomys volans) are known kleptoparasites on the endangered red-cockaded woodpecker’s (RCW; Picoides borealis) cavities and cost land managers time and money to control and the ecology of SFS in habitats managed for RCWs is poorly understood. This study is designed to obtain a better understanding of the general ecology of SFSs surrounding RCW habitat and provide possible non-lethal deterrent methods to prevent harmful interactions between SFSs and RCWs. Spatially-explicit capture-recapture showed generally higher SFS densities and habitat associations outside of RCW cluster partitions. Stable isotope analysis of SFS diets across Mississippi and Alabama revealed a narrow dietary breath relative to food items, thus habitat management may still be viable option to control SFSs. Lastly, investigation of odor deterrents resulted in the greatest avoidance of cavities containing gray rat snake (Pantherophis spiloides) feces and warrants further investigation.
63

The Squirrel Cage

Kloth, Timothy Tom 08 1900 (has links)
The Squirrel Cage is an intermedia composition set in three scenes and two interludes. The composition is based on the short story "The Squirrel Cage" by Thomas M. Disch. Robin Kay Willoughby created the libretto for the composition. The drama for The Squirrel Cage focuses on the actor who is being held captive in a white, padded cell. He does not know how long he has been in the cell or even why he is being held. His only source of stimulation is through the broadcast of National Public Radio that he hears in his cell. The only way he can attempt to communicate with the outside world is through the microphone in his cell, though he never knows if anyone hears his pleas for help. The music is constant expression of his environment and friendly responds directly to the performer's gestures. This volume contains the dissertation text.
64

Food habits of the Uinta ground squirrel (citellus armatus Kennicott) on some meadows of Mt. Timpanogos, Utah

Shaw, Robert K. 01 August 1958 (has links)
Food habits of the Uinta ground squirrel were investigated on some open meadows on the south-east slope of Mt. Timpanogos. Special emphasis was placed on species of plants eaten; and preference of plants in relation to season, succulence, and phenology. Other investigations were made in reference to: parts of plants eaten, non-plant material eaten, daily and seasonal activities in relation to foraging, feeding procedures, and the relationship between plant cover and Uinta ground squirrel activity.
65

A study of the habits and management of the gray squirrel in southwest Virginia

Shipley, Donald Devries 10 July 2010 (has links)
Master of Science
66

THE ADAPTATION OF NEW WORLD MONKEYS TO NEW ENVIRONMENTAL SITUATIONS: FOOD ACQUISITION AND FOOD PROCESSING BEHAVIORS.

LANDAU, VIRGINIA ILENE. January 1987 (has links)
Food cleaning behavior has been observed among laboratory squirrel monkeys. A Wilcoxon signed-ranks test showed that significantly more cleaning behavior occurred when hard monkey chow pellets and soft fruit were coated with edible debris. Monkeys removed fewer pieces of fruit from a food crock containing fruit coated with edible debris in a timed test. A principal component analysis of the food cleaning behaviors showed two underlying correlated factors. The first factor was the use of the body to clean food. The second factor was the use of the environment to clean food. Two groups of squirrel monkeys, one without previous learners and one with previous learners, were subjects in a fishing study. The presence of previous learners in the social group was not significant for monkeys fishing in water filled crocks. But there was a significant difference in the number of fishing attempts made by the No Previous Learners Group when fishing in wading pools. The Previous Learners group did not make significantly more fishing attempts fishing in wading pools than in crocks. A significant difference was observed in fishing attempts during Phase 1 and Phase 2 of the wading pool experiment for both groups. All monkeys in the group fishing experiments ate fish when it could be obtained. Monkeys who did not learn to fish successfully learned alternative behaviors to obtain fish. The Previous Learners group in the wading pool experiment were subjects in a more difficult fishing test. Significantly fewer fishing attempts were made but the number of monkeys that caught fish was larger. Caged squirrel monkeys scored a lower percentage of fishing attempts than squirrel monkeys living in a social group. While Cebus monkeys caught fish, unlike squirrel monkeys, they did not attempt to eat them.
67

Multiple mating and female choice in Richardson's ground squirrels (Urocitellus Richardsonii)

Magyara, Nora, University of Lethbridge. Faculty of Arts and Science January 2009 (has links)
I studied the mating behaviour of Richardson’s ground squirrels (Urocitellus richardsonii) in 2007 and 2008, near Picture Butte, AB, Canada with the goals of evaluating multiple paternities within litters, sperm competition, and female mate choice. Eleven microsatellites and use of behavioural data to eliminate males who could not be putative sires based on their spatial and temporal remoteness from estrous females enabled exclusive assignment of paternity to 82.8% of 598 offspring with known maternity. The frequency of multiple paternities (26.4%, n=87 litters) in my population was lower than that reported for Richardson’s ground squirrels in a Manitoba population (80.0%, n=15 litters). Sperm competition was absent except in litters weaned by those females that mated again within 5 minutes of the first copulation, in which case sperm displacement was evident. Female choice was observed through avoidance of copulation, termination of copulation, and hide-then-run behaviour. / x, 98 leaves ;|c29 cm. --
68

Differential response to fire by an introduced and an endemic species complicates endangered species conservation

Gwinn, R. Nathan, Koprowski, John L. January 2016 (has links)
Fire is a natural component of, and serves as a tool for, the restoration of forested ecosystems worldwide; however, disturbance due to fire also has been implicated in the proliferation of invasive species. How these fires affect occupancy and use of the forest by wildlife is of great concern, in particular, the differential response of non-native and native species. In the North American Southwest, prior to European settlement, frequent wildfires helped to maintain forest structure. We examined the effect of a large wildfire on an introduced population of the Abert's squirrel (Sciurus aberti) that has invaded the high elevation forests inhabited by the critically endangered Mt. Graham red squirrel (Tamiasciurus fremonti grahamensis). We found that introduced Abert's squirrels were more common than native red squirrels in burned areas. Abert's squirrels did not abandon burned areas but nested, foraged, and did not adjust their home range size in burned areas. This suggests that invasive Abert's squirrels are better able to exploit burned areas than native red squirrels and that fire can favor non-native species. This interaction between non-native species, native species, and fire adds new insight into the complexities of conservation and restoration of ecosystems and helps to inform conservation activities worldwide.
69

Challenges faced by foraging Eastern grey squirrels, Sciurus carolinensis : competition, pilferage and predation risks

Jayne, Kimberley January 2014 (has links)
This thesis examines how Eastern grey squirrels, Sciurus carolinensis, modify their foraging and hoarding behaviour in relation to different risks, particularly those which involve a trade-off between securing food resources and avoiding a negative outcome with a competitor. While foraging for food to eat and hoard, squirrels must compete with conspecifics and heterospecifics for access to resources, and they must ensure the safety of their food hoards from onlookers or opportunistic pilferers. While engaging in these behaviours in the most efficient way, they must also avoid being predated upon. Five studies were conducted to further understanding of grey squirrel foraging, hoarding and pilferage behaviours, and how they are affected by different risk factors. The data in this thesis provide experimental evidence that grey squirrels respond directly to conspecific presence as a cue of pilferage risk and adjust their behaviour in ways that may help to reduce cache theft. The data also support the view that conspecific and heterospecific competitors pose risks to foraging and caching, with squirrels modifying their behaviour in ways that serve to avoid negative competitive interactions. Predation risk was found to be particularly disruptive to foraging behaviour, and it also had a seasonal effect upon pilferage rates of experimenter-made caches. A variety of strategies that squirrels might use to pilfer caches were investigated, however, the data did not provide a clear indication of pilferage strategy used by squirrels; they did not seem to use observational spatial memory, and they did not simply pilfer in profitable foraging locations. This thesis raises questions about the mechanisms grey squirrels use to assess pilferage risk and how they engage in pilferage in comparison to other caching species; the studies conducted illustrate different methods that future research could use to investigate food hoarding and pilfering behaviour in wild and captive squirrels.
70

Modeling future range expansion and management strategies for an invasive squirrel species

Goldstein, Emily A., Butler, Fidelma, Lawton, Colin 18 February 2016 (has links)
Successful management of an invasive species requires in depth knowledge of the invader, the invaded ecosystem, and their interactions. The complexity of the species-system interactions can be reduced and represented in ecological models for better comprehension. In this study, a spatially explicit population model was created using the RAMAS software package to simulate the past and future invasion dynamics of the eastern grey squirrel (Sciurus carolinensis) in the fragmented habitat in case study areas in Ireland. This invasive squirrel species causes economic damage by bark stripping forest crops and is associated with the decline of its native congener (S. vulgaris). Three combinations of demographic and dispersal parameters, which best matched the distribution of the species shortly after introduction, were used to simulate invasion dynamics. Future population expansion was modeled under scenarios of no control and two different management strategies: fatal culls and immunocontraceptive vaccination programmes. In the absence of control, the grey squirrel range is predicted to expand to the south and southwest of Ireland endangering internationally important habitats, vulnerable forest crops, and the native red squirrel. The model revealed that region-wide intensive and coordinated culls would have the greatest impact on grey squirrel populations. Control strategies consisting solely of immunocontraceptive vaccines, often preferred by public interest groups, are predicted to be less effective. Complete eradication of the grey squirrel from Ireland is not economically feasible and strategic evidence-based management is required to limit further range expansion. Ecological models can be used to choose between informed management strategies based on predicted outcomes.

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