Thesis (Ph. D.)--University of Wyoming, 2007. / Title from PDF title page (viewed Feb. 9, 2009). Includes bibliographical references.

Thesis (M.Sc.)--Memorial University of Newfoundland, 1997. / Bibliography: leaves 78-87.

One of the major environmental concerns in the world is the loss of biological diversity due to anthropogenic activities. Of special concern is the conservation of endemic species that are particularly vulnerable to extinction. The Mearns's squirrel (Tamiasciurus mearnsi) is endemic to the Sierra de San Pedro Mártir, Baja California. Federally listed as threatened in Mexico and as endangered by the International Union for Conservation of Nature (IUCN), little is known about the ecology of this southernmost Tamiasciurus. Interestingly, Mearns's squirrels exhibit deviations from common behaviors observed in other congeners such as lack of leaf nests (dreys) and larderhoards (middens), suggesting potentially unique adaptations. Herein, I reviewed the diversity and conservation status of the arboreal squirrels of Mexico. Using radio-telemetry and satellite imagery, I examined if the lack of dreys and middens may be associated with differences observed in nesting behavior, home-range dynamics, and life-history and behavioral tactics between Mearns's squirrels and other arboreal squirrels.Mexico harbors 14 species of arboreal squirrels, of which four are endemic, with the states of Chiapas and San Luis Potosí possessing the greatest diversity. Unfortunately, high deforestation rates in Mexico, and a dearth of information on their ecology, pose serious threats to the persistence of this squirrel diversity. Mearns's squirrels apparently are obligate secondary cavity-nesters with specific nesting requirements and their population possibly limited by the low occurrence of tree cavities in their habitat. The species seems to have lost the territorial behavior that is characteristic of the genus Tamiasciurus. Home-range dynamics of Mearns's squirrels are similar to nonterritorial Sciurus squirrels. Although reproduction and survival are similar to other Tamiasciurus, the species is heavier and apparently larger while exhibiting important variations in their behavior compared to other congeners. The lack of dreys and middens appears to be associated with the unique tactics adopted by Mearns's squirrels to persist in the Sierra de San Pedro Mártir. The species provides an important opportunity to learn more about geographic variation in nesting behavior and the evolution of territoriality. Large trees and snags that facilitate cavity formation are critical for the conservation of this species.

Natal dispersal is at the nexus of ecology, ethology, population genetics, and evolution. While abundant research exists on emigration and associated proximate and ultimate causes, less is known about exploration, settlement, and factors that influence settlement decisions. Further, the role of individual behavioral phenotypes in the domains of wildlife ecology and conservation, which include natal dispersal, is a recent and expanding area of inquiry. Understanding the relationships among individual phenotype, environmental conditions, and natal dispersal is increasingly important as landscapes become altered by disturbance, fragmentation, and climate change. I investigated natal dispersal in endangered Mt. Graham red squirrels (Tamiasciurus hudsonicus grahamensis), an isolated, peripheral subspecies of North American red squirrel persisting at the southern edge of the species' range. We tested hypotheses about the importance of proximate and ultimate drivers of emigration, dispersal distance, and settlement, and estimated perceived landscape connectivity within a mosaic of forest damage in the Pinaleño Mountains, Arizona. Compared to other red squirrel populations in North America, natal dispersal in Mt. Graham red squirrels is sex-biased and non-philopatric with mean dispersal distance over 8 times that observed in non-peripheral populations. Resources, indicated by mother's body mass in spring (a reflection of her intrinsic quality and territory quality) and individual body condition, contribute to individual behavioral tendencies for movement and exploration. Individuals with behavioral tendencies for movement and exploration dispersed the farthest, and for both males and females the longest observed dispersal distances and proportion of individuals dispersing occurred in a year of lowest food availability. Our research highlights the important role individual behavioral syndromes may play in observed heterogeneity in life history strategies with populations. Following emigration from the natal area, we provide evidence that individual dispersers rely upon forest structural cues similar to their natal area to select locations for settlement; the first test of natal habitat preference induction in a single vegetation community type. We used circuit theory to evaluate landscape connectivity and identify areas important for long-distance dispersal movements. Because single connectivity models may not adequately represent functional connectivity for an entire population, we summarized landscape connectivity across varying levels of landscape resistance to identify areas that promote movement and long-distance dispersal for individuals with different perceptions of landscape resistance. We show that composite connectivity models are a useful method to identify forest areas important for the promotion of long-distance movements as well as areas that constrain movement.

Natal dispersal outcomes are an interplay between environmental conditions and individual phenotypes. Peripheral, isolated populations may experience altered environmental conditions and natal dispersal patterns that differ from populations in contiguous landscapes. We document nonphilopatric, sex-biased natal dispersal in an endangered small mammal, the Mt. Graham red squirrel (Tamiasciurus hudsonicus grahamensis), restricted to a single mountain. Other North American red squirrel populations are shown to have sex-unbiased, philopatric natal dispersal. We ask what environmental and intrinsic factors may be driving this atypical natal dispersal pattern. We test for the influence of proximate factors and ultimate drivers of natal dispersal: habitat fragmentation, local population density, individual behavior traits, inbreeding avoidance, competition for mates, and competition for resources, allowing us to better understand altered natal dispersal patterns at the periphery of a species' range. A juvenile squirrel's body condition and its mother's mass in spring (a reflection of her intrinsic quality and territory quality) contribute to individual behavioral tendencies for movement and exploration. Resources, behavior, and body condition have the strongest influence on natal dispersal distance, but affect males and females differently. Male natal dispersal distance is positively influenced by its mother's spring body mass and individual tendency for movement; female natal dispersal distance is negatively influenced by its mother's spring body mass and positively influenced by individual tendency for movement. An apparent feedback between environmental variables and subsequent juvenile behavioral state contributes to an altered natal dispersal pattern in a peripheral population, highlighting the importance of studying ecological processes at the both range center and periphery of species' distributions.

Thesis (Ph.D.)--Memorial University of Newfoundland, 2005. / Includes bibliographical references.

The modifications animals make to their environments can be critical to species diversity. Red squirrels (Tamiasciurus hudsonicus) create large piles of conifer cone debris (middens) and are hypothesized to function as a keystone species due to positive associations between middens and other vertebrate species. We assessed vegetation and landscape structure at middens with a resident red squirrel for varying consistencies over the prior 5 years and surveyed mammals and birds at the community and population level. After accounting for vegetation and landscape characteristics, red squirrel-created resources positively influenced species richness of medium and large mammals and ground foraging birds, abundance of deer mice (Peromyscus maniculatus) and ground foraging birds, and activity of cliff chipmunks (Tamias dorsalis). Increased knowledge of the interaction strength of the red squirrel with its environment may be used to inform decisions in forest management and restoration and offer insight on the conservation value of larderhoarding mammals.

Mémoire (M.Ress.Renouv.)-- Université du Québec à Chicoutimi, 1994. / Document électronique également accessible en format PDF. CaQCU