Author: Carolyn Julia McCollPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
The Role of Food, Predation, and Population Density on the Stress Physiology of Arctic Ground Squirrels
Author: Carolyn Julia McCollThe Role of Food, Predation, and Population Density on the Stress Physiology of Arctic Ground Squirrels
Author: Canadian Journal of Zoology
Author: Ecosystem Dynamics of the Boreal Forest
Author: Charles J. KrebsPublisher: Oxford University Press on Demand
ISBN: 9780195133936
Category : Science
Languages : en
Pages : 511
Book Description
The boreal forest is one of the world's great ecosystems, stretching across North America and Eurasia in an unbroken band and containing about 25% of the world's closed canopy forests. The Kluane Boreal Forest Ecosystem Project was a 10-year study by nine of Canada's leading ecologists to unravel the impact of the snowshoe hare cycle on the plants and the other vertebrate species in the boreal forest. In much of the boreal forest, the snowshoe hare acts as a keystone herbivore, fluctuating in 9-10 year cycles, and dragging along secondary cycles in predators such as lynx and great-horned owls. By manipulating the ecosystem on a large scale from the bottom via fertilizer additions and from the top by predator exclosures, they have traced the plant-herbivore relationships and the predator-prey relationships in this ecosystem to try to answer the question of what drives small mammal population cycles. This study is unique in being large scale and experimental on a relatively simple ecosystem, with the overall goal of defining what determines community structure in the boreal forest. Ecosystem Dynamics of the Boreal Forest: The Kluane Project summarizes these findings, weaving new discoveries of the role of herbivores-turned-predators, compensatory plant growth, and predators-eating-predators with an ecological story rich in details and clear in its findings of a community where predation plays a key role in determining the fate of individuals and populations. The study of the Kluane boreal forest raises key questions about the scale of conservation required for boreal forest communities and the many mammals and birds that live there.
Population Ecology of Arctic Ground Squirrels in the Boreal Forest During the Decline and Low Phases of a Snowshoe Hare Cycle
Author: Andrea Elizabeth ByromPublisher:
ISBN:
Category : Arctic ground squirrel
Languages : en
Pages : 412
Book Description
Food and predation were examined as factors limiting arctic ground squirrel (Spermophilus parryii plesius) populations during the decline and low phases of a snowshoe hare cycle (1992-1995). Food and predator limitation were tested experimentally with large-scale (36-ha) experimental manipulations: two food-supplemented areas, a predator exclosure, and a food-supplemented treatment where predators were also excluded. Predator removal doubled population density, while addition of food resulted in a four-fold density increase. Removal of predators and addition of food together resulted in a 10-fold increase in arctic ground squirrel population densities. Population densities and adult survival rates were lower in 1992 and 1993 (two years after the snowshoe hare population decline) than in 1994 and 1995. Food supply and predation interact to limit arctic ground squirrel population densities in the boreal forest during the decline and low phases of the snowshoe hare cycle. Supplemental food did not affect dispersal distances or dispersal frequency of 172 radio-collared juveniles of either sex in any year. Juveniles that moved farther from their natal burrow were more likely to die. Males moved farther than females and died more frequently. Dispersal tendency was unrelated to population density in males. Females increased their tendency to disperse only on a study site with population densities 17 times those of control populations. Male arctic ground squirrels probably disperse to avoid inbreeding, while females may disperse in response to resource limitation at very high densities. Philopatric females had higher fitness than females that dispersed, particularly if survival during dispersal was taken into account. As population density increased from 1992 to 1995, home range overlap of adult females also increased, as daughters survived to reproductive age in contact with their mother's home range. A stage-based simulation model of the annual cycle of activity and hibernation was strongly sensitive to female survival.
Ecosystem Dynamics of the Boreal Forest : The Kluane Project
Author: Vancouver Charles J. Krebs Professor of Zoology University of British ColumbiaPublisher: Oxford University Press, USA
ISBN: 9780199771349
Category : Science
Languages : en
Pages : 542
Book Description
The boreal forest is one of the world's great ecosystems, stretching across North America and Eurasia in an unbroken band and containing about 25% of the world's closed canopy forests. The Kluane Boreal Forest Ecosystem Project was a 10-year study by nine of Canada's leading ecologists to unravel the impact of the snowshoe hare cycle on the plants and the other vertebrate species in the boreal forest. In much of the boreal forest, the snowshoe hare acts as a keystone herbivore, fluctuating in 9-10 year cycles, and dragging along secondary cycles in predators such as lynx and great-horned owls. By manipulating the ecosystem on a large scale from the bottom via fertilizer additions and from the top by predator exclosures, they have traced the plant-herbivore relationships and the predator-prey relationships in this ecosystem to try to answer the question of what drives small mammal population cycles. This study is unique in being large scale and experimental on a relatively simple ecosystem, with the overall goal of defining what determines community structure in the boreal forest. Ecosystem Dynamics of the Boreal Forest: The Kluane Project summarizes these findings, weaving new discoveries of the role of herbivores-turned-predators, compensatory plant growth, and predators-eating-predators with an ecological story rich in details and clear in its findings of a community where predation plays a key role in determining the fate of individuals and populations. The study of the Kluane boreal forest raises key questions about the scale of conservation required for boreal forest communities and the many mammals and birds that live there.
The Effect of Predation Risk and Colony Vegetation on Columbian Ground Squirrel Vigilance, Feeding, Travel, and Burrow Density in Northwestern Montana
Author: Jeffrey Mark BakerPublisher:
ISBN:
Category : Ground squirrels
Languages : en
Pages : 38
Book Description
Behavioral and Spatial Dynamics in a Fluctuating Population of Golden-mantled Ground Squirrels (Callospermophilus Lateralis)
Author: Jaclyn Rebecca AlipertiPublisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
Investigating individual-based habitat settlement and space use decisions (i.e., how individuals distribute themselves across a landscape) is a central theme in ecology, with potential consequences for fitness (e.g., survival, reproduction). Among mammals, habitat selection and spatial organization (home range size and overlap) may be influenced by inter-annual variation in population density, and space use decisions are often related to behavior and social structure. In this dissertation, I combined the results of field work, experimental assays, mapping, and modeling techniques to examine long-term behavioral and spatial dynamics in a high elevation population of golden-mantled ground squirrels (Callospermophilus lateralis), an asocial and presumably territorial species. In chapter one, I described and quantified litter relocation behavior -a poorly documented phenomenon, in which a female moves her litter to a new location -during long-term studies of two species of ground-dwelling squirrels: golden-mantled ground squirrels and yellow-bellied marmots (Marmota flaviventer). In this natural history study, I identified several possible costs (e.g., energy expenditure and predation risk while transporting young) and benefits (e.g., increased habitat quality and social benefits) of litter relocation, and highlighted the need to better understand habitat preferences and the role of kinship on space use in golden-mantled ground squirrels. Accordingly, chapters two through four focused on patterns of habitat selection, behavior, and the social and spatial organization of this species, with particular emphasis on the effects of density, behavior, and kinship on space use. Habitat selection dictates the distribution of individuals across space and time, which influences access to key resources such as preferred food items and cover from predators. As population density increases in high quality habitat and competition for limited resources becomes intense, animals are believed to preferentially settle in lower quality habitat, where they are equally likely to survive or reproduce due to lack of competition; however, studies that quantify density-dependent habitat selection or tie fitness measures to resource selection decisions in free-ranging animal populations remain rare. In chapter two, I quantified habitat selection in adult female golden-mantled ground squirrels across two spatial scales (home range placement, and occurrence within the home range) by using 11 consecutive years of data on individual space use, and I used compositional analysis, resource selection functions, and multilevel modeling to address how habitat preferences may be influenced by density or linked to fitness outcomes. Squirrels preferred dry meadow over all other habitat types (aspen, spruce, wet meadow, and willow) at both spatial scales, and were more likely to use dry meadow that contained shorter vegetation and vision-enhancing prominences such as rocks ("perches"). Use of dry meadow at each spatial scale was not influenced by changes in density, and use of dry meadow did not influence fitness (as measured by litter size, pre-hibernation mass, or survival). However, squirrels that experienced a greater number of perches or smaller local densities had higher survival rates, suggesting that a lack of visual obstruction, probably to promote detection of predators, drives habitat selection in this system. Surprisingly, squirrels maintained their preference for dry meadow as density increased, and they experienced reduced survival as a result, perhaps because marginal habitat of sufficient quality was not available. Although spatial patterns are typically studied at the population or species level, individual differences in space use dynamics often account for a substantial amount of the variation exhibited at higher levels of biological organization, and thus may act as a link between process and pattern in ecology. A growing body of research suggests that variation in patterns of space- and resource use in wild animals may in part be explained by consistent individual differences in behavior across time or contexts, a concept known as animal personality. In chapter three, I used repeated standardized assays to perform the first characterization of personality in golden-mantled ground squirrels, and I used multilevel modeling to determine if personality influenced 95% home range size, 50% core area size, movement speed, or use of perches in nature. Data collected over three years showed that squirrels consistently differed in activity, sociability, boldness, and aggressiveness, and that individual squirrels differed in space- and perch use in a non-random manner that was dependent on their personality type. I found that bolder individuals maintained larger core areas, more active and bold individuals moved faster, and more active, bold, and aggressive individuals had greater access to fitness-enhancing perches in their home ranges. I also found that sociability was associated with access to perches in the home range, suggesting there is a potential benefit within an asocial species of being relatively more social. Spatial organization may be influenced by kinship, and tolerance among kin is believed to play a role in the evolution of sociality. Ground-dwelling squirrels exhibit a wide range of sociality, from solitary to highly gregarious. Golden-mantled ground squirrels are considered to be asocial and presumably territorial, with the expectation that adults, including close kin, have home ranges that are distinct and non-overlapping; however, this classification was supported by sparse data. In chapter four, I characterized the spatial organization, including the role of kinship, in a population of golden-mantled ground squirrels, and I capitalized on changes in population size over 25 years to quantify the influence of density on that spatial organization. I found extensive overlap between female home ranges (30%), and between male and female home ranges (28%) after the breeding season. However, the core areas of adult female home ranges overlapped minimally (7%), suggesting squirrels were territorial, but only for the inner part of their home range. We did not find an effect of population density on home range or core area size, but local-level intruder pressure led to an increase in home range size, perhaps because females ranged farther to either gain familiarity with neighbors or shift into less crowded areas. Contrary to expectation, females shared more space with kin than non-kin, but only at high densities. This density-mediated increase in space-sharing among kin suggests that familiarity and inclusive fitness benefits may offset costs of competition and promote philopatry under certain conditions. Overall, I provide evidence of a facultative transition in this species from asociality to the formation of single-family kin clusters, the first step towards developing sociality. Together, these chapters further our understanding of the causes and consequences of changes in habitat use, providing insight to the fields of wildlife management and conservation. This work highlights how the personality of free-ranging animals may interact with environmental variables to differentially affect space- and resource use, with potentially important consequences for population-level processes. In addition, this dissertation emphasizes the importance of considering familiarity among neighbors in asocial species, as well as the interactive effects of environmental conditions and kinship when assessing the spatial and social organization of mammals. I hope this work serves as a valuable contribution to our understanding of ground squirrel ecology, as well as inspires future research that links individual processes to spatial patterns of wildlife populations in natural ecosystems.
Rodent Societies
Author: Jerry O. WolffPublisher: University of Chicago Press
ISBN: 0226905381
Category : Science
Languages : en
Pages : 627
Book Description
Rodent Societies synthesizes and integrates the current state of knowledge about the social behavior of rodents, providing ecological and evolutionary contexts for understanding their societies and highlighting emerging conservation and management strategies to preserve them. It begins with a summary of the evolution, phylogeny, and biogeography of social and nonsocial rodents, providing a historical basis for comparative analyses. Subsequent sections focus on group-living rodents and characterize their reproductive behaviors, life histories and population ecology, genetics, neuroendocrine mechanisms, behavioral development, cognitive processes, communication mechanisms, cooperative and uncooperative behaviors, antipredator strategies, comparative socioecology, diseases, and conservation. Using the highly diverse and well-studied Rodentia as model systems to integrate a variety of research approaches and evolutionary theory into a unifying framework, Rodent Societies will appeal to a wide range of disciplines, both as a compendium of current research and as a stimulus for future collaborative and interdisciplinary investigations.
Ecology
Author: Charles J. KrebsPublisher: Benjamin-Cummings Publishing Company
ISBN: 9780321068798
Category : Science
Languages : en
Pages : 695
Book Description
This best-selling majors ecology book continues to present ecology as a series of problems for readers to critically analyze. No other text presents analytical, quantitative, and statistical ecological information in an equally accessible style. Reflecting the way ecologists actually practice, the book emphasizes the role of experiments in testing ecological ideas and discusses many contemporary and controversial problems related to distribution and abundance. Throughout the book, Krebs thoroughly explains the application of mathematical concepts in ecology while reinforcing these concepts with research references, examples, and interesting end-of-chapter review questions. Thoroughly updated with new examples and references, the book now features a new full-color design and is accompanied by an art CD-ROM for instructors. The field package also includes The Ecology Action Guide, a guide that encourages readers to be environmentally responsible citizens, and a subscription to The Ecology Place (www.ecologyplace.com), a web site and CD-ROM that enables users to become virtual field ecologists by performing experiments such as estimating the number of mice on an imaginary island or restoring prairie land in Iowa. For college instructors and students.