Ecology and Reproductive Strategies of the Arctic Ground Squirrel, Spermophilus Parryii PDF Download
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Author: Mark R. Simpson
Publisher:
ISBN:
Category : Arctic ground squirrel
Languages : en
Pages : 436
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Field work was conducted 7 km. northwest of the town of Rankin Inlet, Northwest Territories (now in Nunavut) during the summers of 1989 to 1991.
Author: Mark R. Simpson
Publisher:
ISBN:
Category : Arctic ground squirrel
Languages : en
Pages : 436
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Field work was conducted 7 km. northwest of the town of Rankin Inlet, Northwest Territories (now in Nunavut) during the summers of 1989 to 1991.
Author: Timothy J. Karels
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Populations of arctic ground squirrels in the boreal forest of the southwest Yukon were studied in order to answer the following questions: (1) What are the mechanisms of population regulation in arctic ground squirrel populations, (2) How does variation among individuals and their environment influence their reproduction and survival, and (3) How does variation in habitat influence hibernating strategies of arctic ground squirrels? In spring 1996, control densities of ground squirrels were 1.6 per ha, and four other populations ranged in density from 3.2 to 30.1 per ha as a result of a 10-year (1987-96) large scale manipulation of food and predators in the boreal forest of the Kluane Boreal Forest Ecosystem Project. When the Kluane project terminated in spring 1996, I measured population densities, reproduction, emigration, and survival in all populations using live-trapping and radio-telemetry techniques until spring 1998. Arctic ground squirrel populations were strongly regulated because all experimental populations declined to control densities within two years after the termination of the experimental manipulations. Two factors proved strongly density-dependent and hence were regulatory: (1) the proportion of females that weaned their litter and (2) overwinter survival. Simultaneous density-independent changes in weaning rate were also detected and were attributed to changes in the previous year's snow accumulation. Female ground squirrels exhibited positive associations of life history traits. Squirrels in better condition at spring emergence were more likely to give birth, wean their litter, survive to the next breeding season, and reproduce once again. Nearly all females who failed during lactation did not survive to the next breeding season. The overwinter survival rate of females that successfully weaned a litter declined at a greater rate with increasing population density than did squirrels that never gave birth, indicating a cost to reproduction. Ground squirrels hibernated distantly (24 m) from their summer burrows in relation to population density and in open or shrubby habitats that were likely to accumulate the most snow. Increased snow accumulation over hibernacula increased the minimum soil temperatures and decreased the rate of mass loss of hibernating squirrels suggesting a selective mechanism for the ability of ground squirrels to identify habitats that minimize their energy expenditure during hibernation.
Author: Eileen Anne Lacey
Publisher:
ISBN:
Category : Arctic ground squirrel
Languages : en
Pages : 486
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first mate. I found that male reproductive behavior varied as a function of mating order and, hence, the likelihood of siring young. Specifically, reproductive competition among males appeared to be most intense prior to a female's first copulation.
Author: Ian Gordon McLean
Publisher:
ISBN:
Category : Arctic ground squirrel
Languages : en
Pages : 149
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Doctoral thesis. Study of arctic ground squirrels near Haines Junction, Yukon, during the summers of 1977, 1978 and 1979. Includes four papers as appendices.
![Reproduction, Hibernation, and Population Regulation of Arctic Ground Squirrels (Spermophilus Parryii Plesius) [microform] PDF](https://books.google.com/books/content/images/frontcover/arEYAAAACAAJ?fife=w80-h100)
Author: Timothy J. (Timothy Jack) Karels
Publisher: National Library of Canada = Bibliothèque nationale du Canada
ISBN: 9780612538856
Category :
Languages : en
Pages : 366
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Author: Andrea Elizabeth Byrom
Publisher:
ISBN:
Category : Arctic ground squirrel
Languages : en
Pages : 412
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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.
Author:
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ISBN:
Category :
Languages : en
Pages :
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Author: Thomas Wynn Pearson
Publisher:
ISBN:
Category : Ground squirrels
Languages : en
Pages : 192
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Author: Vancouver Charles J. Krebs Professor of Zoology University of British Columbia
Publisher: Oxford University Press, USA
ISBN: 9780199771349
Category : Science
Languages : en
Pages : 542
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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.
Author: Arctic Aeromedical Laboratory (U.S.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 562
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