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Articles 1 - 9 of 9
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The Columbia River As A Barrier To Gene Flow In The Vagrant Shrew, Sorex Vagrans Vagrans Baird, James J. Kirk
The Columbia River As A Barrier To Gene Flow In The Vagrant Shrew, Sorex Vagrans Vagrans Baird, James J. Kirk
Dissertations and Theses
Twenty-one morphological characters were measured in shrews from four islands in the Columbia River and from the adjacent Oregon and Washington shores. Information on the history and characteristics of the river islands was gathered to facilitate interpretation of the shrew’s morphology data. Significant differences between character means of different populations were detected and average taxonomic distances between pairs of populations were calculated. The Columbia River is an incomplete barrier to gene flow, but its influence has been sufficient to allow divergence of island populations. Natural selection on the small gene pools of island populations has probably contributed to the divergence. …
Some Aspects Of The Ecology Of The Virginia Opossum (Didelphis Virginiana Virginiana Kerr 1792) In An Urban Environment, David Hopkins
Some Aspects Of The Ecology Of The Virginia Opossum (Didelphis Virginiana Virginiana Kerr 1792) In An Urban Environment, David Hopkins
Dissertations and Theses
Eighty-three Didelphis virginiana from the Portland metropolitan area were collected and studied from December 1974 through May 1976. Males averaged 3394 g, females 2318 g. An annual sex ratio of 68.7:31.3 was recorded. Data indicate the possibility of a year-round breeding season and suggest the occurrence of three peaks of reproductive activity: January-February, April-May and October-November. The six primary foods consumed annually are: leaf litter, mammals, gastropods, earthworms, grasses and pet food. Seasonal composition and diversity in the diet is marked. Five new parasite-host records were established. These include mites: Androlaelaps fahrenholsi, Haemogamasus nidi, Eulaelape stabularis tick, Ixodes angustus, and …
Thermal Ecology And Movement In The Leopard Lizard, Gambelia Wislizeni, Baird And Girard, Marvin Lynn Abts
Thermal Ecology And Movement In The Leopard Lizard, Gambelia Wislizeni, Baird And Girard, Marvin Lynn Abts
Dissertations and Theses
Thermal ecology and movement of the Leopard Lizard, G. wistizeniwere studied at Frog Spring, adjacent to the Alvord Desert, and at various locations throughout the Alvord Basin. Seasonal activity is known to occur from early May to mid-October, but abundance. gradually decreases after late July. During favorable late spring, and summer weather lizards exhibit a bimodal pattern of diel activity with some activity occurring at all hours of the day between 0600 and 1800 H. At other times activity was unimodal. Emergence was apparently largely temperature dependent and did not occur until sand temperature approximated 21°C. Retreat appeared to …
The Chromosome Constitutions Of A Hybrid Salmonid And Its Parental Types: Salmo Gairdneri And Salmo Clarki, Peter Bruce Valentine Jacky
The Chromosome Constitutions Of A Hybrid Salmonid And Its Parental Types: Salmo Gairdneri And Salmo Clarki, Peter Bruce Valentine Jacky
Dissertations and Theses
A study was undertaken to investigate the application of tissue culture and histochemical banding techniques normally used in mammalian studies to fish cells and to examine the mechanisms of chromosome evolution and speciation in salmonids by comparing the chromosomes of the hybrid to those of the parental types. The application of banding techniques was generally unsuccessful in revealing bands, though quinacrine staining did reveal the presence of two fluorescent spots in the vicinity of the centromere. These were thought to be heterochromatic blocks, possibly related to the high incidence of centric fusion or fission in salmonids. Results of chromosome analysis …
A Survey Of Small Mammals On Islands In The Columbia And Willamette Rivers, Gayle Kirk
A Survey Of Small Mammals On Islands In The Columbia And Willamette Rivers, Gayle Kirk
Dissertations and Theses
A survey of small mammals on eight islands in the Columbia and Willamette Rivers near Portland, Oregon was conducted in 1974. The islands were Govermnent , Sand, Lemon, McGuire and Sandy Islands in the Columbia River and East, Ross and Hardtack Islands in the Willamette River. The objectives of the study were to ascertain and compare the kinds, distribution and relative densitites of small mammals . A variety of traps was used to capture the animals including Museum Special Rodent Traps , back- break mouse traps, scissor and guillotine- type stab mole traps , Sherman traps , modified Young traps …
The Androgenic Glands Of The Pacific Crayfish, Pacifastacus Leniusculus Trowbridgii Stimpson, 1859, Larry L. Sanders
The Androgenic Glands Of The Pacific Crayfish, Pacifastacus Leniusculus Trowbridgii Stimpson, 1859, Larry L. Sanders
Dissertations and Theses
The androgenic glands of the Pacific crayfish, Pacifastacus leniusculus trowbridgii Stimpson, 1859, were studied experimentally and by light and electron microscopy. The androgenic glands proliferate in the spring of the year concurrently with an increase in mitotic activity in the testes. Degeneration of a major portion of the glands occurs in the fall, when spermatogenic activity in the testes is near completion. Cellular development appears to progress from small undifferentiated cells through stages of vacuolization and hypertrophy and terminates with degeneration or lysis. The fine structure of the vacuolated gland cells is indicative of increased metabolic activity and probable hormone …
Mammals Of The Bull Run, Edward M. Thatcher
Mammals Of The Bull Run, Edward M. Thatcher
Dissertations and Theses
This study of mammals of the Bull Run Planning Unit has a dual character. First, mammals of special scientific or natural history interest such as threatened or endangered species were sought. This was in conjunction with a Mt. Hood Bull Run Planning Unit. Second, a zoogeographical study of mammals of the Bull Run was performed. Abundance and distributional data was recorded for each species observed. This data was related to availability to moisture as indicated by plant associations trapped. Difference in habitat utilization along a moisture gradient was investigated as a possible coexistence mechanism for sympatric small mammals in the …
Some Coyote Food Habitat Patterns In The Shrub-Steppe Of South-Central Washington, Peter Frederick Stoel
Some Coyote Food Habitat Patterns In The Shrub-Steppe Of South-Central Washington, Peter Frederick Stoel
Dissertations and Theses
Coyote food habits were ascertained by identifying the undigested material in 1143 scats collected at monthly intervals from specific road transects on the USERDA Hanford Reservation in Washington from 1974 to 1976. Tracks at artificially established scent posts along the principal transect provided evidence that the scats were left by coyotes and not bobcats or badgers. On the basin plain (150m elevation) where the Aptemisia tpidentata/Poa sandbepgii Association predominates, the average monthly percent occurrences in the 491 scats collected in 1975 2 were pocket mouse 60, leporid 39, pocket gopher 12, grasshopper 12, fruit 10, cricetine mice 7, darkling beetle …
Influence Of Light On Algal Growth In The Lower Willamette River, Stephen Arthur Wille
Influence Of Light On Algal Growth In The Lower Willamette River, Stephen Arthur Wille
Dissertations and Theses
During the summer of 1974 chemical conditions in the lower reaches of the Willamette River, Oregon were similar to those in other rivers currently experiencing nuisance algal growth problems. Temperature and chemical nutrients are not limiting. Relatively high populations of phytoplankton and productivity values for upstream periphyton beds and surface waters suggest moderately eutrophic conditions. However, with increased depth in the lower river, and a constant euphotic zone, the amount of photosynthetically available light is reduced. With sufficient depth and complete mixing the critical depth is exceeded. Primary productivity rates are subsequently limited by low light availability in the lower …