Thesis (M.S.)--Ohio State University. / Bibliography: leaves 99-103. Available online via OhioLINK's ETD Center

Trichostrongylus tenuis is a nematode that lives in the caeca of wild red grouse. It causes disease in red grouse and can cause fluctuations in grouse pop ulations. The aim of the work described in this thesis was to study aspects of the ecology of the infective-stage larvae of T.tenuis, and also certain aspects of the pathology and immunology of red grouse and chickens infected with this nematode. The survival of the infective-stage larvae of T.tenuis was found to decrease as temperature increased, at temperatures between 0-30 C? and larvae were susceptible to freezing and desiccation. The lipid reserves of the infective-stage larvae declined as temperature increased and this decline was correlated to a decline in infectivity in the domestic chicken. The occurrence of infective-stage larvae on heather tips at caecal dropping sites was monitored on a moor; most larvae were found during the summer months but very few larvae were recovered in the winter. The number of larvae recovered from the heather showed a good correlation with the actual worm burdens recorded in young grouse when related to food intake. Examination of the heather leaflets by scanning electron microscopy showed that each leaflet consists of a leaf roll and the infective-stage larvae of T.tenuis migrate into the humid microenvironment' provided by these leaf rolls. Scanning electron microscopy showed that the adult nematodes burrowed into the mucosa as well as lying on its surface and that the caecal mucosa of heavily infected grouse became disrupted in areas of nematode activity. The caecal mucosa of lightly infected grouse exhibited little damage and the caecal mucosa of grouse treated with an anthelmintic and shot 5-6 months later was similar to that of lightly infected birds. Some of the nematodes from these treated birds were covered in rosette-shaped cells which have been tentatively identified as adherent lymphocytes. The cuticle of adult T.tenuis was superficially annulated but did not possess cuticular ridges, as described in some other trichostrongyle nematodes. Primary and challenge infections with T.tenuis were established in the domestic chicken and these reached patency but nematodes were expelled in blood-stained balls of mucus and all adult nematodes had been expelled from the birds 30 days after dosing with infective-stage. Following trickle doses of larvae, there was a rise and then a fall in nematode egg output but larvae administered later in the trickle infection appeared to fail to establish. Light and scanning electron microscopy showed haemorrhagic lesions and blood spots on the caecal mucosa of infected chickens and nematodes were found to burrow beneath mucus secreted on the mucosal surface. There were significant increases in the proportions of circulating leucocytes in infected chickens, but only on certain days of infection. No antibodies to T.tenuis were detected in the blood of infected chickens. There was a decrease in the length of the caeca of infected chickens during the period when the Ill nematodes were being expelled from the caeca. Nematode egg output continued to rise during an infection in young red grouse and there was no expulsion of nematodes from these infected birds. Infective-stage larvae that had been attenuated by cobalt 60 irradiation stimulated some degree of resistance to challenge infection in the domestic chicken but not in the red grouse. It was concluded that immunization with irradiated larvae would be of little use in the control of T.tenuis in red grouse.

The pathological effects of infections of Dlspharynx nasuta (Nematoda: Acuariidae) on confined, experiment ally-infected chicks of the blue grouse, Dendragapus obscurus, have been studied. The severity of the infection was found to be directly proportional to the number of worms present and the youth of the host. The development of the lesion produced at the site of infection, the proventriculus of the host, is described and its papillomatous nature confirmed. The previously unknown developmental stages of D. nasuta in the avian host are described and related both to the formation of the lesion and to the disease process. The growth of infected birds, expressed as gain in weight, was less than that of the controls although food intake studies indicated that the amount of food eaten by both groups was comparable. Calcium and phosphorus analyses on bones gave no indication that the mineral metabolism of infected birds was affected although their bones broke more readily than those of the controls. Development of the Juvenal feathers which appear from 3 to 5 weeks of age may be severely retarded. These observations suggest that the protein metabolism of the host is impaired. The numbers of hemocytes of infected grouse fluctuate greatly and show two critical low periods. The first, occurring immediately after infection, can be correlated with the invasion of the larvae and possibly to a substance secreted by them. The second occurs 2 to 3 weeks after initial infection and can be correlated with local irritation and hemorrhages and perhaps the moult of the larvae. Chronic hematological symptoms are anemia and leucocytosis. The latter is characterized by heterophil ia, eosinophilopenia, lymphocytosis of small forms and lymphopenia of the larger forms. The presence of circulating antibodies for D. nasuta was not demonstrated with the techniques used. The evidence suggests that the host tissue reaction may be an allergic response. Several ecological questions concerning the survival of D. nasuta during the winter months, temperature for larval development in the intermediate host, longevity of adult D. nasuta in the definitive host, infection and reinfection of adult blue grouse, are considered. In the laboratory, infections of 16 and 22 worms, administered to the host before 2 weeks of age, were fatal. Results of these experiments indicate that D. nasuta is a debilitating pathogen which may prove fatal and, may act as a controlling factor of natural grouse populations. / Science, Faculty of / Zoology, Department of / Graduate

The late spring and slimmer diet of blue grouse on lowland breeding ranges on Vancouver Island was determined by examination of the contents of 875 crops taken from birds collected on 3 study areas in the years 1950 through 1952 and 1957 through 1966. The spring and early summer diet of males was mostly conifer needles, while adult females ate mainly leaf material and flowers during the same period. The food of chicks was mainly invertebrates until the birds reached the age of approximately three weeks, at which time plant material formed the greater portion of the diet. In late summer the diet of both adult and juvenile grouse was primarily fruits and seeds of trailing blackberry, salal, huckleberry, and other plants. Selection of plant foods occurred at the time of ovulation and moult. As a result, the protein and mineral content of the diet was highest during periods of greatest need. No apparent differences in the spring diet of females were found which could be related to poor early survival of chicks, or to a delayed hatch in 1962. The various food types were eaten in similar relative proportions by adult and yearling grouse, and differences in reproductive performance of these two age classes could not be related to the diet of the grouse. The altitudinal migration of blue grouse in late summer and autumn does not appear to be related to the availability or condition of the food supply at the time of departure of the birds. / Science, Faculty of / Zoology, Department of / Graduate

A general property of animal populations is their failure to continue increasing in number indefinitely, even when the habitat may contain enough resources to support more animals than are present at the time. Certain populations of blue grouse have expressed this property by failing to increase when the habitat has undergone changes that have produced striking increases in past cases. Other populations have expressed it by arresting their increase before the resources of the habitat were exhausted. In blue grouse populations on Vancouver Island, adult mortality is constant and it is restricted recruitment that has held these populations stable in the periods they have been studied, even though sufficient young have been produced to support an increase. The hypothesis that the behavior of territorial adult males affects the local occurrence of recruits and other grouse in general on the summer range was tested by studying dispersion during the breeding period. Information on dispersion and social behavior were obtained from nine grouse fitted with miniature radio transmitters. Data from non-instrumented birds supplement this work. The principal finding is that there was no evidence of social interaction causing females and immature males to occur in special places, and that no interaction of a sort that could affect recruitment occurs between blue grouse on their summer range. It is alternatively suggested that such behavior occurs in winter. Other conclusions are that the onset of estrus induces hens to seek out and become localized near a mate, that several hens may seek out the same mate, and that no lasting pair-bonds are formed. Each type of reproductive activity in blue grouse has a distinctive movement pattern, and perhaps movement rate, associated with it. Excepting for hens In estrus who briefly seek out mates, and some yearling males who are prevented by adults from remaining on territories, movements and local occurrence within the breeding range are unaffected by social interaction with other grouse. / Science, Faculty of / Zoology, Department of / Graduate

The dispersion of a population of blue grouse was analyzed using data from a breeding range on east-central Vancouver Island. During the summers of 1959-1962, the locations, densities, habitat preferences, and behaviour of grouse were studied using several habitats with varying densities of vegetation. A removal experiment was performed in different habitats to test the effect of interaction and selection of habitat on the dispersion of males. All adult males and a few yearling males were territorial, and territories were spaced in a near-uniform pattern. Within a given season, males removed from their territories were seldom replaced by other adults, suggesting that no surplus of non-territorial adults was present. About half of the yearling males were prevented from establishing territory by the presence of adults, and these yearlings were attracted to the vicinity of territorial males. The location of territories by newly-adult males did not depend significantly on the number of territories already present, even though the tendency toward uniform spacing was preserved. Comparison with other studies indicated that territory size and possibly the fraction of yearling males in the population were inversely related to the density of males. Females restricted their movements while on the breeding range but were not territorial. No pair-bonds were observed but females stayed near territorial males prior to nesting. After the hatch, the locations of females and broods bore no relation to each other or to the positions of males. Interaction apparently had no effect on breeding numbers. All birds preferred sparse vegetation to dense. When compared to randomly-chosen points, territories were found more often in areas with sparse vegetation, elevated points, and patches of open ground. Within open habitats, nests were usually located where cover by logs, stumps, and ground-level vegetation was high, and cover by dead plants and litter was low. Broods were associated with moist areas and other areas having heavy cover by vegetation at the ground level. Chicks apparently dispersed widely between their first and second summers. In their third summer, males usually returned within one-half mile of the positions they used as yearlings. Once territories were established, the owners returned to them in succeeding summers. Females one year and older showed a fairly accurate return to their previous locations. The dispersion was described somewhat theoretically by considering the summer population to be grouped into two types of aggregations. The first, found in the earlier half of the summer, was caused by the attraction of yearling males and lone females to territorial males. Later, hens with their broods were the dominant groupings. The spacing, movements, and habitat preferences seemed to be adaptations allowing such populations to rapidly exploit new habitats. / Science, Faculty of / Zoology, Department of / Graduate

In Oregon, sage grouse (Centrocercus urophasianus) were common in the eastern portion of the state. Since 1940 populations declined because of decreased productivity. The western subspecies (C. u. phaios) was listed as a candidate for threatened and endangered status in 1985 because of declines in Oregon and Washington and extirpation from British Columbia. Habitat availability and habitat condition were factors associated with impaired productivity. Stand structure and forb availability were characteristics most associated with habitat selection by hens with broods. The objectives of this study were to determine habitat use and selection by hens with broods and the relationship between food availability, habitat use by hens, and diets of juvenile sage grouse. Of the 2 study areas used, Hart Mountain had greater long term productivity and abundance than Jackass Creek. Use of cover types and habitat components were compared within and between study areas. In this study, sage grouse hens selected low sagebrush (Artemisia sp.) cover types during early brood-rearing then switched to use of big sagebrush cover types during late brood-rearing. In general, cover types used selectively had greater availability of forbs, and changes in forb availability within cover types from early to late brood-rearing corresponded to changes in cover type use. Differences in forb availability between study areas may have affected productivity. Hens at Jackass Creek selected sites with forb cover similar to that available to broods at Hart Mountain and home ranges were larger at Jackass Creek. Furthermore, diets of juvenile sage grouse were higher in forbs and insects at Hart Mountain. Larger home ranges and less nutritious diets were potentially responsible for lower productivity at Jackass Creek. Results indicated that management to improve brood habitat should focus on maintenance of cover type diversity and availability of forbs. / Graduation date: 1993

Thesis (M.S.)--Oregon State University, 2002. / Typescript (photocopy). Includes bibliographical references (leaves 38-45). Also available online.

The interaction between the parasite Trichostrongylus tenuis and food quality was investigated in red grouse Lagopus lagopus scoticus, to determine the cause of variation in population cycles between different areas (Scotland and England). Analysis of long-term data, field experiments and population modelling were carried out. Food quality, in terms of nutrient content of heather, was lower on Scottish grouse moors than on English moors. Parasite burdens were also lower in Scottish grouse populations, than in English grouse populations. A three-way interaction, between food, parasites and area (ScotlandlEngland), acting on breeding production, could explain the variation in population cycle period between areas. However, body condition of grouse was not affected by a food-parasite interaction. Experimental manipulation of food quality and parasite burden did not influence the breeding production of female grouse. Modelling the effects of a food-parasite interaction on grouse populations provided evidence that such an interaction could explain variation in cycle period between areas, although other factors are likely to be important in some cases. Red grouse are not unique, as other species also have cycles driven by food and parasites. Other species do not show cyclic population fluctuations because of having shared parasites, and a strong immune response. There is a specialist predator-prey relationship between red grouse and T. tenuis.

Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 90-100). Also available on the World Wide Web.