• Assessing The Health Of Harbor Seals In Alaska

      Trumble, Stephen John; Castellini, Michael (2003)
      Declining populations of pinnipeds in the Gulf of Alaska, possibly resulting from changes in prey quality, prompted research to determine the population health status of harbor seals (Phoca vitulina) using blood chemistry and digestive constraints. Blood chemistry and morphology reference range values between two harbor seal pup populations in Alaska, one population in continued decline, Prince William Sound, and another in recent increase, Tugidak Island, offered clues that blood values can vary on the population scale and that health assessment must utilize an appropriate set of reference values for valid comparisons. Subsequently, a captive study involving harbor seals yielded changes in ten blood chemistry or hematology values as a function of season and diet. These data provided evidence that populations may have distinct "identities" based on blood chemistry values. The "metabolic identity" of a population provides evidence of the relationship between environmental stressors and the genetic capacity of the animal to respond to metabolic demands. This made it possible to better understand population level differentiation in plasma chemistry values and thus assess the health of animals occupying the outlier regions of populations, since these regions are often suggestive of poor health. A captive study involving harbor seals, which are known to consume the low quality prey (pollock) implicated in the declines of many species of birds and mammals in the Gulf of Alaska, yielded consistent dry matter digestibility resulting in greater gut fill from pollock than from herring. Digestible energy intakes from pollock were greater than from either herring or the mixed diet. Lipid digestibility of herring declined from 90% to 50% when lipid intake exceeded 60 g kg -0.75 d-1. Results of this study imply that a flexible digestive system for harbor seals can compensate for ingesting a prey of low energy density by increasing gut fill and enhancing protein and lipid assimilation, to sustain digestible energy intake. In other words, harbor seals can offset differences in prey quality if prey availability and abundance does not limit the physiological plasticity of their digestive system to maintain their supply of energy and nutrients.
    • Comparative foraging ecology and social dynamics of caribou (Rangifer tarandus)

      Post, Eric Stephen; Klein, David R. (1995)
      The Southern Alaska Peninsula Caribou (Rangifer tarandus) Herd (SAPCH) and its two sub-groups were the focus of a study addressing the hypotheses: (1) food limitation during winter caused a decline in the herd; and, (2) higher calf productivity within the Caribou River group than within the Black Hill group was related to greater forage availability on the seasonal ranges of the Caribou River group. Intense, systematic range and calving surveys in 1991 and 1992 supported the hypothesis of food limitation during winter, and indicated that greater calf production in the Caribou River group was related to earlier commencement of the season of plant growth and greater forage availability on the summer range of that group, coupled with earlier parturition among females of the Caribou River herd. In a comparative study involving the two SAPCH groups and the West Greenland Caribou Herd, daily variation in sizes of foraging groups, densities of caribou within feeding sites, distances between individuals within feeding sites, distances moved by foraging groups, and frequency of group movement was modeled using the following ecological parameters: predation risk, insect harassment (by mosquitos), range patchiness, feeding-site patchiness, feeding-site area, and range-wide density of caribou. Models revealed that intraseasonal social dynamics of foraging caribou were governed in most instances by patterns of forage availability and distribution across landscapes and within feeding sites, in some instances by insect harassment and social pressures, but in no instance by levels of predation risk inherent to the ranges on which they foraged. In a study of the interrelationships between characteristics of graminoids and intensity of grazing by caribou, vegetation on each of the Black Hill and Caribou River ranges was sampled and tested for responses to clipping. Biomass density (g/m$\sp3$) of forage, shoot density (#/m$\sp2$), and nutrient and mineral densities (g/m$\sp3$) and concentrations (g/100g tissue) correlated positively with use of sites by caribou. Productivity and responses to clipping were independent of previous use, but consistent within ranges. These results indicate that caribou are sensitive to local variation in forage quantity and quality, and preferentially use sites with higher returns of nutrients and minerals.
    • Diet-induced thermogenesis in a carnivore, the arctic fox, Alopex lagopus

      Tallas, Peter George; White, Robert G. (1986)
      Carnivores consume diets low in carbohydrate and high in protein and fat. The high dietary levels of protein and fat are thought to contribute greatly to diet-induced thermogenesis (DIT), i.e. the increase in metabolic rate associated with feeding. Low dietary levels of carbohydrate cause the carnivore to stress gluconeogenesis. Consequently, a well developed capacity for gluconeogenesis may be an important adaptation in the carnivorous arctic fox (Alopex lagopus), and may participate in DIT. The objectives of this study of the arctic fox were to (i) determine DIT associated with four diets that varied in the proportion of fat, protein, and carbohydrate, and (ii) assess glucose utilization in the fed and fasted arctic fox. Fox were fed four diets (high protein, high fat, high carbohydrate, and high protein/fat) at three levels of energy intake (sub-maintenance, near/above maintenance, and above maintenance). Pre- and postfeeding metabolic rates were measured by open circuit indirect calorimetry. The results indicate that (i) DIT contributes significantly to total heat production of the fox, but is dependent on diet type and energy intake, (ii) DIT is non-existent at sub-maintenance energy intake, regardless of dietary nutrients, and (iii) the high fat diet is associated with the highest prefeeding and postfeeding metabolic rate at sub-maintenance energy intake, although DIT is non-existent at all levels of energy intake. For the assessment of glucose turnover, four arctic fox were fed, over a long term, a low carbohydrate, high protein/fat diet. Fed and fasted fox were injected intravenously with radiolabeled glucose, and their blood assayed over time for disappearance of the labeled glucose. The results indicate that glucose metabolism, i.e. total entry rate and irreversible loss, is high compared to other animals, and may support the high blood glucose concentrations of the arctic fox, but does not participate in DIT.
    • Habitat selection by mule deer: Effects of migration and population density

      Nicholson, Matthew Christopher (1995)
      I investigated effects of migration and population density on habitat and diet selection in a population of mule deer (Odocoileus hemionus) in southern California from 1989 to 1991. All male deer were migratory, whereas females exhibited a mixed strategy with both migrant and resident individuals. No difference occurred in sizes of home ranges for migratory or resident deer. Home-range size of deer was smaller in summer than in winter, however. Size of home range was positively associated with proximity to human disturbance and the amount of avoided habitat (use $<$ available) in the home range. Deer avoided human disturbance in all seasons. Clear tradeoffs existed for deer in montane southern California with respect to whether they migrated. Migratory females were farther from human disturbance and used high-quality habitats more often than did their nonmigratory conspecifics. Nonetheless, during migration deer were at increased risk of predation, and in years of low precipitation (low snow) had higher rates of mortality than did resident deer. Thus, in areas with extremely variable precipitation and snow cover, a mixed strategy for migration can be maintained. Migration patterns of deer resulted in drastic shifts of population density between seasons as deer migrated into and out of ranges. Quality of diet (as indexed by fecal crude protein) for deer in a low-density area was higher than that of a high-density area in winter, when deer densities were most different. Diet quality was similar in summer when both areas had similar densities of deer. Contrary to predictions of the ideal-free distribution, diet quality was different between the two areas in autumn when population densities were similar; this may have been due to an elevated availability of graminoids on the high-density area. Niche breadth, as measured by diet diversity, differed in a manner opposite to the predictions of the ideal-free distribution. During winter, when differences in density between the two study areas were most evident, niche breadth along the dietary axis in the low-density group was twice the size of this measure for the high-density area. Theoretical models for changes in niche dimension need to consider such empirical outcomes.
    • Habitat Utilization By Sea Otters (Enhydra Lutris) In Port Valdez, Prince William Sound, Alaska

      Anthony, Jill Ada Marie; Fay, Francis H. (1995)
      Environmental constraints and human activity influence sea otter habitat use in Port Valdez. Nonetheless, a small subpopulation consistently uses food and space resources there. Otter number, distribution, response to human activity, energetics, and behavior in the Alyeska Marine Terminal (an industrial area) were compared to Shoup Bay (an area with low human activity) from September 1989 to September 1991. Low numbers averaged 102 otters monthly and were predominantly juvenile males. Shoup Bay densities were higher than the Terminal. Terminal boat traffic was more than twice Shoup Bay, resulting in more otter encounters with moving boats and more behavioral changes. Petroleum hydrocarbon levels were low or undetectable in mussels, the main otter prey in the port. Diets varied more in the Terminal than Shoup Bay. Despite lower mussel caloric content in Shoup Bay, otters spent significantly more time feeding at the Terminal. Time-activity budgets in Shoup Bay were more variable. <p>
    • Influence of weather on movements and migrations of caribou

      Eastland, Warren George (1991)
      Caribou (Rangifer tarandus granti) are typified by use of calving grounds and by making twice-annual migrations between summer and winter ranges. This study used satellite technology to examine the influence of weather on calving site selection, autumn and spring movements, and timing and directionality of migrations of the Porcupine Caribou Herd (PCH) that calves in northeast Alaska and northwestern Canada adjacent to the Beaufort Sea. The reigning hypothesis that females select areas that become free of snow early for calving sites was rejected because females selected areas of $>$75% snowcover ($P=0.02$) preferentially for calving. Benefits from use of mottled snow for calving were access to vegetation in its early phenological stages and protection for their calves from predators. Access to nutritious forage and predator avoidance appeared to be the main reasons for calving site selection. Multiple linear regression models were used to examine rate and direction of autumn and spring migrations using weather data from U.S. and Canadian sources. Weather was found to be both an ultimate and an approximate influence on the rate and direction of autumn migration ($P<0.05$). Explanatory power of the equations was low ($R\sb{a}\sp2<0.41$). Proximal causes of movement were best explained by caribou tracking of vegetation phenology. Pre-rut movements in September lacked concurrence between rate and direction whereas rate and direction were related in October. Models of spring migration of parturient females indicated a common timing among years, late April and early May, and movements were significantly affected by weather ($P<0.02$), in particular snow depths and conditions that would affect foraging and traveling conditions. This study suggests that: (1) females preferentially use areas of delayed snow melt for calving, and (2) weather influences both spring and autumn migration of caribou, although the effect of weather may be more indirect than direct.
    • Investigations of health status and body condition of harbor seals (Phoca vitulina) in the Gulf of Alaska

      Fadely, Brian Scott; Castellini, Michael A. (1997)
      Harbor seal (Phoca vitulina) declines during the past 20 years in the Kodiak Island and Prince William Sound regions contrast with stable or slightly increasing populations in southeastern areas of Alaska. Aspects of health status and body condition were investigated to test the hypothesis that these declines were driven by nutritional limitation, and to determine whether recent differential population trajectories among Kodiak Island, Prince William Sound, and southeast Alaska could have health-related components. For comparisons between 1992-96, three aspects of health status were examined; blood chemistry, blubber distribution and quantity; and blubber quality. Clinical ranges of plasma chemistries and hematologies were established for free-ranging seals in the Gulf of Alaska. Significant handling, individual, and seasonal effects were found on many blood parameters that could bias interannual and interregional comparisons if not incorporated in models. Based on statistical modeling, some seals showed more clinically aberrant values than expected by chance, but these were not clumped among regions or years. Differences existed in interannual blood chemistry and hematology patterns between juveniles and adults. Likewise, there were regional differences in blood chemistries of unknown significance. Morphometric indices were poor indicators of condition defined as size-at-age or blubber content. This was related to patterns of blubber distribution and variability, which differed between males and females. Blubber quality, measured as lipid content, did not substantially vary seasonally or between geographic regions, but blubber from Prince William Sound was less hydrated than blubber from non-declining areas. There were no detectable differences in body condition of seals from the Gulf of Alaska sampled during 1963/64 (pre-decline), 1976-78 (during decline) and 1995-96. However, sample sizes were small and patchily distributed throughout locations and years. Thus, the likelihood of detecting body condition changes in response to environmental conditions was poor. Body condition was not substantially different among seals from Prince William Sound, Kodiak Island and southeast Alaska measured during 1993-96. However, interannual blood chemistry and body condition patterns were evident among Prince William Sound seals that may have been associated with environmental conditions.
    • Lynx And Coyote Diet And Habitat Relationships During A Low Hare Population On The Kenai Peninsula, Alaska

      Staples, Winthrop R., Iii; Dean, Frederick C. (1995)
      Food habits and habitat use of lynx and coyote were compared 1987-1991 on the Kenai Peninsula, Alaska when the snowshoe hare population was low ($<$0.5 hares/ha). During snow seasons, lynx fed primarily on hares (64% total items), whereas coyotes relied heavily on moose carcasses (42% total items). Diet overlap was 42% and hare use overlap was 16%. Habitat use overlap was 92%, but coyotes used roads more than lynx. Both carnivores selected 1947 burn and avoided 1969 burn and large expanses of mature forest. I conclude that there was exploitation competition for food between these predators, because both used the same habitats and hares, a major food, were scarce. The coyote, however, may be using resources that were previously used by red fox, which have been reduced to low levels. Lynx displayed little fear of humans and were vulnerable to shooting incidental to hunting and depredation events. <p>
    • Maternal Investment And Habitat Selection By Dall's Sheep

      Rachlow, Janet L.; Bowyer, R. Terry (1991)
      Maternal behaviors and selection of habitat during lambing by Dall's sheep (Ovis dalli) were studied in Denali National Park and Preserve, Alaska, from April through July in 1988 and 1989. Climatic conditions in early spring differed between years; plant phenology was delayed by two weeks in 1989. Births were later and less synchronous in 1989. Females appeared to respond to variation in timing of births by modifying patterns of maternal investment; ewes nursed lambs for greater total time following parturition, but reduced total time spent nursing more rapidly in 1989. Selection of habitat characteristics varied with lambing chronology; terrain features related to avoidance of predators and sites with milder climatic conditions were selected during peak lambing. Variation between years in group sizes strongly influenced habitat selection. When corrected for variation in group size, no significant differences between years in selection of habitat were identified. <p>
    • Nutritional and ecological determinants of growth and reproduction in Caribou

      Gerhart, Karen Lynn (1995)
      I investigated the mechanisms by which differences in body weight and body composition (fat, protein) of female caribou (Rangifer tarandus granti) from the Central Arctic and Porcupine herds might determine changes in pregnancy rate and calf growth. Allometric relations between chemical components and body weight variables were highly significant, despite tremendous seasonal changes in composition. Between October 1989 and May 1990, body fat and body protein of adult females of the Central Arctic Herd declined by maxima of 45 and 29%, respectively; an additional 32% of fat was lost by July. Extensive mobilization of fat and protein indicates winter undernutrition. Marked hypertrophy of liver and kidneys in summer suggests the presence of mobilizable protein reserves. Birth weights of calves were similar between sexes, but male calves grew relatively faster during summer and were significantly heavier than females in autumn. Both fat content and growth rate of calves declined between 4 and 6 weeks post-calving, perhaps in response to insect harassment. Weight gains of wild calves were greatly reduced or absent after 100 d of age, while captive calves continued to grow until 175 d, suggesting that first-summer growth of caribou is determined in part by nutrient availability. Birth weight and growth rate of wild calves from birth to 3-4 weeks of age accounted for nearly 79% of the variability in autumn weights, again implying summer nutrient limitation. Female caribou were unable to entirely compensate for the metabolic and ecological costs of lactation: in autumn, lactating females had 42% less fat and 9% less protein than nonlactating females. Unlike females from the Central Arctic Herd, those from the Porcupine Herd did not demonstrate compensatory weight gains over summer; instead, autumn weight was highly correlated to June weight. Probability of pregnancy was positively correlated with body weight and fat content in early winter. Females that extended lactation into November were less fertile than predicted by body size or condition. I believe that these females were exhibiting lactational infertility.