• A Multiple Stable Isotope Study Of Steller Sea Lions And Bowhead Whales: Signals Of A Changing Northern Environment

      Dehart, Pieter Andrew Philip; Wooller, Matthew J. (2006)
      The North Pacific and Arctic marine realm is currently experiencing dramatic environmental changes as a result of global climate change. Stable isotope analysis of western arctic bowhead whales (WABW, Balaena mysticetus ) and Steller sea lions (SSL, Eumetopias jubatus) were conducted to examine the influence of these changes on life history characteristics (migration and foraging) of these marine mammals. WABW baleen plates were analyzed for their stable oxygen and hydrogen isotope composition (delta 18O and deltaD) and were compared to the delta18O and deltaD in water and zooplankton prey along their seasonal migratory route. The delta18O and deltaD varied along the baleen (8 to 18�; -180 to -80�, respectively) and corresponded to stable isotopic differences in zooplankton from the winter (Bering Sea) and summer (eastern Beaufort Sea) habitats of WABW. Baleen delta18O and deltaD confirmed the seasonal annual migration of WABW and were subsequently compared to historical sea ice concentrations (SIC). This illustrated that WABW migration patterns appeared to have altered concomitant with changes in SIC. Years with a higher SIC (colder climate regimes) correlated with the largest difference in deltaD between winter and summer in WABW baleen during the period from 1972 to 1988. For a similar time period (1955 to 2000), the feeding ecology of SSL was also examined by analyzing the stable carbon and nitrogen isotope compositions (delta13C and delta 15N, respectively) of archived SSL bone and tooth collagen. Both delta 15N and delta13C varied greatly with location and sample year (14.6 to 20.5�; - 16.7 to -11.8�, respectively), with a significant change in delta13C observed around the 1976 regime shift. Bottom-up processes may have limited growth of SSL populations throughout this region over time, with animals focusing their foraging on offshore regions to mitigate this environmental change. Stable isotope analyses of historical samples of WABW (baleen) and SSL (bone and tooth collagen) both illustrated that recent environmental changes influenced the ecology (migration and feeding) of these marine mammals in the recent past.
    • 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.
    • Cytogenetics and sex determination in collared lemmings

      Jarrell, Gordon Hamilton; Shields, Gerald F. (1989)
      Collared lemmings (Dicrostonyx groenlandicus rubricatus) from northeastern Alaska were found to have sex chromosomes that differ from those of their Siberian congeners, because of fusion to a particular pair of autosomes. But, as in Siberian lemmings, breeding experiments showed that sex determination involves an X-linked "male-repressor," which causes carriers to develop as fertile females, despite the presence of a Y chromosome. Genotypic frequencies in offspring are consistent with Mendelian expectations of such a system, hence natal sex ratios normally favor females. X-linkage of the male-repressor in Siberia and in Alaska indicates that the gene is probably located on the "original" arms of the X chromosome rather than on the fused autosomal arms, which differ on the two continents. One consequence of the autosomal fusion to the sex chromosomes is that deleterious recessive alleles on the autosome fused to the X chromosome are more resistant to selection than at truly autosomal loci. Another consequence is that, because males are heterozygous for loci fused to the sex chromosomes, they are more resistant to inbreeding depression than XX females. One inbred line produced a natal sex ratio of 67% males. The male-bias probably resulted from loss of the male-repressor and from a lethal carried on the formerly autosomal arm of the X chromosome. As inbreeding coefficients approached 0.3, the lethal would have been homozygous in half of the homogametic (female) zygotes. This phenomenon may explain the excess of males and XY females observed in earlier work. Also, if under the natural mating system, inbreeding depression limits fitness, then fusions of autosomal chromatin to the heterochromosomes could be an adaptation to reduce inbreeding depression in heterogametic individuals. Some other genetic features of collared lemmings do suggest endogamy. Female-biased sex ratios can evolve when mating occurs between neighboring individuals who are more related than if mating occurred randomly. Two proposed sources of such "viscous" gene flow in lemmings are cyclical changes in population density and mosaic habitat. Alternatively, could climate may favor winter aggregation and inhibit the dispersal of winter-born offspring, which would mature and mate with close relatives; dispersal and outbreeding would occur in summer. Thus, inbreeding would be seasonal rather than density-dependent and it is unnecessary to suppose discontinuous habitat.
    • 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.
    • Ecogeographic, Adaptive, And Phylogenetic Variations In The Crested Duck (Lophonetta Specularioides) And Their Hemoglobins In The Andes

      Bulgarella, Mariana; McCracken, Kevin; Takebayashi, Naoki; Tubaro, Pablo L.; Winker, Kevin S. (2010)
      Tolerance to high-altitude hypoxia in animals varies widely and is a key factor in determining survival at high elevation. The Andean Cordillera of South America, which spans large elevational and latitudinal gradients, enables the study of native highland populations and the characteristics of hemoglobin proteins that are locally adapted for high-altitude respiration. The waterfowl populations of South America are understudied, little data on demographics and behavior are currently available, and only recently have they been investigated using molecular tools. We studied population genetics, phylogeography, and ecogeographic variation in the crested duck ( Lophonetta specularioides). The crested duck is a dabbling duck, and it comprises two subspecies endemic to highland and lowland regions of South America. The primary objective of this study was to investigate the genetic differentiation between highland and lowlands populations of crested ducks using molecular markers with varying modes of inheritance and rates of substitution. The second objective was to evaluate morphological differences between the subspecies to better understand the forces shaping morphology in the two different environments. A third objective was to provide additional information on the taxonomic relationships and natural history of the crested duck. First, we examined the population genetics of the three adult hemoglobins (alphaD, alphaA, betaA), six autosomal introns, and mtDNA. This multi-locus analysis revealed a significant pattern of differentiation between highland and lowland populations. Four hemoglobin amino acid replacements were found in crested duck that may play a role in influencing high-altitude respiration. The lack of evidence for gene flow for hemoglobin alleles between highland and lowland populations and the biochemical properties of the amino acid substitutions themselves are consistent with the effects of selection acting on these loci. Overall body size was larger for the highland subspecies, body size was intermediate in mid-elevation environments, and smaller individuals were found in the lowlands of Patagonia. We also performed a multi-locus phylogenetic analysis to determine the relationships of Lophonetta within the South American duck clade. Finally, we determined the proportion of genes expressed in bone marow of adult crested duck finding mostly genes related to hemopoietic and immune function.
    • Epizootic Of Beak Deformities In Alaska: Investigation Of An Emerging Avian Disease

      Van Hemert, Caroline; O'Hara, Todd; O'Brien, Diane; Handel, Colleen; Blake, John; Sharbaugh, Susan (2012)
      The sudden appearance of morphological abnormalities in a wild population is often associated with underlying ecological disturbances, including those related to introduction of new pathogens or pollutants. An epizootic of beak deformities recently documented among Black-capped Chickadees (Poecile atricapillus) and other resident bird species in Alaska has raised concern about underlying causes. This dissertation describes results from several recent studies of what we have termed "avian keratin disorder." The primary objectives of the research were to characterize the physiology and pathology of beak deformities and to address specific ecological questions related to this emerging avian disease. In a study of beak growth rates in captive chickadees, I determined that accelerated epidermal growth is the primary physical mechanism by which beak deformities develop and are maintained. Affected birds also exhibited high rates of mortality and skin lesions, suggesting that this disorder significantly compromises individual health. I used radiography, histopathology, and electron microscopy to describe the pathology of avian keratin disorder. As part of this effort, I established baseline information about normal passerine beak and claw structure and developed methods for processing hard-cornified tissues. The suite of lesions that I observed in affected chickadees does not correspond with any known avian diseases, suggesting the presentation of a novel disorder in wild birds. In addition, the detailed characterization of gross and microscopic changes has allowed me to eliminate a number of likely etiologies, including nutritional problems, microbial pathogens, and select toxicants. As a complement to diagnostic pathology, I conducted field studies to investigate possible causes and patterns of occurrence of beak deformities. I used stable isotope analysis to investigate the association between diet and beak deformities. I found that winter dietary patterns differed between chickadees with normal beaks and those with beak deformities, but that such differences are more likely a result than a cause of avian keratin disorder. My field research on Northwestern Crows in Alaska confirmed high prevalence of a nearly identical condition to that observed in chickadees. These findings indicate that avian keratin disorder affects multiple, ecologically-distinct species across a large geographic area. Together, the studies presented in this dissertation provide new insights and identify priority research areas for a rapidly emerging disease in wild birds.
    • Factors affecting the growth of a black guillemot colony in northern Alaska

      Divoky, George Joseph (1998)
      Annual variation in breeding populations at seabird colonies has been well documented, but there have been few long-term attempts to examine the environmental and demographic forces responsible. I studied breeding chronology and demography Black Guillemot in northern Alaska from 1975-1997 to identify the factors responsible for colony establishment and growth. The Black Guillemot is a cavity-nesting seabird whose populations are frequently limited by nest-site availability. Snowmelt in spring and snow accumulation in autumn had major effects on annual nesting initiation and success, respectively. Annual arrival at the colony and median date of egg laying was well correlated with the date of snow disappearance, with annual clutch initiation advancing 4.5 days per decade in response to regional climate amelioration. Successful breeding requires a snowfree cavity for ${>}80$ days. Decreased breeding success and post-fledging survival occurred in a year with a snow-free period ${<}80$ days. Historic weather records indicate annual snowfree periods ${>}80$ days were uncommon until the 1960's, when the species was first recorded breeding in northern Alaska. When additional nest sites were provided, growth of the colony was rapid, increasing from 18 pairs in 1975 to 225 pairs in 1989. Breeding numbers then decreased to 150 in 1996 as factors other than nest-site availability controlled population size.
    • Foraging ecology and conservation biology of African elephants: Ecological and evolutionary perspectives on elephant-woody plant interactions in African landscapes

      Dudley, Joseph Paine; Bryant, John P. (1999)
      The available scientific evidence indicates that African forest elephants and bush elephants are ecologically and evolutionarily distinct taxa. The current practice of regarding these two taxa as ecotypes of a single species, Loxodonta africana (i.e., L. a. africana Blumenbach 1797, L. a. cyclotis Matschie 1900) appears unwarranted, and obscures issues of major significance to the conservation biology of African elephants. Under a proposed taxonomic revision, the African bush elephant retains the designation Loxodonta africana Blumenbach 1797 while the African forest elephant is recognized as Loxodonta cyclotis Noack 1906. The browsing of woody plants by African bush elephants is a major factor in the structural dynamics of semi-arid woodland and scrubland habitats in Hwange National Park (HNP) and the Sengwa Wildlife Research Area (SWRA), Zimbabwe. Drought, frost and fire also influence the structure and species composition of woody vegetation within HNP. Interactions among these three abiotic factors and elephant browsing may have significant impacts on the dynamics of semi-arid woodland and scrubland habitats of HNP. Mortality attributable to elephant damage was identified as a principal cause of death among large trees (>5.0 in height), and a relatively minor but not insignificant cause of death for shrubs and trees in the 1.0--5.0 in height class. The responses of Colophospermum mopane in SWRA to fertilization treatments corresponded to those predicted by the carbon/nutrient hypothesis of plant anti-herbivore defense. Comparisons of these results with those of previous studies suggest possible changes in the ecology and population biology of elephants in HNP during the past decade. Observed differences in the age-specific mortality of elephant in HNP during die-offs in 1993--1995 and 1980--1984 provide independent evidence of changes in the ecology of elephants in HNP during the period 1983--1993. The population of L. a. africana inhabiting the Matabeleland-Ngamiland-Okavango region of southern central Africa (which includes the HNP population), is the largest extant elephant population on Earth. The magnitude of this population (110,000--120,000), and the high proportion of its range currently under protection as wildlife reserves, indicate that this population may rank as the most viable and potentially sustainable elephant population on Earth.
    • Foraging Ecology And Nutritional Stress Of Tufted Puffins (Fratercula Cirrhata) Inferred From Stable Isotopes, Fatty Acid Signatures, And Field Endocrinology

      Williams, Cory T.; Buck, C. Loren (2008)
      Prey availability has a major impact on the reproductive output of seabirds, yet information on seabird diets throughout the breeding season is often lacking. Although reduced prey availability is known to affect the growth and survival of nestling seabirds, few studies have demonstrated similar effects on indices of adult body condition. I used stable isotopes and fatty acid (FA) signatures to investigate seasonal and age-related variation in the foraging niches of tufted puffins (Fratercula cirrhata). I conducted captive feeding experiments to determine whether inferences based on these techniques are affected by moderate food restriction during growth. I also examined how adult puffins prioritize the competing goals of maximizing the growth rate of their offspring and maintaining their own condition, as measured by body mass and by the stress hormone, corticosterone (CORT). Food restriction during nestling growth affected adipose tissue FA signatures and resulted in blood that was depleted in 15N and 13C relative to well-fed controls. However, effects of nutritional restriction on delta 15N, delta13C, and FA signatures were small compared to variability in prey, indicating physiological effects do not preclude use of these techniques as dietary tracers. Stable isotopes and FA signatures of free-living adults indicated foraging niches changed over the course of the breeding season. Stable isotopes suggest chick-rearing adults and nestlings feed at the same trophic level while FA signatures indicate that parents feed nestlings a diet different from their own. Body mass of adult puffins declined between incubation and chick rearing periods. For females the magnitude of mass decline did not differ between years, whereas for males the decline was greater in the year where young puffins fledged at a lower mass. In a separate analysis, baseline CORT values of adults of both sexes did not differ between years, but were lower than those observed in a separate study area during two consecutive years with low rates of nestling growth and survival. Assuming elevated CORT and reduced body mass impact survival and/or future fecundity, these results suggest the cost of reproduction may be higher for those adults able to fledge young in years characterized by low productivity.
    • Foraging Ecology And Sociality Of Muskoxen In Northwestern Alaska

      Ihl, Claudia; Ruess, Roger; Klein, David (2007)
      I investigated sociality and winter foraging ecology of muskoxen ( Ovibos moschatus) in Cape Krusenstern National Monument, northwestern Alaska. The nutritional value of moss (Hylocomium splendens, Tomenthypnum nitens) for muskoxen was evaluated by incubating moss in rumen-fistulated muskoxen and simulating post-ruminal digestion by incubation in acid-pepsin. Moss was indigestible in muskoxen and gained mass and nitrogen in the rumen. Consequently, high moss consumption during winter may result in net loss of nitrogen from a muskoxen's system. Local and regional differences in moss use by muskoxen and caribou or reindeer (Rangifer tarandus) were investigated in northwestern Alaska in relation to indicators of winter range quality. On muskox winter ranges, increases in fecal moss indicated decreased graminoid cover, harder snow, increased moss cover, and greater animal densities. Higher mobility of caribou than muskoxen during winter limits use of their feces to reflect local forage selection, but fecal moss may indicate caribou winter range quality on a larger, regional scale. Increasing proportions of moss in muskoxen feces may alert wildlife managers to shifts in forage availability due to changing snow conditions. Roles of male and female muskoxen in coordinating group movements were investigated during the snow-free season. Adult females led most activity initiations, foraging-bout movements, and spontaneous group movements. Rutting males actively manipulated female-led movements through herding and blocking. Leaders incurred no costs in terms of lost foraging time. Habitat use by muskoxen shifted from upland habitats in early summer towards lowland sedge meadows during rut. Muskox group sizes decreased from winter to summer to rut. Muskoxen foraging efficiency decreased with group size in spatially unlimited but not in spatially limited habitats. Adult males contributed least to group cohesion, and their presence may contribute to group fission during rut. A conceptual model is presented which discusses how habitat, foraging, social behavior, and predation threat contribute to group sizes, fission and fusion of muskox groups. Results from this study indicate that winter ranges used by muskoxen in Cape Krusenstern may be limiting, which suggests that numbers of muskoxen in this area will likely remain small. Therefore, hunting quotas should be low and limited to males only.
    • Forest Ecology And Distribution Of Bats In Alaska

      Parker, Doreen Ingrid; Cook, Joseph A.; Klein, David R.; Rexstad, Eric A. (1996)
      This thesis documents distribution of bat species in Alaska and effects of clearcutting on bat activity in temperate rainforests of southeastern Alaska. Occurrence of Myotis lucifugus, M. californicus, M. volans, M. keenii, and Lasionycteris noctivagans is confirmed in southeastern Alaska. I describe new specimens of M. keenii from southeastern Alaska, the first in over 100 years. Myotis lucifugus and Eptesicus fuscus are documented north of 64$\sp\circ$ N latitude. Environmental conditions and geography which influence distribution and latitudinal diversity gradients are discussed. Low bat activity in second-growth forests and clearcuts suggests that these areas provide little summer habitat. Higher activity levels in old-growth and riparian forests suggest these areas are important summer habitat. A change in activity between lactation and post-lactation periods is also noted. Unusual aspects of M. lucifugus ecology in southeastern Alaska are: consumption of spiders; presence of maternity colonies in a temperate rainforest; and intermittent use of hibernacula. <p>