• Contaminant Exposure And Associated Biological Responses In Southern Beaufort Sea Polar Bears

      Knott, Katrina K.; O'Hara, Todd; Miller, Debra; O'Brien, Diane; Hueffer, Karsten (2011)
      Concentrations of mercury (Hg) and polychlorinated biphenyls (PCBs) were examined in polar bear (Ursus marititnus) to assess variations among sex and age cohorts, and evaluate possible adverse impacts of combined toxicant exposures. Biomarkers of selenium (Se) status (whole blood and serum Se concentrations, glutathione peroxidase activity), and thyroid status (total and free concentrations of thyroxine and tri-iodothyronine) were examined in Southern Beaufort Sea (SBS) polar bears. Both Hg and PCBs tended to be greater in female than in male polar bears and likely related to the type and proportion of marine-based prey in their overall diet. Significant positive relationships between circulating concentrations of PCBs, specific blood lipids (e.g., triglycerides and free fatty acids) and reduced body condition scores suggest combined contaminant-environmental stressors for SBS polar bears. Polar bear milk contained detectable concentrations of both Hg and PCBs. Estimated tolerable daily intake levels for PCBs through milk consumption by cubs of the year (< 6 months of age) exceeded available toxicity thresholds and could indicate possible adverse consequences of contaminant exposure during critical stages of neonatal development. Significantly positive and negative associations between contaminants and biomarkers indicated a possible oxidative stress response and thyroid disruption in SBS polar bears. Definitive relationships between contaminants and these physiologically-based biomarkers, however, could not exclude natural variations and equally possible impacts of nutritional stress and changes in physiological status. Female and young polar bears are the cohorts of concern for chronic low-level exposure to chemical mixtures. These data provide a better understanding of the physiological interactions underlying toxicity, and the multiple environment-toxicant stressors projected for arctic species with changes in climate.
    • Expression And Mechanisms Of Hibernation In The Artic: The Alaska Marmot And Arctic Ground Squirrel

      Lee, Trixie Nicole; O'Brien, Diane; Buck, Loren; Taylor, Barbara; Barnes, Brian (2012)
      The Arctic is home to animals that have taken adaptations to overwintering to extremes. In this dissertation, I have investigated one of these adaptations, hibernation, in two species from the Arctic, the Alaska marmot (Marmota broweri) and the arctic ground squirrel (Urocitellus parryii ). The expression of hibernation under natural conditions in these species was compared by collecting body temperature records of free-living individuals. The Alaska marmot, a highly social species, demonstrated extreme synchrony in body temperature patterns among a family group, indicating a strong reliance on social thermoregulation. In contrast, the arctic ground squirrel was confirmed to be a solitary hibernator that reduces body temperature below freezing during torpor. Both species must produce heat when soil temperatures are significantly below freezing for most of the winter. At these subfreezing ambient temperatures, the arctic ground squirrel has shown an increasing reliance on nonlipid fuel during torpor, driving a loss of lean mass during hibernation of ~20%. I calibrated deuterium dilution to repeatedly estimate body composition in this species, which dramatically changes adiposity through its annual cycle, and used this technique to quantify lean mass loss throughout hibernation in a study of tissue metabolism. I also developed and applied the natural abundance of nitrogen and carbon stable isotopes as tools for monitoring differential tissue metabolism and differentiating mixed metabolic fuel use in the arctic ground squirrel. These data clarified the mechanism of change in nitrogen stable isotopes and indicated that hibernating ground squirrels rebuild organ tissues while breaking down muscle tissue to meet energetic demands. Furthermore, I corroborated a shift in metabolic fuel use toward nonlipid sources during torpor at low ambient temperatures by using the carbon isotope ratio in exhaled breath in combination with respiratory quotient. This dissertation combines studies of hibernation patterns in free-living animals with experimental data on the tissues and fuels being catabolized at very low temperatures to broaden our understanding of how small mammals successfully hibernate in severe winter conditions. It also presents the development and use of stable isotope ratios as physiological tools in hibernating species.
    • Lake Area Change In Alaskan National Wildlife Refuges: Magnitude, Mechanisms, And Heterogeneity

      Roach, Jennifer; Griffith, Brad; Harden, Jennifer; Verbyla, David; Jones, Jeremy (2011)
      The objective of this dissertation was to estimate the magnitude and mechanisms of lake area change in Alaskan National Wildlife Refuges. An efficient and objective approach to classifying lake area from Landsat imagery was developed, tested, and used to estimate lake area trends at multiple spatial and temporal scales for ~23,000 lakes in ten study areas. Seven study areas had long-term declines in lake area and five study areas had recent declines. The mean rate of change across study areas was -1.07% per year for the long-term records and -0.80% per year for the recent records. The presence of net declines in lake area suggests that, while there was substantial among-lake heterogeneity in trends at scales of 3-22 km a dynamic equilibrium in lake area may not be present. Net declines in lake area are consistent with increases in length of the unfrozen season, evapotranspiration, and vegetation expansion. A field comparison of paired decreasing and non-decreasing lakes identified terrestrialization (i.e., expansion of floating mats into open water with a potential trajectory towards peatland development) as the mechanism for lake area reduction in shallow lakes and thermokarst as the mechanism for non-decreasing lake area in deeper lakes. Consistent with this, study areas with non-decreasing trends tended to be associated with fine-grained soils that tend to be more susceptible to thermokarst due to their higher ice content and a larger percentage of lakes in zones with thermokarst features compared to study areas with decreasing trends. Study areas with decreasing trends tended to have a larger percentage of lakes in herbaceous wetlands and a smaller mean lake size which may be indicative of shallower lakes and enhanced susceptibility to terrestrialization. Terrestrialization and thermokarst may have been enhanced by recent warming which has both accelerated permafrost thawing and lengthened the unfrozen season. Future research should characterize the relative habitat qualities of decreasing, increasing, and stable lakes for fish and wildlife populations and the ability of the fine-scale heterogeneity in individual lake trends to provide broad-scale system resiliency. Future work should also clarify the effects of terrestrialization on the global carbon balance and radiative forcing.
    • Population Structure And Hybridization Of Alaskan Caribou And Reindeer: Integrating Genetics And Local Knowledge

      Mager, Karen H.; Hundertmark, Kris J.; Chapin, F. Stuart III; Kielland, Knut; Schneider, William S. (2012)
      Alaskan caribou (Rangifer tarandus granti) are a valued game species and a key grazer in Alaska's terrestrial ecosystem. Caribou herds, defined by female fidelity to calving grounds, are management units. However, the extent to which herds constitute genetic populations is unknown. Historical fluctuations in herd size, range, and distribution suggest periods of contact and isolation between herds. Likewise, historical contact between caribou and introduced domestic reindeer (R.t. tarandus) created opportunities for hybridization, but its extent is not known. I conducted an interdisciplinary study to understand how historical processes influence genetic identity and population structure of caribou and reindeer. Interviews with herders and hunters in Barrow, Alaska, revealed that many reindeer migrated away with caribou in the 1940s despite herder efforts to prevent mixing. Local observations of reindeer-like animals in caribou herds today suggest feral reindeer may survive and interbreed. Using genetic analysis of North Slope caribou and Seward Peninsula reindeer (n = 312) at 19 microsatellite loci, I detected individuals with hybrid ancestry in all four caribou herds and in reindeer. Selective hunting of reindeer-like animals, along with herd size and natural selection, may remove reindeer from caribou herds over time. I used genetics as well to describe caribou population structure and determine how it is influenced by geography, historical demography, and ecotypes. I found that Alaskan caribou from 20 herds (n = 655) are subdivided into two genetic clusters: the Alaska Peninsula and the mainland. Alaska Peninsula herds are genetically distinct, while many mainland herds are not. I hypothesize that Alaska Peninsula herds have diverged due to post-glacial founder effects and recent bottlenecks driven by constraints to population size from marginal habitat and reduced gene flow across a habitat barrier at the nexus of the peninsula. I hypothesize that mainland herds have maintained genetic connectivity and large effective population size via range expansions and shifts over time. However, I find evidence that herds of different ecotypes (migratory, sedentary) can remain differentiated despite range overlap. Genetic evidence provides information for herd-based management, while also demonstrating the importance of spatial connectivity of herds and their habitats over the long-term.
    • Postbreeding Ecology Of Shorebirds On The Arctic Coastal Plain Of Alaska

      Taylor, Audrey R.; Powell, Abby N.; Lanctot, R. B.; Huettmann, F.; Kitaysky, A. S.; Williams, T. D. (2011)
      Previous research on the Arctic Coastal Plain (ACP) of Alaska has shown that postbreeding shorebirds congregate at coastal sites prior to fall migration. Relatively little has been done to compare distribution, community characteristics, or behavior broadly across the ACP landscape, but this information is necessary to set the context for interpreting population demographics and setting conservation priorities. I collected data on distribution, species composition, phenology, and habitat use of postbreeding shorebirds in 2005--2007. I found that distribution of shorebirds across the ACP was not uniform: I identified persistent "hotspots" at Peard Bay, Pt. Barrow/Elson Lagoon, Cape Simpson, Smith Bay to Cape Halkett, and at the Sagavanirktok and Kongakut Deltas. Staging phenology varied by species and location, and differed than that reported in previous studies for several species. Three foraging habitat guilds existed with birds favoring gravel beach, mudflat, or salt marsh/pond edge habitats. Using VHF telemetry. I examined how shorebirds moved from tundra breeding sites to and between coastal postbreeding sites. I found that most species exhibited a variable direction of movement compared to their ultimate migration direction; this may be related to each species' overall length of stay on the ACP. I also found species-specific patterns of movements and residence time that were indicative of differing life history strategies. Lastly, I examined the use of physiological tools (triglyceride and corticosterone levels) to assess function and quality of foraging sites for postbreeding shorebirds, taking into account varying molt strategies. I determined that molt strategies affected physiological profiles and physiologic metrics varied through space and time. However, my hypotheses for variation in physiological patterns for shorebirds employing different molt strategies and using sites of varying quality were not completely upheld. I suggest that assessments of site quality for postbreeding shorebirds should consider species-specific life history strategies, and use multiple species and physiological metrics as indicators. Given suspected declines in North American shorebird populations, and accelerated rates of environmental change in northern Alaska, this contextual information regarding postbreeding distribution, population characteristics, behavior, and physiology may help interpret changes in shorebird populations or behavior and establish strategies to protect important habitat.
    • Sentinels Of Arctic Ecosystem Health: Polar Bear And Arctic Fox

      Kirk, Cassandra M.; O'Hara, Todd (2010)
      Climate change is impacting human, wildlife, and ecosystem health in the Arctic. Currently, we lack sufficient information to fully appreciate the ramifications of these changes and are thus ill equipped for predicting, mitigating or adapting to the outcome of such impacts. Warming in the Arctic has generated a need for baseline information on biodiversity and ecosystem health such that change over time may be assessed. Sentinel species can be used to monitor and therefore, intervene to prevent adverse health outcomes before they manifest at the population level. This dissertation examines the use of polar bears (Ursus maritimus) and arctic foxes ( Alopex lagopus) as sentinels for climate change in the Arctic. To this end we: develop hematological biomarkers in polar bears which can be used to model change over time in health; demonstrate relationships between this biomarker and infectious agent exposure (e.g serology); and establish prevalence and risk factors for infectious agents that can serve as indicators of change in disease occurrence at the Arctic marine-terrestrial interface. We found that den emergent female polar bears with dependent young were the most immunologically vulnerable cohort and suggest therefore, that they be targeted in future monitoring efforts. We also detected evidence suggesting serologic exposure of polar bears to morbillivirus and Toxoplasma gondii may be associated with immunological status and age (morbillivirus only). Furthermore, we used molecular epidemiologic techniques to identify the strain of the highly lethal morbillivirus in arctic fox as "arctic" canine distemper virus and the species of Echinococcus in arctic fox on the Alaska North Slope as Echinococcus multilocularis. The results of this study illustrate the utility of the "One Health" approach in addressing the impacts of climate change. Understanding Arctic ecosystem health will require the collaborative efforts of experts in diverse fields as well as input from local, traditional ecological knowledge over the proper spatial and temporal scales.
    • Spatio-Temporal Recruitment Dynamics Of Mountain-Dwelling Caribou In The Yukon Territory, Canada

      Hegel, Troy M.; Huettmann, Falk (2010)
      Understanding processes and mechanisms resulting in observed ecological patterns is critical information for biologists charged with effectively managing and conserving wildlife populations. In many areas across North America woodland caribou (Rangifer tarandus caribou Gmelin) populations are declining, as are caribou and reindeer populations globally. Why these declines are occurring is a key research question of biologists and managers. I investigated factors influencing recruitment of mountain-dwelling woodland caribou using long-term time series from ten herds (populations) in the Yukon Territory, Canada (Yukon). Recruitment was indexed by the calf:cow ratio observed during the fall breeding season using data collected during aerial monitoring surveys. I first examined the seasonal effects of the Pacific Decadal Oscillation (PDO), on observed recruitment in these herds. The PDO was positively related to recruitment and had its strongest effect during the winter preceding birth and immediately before calving. These results indicate that female body condition, and hence conception rates, were not affecting observed recruitment patterns. Rather, parturition and/or early calf survival were the most likely vital rates affecting the number of calves being recruited into the breeding population. I next examined the interacting effect of large-scale climate (PDO) and predation [wolf (Canis lupus L.) density] on recruitment in the Finlayson herd of east-central Yukon. A large-scale wolf control program in the 1980s allowed me to assess recruitment over a range of wolf densities and climatic conditions. The effect of the PDO immediately before calving was negligible when wolf numbers were significantly reduced indicating the climatic effect was modified by wolf density. Additionally, as springtime climate improved (i.e. increasing PDO) the difference in recruitment between years with and without wolf removals was reduced.