For Marine Biology, see the Marine Sciences collection.

Recent Submissions

  • Smoke without fire: wildfire smoke affects phenolic composition of wild blueberry fruits (Vaccinium uliginosum)

    Weingartner, Laura G.; Mulder, Christa; Tomco, Patrick; Bret-Harte, Syndonia (2023-12)
    Wildfire smoke can induce changes in plant growth, phenology, and chemical composition. The frequency and intensity of wildfires have increased over the last thirty years in Alaska, and smoke has the potential to affect important wild fruit plants, such as bog blueberry (Vaccinium uliginosum L.), a food source for many Alaskans and wild animals. We exposed bog blueberry plants to wood smoke at different stages in fruit development: early-season when the plants were flowering ("early-smoked"), mid-season when fruits were unripe ("mid-smoked"), and late-season when fruits were fully ripe ("late-smoked"). We measured anthocyanins, proanthocyanidins, and total phenolics in the ripe fruits, as well as branch growth, leaf anthocyanin levels, fruit set, and flower, fruit, and leaf phenology. Impact of smoke exposure on anthocyanins depended on fruit developmental state: fruits exposed late in the season had no changes in anthocyanin concentration, while early- and mid-smoked fruits showed increases in anthocyanins. Changes in proanthocyanidins followed a similar pattern to anthocyanins, but differences between treatments were not statistically significant. Total phenolic compounds were not different across treatments. Leaf anthocyanins from mid-smoked and late-smoked plants were higher than the control, while early-smoked leaves were unaffected. Early-smoked plants had lower fruit set than the control, but there was no effect of smoke exposure on mid- and late-smoked fruit abundance. Smoke caused treated plants to lose leaves at a faster rate than control plants, but did not change the timing of leaf color change. Smoke did not affect branch growth or flower and fruit phenology. Our study shows that smoke has immediate effects on bog blueberry in the increase of anthocyanins in leaves and fruits, and seasonal effects in lower leaf longevity and limited fruit set in plants exposed while flowering. These results indicate higher stress levels in smoke-exposed plants that might result in higher fruit quality due to the health benefits of anthocyanins, but at the expense of fruit abundance.
  • Effects of desformylflustrabromine on compulsive-like and social behaviors in mouse models of OCD and autism

    Van Flein, Isaac; Bult-Ito, Abel; Drew, Kelly; Kitaysky, Alexander (2023-12)
    Obsessive-Compulsive Disorder (OCD) and autism spectrum disorders (ASD) share a number of similar deficits, including altered cholinergic activity in the central nervous system (CNS), manifestation of repetitive, restricted, and compulsive-like patterns of behavior, and frequent co-morbid presentation. Desformylflustrabromine is a novel positive allosteric modulator of α4β2 nicotinic acetylcholine receptors, which has recently been shown to be able to reduce compulsive-like behavior in a non-induced mouse model of OCD. In this study, I attempted to replicate the compulsive-like behavior-reducing effects of desformylflustrabromine in the mouse model of OCD, as well as expose the model to a novel assessment; social behavior, as measured by the 3-Chamber Social test. Furthermore, I altered the model with prenatal exposure to valproic acid to induce an ASD-like construct. This ASD animal model has been used extensively to study the social deficits and neurochemistry of ASD, although limited data exists on co-morbid models. By exposing the OCD model to valproic acid, I attempted to establish two additional models; a comorbid OCD / ASD model in the compulsive-like high-activity (HA) strain and an ASD model in the non-compulsive-like low-activity (LA) strain. All mouse models and controls participated in a battery of behavioral tests quantifying compulsive-, anxiety-, and depression-like behaviors, as well as the 3-chamber social test to quantify social preference behaviors. The ASD model was not strongly established, and the desformylflustrabromine appeared to be inactive in all strains and models. I assessed potential reasons for the failure to establish a robust ASD construct in the OCD mouse model, and the failure of desformylflustrabromine to have any significant effect, in contrast with previous research using the drug in the OCD mouse model.
  • Microplastics in spotted seal stomachs from the Bering and Chukchi Seas in 2012 and 2020

    Sletten, Alexandria; Horstmann, Lara; Iken, Katrin; Bryan, Anna (2023-12)
    Microplastics pose a significant threat to marine ecosystems across multiple trophic levels. Spotted seals (Phoca largha) are piscivorous and occupy one of the higher trophic positions in the Bering and Chukchi seas, putting them at risk of ingesting microplastics through prey. This project aimed to determine if microplastics are present in the stomachs of spotted seals harvested for subsistence purposes and compare their presence spatially between two harvest locations, Gambell and Shishmaref, AK. Microplastics are predicted to increase in the Arctic over time due to climate warming and subsequent deposition of microplastics from melting sea ice. Therefore, we examined stomachs from 2012 and 2020 to explore temporal changes. Furthermore, as spotted seal pups (<1 yr of age) and non-pups forage differently, we expected a difference in microplastic ingestion between age classes. We processed stomachs using enzymatic digestion and vacuum filtration. Use of the enzyme digestion method enabled microplastic detection while preserving the hard parts of prey items (e.g., fish otoliths and shrimp carapaces) for diet analysis. We then examined filters with a stereomicroscope, and calculated microplastic frequency of occurrence (FO). A total of 34 (16 from 2012 and 18 from 2020) stomachs from Gambell and Shishmaref have been examined, and a total of 211 microplastic particles were isolated from 33 stomachs (97.1% FO), containing 1 to 23 particles per stomach. Our analysis showed no significant difference in FO between pups and non-pups, between the two harvesting locations, or between harvest years. Additionally, there was no significant difference in the microplastic concentration among the spotted seal stomachs examined in this study. Our data indicate that microplastic ingestion has not changed in frequency between age class, harvest location, or year. This baseline study was successful in isolating microplastics in the stomachs of spotted seals and showed that microplastics have been ingested consistently by spotted seals for at least the past decade. Furthermore, we found increased microplastic abundance in spotted seal stomachs when seals consumed prey at higher trophic levels and prey from benthic zones. Continued study of microplastic ingestion, including absorption and accumulations of the contaminants, is needed to assess potential impacts on the health of spotted seals and other ice-associated pinnipeds, who serve as indicators of ecosystem health in the Bering and Chukchi seas.
  • Avian divergence and speciation across Beringia examined using comparative mitogenomics

    Collier, K. A.; Winker, Kevin; Wolf, Diana; Sikes, Derek (2023-12)
    Accurate knowledge of divergence and speciation processes is critical for understanding key aspects of biodiversity. As a well-known, speciose group of vertebrates, an increased understanding of how birds diverge and speciate allows us to better manage extant avian diversity and understand how it develops over time. Additionally, birds often exhibit complex and variable patterns of divergence, resulting in complexes of taxonomic uncertainty. Filling gaps in our knowledge of divergence across time and space increases our ability to correctly identify and understand not just avian diversity but clade-level patterns in speciation processes. These higher-order findings give us tools to compare and understand biodiversity more broadly across a wide range of taxa. In this thesis, I investigated both temporal and spatial elements of avian divergence, with an emphasis on the high-latitude system of Beringia, which is of particular interest for speciation due to its position at the meeting point of the Eurasian and American continental avifaunas. Chapter 1 describes my investigation of the temporal dynamics of Beringian divergence. The cyclic opening and closing of the Bering Strait due to glacial cycles intermittently isolated and reunited Asia and North America during the Pleistocene (2.6 Mya to 10 Kya). This was hypothesized to produce an uncertain number of associated 'pulses' of avian divergence events spanning that time period. I used a pairwise sampling approach among 39 taxa and a mitogenomic dataset under Bayesian modeling and found no statistical evidence for multiple vicariance events. Instead, divergence times were spread fairly evenly across a large period of time, appearing as a single vicariance event. This is biologically unusual given the system and the cyclic nature of the most likely abiotic driver (glacial cycles) and may be the result of multiple overlaid periods of divergence and gene flow in taxa with older divergence dates. In Chapter 2, I examine the relative contributions of phenotypic and genetic divergence in pairwise comparisons of diverging bird lineages in high- versus low-latitude systems in Beringia and the Philippines. Phenotypic divergence in birds is assumed to be largely due to selection (Price 2008), with genetic divergence assumed to be more driven by time in isolation. I hypothesize that the Beringian system should have less divergence overall than the Philippines, but that a greater proportion of the divergence should be phenotypic, due in part to increased population connectivity in high-latitude systems as a result of larger long- term range fluctuations as a result of Pleistocene glacial cycles. Increased connectivity should be particularly effective in removing neutral, rather than phenotypic, divergence, where selection may be in operation, in part due to a nonlinear, inverse relationship between gene flow and neutral divergence. To test this, I used standardized measures of phenetic and genetic divergence and used linear regressions to quantify the relationship between divergence metrics and the rates of divergence in each system. Beringia showed lower levels of genetic and phenotypic divergence than the Philippines, but the relationship between data types was stronger and the rate of divergence higher than in the Philippine system. I suggest that this is a result of decreased time spent in allopatry in high-latitude systems, but recognize that an increased rate of phenotypic divergence, possibly due to increased selection pressure at high latitudes, also might play a role.
  • The effect of cold exposure and activity on skeletal muscle physiology: a study of human and animal models

    Johannsen, Michelle M.; O'Brien, Kristin; Fedorov, Vadim; Oliver, Scott Ryan; O'Brien, Diane; Barnes, Brian (2023-12)
    Environmental factors and physical activity have the potential to modulate skeletal muscle physiology in beneficial ways. Cold exposure and endurance exercise, specifically, may improve aerobic capacity and atrophy resistance. I utilized three models to examine the effect of cold exposure and activity level on skeletal muscle physiology: quantitation of body composition and energy expenditure estimates in humans participating in a transmountain race, comparative proteomic analysis of skeletal muscle in hibernating and summer active American black bears (Ursus americanus), and an experimental study of the combined effects of cold exposure and endurance training on white adipose tissue, and gastrocnemius and soleus muscles in Sprague-Dawley rats. Body composition analysis of participants of the transmountain race revealed significant fat but not lean body mass loss despite significant caloric deficit. Proteomic analysis of American black bear skeletal muscle revealed an upregulation of glycolytic, inflammatory, immune response, and lipid transport proteins, and a decrease of lipid, and amino acid catabolism proteins during hibernation. Modulation of metabolism and the immune system during hibernation appears to mitigate skeletal muscle atrophy, despite prolonged inactivity and fasting. In Sprague-Dawley rats, cold or exercise alone have similar effects on body composition but exert unique effects on oxidative and glycolytic skeletal muscles that overall supports enhanced aerobic capacity. When combined, cold and exercise appear to improve oxygen diffusion via reduced cross-sectional area of some fiber types in oxidative skeletal muscle but have opposing effects in glycolytic muscles. In summary, skeletal muscle is highly plastic and perturbations such as cold, fasting, and endurance training result in cellular remodeling and changes in protein expression that improves aerobic capacity and conserves skeletal muscle mass across species.
  • Cross-seasonal effects in a sea ice-associated sea duck: do winter conditions affect breeding spectacled eiders?

    Friendly, Randall J.; Brinkman, Todd; Lindberg, Mark; Mulder, Christa; Rizzolo, Daniel (2023-12)
    Climate change in the Arctic is more rapid than anywhere on the globe and changes in the marine environment can impact the distribution and abundance of Arctic and sub-Arctic species. Understanding how a species responds to climate change can aid conservation planning and recovery. Spectacled eiders (Somateria fischeri), sea ducks listed as "threatened" under the Endangered Species Act, winter at the Bering Sea and nest along the coastal areas of Alaska and Arctic Russia. Severity of winter conditions in the Bering Sea have been associated with both reduced annual survival and reduced breeding abundance and may have sublethal effects during the breeding season. In this study, we used 24 years of nesting data from Kigigak Island, a sub-Arctic site on the Yukon-Kuskokwim Delta, and 10 years from Utqiaġvik, on the Arctic Coastal Plain, to examine the hypothesis that winter conditions in the Bering Sea influence the reproductive performance of eiders in the following breeding season. For both sites, we examined the effects of winter ice conditions and spring temperature and wind on nest initiation date, clutch size, and nest survival. Nest initiation date was not strongly associated with conditions experienced prior to the breeding season. Estimates of nest initiation date following extreme high and extreme low winter ice conditions differed by only 2 days. In contrast, the difference in mean initiation dates between sites was 20 days. We found no evidence that winter and spring conditions preceding the breeding season explained variation in clutch size (mean clutch size = 4.8, 95% CI: 4.7, 4.8), suggesting that breeding propensity may buffer against variation in clutch size. Nest survival varied among years; annual estimates ranged from 0.11 (95% CI: -0.02, 0.24) to 0.95 (95% CI: 0.92, 0.98) at Kigigak Island and 0.40 (95% CI: 0.16, 0.63) to 0.83 (95% CI: 0.66, 0.99) at Utqiaġvik. At both sites, low days of high ice during winter were associated with lower nest survival and moderate to high counts of high ice cover conditions during winter were associated with higher nest survival. After accounting for the effect of days of high ice during winter, nest survival was higher at Utqiaġvik than Kigigak Island, potentially related to later nest initiation in the Arctic. We concluded that for breeding spectacled eiders, low sea ice winters are associated with reduced nest survival through reduced body condition, and we speculate that following winters with high sea ice more individuals may possibly decide not to breed. Delayed nest initiation at Arctic breeding sites may provide additional time for spectacled eiders to recover from low ice winters and contribute to higher nest survival at Utqiaġvik compared to the sub-Arctic breeding site. Associations between changing ice conditions on multiple demographic rates may lead to future population declines for spectacled eiders at rates higher than previously predicted.
  • Alnus viridis ssp. Fruticosa modulates local conditions to influence intra and interspecies growth

    Drew, Jackson W.; Bret-Harte, Marion Syndonia; Ruess, Roger W.; Drown, Devin M.; Buchwal, Agata (2023-12)
    The Arctic is warming rapidly due to anthropogenic greenhouse gas emissions. Concurrent with warming, some Arctic plant communities have transformed from short statured evergreen and graminoid shrub tundra to tall deciduous shrubs in recent decades. As warming continues, plant-plant interactions will likely change and influence future community composition. Alnus viridis ssp. fruticosa (Siberian alder) is rapidly expanding across Arctic regions and is particularly important because Siberian alder is the Arctic's only large N-fixing shrub, may alter N-cycling to further influence both C-cycling and community composition as it spreads. This dissertation addressed two main questions to better understand how Arctic deciduous shrub communities have changed, and may continue to change as Arctic warming proceeds. First, how did the climate sensitivity of Siberian alder's growth change over the past century (1920 - 2017), and how did climate sensitivity change as Siberian alder grew older? Second, how has Siberian alder affected the long-term growth of two nearby dominant deciduous shrub species: Betula nana ssp. exilis (dwarf birch) and Salix pulchra (diamondleaf willow)? I used dendrochronological techniques to assess how sensitive the growth of each of these three species was to climate over the last century. For dwarf birch and diamondleaf willow, I compared growth near and away from Siberian alder. I hypothesized that Siberian alder shrubs would become more sensitive to climate as they grew both older and larger. I expected that older alder would enhance soil N availability over time, due to the accumulated products of N-fixation. I also expected that the growth of larger, older alders would be more sensitive to climate than the growth of younger alder, because of having both a greater photosynthetic capacity (enabling more growth under good conditions), but also higher maintenance respiration (leading to less growth under poor conditions). I found that Siberian alder overall has become more sensitive to July air temperatures in the second half of the past century as climate has warmed. Also, older shrubs were more sensitive to June and July air temperatures than younger shrubs. Thus, these findings support my hypothesis. Siberian alder frequently grows in close association with dwarf birch and diamondleaf willow. However, these two deciduous neighbors differ in several functional traits. Dwarf birch is a low statured, many branched shrub that mainly grows laterally, and thus is often found on the margins of the Siberian alder canopy. In contrast, diamondleaf willow has fewer branches, grows more vertically, and often is found almost entirely within the Siberian alder canopy. Thus, I hypothesized Siberian alder would facilitate the growth of dwarf birch growth, by alleviating both resource and abiotic stressors, but would reduce diamondleaf willow growth, due to increased light competition. Siberian alder promoted dwarf birch growth and reproduction, likely by alleviating N-limitations and reducing frost damage, though growth was delayed by two weeks. In contrast, diamondleaf willows growing near alder had much smaller growth rings than diamondleaf willows growing away from alder, likely due to light competition. This negative effect on willow growth near alder occurred despite these willows likely receiving greater access to soil N and protection from herbivory damage from the neighboring alder. Overall, these results demonstrate that Siberian alder will likely grow better as they get both older and larger, and as the Arctic continues to warm. Siberian alder influence the growth of neighboring deciduous shrubs over the long term, and those effects are species-specific because they depend on the functional traits of their neighbors. Thus, the continued spread of Siberian alder will likely alter vegetation community composition, and thus influence C and N cycling.
  • Effects of browser exclusion on the willow leafblotch miner (Micrurapteryx salicifoliella): host plant availability, oviposition, and survival

    Cummings, Martha M. T.; Wagner, Diane; Kielland, Knut; Mulder, Christa (2023-12)
    Herbivores can affect the quality and quantity of their food plants in ways that indirectly influence the food resources and habitat available to other herbivores present. This study examined indirect interactions between a mammalian browser and an insect folivore that feed on shared plant species during different seasons. On a boreal floodplain in interior Alaska, we investigated how a history of winter browsing by moose (Alces alces) affected the behavior and performance of the willow leafblotch miner moth, Micrurapteryx salicifoliella in summer. Excluding moose browsing for 8 years did not change plant density, but strongly increased canopy height, vegetative cover and overstory density. These vegetation changes led to slightly higher relative humidity and lower air and soil temperatures on moose exclosure relative to control plots. Excluding browsers did not alter the foliar quality (leaf area, water content, leaf mass per unit area, nitrogen concentration) of the three focal willow host species examined. Browsing-related effects on willow morphology and canopy structure did not influence patterns of oviposition by M. salicifoliella on host plants. However, larvae feeding within control plots exposed to vertebrate browsing were less likely to survive to pupation than those excluded from browsing, perhaps because larval predation was more frequent on the warmer and more open browsed plots. Both oviposition and subsequent larval survival were strongly affected by host species. Interestingly, the willow host species on which leaf miner larvae survived best did not correspond to that which received the highest egg abundance during oviposition. We conclude that a history of browsing reduced canopy height, cover and overstory density, which in turn affected the performance of the outbreak insect M. salicifoliella by reducing the proportion of larvae to survive to pupation.
  • Avian divergence and speciation across Beringia examined using comparative mitogenomics

    Collier, K. A.; Winker, Kevin; Wolf, Diana; Sikes, Derek (2023-12)
    Accurate knowledge of divergence and speciation processes is critical for understanding key aspects of biodiversity. As a well-known, speciose group of vertebrates, an increased understanding of how birds diverge and speciate allows us to better manage extant avian diversity and understand how it develops over time. Additionally, birds often exhibit complex and variable patterns of divergence, resulting in complexes of taxonomic uncertainty. Filling gaps in our knowledge of divergence across time and space increases our ability to correctly identify and understand not just avian diversity but clade-level patterns in speciation processes. These higher-order findings give us tools to compare and understand biodiversity more broadly across a wide range of taxa. In this thesis, I investigated both temporal and spatial elements of avian divergence, with an emphasis on the high-latitude system of Beringia, which is of particular interest for speciation due to its position at the meeting point of the Eurasian and American continental avifaunas. Chapter 1 describes my investigation of the temporal dynamics of Beringian divergence. The cyclic opening and closing of the Bering Strait due to glacial cycles intermittently isolated and reunited Asia and North America during the Pleistocene (2.6 Mya to 10 Kya). This was hypothesized to produce an uncertain number of associated 'pulses' of avian divergence events spanning that time period. I used a pairwise sampling approach among 39 taxa and a mitogenomic dataset under Bayesian modeling and found no statistical evidence for multiple vicariance events. Instead, divergence times were spread fairly evenly across a large period of time, appearing as a single vicariance event. This is biologically unusual given the system and the cyclic nature of the most likely abiotic driver (glacial cycles) and may be the result of multiple overlaid periods of divergence and gene flow in taxa with older divergence dates. In Chapter 2, I examine the relative contributions of phenotypic and genetic divergence in pairwise comparisons of diverging bird lineages in high- versus low-latitude systems in Beringia and the Philippines. Phenotypic divergence in birds is assumed to be largely due to selection (Price 2008), with genetic divergence assumed to be more driven by time in isolation. I hypothesize that the Beringian system should have less divergence overall than the Philippines, but that a greater proportion of the divergence should be phenotypic, due in part to increased population connectivity in high-latitude systems as a result of larger long- term range fluctuations as a result of Pleistocene glacial cycles. Increased connectivity should be particularly effective in removing neutral, rather than phenotypic, divergence, where selection may be in operation, in part due to a nonlinear, inverse relationship between gene flow and neutral divergence. To test this, I used standardized measures of phenetic and genetic divergence and used linear regressions to quantify the relationship between divergence metrics and the rates of divergence in each system. Beringia showed lower levels of genetic and phenotypic divergence than the Philippines, but the relationship between data types was stronger and the rate of divergence higher than in the Philippine system. I suggest that this is a result of decreased time spent in allopatry in high-latitude systems, but recognize that an increased rate of phenotypic divergence, possibly due to increased selection pressure at high latitudes, also might play a role.
  • Movement ecology, survival, and territorial dynamics in Canada lynx (Lynx canadensis) over a cyclic population decline

    Arnold, Derek; Kielland, Knut; Breed, Greg; Crimmins, Shawn; Laufenberg, Jared (2023-12)
    As the quintessential predator-prey cycle, research into Canada lynx (Lynx canadensis) and snowshoe hares (Lepus americanus) have led to many discoveries in population biology; however, much remains unknown about the nuances of their populations. In this dissertation, I examined the ways in which population cycles influence survival, reproduction, territoriality, and connectivity. First, I examined ways in which climate change induced shifts in fire regimes have affected lynx persistence in their current refugia. Lynx mainly sought out areas of higher hare density and lower cover, such as intermediately aged coniferous and deciduous forests. This type of forest was predicted to persist in the near future, so long as fire intervals remained higher than current levels. Secondly, I investigated how landscape connectivity varied as a function of dispersal status and survival. We found that although the landscape was physically well connected based on resident lynx, it was even more so given dispersing lynx tolerance of poor habitat. This was dampened by survival declines in dispersing lynx over the course of a population crash to a near complete loss of connectivity. Thirdly, I assessed the degree to which dispersal, reproduction, and survival patterns were consistent with those displayed by populations exhibiting a traveling wave. My results supported the hypothesized westward moving population wave, but one mediated by differential survival and spatially varying reproduction rather than directionally-biased dispersal. Additionally, these characteristics were consistent with lynx as driving a similar population wave in snowshoe hare. Finally, I applied a novel mathematical approach to parameterizing advection-diffusion equations to examine how territorial formation occurs at population highs. I found evidence for hierarchical formation of territories in available space, with boundaries defined by preferred habitat. This methodology was a considerable improvement over previous descriptive methods typically used to define territories, as evidenced by the model's ability to predict territorial annexation following sudden vacancy following harvest. These results underscore the importance of maintaining population refugia and existing physical connectivity for the duration of a population downturn, likely on wildlife refuges and national parks across the state, even as the impacts of climate change remain small in the near future.
  • Effects of calcium magnesium acetate on small ponds in interior Alaska

    Rea, Caryn L. (1986-09)
    Deicing winter roads with chlorides has been common practice in northern areas. Corrosion of vehicles, structures, and pavements has resulted in damage, and roadside vegetation and public water supplies have been severely impacted by heavy salt usage. Calcium magnesium acetate (CMA) was identified as a promising alternative to chloride salts. This research focused on the effects on planktonic algae and bacteria in small ponds, to help assess the environmental acceptability of CMA in Alaska. The most serious consequence resulting from CMA was a dissolved oxygen concentration decrease, partly attributable to increased bacteria populations utilizing oxygen during degradation of acetate. Algal biomass recovered toward the end of the summer indicating that the algae may be utilizing some of the carbon dioxide being released by the bacteria. Rapid turnover times of acetate by bacteria in the fall and continued low dissolved oxygen indicated that some of the acetate was being recycled.
  • Seasonal changes in body mass and composition of northern red-backed voles (Clethrionomys rutilus) in interior Alaska

    Zuercher, Gerald Lawrence (1995-12)
    Northern red-backed voles (Clethrionomys rutilus) undergo a pronounced annual cycle in body mass: highest in summer, lowest in winter. I trapped voles throughout 1994 to determine how body composition and relative size of body components contributed to this cycle. Seasonal changes in body mass were primarily due to changes in body water and lean dry matter. Total body fat was low throughout the year, peaking in spring and early summer. Relative ash content was lowest in early summer. Most body components declined in dry mass and percent water during autumn, with skeletomuscular components contributing most to loss of body mass. Most body components declined in proportion to declines in body mass, but a few components declined proportionally greater than or less than body mass. Total Body Electrical Conductivity (TOBEC) of live voles explained 94% of the variation in lean mass and body water, but accuracy of fat estimates was poor.
  • Effects of military overflights on habitat use and selection by female Dall's sheep, Yukon-Tanana uplands, Alaska

    Wendling, Bradley R. (2008-12)
    "My objective was to assess the potential effects of military overflights on home range size, movement rates, habitat use, and habitat selection of female Dall's sheep (Ovis dalli) during 2-week sequential periods, April-July, 1999-2002. I examined sheep in 2 study areas overlain with designated military training airspace within the Yukon-Tanana uplands, Alaska. I examined the effects of study area, year, and sequential time period on: 1) mean home range size, 2) mean minimum hourly distance traveled by sheep, and 3) mean use and selection ratios for the habitat variables of elevation, slope, terrain ruggedness, aspect, and landcover class. Mean number of daily military sorties within sequential periods was used as a covariate in all analyses. I assessed habitat selection at 3 successive spatial scales defined as: 1) the regional geographical range of female Dall's sheep in the Yukon-Tanana uplands, 2) study areas (defined as the distribution of sheep within a localized area), and 3) selection within individual 2-week home ranges. Sheep home range size, movement rates, habitat use and selection ratios at the scale of region and study area differed between study areas, among years within study areas, and among sequential time periods within years within study areas, but did not vary in relation to military overflight intensity. I detected an effect of sorties on selection ratios at the home range scale; however, sorties explained <4% of the residual variation in these variables. I conclude that increases in intensity of military training operations during Major Flying Exercises (MFE's) over the Yukon-Tanana uplands were a relatively insignificant source of variance in activity and habitat use compared to the effects of seasons, years, and study areas"--Leaf iii
  • Human impacts on brown bears at Pack Creek, Admiralty Island, Alaska

    Warner, Susan H. (1987-05)
    Human disturbance of brown bears (Ursus arctos) was studied at Pack Creek on Admiralty Island in Southeast Alaska during 1983 and 1984. The Pack Creek watershed is closed to bear hunting. Use of the area by bear-watchers is increasing. Instantaneous scan sampling was used to observe bears at a control area with negligible human activity and at the popular Pack Creek area. Six bears were radio-collared to assess movements away from Pack Creek. Bears were crepuscular in the two areas. Individuals that were highly tolerant of visitors used the Pack Creek area during the mid-day period of high visitor use more than other bears. Over 80% of the observations of Pack Creek bears were of females, suggesting that visitor use may differentially affect sexes. Food-conditioned bears showed boldness that could cause undesirable incidents. Except for occasional sallies, Pack Creek females remained within the watershed. Males frequented several watersheds.
  • The morphology and chemistry of two willow species in relation to moose winter browsing

    Suter, Suzanne M. (1992-12)
    This study examines the interaction between moose (Alces alces gigas) and winter dormant willows (Salix alaxensis and Salix pulchra) in Alaska, emphasizing the impact of moose browsing on the forage produced by willow. In a two year field study, plant responses were examined with clipping treatments designed to simulate browsing by moose. The plant responses examined included biomass production, plant architecture, and concentration of plant tannins. Forage selection by moose in the study area is also addressed. Results suggest that a plant response of increased growth, decreased chemical defense, and redistribution of new biomass may explain the pattern of repeated browsing of plants by moose. The responses of clipped plants indicate that moose improve the quality of their willow hosts by browsing and repeated browsing negatively affects carbon reserves of willows. Among and within plant variation in tannin content was also examined among 5. alaxensis trees. Observations are related to within and among tree measurements of growth rate.
  • Marbled murrelet distribution and abundance in relation to the marine environment

    Speckman, Suzann G. (1996-08)
    I examined the effects of the physical variables season, time of day, tide stage, sea surface temperature, and weather and the biological variables phenology and productivity on Marbled Murrelet (Brachyramphus marmoratus) abundance and distribution in Auke Bay and Fritz Cove, Alaska. I surveyed murrelets daily from the shore and a small boat from May through August, 1992 and 1993, and evaluated the impacts of murrelet abundance patterns on a monitoring strategy. I also examined the breeding biology, behavior, and social structure of Marbled Murrelets in an effort to gauge the effects of declining populations on their daily activities, such as foraging and courtship behavior of adults, and foraging strategies of juveniles. I found significant effects of year, season, time of day, and tide stage on Marbled Murrelet numbers at sea that have important implications for designing monitoring surveys to assess changes in Marbled Murrelet populations in Alaska and elsewhere.
  • Distribution, abundance, and quality of forage within the summer range of the central Arctic caribou herd

    Smith, Michael D. (1996-12)
    Distribution, abundance, and quality of summer forage available to caribou (Rangifer tarandus granti) of the Central Arctic Herd were determined in July and August, 1989 -1990. Plant cover, an index of available biomass, was measured at three sites within 50 km of the arctic coast. In general, plant cover increased with distance from the coast. Cover of forbs and evergreen shrubs was higher at inland sites (P < 0.001), whereas cover of willows (Salix spp.) was highest at the coastal site (P < 0.001). Higher plant cover inland is largely attributable to a greater proportion of drier habitats. Differences in forage quality among sites, however, were small and inconsistent. I conclude that by feeding inland during insect-free periods, caribou realize a net energy benefit, because of higher plant biomass, higher proportion of drier habitat, and greater species diversity than coastal areas.
  • Seasonal distribution and winter habitat use by Sitka black-tailed deer in the Prince William Sound region, Alaska

    Shishido, Neil (1986-05)
    Intensity of winter use of a variety of forest stands by deer (Odocoileus hemionus sitkensis) was measured. Information on vegetation, timber type, and topography was collected to find relationships between deer use and habitat variables. Seasonal use of forest stands by deer is best described in terms of: basal area of trees, amount of deer forage (Vaccinium spp. and Coptis aspleniifolia)r deviation in crown closure, and timber volume. Information from radio-collared deer indicated high use of forest habitat, particularly during winter. Alpine areas received more use than any other habitat during summer. South-facing slopes were used more often than other aspects across all seasons. Average winter home range size was 160 ha, significantly smaller than the spring average (282 ha). Most radio-collared deer made seasonal elevational movements within a single drainage. Retention of high timber volume, old growth forest is recommended to maintain preferred deer habitat in Prince William Sound.
  • Walrus feeding: a re-examination

    Sheffield, Gay Glover (1997-08)
    A new approach for analyzing walrus (Odobenus rosmarus) diet was examined. Controlled gastric digestion experiments determined the relative rates at which different kinds of food items became unidentifiable. The ability to identify prey items varied within and among prey types. The laboratory experiments provided a new basis for examining diet data by characterizing the condition of stomach samples based on the rates at which different prey types were digested. Stomach content data acquired during 1952-1991 from 798 Pacific walruses were compiled, and interpretations about feeding habits were re-examined. Walruses regularly consumed a wider assortment of benthic prey than was previously thought. The diet of the Pacific walrus varied seasonally and regionally. Males and females consumed essentially the same food items when in the same location.
  • Effects of weather and parasitic insects on summer ecology of caribou of the Delta herd

    Mörschel, Frank Matthias (1996-08)
    The roles of weather and parasitic insects in caribou (Rangifer tarandus) ecology were investigated to determine their influence on population dynamics of the Delta Herd. Data on weather, insect abundance, and caribou behavior were collected during two summers. Mosquito season started 21 and 11 June and oestrid fly season 11 July and 21 June in 1994 and 1995, respectively. Mosquito activity was limited by windspeed at temperatures >7°C. Oestrid fly presence was influenced mainly by temperature. Presence of insects and temperature positively influenced, and windspeed negatively influenced rate of activity changes of caribou. Feeding decreased and standing increased with insect presence and temperature. Increasing temperature affected activity budgets even in the absence of insects by decreasing feeding activities. Weather, especially temperature, and parasitic insects, especially oestrid flies, affected caribou mainly by limiting forage intake and increasing energy expenditure. Estimated activity budgets in summers of 1976-1995 indicated possible limiting effects of temperature on population dynamics.

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