• Arctic fox winter movement and diet in relation to industrial development on Alaska's North Slope

      Lehner, Neil S.; Person, Brian; Kielland, Knut; O'Brien, Diane; Hunter, Christine (2012-12)
      I examined winter movement and diet of Arctic foxes (Vulpes lagopus) in the Prudhoe Bay oilfields and an adjacent undeveloped area (National Petroleum Reserve-Alaska (NPR-A)). Movement metrics were compared between these areas using data from satellite collars. Daily travel rate was approximately 5 times greater in the undeveloped area than in Prudhoe Bay. Four adult foxes collared in NPR-A used the sea ice for extensive time periods. One of these foxes traveled 338 km in three days while another traveled to Banks Island (Northwest Territories, Canada), over 1050 km from its capture location. Prudhoe Bay foxes did not make these long distance movements and remained near their summer capture location throughout winter. I used stable isotope analysis and a mixing model (SIAR) to estimate the contribution of marine, terrestrial, and anthropogenic foods to fox diet. Based on muscle tissue, the average contribution of anthropogenic foods to Prudhoe Bay fox diet was more that 50%. Marine foods were utilized in NPR-A, but not in Prudhoe Bay. Results demonstrate that anthropogenic foods are heavily utilized by foxes that overwinter in the oilfields and this food source is likely responsible for reduced winter movements of Prudhoe Bay foxes. Therefore, industrial development strongly affects winter movement and diet of foxes.
    • Terrestrial invertebrate prey for juvenile chinook salmon: abundance and environmental controls in an Interior Alaska river

      Gutierrez, Laura; Wipfli, Mark S.; Blanchard, Amy L.; Rosenberger, Amanda E. (2011-12)
      Terrestrial prey subsidies can be a key food source for stream fish, but their importance and environmental controls on their abundance have not been widely documented in high latitude ecosystems. This study investigated terrestrial invertebrate prey availability and predation by age-0+ juvenile chinook salmon (Oncorhynchus tshawytscha), overlap between terrestrial infall and drift to diet, and the relationship between diet to stream temperature and discharge in the Chena River, Interior Alaska. Terrestrial infall, drift, and juvenile chinook diet varied widely through the summers (May-September) of 2008 and 2009. Drift was comprised of 33% terrestrial and 67% aquatic invertebrate mass, while juvenile chinook diet contained 19% terrestrial, 80% aquatic, and 1% unidentifiable invertebrate mass. The proportion of terrestrial invertebrate mass consumed increased through summer and, at times, made up to 39% of total diet. Low similarity of invertebrates in diet and infall, and diet and drift suggested that fish were, in part, prey-selective, selecting hymenopterans and chironomid midges (Diptera). In both years, prey mass consumed and discharge varied inversely, but no correlation was found between proportion of terrestrial invertebrates consumed and discharge. However, the two sampling dates with the highest proportion of terrestrial invertebrates consumed occurred shortly after a 60-year flood, indicating that terrestrial invertebrates may be important during rain and associated high water. This study found that, although terrestrial infall and drift are highly variable, terrestrial invertebrates are an important prey resource for rearing chinook salmon in this high latitude riverine system, especially later in the summer.