• Ecological and physiological aspects of caribou activity and responses to aircraft overflights

      Maier, Julie Ann Kitchens (1996)
      I investigated the use of remote-sensing of caribou (Rangifer tarandus) activity to assess disturbance of low-altitude overflights by jet aircraft. Resource management agencies are concerned about the potential effects of these overflights on important species of ungulates. I hypothesized that low-altitude overflights would affect activity and movements of caribou, and thereby constitute a disturbance with negative consequences on energetics. I used caribou of the Delta Herd (DCH) and captive animals at the Large Animal Research Station (LARS) to address the hypotheses: caribou (1) exhibit equal activity day and night; (2) do not time activity to light; and (3) activity patterns do not change seasonally in response to daylength. Caribou were nychthemeral and exhibited uniform activity with no apparent timing to light. DCH caribou responded to seasonal changes in the environment by modifying activity (increased activity in response to insect harassment), whereas LARS caribou altered activity in response to fluctuating physiological variables (increased activity during rut). Changes in daylength did not affect activity. Data on activity from LARS and DCH caribou were compared with extant data on caribou of the Denali and Porcupine herds. Poor quality forage in winter was inferred from long resting bouts, and low availability of forage was inferred from long active bouts of post-calving caribou of the DCH. In midsummer, caribou of the DCH exhibited significantly longer active and shorter resting bouts than did LARS caribou, consistent with a moderate level of insect harassment. Responses of caribou to overflights were mild in late winter and, thus, overflights did not constitute a disturbance. Post-calving caribou responded to overflights by increasing daily activity, linear movements, incremental energy cost, and average daily metabolic rate. Energetic responses and movements were significantly related to the loudest overflight of the day. In the insect season, activity levels increased significantly in response to overflights but with no corresponding increase in linear movements or energetics. My recommendations are to prohibit aircraft overflights of caribou during calving and post-calving periods and during key feeding times in insect harassment seasons. Research indicates the possibility of more severe effects in nutritionally stressed animals.
    • Molecular phylogenetics of arvicoline rodents

      Conroy, Christopher John; Cook, Joseph A. (1998)
      The impetus for this dissertation was an interest in geographic variation in Microtus longicaudus with a particular focus on populations in the Alexander Archipelago of southeastern Alaska. To establish a framework for interpreting intraspecific variation in M. longicaudus, I examined the phylogenetics of 28 species of the genus Microtus, including all North American species (Chapters 2 and 4). That study, which corroborates a rapid pulse of diversification noted in the fossil record, necessitated a deeper phylogenetic perspective. Thus, a third objective of the dissertation was to investigate relationships among genera of arvicolines within the framework of other murid rodents. I examined variation in the mitochondrial cytochrome b and ND4 genes using maximum parsimony, distance, and maximum likelihood phylogenetic analyses. Relationships at several taxonomic levels appear intractable due to rapid accumulation and survival of genetic lineages. These rapid radiations were found among species, genera, and possibly subfamilies; however, strong support at these levels for other taxa (e.g., the monophyly of Microtus) suggests these genes have strong phylogenetic signal. Many of the well-supported sister species pairs within Microtus (Chapters 2 and 4) had been previously identified based on morphologic or allozyme work (e.g., M. pennsylvanicus and M. montanus, M. pinetorum and M. quasiater). The sequence data supported a clade of taiga dwelling species in North America and a clade of eastern and central Asian species. The southernmost arvicoline species of Mexico and Guatemala, though previously suggested to be derived from a single ancient invasion, did not appear to be either ancient or monophyletic. Within M. longicaudus, a large east-west phylogeographic break was detected that is equivalent in genetic distance to other sister species pairs in the genus. This break may indicate mid to late-Pleistocene differentiation (Chapter 3) within the genus. At higher latitudes, populations of M. longicaudus exhibited evidence of recent range expansion including absence of correlation between geographic and genetic structure; and pairwise mismatches among DNA sequences with a single peak and few differences.