Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 68-82). Also available on the World Wide Web.

Global amphibian declines have been attributed to numerous and often synergistic causes, such as invasive species, pathogens, and ultraviolet-B (UV-B) radiation. The effects of these stressors are context dependent and can vary with location, species, and populations. As sensitivity to UV-B has shown inconsistencies across amphibian taxa, it can be expected that variation also occurs between populations of a single species. High elevation populations of the long-toed salamander (Ambystoma macrodactylum) face exponentially higher UV-B radiation levels relative to low elevation populations and these levels are predicted to increase in conjunction with continued ozone depletion. We hypothesized that breeding long-toed salamander females at high elevations have modified oviposition behavior to better protect embryos from UV-B induced damage. In addition, we hypothesized that long-toed salamander embryos at high elevation would exhibit elevated photolyase activity, a photo-reactivating enzyme that repairs UV-B radiation-induced damage to DNA. We predicted that this behavioral defense strategy would be employed together with an elevated physiological response as a correlated defense response to increased levels of UV-B radiation in high elevation populations. We surveyed high and low elevation long-toed salamander breeding sites throughout Oregon to quantify oviposition site characteristics and associated UV-B profiles. We simultaneously collected embryos for quantification of photolyase activity in a bacterial transformation assay. We found significant differences in oviposition behavior across elevations, with high elevation breeding females ovipositing in deeper water and using UV-B protective refugia. Oviposition sites at low elevations, however, were most often found in UV-B exposed microhabitats located at the surface of the water. This population difference in oviposition behavior resulted in a standardization of UV-B and temperature conditions for long-toed salamander embryos across elevation. In contrast, we found no population differentiation in photolyase activity between high and low elevation breeding sites. This indicates that behavioral selection for UV-B protected oviposition substrates may either be negating the need for increased photolyase activity in long-toed salamander embryos, or that populations lack the capacity to adapt a heightened physiological response to UV-B at high elevations. Together, these results show how trade-offs in physiology and behavior are a unique adaptation to a significant environmental stressor. Further research into the susceptibility of amphibian species to changing environmental conditions may help to demonstrate the effectiveness of correlated trait responses and plasticity in behavior, and species persistence under changing climate regimes. / Graduation date: 2012

The long-toed salamander (Ambystoma macrodactylum) is the top vertebrate predator in fishless high-elevation lakes in North Cascades National Park Service Complex (NOCA), Washington. The purpose of this research was to determine the effects of physico-chemical factors and introduced trout on abundance and behavior of A. macrodactylum larvae. Although high-elevation lakes in NOCA were naturally fishless, trout were stocked in many lakes during this century to provide recreational angling opportunity. Twenty fishless lakes and 25 lakes with fish were sampled from 1990 to 1994. Larval salamander density and behavior were assessed by snorkeling lake perimeters and searching through nearshore substrate material and aquatic vegetation. In fishless lakes, larval salamander densities were positively related to total Kjeldahl-N concentration (TKN) and negatively related to lake elevation. Based on analysis of salamander stomach contents, crustacean zooplankton, especially cladocerans, were important food resources for larval A. macrodactylum. Total crustacean zooplankton, as well as cladoceran densities, were positively related to TKN concentration, suggesting that increased zooplankton food resources contributed to increased densities of A. macrodactylum. The effects of fish introductions on larval salamander densities depended on TKN concentration and whether or not trout had established reproducing populations. Mean larval salamander densities for fishless lakes with TKN<0.05 mg/l, generated from a linear regression equation with TKN and lake elevation as independent variables, were not significantly different from mean larval densities in lakes with either reproducing trout or in lakes with non-reproducing trout. However, in fishless lakes with TKN���0.05 mg/l, mean larval densities were significantly higher than in lakes with reproducing fish where trout reached high densities. In fishless lakes with TKN���0.095 mg/l, mean larval densities were significantly higher than in lakes with non-reproducing fish where trout fry were periodically stocked at low densities. Reduced larval salamander densities in lakes with trout likely was a consequence of trout predation. Although most larvae were associated with boulder, cobble, and woody debris substrates in nearshore areas of NOCA lakes, differences in the proportion of larvae hidden in benthic substrates between lakes with fish and without fish were not statistically significant. / Graduation date: 1997

Species that are introduced outside of their native ranges are an important threat to biodiversity. In southwestern Alberta, Canada, sport and bait fish have been introduced into most waterbodies. I examined the effects of introduced trout and minnows on the distribution, demography and behaviour of larval long-toed salamanders through a combination of field surveys, laboratory experiments and an outdoor mesocosm experiment. Results from field surveys at 30 high-elevation (>1500m) lakes confirmed previous studies showing an allopatic distribution of trout and long-toed salamanders. The same pattern was also documented at 27 low-elevation (<1500m) ponds. In a mesocosm experiment, salamander survival was significantly reduced in ponds containing trout or minnows. Surprisingly, larvae exposed to minnows were 28-65% smaller than larvae in control ponds, suggesting strong interspecific competition for zooplankton prey. In a series of laboratory studies, trout preyed directly on salamander hatchlings and larvae, whereas minnows injured hatchlings but did not consume them. In laboratory aquaria, salamander larvae spent significantly more time within a refuge when exposed to minnow cues, but showed no behavioural response to trout. This confirmed my expectation that long-toed salamanders lack specific behavioural responses to trout, but respond generally to disturbances within the water column. Thus, direct predation and a lack of specific antipredator behaviour are among the likely mechanisms responsible for the observed allopatic distribution of trout and long-toed salamanders. My data also show that gape-limited fish reduce growth and survival of salamanders, perhaps more so than trout, through mechanism such as competition and behavioural alteration. / ix, 76 leaves : ill., map ; 29 cm.

No description available.

Canada is the second highest producer of hydroelectric energy in the world. Nearly 50 of the hydroelectric reservoirs in the country have a capacity larger than 1 billion m3. Despite the great number and extent of hydropower developments in Canada and around the world, relatively little is known about how dams and their operations influence terrestrial and semi-aquatic wildlife. Reservoirs at northern latitudes are characterized by large fluctuations in water level, which create modified shorelines called drawdown zones. To evaluate the impact of these disturbances on amphibians and reptiles, I conducted visual encounter surveys at two sites in the drawdown zone of Kinbasket Reservoir, near Valemount, B.C. From April to August of 2010 and 2011, I documented the habitat use, reproductive phenology, and body condition of two amphibian species (Anaxyrus boreas and Rana luteiventris) as well as the growth, movements, diet, and distribution of one species of garter snake (Thamnophis sirtalis). At two sites in the drawdown zone, A. boreas and R. luteiventris were present for the duration of the summer and utilized several ponds for reproduction. The presence and abundance of Rana luteiventris eggs were generally associated with ponds that had higher mean temperatures, higher mean pH, and the presence of fish. In 2010, there was sufficient time for amphibian breeding and metamorphosis to occur before the reservoir inundated the drawdown zone, but low precipitation levels in that year led to desiccation of many breeding ponds. In 2011, high rainfall and snowmelt led to early inundation of breeding ponds, and thousands of tadpoles were presumably swept into the reservoir. Gravid Thamnophis sirtalis were found at just one of two sites in the drawdown zone, but both sites were frequented by foraging individuals of this species. Anaxyrus boreas appears to be the primary prey of T. sirtalis in the drawdown zone. An improved understanding of how the amphibians and reptiles at Kinbasket Reservoir have persisted in this highly disturbed environment may be vital to their conservation — the activation of a new generating unit at Mica Dam in 2014 will alter the pattern and timing of reservoir inundation for the first time since it was constructed 40 years previously. / Graduate

I investigated the value of under-road tunnels as a conservation strategy to protect a long-toed salamander population, in south-west Alberta, whose overwintering sites and breeding habitat (Linnet Lake) are separated by a road. I conducted a mark-recapture study from 2008-2009, capturing salamanders using roadside fences and pitfall traps. Four tunnels were monitored in 2009 using traps and cameras. A 2008 estimate indicated that the population declined by 60% since 1994, however, road mortality was dramatically reduced following installation of fences and tunnels. Camera and trap data documented 130 salamanders navigating tunnels in 2009. I found little evidence of juvenile recruitment from Linnet Lake, likely because of predation by lake chub. Experiments showed that lake chub consumed salamander larvae, and fish presence altered larval behaviour. Continued monitoring is needed to determine if reduced road mortality translates into population gains, and whether fish predation threatens the persistence of the long-toed salamander population. / Ecology