Direct and indirect effects of wolves on interior Alaska's mesopredator community

Thesis (M.S.) University of Alaska Fairbanks, 2015Large carnivores may indirectly benefit small predators by suppressing competitively dominant mesopredators. However, our current understanding of interactions within the carnivore guild does not account for carrion subsidies provided by large carnivores, which could facilitate mesopredators during times of prey scarcity. This could be particularly relevant in northern ecosystems characterized by long harsh winters and decadal prey cycling. In Alaska, state-sponsored wolf (Canis lupus) control programs reduce wolf populations by as much as 50-80% across 8 game management units that collectively total over 165,000 km2, yet the impact of this practice on the Alaska's diverse mesopredator community remains unknown. We used a quasi-experiment resulting from a wolf control program in the upper Susitna River Basin that was adjacent to Denali National Park and Preserve lands, where wolves occur at naturally regulated densities. From January-March 2013 and 2014, we collected coyote (Canis latrans) and red fox (Vulpes vulpes) scats and conducted snow track surveys for wolves, mesocarnivores, and their prey. I quantified the relative strengths of direct and indirect effects of wolves on 5 mesopredator species while accounting for snowpack characteristics and small mammal abundance, and assessed winter diet overlap and composition by coyotes and red foxes in response to wolves and small prey availability. My findings indicated that wolves could strongly influence mesocarnivore communities in the Denali and Susitna systems, however despite a strong effect of wolves on coyotes, there was no evidence to support a mesopredator release cascade mediated by coyotes. Rather, I observed a near guild-wide response to wolf presence, whereby mesopredators were positively associated with wolves within each study area. The relative strength of top down versus bottom up effects in this study system further indicated that during a period characterized by low small mammal abundance, wolves were the strongest predictor of canid and wolverine occurrence. Coyote and red fox diet further revealed that carrion was a heavily used resource during this time of low prey abundance, yet red foxes may minimize competition with coyotes for carrion by increasing their use of voles. Finally, I present a hypothesis that local scale facilitation by large carnivores could lead to landscape patterns of suppression by large carnivores, suggesting a key link between abundance patterns and the structure of carnivore communities at different spatial scales relevant to conservation and management

Fatal Attraction?: Intraguild Facilitation and Suppression Among Predators

Competition and suppression are recognized as dominant forces that structure predator communities. Facilitation via carrion provisioning, however, is a ubiquitous interaction among predators that could offset the strength of suppression. Understanding the relative importance of these positive and negative interactions is necessary to anticipate community-wide responses to apex predator declines and recoveries worldwide. Using state-sponsored wolf (Canis lupus) control in Alaska as a quasi experiment, we conducted snow track surveys of apex, meso-, and small predators to test for evidence of carnivore cascades (e.g., mesopredator release). We analyzed survey data using an integrative occupancy and structural equation modeling framework to quantify the strengths of hypothesized interaction pathways, and we evaluated fine-scale spatiotemporal responses of nonapex predators to wolf activity clusters identified from radio-collar data. Contrary to the carnivore cascade hypothesis, both meso- and small predator occupancy patterns indicated guild-wide, negative responses of nonapex predators to wolf abundance variations at the landscape scale. At the local scale, however, we observed a near guild-wide, positive response of nonapex predators to localized wolf activity. Local-scale association with apex predators due to scavenging could lead to landscape patterns of mesopredator suppression, suggesting a key link between occupancy patterns and the structure of predator communities at different spatial scales

Spring food habits of Wolverine (Gulo gulo) in the Colville River watershed, Alaska

Wolverines (Gulo gulo) are relatively abundant on the North Slope of Alaska, an Arctic ecosystem dominated by tundra habitats that run north from the Brooks Range across a wide coastal plain to the Beaufort Sea. The region contains a range of potential Wolverine prey species, including ungulates (Caribou [Rangifer tarandus], Moose [Alces americanus]), Arctic Ground Squirrel (Urocitellus parryii), and both Soricidae and Cricetidae species. The seasonal composition of these, and other prey species, in the Wolverines’ diet is not well understood. We collected Wolverine scats during spring (March–May) on the North Slope while tracking animals from snowmobiles and with helicopters that visited areas identified as of interest during ground surveys or using global positioning system collared animals. We analyzed prey remains in 48 scat samples based on hair, bone, and other prey fragments. We then calculated frequency of occurrence, percentage of occurrence, and weighted percent volume for each major prey category detected. We confirmed species identity of scats as Wolverine by amplifying the control region of the mitochondrial DNA. We estimated spring diet diversity and richness based on nine major prey categories detected in scats. Ungulates and cricetids together constituted 69% of the Wolverines’ spring diet, with Snowshoe Hare (Lepus americanus) constituting 9%, fox (Vulpes spp.) 6%, Arctic Ground Squirrel 2%, birds 2%, American Beaver (Castor canadensis) less than 1%, and unknown 6%

Effects of Rodent Species, Seed Species, and Predator Cues on Seed Fate

Seed selection, removal and subsequent management by granivorous animals is thought to be a complex interaction of factors including qualities of the seeds themselves (e.g., seed size, nutritional quality) and features of the local habitat (e.g. perceived predator risk). At the same time, differential seed selection and dispersal is thought to have profound effects on seed fate and potentially vegetation dynamics. In a feeding arena, we tested whether rodent species, seed species, and indirect and direct predation cues influence seed selection and handling behaviors (e.g., scatter hoarding versus larder hoarding) of two heteromyid rodents, Ord’s kangaroo rat (Dipodomys ordii) and the Great Basin pocket mouse (Perognathus parvus). The indirect cue was shrub cover, a feature of the environment. Direct cues, presented individually, were (1) control, (2) coyote (Canis latrans) vocalization, (3) coyote scent, (4) red fox (Vulpes vulpes) scent, or (5) short-eared owl (Asio flammeus) vocalization. We offered seeds of three sizes: two native grasses, Indian ricegrass (Achnatherum hymenoides) and bluebunch wheatgrass (Pseudoroegneria spicata), and the non-native cereal rye (Secale cereale), each in separate trays. Kangaroo rats preferentially harvested Indian ricegrass while pocket mice predominately harvested Indian ricegrass and cereal rye. Pocket mice were more likely to scatter hoard preferred seeds, whereas kangaroo rats mostly consumed and/or larder hoarded preferred seeds. No predator cue significantly affected seed preferences. However, both species altered seed handling behavior in response to direct predation cues by leaving more seeds available in the seed pool, though they responded to different predator cues. If these results translate to natural dynamics on the landscape, the two rodents are expected to have different impacts on seed survival and plant recruitment via their different seed selection and seed handling behaviors

Metabolic engineering for the microbial production of carotenoids and related products with a focus on the rare C50 carotenoids

Heider S, Peters-Wendisch P, Wendisch VF, Beekwilder J, Brautaset T. Metabolic engineering for the microbial production of carotenoids and related products with a focus on the rare C50 carotenoids. Applied Microbiology and Biotechnology. 2014;98(10):4355-4368