Efficacy of a Multiple-Capture Live Trap for Small Mammals

Author Institution: National Park Service, Pictured Rocks Science CenterAuthor Institution: School of Forest Resources & Environmental Sciences, Michigan Technological UniversityWe compared the efficacy of Victor® Tin Cat® and Sherman live traps for capturing small mammals in northern hardwood and red pine (Pinus resinosa) stands in the north-central Upper Peninsula of Michigan during 2001. Overall mean capture rates (total captures/100 adjusted trap nights) by habitat were greater (P <0.030) for Sherman traps than for Tin Cat traps. Capture rates remained lower for Tin Cat traps in northern hardwood (P = 0.004) but not red pine (P = 0.936) habitat after adjusting for species (sciurids) unable to enter them. Greater species diversity values were obtained using Sherman traps in both habitats. We conclude that in sampling arrays tested, Victor Tin Cat traps were less effective than Sherman traps for estimating small mammal abundance and diversity

Small Mammal Abundance and Diversity in Forests With and Without Canada Yew, Taxus canadensis

Canada Yew (Taxus canadensis) has been extirpated from much of its former range in northeastern North America possibly due to logging, fire, agriculture, and browsing by White-tailed Deer (Odocoileus virginianus). We compared the relative abundance and species diversity of small mammals in five northern hardwood stands containing Canada Yew to five adjacent stands without Canada Yew in the Upper Peninsula of Michigan, during October-November 2000. Overall, 72 individuals were captured (53 in yew, 19 in non-yew); dominant species were Short-tailed Shrew (Blarina brevicauda), Deer Mouse (Peromyscus maniculatus), and Red-backed Vole (Clethrionomys gapperi). Overall mean (+ sd) capture rate (individuals/100 adjusted trap nights) in sites with yew (5.5 + 2.2) was greater (P = 0.04) than mean capture rate in sites without yew (1.9 + 1.0). Three indices of species diversity suggested greater small mammal diversity in stands with Canada Yew understories in northern hardwood forests

Estimating biomass of berries consumed by gray wolves

Gray wolves (Canis lupus) consume berries and other wild fruits seasonally when available or abundant. However, a method to convert percent frequency of occurrence or percent volume of berries in wolf scats to percent biomass has not yet been developed. We used estimates of the average number of blueberry (Vaccinium spp.) seeds in 10 individual wolf scats collected in and adjacent to Voyageurs National Park, Minnesota, USA, along with published values of the number of seeds per blueberry and blueberry masses to estimate that a wolf scat containing only berries equated to an average of 0.468 kg of berries consumed. We recommend using this berry conversion factor (0.468 kg/scat) to convert the percent frequency of occurrence or percent volume of berries and other wild fruits to percent biomass when estimating wolf diets from scats

Using Beaver Works to Estimate Colony Activity in Boreal Landscapes

Beaver ponds and beaver-impounded vegetation are indicators of past or present beaver activity that can be detected from aerial photography. A method to quantitatively relate these beaver works with the density of active beaver colonies could benefit beaver management, particularly in areas lacking beaver population data. We compared historical maps (1961–2006) of beaver works at Voyageurs National Park, Minnesota, USA with concurrent aerial surveys of beaver colonies. We tested 2 landscape-scale models of beaver colony density previously developed for a period of beaver population expansion (1940–1986), but they failed to predict colony density after 1986, a period of declining beaver population. We developed a new landscape-scale regression, calculating that 2.15% of the landscape would be flooded by every 100 additional beaver colonies (R2 = 0.53, P = 0.027). Classification tree analysis of individual pond sites showed that open water pond and impounded marsh area were the primary predictors of beaver colony presence or absence, but that the classification trees were far better at identifying inactive sites (\u3e 93% correct) than active sites (35–38% correct). The area of open water in beaver ponds is a good but not perfect indicator of beaver activity that can be used by wildlife managers as a landscape-scale indicator of beaver colony density

Where and How Wolves (Canis lupus) Kill Beavers (Castor canadensis)

Beavers (Castor canadensis) can be a significant prey item for wolves (Canis lupus) in boreal ecosystems due to their abundance and vulnerability on land. How wolves hunt beavers in these systems is largely unknown, however, because observing predation is challenging. We inferred how wolves hunt beavers by identifying kill sites using clusters of locations from GPS-collared wolves in Voyageurs National Park, Minnesota. We identified 22 sites where wolves from 4 different packs killed beavers. We classified these kill sites into 8 categories based on the beaver-habitat type near which each kill occurred. Seasonal variation existed in types of kill sites as 7 of 12 (58%) kills in the spring occurred at sites below dams and on shorelines, and 8 of 10 (80%) kills in the fall occurred near feeding trails and canals. From these kill sites we deduced that the typical hunting strategy has 3 components: 1) waiting near areas of high beaver use (e.g., feeding trails) until a beaver comes near shore or ashore, 2) using vegetation, the dam, or other habitat features for concealment, and 3) immediately attacking the beaver, or ambushing the beaver by cutting off access to water. By identifying kill sites and inferring hunting behavior we have provided the most complete description available of how and where wolves hunt and kill beavers

Finding wolf homesites: improving the efficacy of howl surveys to study wolves

Locating wolf (Canis lupus) homesites is valuable for understanding the foraging behavior, population dynamics, and reproductive ecology of wolves during summer. During this period wolf pack members (adults and pups) readily respond to simulated wolf howls (i.e., howl surveys), which allows researchers to estimate the location of the homesite via triangulation. Confirming the actual locations of homesites via ground truthing is labor intensive because of the error surrounding estimated locations. Our objectives were (1) to quantify observer error during howl surveys and compare amongst experience levels, (2) provide a simple method for locating homesites in the field by incorporating observer error, and (3) further document the value of this method for monitoring wolf packs throughout the summer. We located 17 homesites by howl surveys during 2015–2017 in the Greater Voyageurs Ecosystem, Minnesota, USA. Of 62 bearings taken by observers during howl surveys, bearings erred by an average of 7.6° ± 6.3° (SD). There was no difference in observer error between novice and experienced observers. A simple way to increase efficiency when searching for homesites is to search concentric areas (bands) based on estimated observer error, specifically by: (1) adding ±10° error bands around howl survey bearings when ≥3 bearings can be obtained, (2) ±10° and ±20° error bands when 2 bearings are obtained, and (3) ±10° and ±26° error bands when 1 bearing is obtained. By incorporating observer error and understanding how frequently and how far wolves move homesites, it is possible to monitor wolf packs and confirm most, if not all, homesites used by a pack from at least June until August without having a collared individual in a pack

Clonal structure of invasive cattail (Typhaceae

Abstract There is mounting evidence that the clonal dynamics of foundational plant species, including exotic invaders such as hybrid Typha x glauca, have a profound effect on wetland function. Here, we report on the clonal structure of five intensively sampled Typha stands from the Upper Midwest region where invasions have been especially disruptive. Each of these stands consisted of a large proportion of F 1 hybrids between T. latifolia and T. angustifolia, although backcrosses to both parents were also observed, and provided a means of determining relative age of invasion. We found clonal richness, measured as the proportion of ramets representing distinct genets, to vary positively with age of invasion over a range from 0.20 to 0.45, whereas Simpson&apos;s Evenness was relatively consistent among sites due to a pattern of dominance by a few large clones accompanied by many smaller clones. Ramets were significantly clumped within genets over a range of approximately 20 m, although many clones included ramets separated by as much as 60 to 90 m, suggesting some degree of clone fragmentation over time. Related genets were significantly clumped over approximately 10 m, suggesting that seedling cohorts may frequently recruit in close proximity to one another

Influence of Invasive Hybrid Cattails on Habitat Use by Common Loons

An invasive hybrid cattail species, Typha x glauca (T. x glauca), is rapidly expanding across the United States and Canada. Dense clonal stands of T. x glauca outcompete native wetland plants, reduce open-water habitats, and negatively affect native wetland plant diversity; however, effects of hybrid cattail expansions on native wildlife are still unclear. We used multiple surveys and single-season occupancy models to examine how the relative coverage of T. x glauca affected habitat use by common loons (Gavia immer) at 71 wetland sites in Voyageurs National Park, Minnesota, USA, during summer 2016. Delineated wetland sites (2 ha) were considered potential resource patches for common loons and positioned along a gradient of relative T. x glauca coverage. Detection of common loons was influenced negatively by the time of day surveys were conducted. Occupancy probabilities were greater at sites with deeper water levels, possibly indicating selection for areas with adequate water depths for pursuit-based foraging for fish. Contrary to our hypothesis, common loons appeared insensitive to the relative coverage of T. x glauca at wetland sites. Future research should focus on elucidating potential threshold-effects of T. x glauca expansions on additional loon demographic rates

MOOSE MODIFY BED SITES IN RESPONSE TO HIGH TEMPERATURES

Moose (Alces alces) employ physiological and behavioral mechanisms to enable them to dissipate excess heat when ambient temperature is above the upper critical temperature of their thermoneutral zone. In this note, we describe 2 cases where GPS radio-collared female moose modified summer bed sites as a potential thermoregulatory response to high temperatures. The first case occurred on 18 - 21 July 2011 when ambient temperatures averaged 25 °C (8 °C above the upper critical temperature of moose) and reached 32 °C and 96% relative humidity. Based on field observations of the bed site immediately after use, the moose cleared litter and duff to expose 3 m2 of mineral soil under a closed-canopy balsam fir (Abies balsamea) stand. The moose spent 64% of the time bedded during a 4-day event, with ≤11 individual bedding events in the same bed site. A second case was observed on 5 July 2013 during similar weather conditions (29 °C and 70% relative humidity) when a different moose cleared a bed site and used it continuously for 10 hours

Effects of Water-Level Management on Nesting Success of Common Loons

Water-level management is widespread and illustrates how contemporary climate can interact directly and indirectly with numerous biological and abiotic factors to influence reproductive success of wildlife species. We studied common loons, an iconic waterbird sensitive to timing and magnitude of waterlevel changes during the breeding season, using a before-after-control-impact design on large lakes in Voyageurs National Park (Minnesota, USA), to assess the effect of anthropogenic changes in hydroregime on their nesting success and productivity. We examined multiple competing a priori hypotheses in an information-theoretic framework, and predicted that magnitude of changes in loon productivity would be greater in the Namakan Reservoir, where water-level management was altered to mimic a more natural hydroregime, than in Rainy Lake, where management remained relatively unchanged. We determined outcomes from 278 nests during 2004–2006 by performing boat-based visits every 3–5 days, and measuring hydrologic, vegetative, and microtopographic covariates. Relative to comparably collected data for 260 total loon pairs during 1983–1986, productivity (chicks hatched/territorial pair) increased 95% in the Namakan Reservoir between the 2 time periods. Nest success declined in both lakes over the 2 study periods but less so in the Namakan Reservoir than in Rainy Lake. Flooding was a primary cause of nest failures (though second nests were less likely to flood). Nest predation appears to have increased considerably between the 2 study periods. Top-ranked models suggested that timing of nest initiation, probability of nest flooding, probability of nest stranding, and probability of nest success were each related to 2–4 factors, including date of initiation, timing of initiation relative to peak water levels, changes in the elevation of the nest edge, maximum waterlevel change between initiation and peak water levels, and maximum water-level change between initiation and nest outcome. The top model for all variables except stranding each garnered \u3e82% of total model weight. Results demonstrate that water-level management can be altered to benefit productivity of common loons. However, nuanced interactions between land-use change, invasive species, human development, recreation, climate change, and recovery of top predators may often complicate both management decisions and interpretation of water-level impacts on wildlife