Voyageurs National Park

National Park, MN, United States

Voyageurs National Park

National Park, MN, United States
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Kerfoot W.C.,Michigan Technological University | Yousef F.,Michigan Technological University | Hobmeier M.M.,Michigan Technological University | Maki R.P.,Voyageurs National Park | And 2 more authors.
Biological Invasions | Year: 2011

The spiny water flea (Bythotrephes longimanus) is spreading from Great Lakes coastal waters into northern inland lakes within a northern temperature-defined latitudinal band. Colonization of Great Lakes coastal embayments is assisted by winds and seiche surges, yet rapid inland expansion across the northern states comes through an overland process. The lack of invasions at Isle Royale National Park contrasts with rapid expansion on the nearby Keweenaw Peninsula. Both regions have comparable geology, lake density, and fauna, but differ in recreational fishing boat access, visitation, and containment measures. Tail spines protect Bythotrephes against young of the year, but not larger fish, yet the unusual thick-shelled diapausing eggs can pass through fish guts in viable condition. Sediment traps illustrate how fish spread diapausing eggs across lakes in fecal pellets. Trillions of diapausing eggs are produced per year in Lake Michigan and billions per year in Lake Michigamme, a large inland lake. Dispersal by recreational fishing is linked to use of baitfish, diapausing eggs defecated into live wells and bait buckets, and Bythothephes snagged on fishing line, anchor ropes, and minnow seines. Relatively simple measures, such as on-site rinsing of live wells, restricting transfer of certain baitfish species, or holding baitfish for 24 h (defecation period), should greatly reduce dispersal. © 2011 The Author(s).

Smith J.B.,Savannah River Ecology Laboratory | Windels S.K.,Voyageurs National Park | Wolf T.,Apple Inc | Wolf T.,University of Minnesota | And 2 more authors.
Wildlife Biology | Year: 2016

One key assumption often inferred with using radio-equipped individuals is that the transmitter has no effect on the metric of interest. To evaluate this assumption, we used a known fate model to assess the effect of transmitter type (i.e. tail-mounted or peritoneal implant) on short-term (one year) survival and a joint live--dead recovery model and results from a mark--recapture study to compare long-term (eight years) survival and body condition of ear-tagged only American beavers Castor canadensis to those equipped with radio transmitters in Voyageurs National Park, Minnesota, USA. Short-term (1-year) survival was not influenced by transmitter type (wi = 0.64). Over the 8-year study period, annual survival was similar between transmitter-equipped beavers (tail-mounted and implant transmitters combined; 0.76; 95% CI = 0.45-0.91) versus ear-tagged only (0.78; 95% CI = 0.45-0.93). Additionally, we found no difference in weight gain (t9 = 0.25, p = 0.80) or tail area (t11 = 1.25, p = 0.24) from spring to summer between the two groups. In contrast, winter weight loss (t22 = - 2.03, p = 0.05) and tail area decrease (t30 = - 3.04, p = 0.01) was greater for transmitterequipped (weight = - 3.09 kg, SE = 0.55; tail area = - 33.71 cm2, SE = 4.80) than ear-tagged only (weight = - 1.80 kg, SE = 0.33; tail area = - 12.38 cm2, SE = 5.13) beavers. Our results generally support the continued use of transmitters on beavers for estimating demographic parameters, although we recommend additional assessments of transmitter effects under different environmental conditions. © 2016 Norwegian Institute for Nature Research.

PubMed | Upper Midwest Environmental science Center, Voyageurs National Park and University of Wisconsin-La Crosse
Type: Journal Article | Journal: Archives of environmental contamination and toxicology | Year: 2016

Most investigations of the environmental effects of mercury (Hg) have focused on aquatic food webs that include piscivorous fish or wildlife. However, recent investigations have shown that other species, including passerine songbirds, may also be at risk from exposure to methylmercury (MeHg). We quantified Hg concentrations in eggs of two species of songbirds, red-winged blackbirds (Agelaius phoeniceus) and tree swallows (Tachycineta bicolor), nesting in Voyageurs National Park, Minnesota, USA. Geometric mean concentrations of total Hg (THg) were lower in red-winged blackbird eggs [218 and 107ng/g dry weight (dw) for 2012 and 2013, respectively] than in tree swallow eggs (228 and 300ng/g dw for 2012 and 2013, respectively), presumably reflecting differences in the trophic positionsof these two species. Concentrations of MeHg averaged 98.4% of THg in red-winged blackbird eggs. Levels of THg observed in this study were well below critical toxicological benchmarks commonly applied to eggs of avian species, suggesting these breeding populations were not adversely affected by exposure to MeHg. In red-winged blackbirds, concentrations of THg in eggs collected in 2012 were twice those in eggs collected in 2013. Hg levels in eggs of both species increased with date of clutch initiation. In red-winged blackbirds, for example, temporal patterns showed that a 3-week delay in clutch initiation increased egg THg by 60%. These observations indicate that in ovo exposure of wetland birds to MeHg can vary significantly within nesting season as well as between years.

Shaw S.L.,South Dakota State University | Chipps S.R.,U.S. Geological Survey | Windels S.K.,Voyageurs National Park | Webb M.A.H.,U.S. Fish and Wildlife Service | And 2 more authors.
Journal of Applied Ichthyology | Year: 2012

Quantified were the age, growth, mortality and reproductive structure of lake sturgeon (Acipenser fulvescens) collected in the US and Canadian waters of the Namakan Reservoir. The hypotheses were tested that (i) age and growth of lake sturgeon in the Namakan Reservoir would differ by sex and reproductive stage of maturity, and (ii) that the relative strength of year-classes of lake sturgeon in the reservoir would be affected by environmental variables. To quantify age, growth and mortality of the population, existing data was used from a multi-agency database containing information on all lake sturgeon sampled in the reservoir from 2004 to 2009. Lake sturgeon were sampled in the Minnesota and Ontario waters of the Namakan Reservoir using multi-filament gillnets 1.8m high and 30-100m long and varying in mesh size from 178 to 356mm stretch. Reproductive structure of the lake sturgeon was assessed only during spring 2008 and 2009 using plasma testosterone and estradiol-17β concentrations. Ages of lake sturgeon >75cm ranged from 9 to 86years (n=533, mean=36years). A catch-curve analysis using the 1981-1953year classes estimated total annual mortality of adults to be 4.8% and annual survival as 95.2%. Using logistic regression analysis, it was found that total annual precipitation was positively associated with lake sturgeon year-class strength in the Namakan Reservoir. A 10cm increase in total annual precipitation was associated with at least a 39% increase in the odds of occurrence of a strong year class of lake sturgeon in the reservoir. Plasma steroid analysis revealed a sex ratio of 2.4 females: 1 male and, on average, 10% of female and 30% of male lake sturgeon were reproductively mature each year (i.e. potential spawners). Moreover, there was evidence based on re-captured male fish of both periodic and annual spawning, as well as the ability of males to rapidly undergo gonadal maturation prior to spawning. Knowledge of lake sturgeon reproductive structure and factors influencing recruitment success contribute to the widespread conservation efforts for this threatened species. © 2012 Blackwell Verlag, Berlin.

Moen R.,University of Minnesota | Windels S.K.,Voyageurs National Park | Hansen B.,University of Minnesota
Natural Areas Journal | Year: 2012

Voyageurs National Park (VNP) is within the historical distribution of Canada lynx (Lynx canadensis), a federally threatened species. Sightings of lynx in and near VNP have existed since the 1970s, and three recent sightings have been confirmed with DNA analysis. However, population status and habitat suitability for lynx in VNP are unknown. We used remote cameras and snow-tracking to search for lynx in and near VNP in 2007 and 2008 and did not document lynx presence. We estimated the density of the lynx's primary prey, snowshoe hare (Lepus americanus), with hare pellet counts, extrapolated hare density to the landscape level, and compared habitat in VNP to habitat in lynx home ranges in northeastern Minnesota. Hare pellet densities in VNP were about half of hare pellet densities in lynx home ranges in northeastern Minnesota. Even though patches of high-density hare habitat exist in the VNP area, the low density of snowshoe hares at the landscape level would not support resident lynx, and most of the lynx recently documented in and near VNP are, therefore, probably transient animals. A female lynx with a kitten west of VNP in winter of 2010 was the only probable resident lynx confirmed near VNP from 2001 to 2010. Habitat management or natural disturbance processes that increase snowshoe hare densities would be required to support a resident lynx population in VNP.

Larson J.H.,U.S. Geological Survey | Maki R.P.,Voyageurs National Park | Knights B.C.,U.S. Geological Survey | Gray B.R.,U.S. Geological Survey
Ecotoxicology | Year: 2014

Mercury (Hg) contamination of fisheries is a major concern for resource managers of many temperate lakes. Anthropogenic Hg contamination is largely derived from atmospheric deposition within a lake’s watershed, but its incorporation into the food web is facilitated by bacterial activity in sediments. Temporal variation in Hg content of fish (young-of-year yellow perch) in the regulated lakes of the Rainy–Namakan complex (on the border of the United States and Canada) has been linked to water level (WL) fluctuations, presumably through variation in sediment inundation. As a result, Hg contamination of fish has been linked to international regulations of WL fluctuation. Here we assess the relationship between WL fluctuations and fish Hg content using a 10-year dataset covering six lakes. Within-year WL rise did not appear in strongly supported models of fish Hg, but year-to-year variation in maximum water levels (∆maxWL) was positively associated with fish Hg content. This WL effect varied in magnitude among lakes: In Crane Lake, a 1 m increase in ∆maxWL from the previous year was associated with a 108 ng increase in fish Hg content (per gram wet weight), while the same WL change in Kabetogama was associated with only a 5 ng increase in fish Hg content. In half the lakes sampled here, effect sizes could not be distinguished from zero. Given the persistent and wide-ranging extent of Hg contamination and the large number of regulated waterways, future research is needed to identify the conditions in which WL fluctuations influence fish Hg content. © 2014, Springer Science+Business Media New York (outside the USA).

Windels S.K.,Voyageurs National Park
Wildlife Society Bulletin | Year: 2014

External marking of American beavers (Castor canadensis) is essential to studies of population dynamics and behavior of individuals. Application of metal ear tags is a common method used to mark beavers but rates and causes of ear-tag loss have been insufficiently documented. I live-trapped and tagged 627 beavers in Voyageurs National Park, Minnesota, USA, from 2006 to 2012 with a single, uniquely numbered no. 3 monel ear tag in each ear. Beavers recaptured or recovered via live-trapping (n=178), legal harvest outside of the park (n=55), or death (n=4) up to 6 years after initial release were inspected for tag loss. An additional 31 beavers were secondarily marked with radiotransmitters and used to test the assumption that loss of one ear tag was independent of loss of the other. Six percent (15 out of 237) of beavers lost a single ear tag. Overall probability of beavers losing a single ear tag was low (3.3%) and did not differ by sex, age class, or method of recapture-recovery. Tag loss was highest within 6 months of initial tagging, but probability of tag loss was not related to time between tagging and recovery up to 6 years after tagging. None of the radioed beavers lost both ear tags, supporting the assumption of independence of ear-tag loss among individual beavers. Ear-tag loss rates are sufficiently low that studies of American beavers that rely on mark- recapture methods do not need to account for bias from ear-tag loss. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

Windels S.K.,Voyageurs National Park | Flaspohler D.J.,Michigan Technological University
Botany | Year: 2011

Canada yew (Taxus canadensis Marsh.) is a shade-tolerant evergreen shrub native to the understories of the boreal and deciduous forests of northeastern North America. Canada yew has a relatively unique growth form, with low sprawling branches capable of forming dense clusters of stems. Historic accounts suggest that before Euro-American settlement, Canada yew was a common plant across its range in many forest types and that it was locally abundant or dominant in 5%-20% of forest stands in the northern part of its range. Canada yew's range has declined during the last century as a result of browsing by native ungulates, fire, intensive forest management, and clearing of land for agriculture and other development. It is considered uncommon throughout most of its present North American range, except for often isolated populations in areas that remain free from heavy browsing pressure by moose and deer (e.g., islands, areas with heavy snow cover, or areas naturally low in ungulate abundance). Its decline has likely resulted in changes to abiotic and biotic conditions, including structure and composition of understory vegetation and concomitant effects on understory vertebrates. Increasing whitetailed deer populations and reduced snowfall as a result of climate change in eastern North America threaten to extirpate this species from additional parts of its range in the next century. Suggestions for future research are discussed.

Windels S.K.,Voyageurs National Park | Hewitt D.G.,Texas A&M University-Kingsville
Rangeland Ecology and Management | Year: 2011

Carrying capacity estimates based on digestible protein (DP) and energy (DE) are useful in comparing effects of land management practices or the ability of different vegetation communities to support herbivores. Plant secondary compounds that negatively affect forage quality would be expected to change nutritionally based estimates of carrying capacity. We evaluated the effect of plant secondary compounds on nutritionally based carrying capacity estimates of white-tailed deer (Odocoileus virginianus Zimmerman) in Tamaulipan thorn scrub of northern Mexico. Forage biomass, nutrient concentration, and tannin concentration (protein-precipitating capacity) were measured for 23 forage items during spring and summer in three replicate pastures. Nitrogen in phenolic amines was estimated for the two principal woody browse species in deer diets and was assumed to be unavailable for amino acid synthesis. Carrying capacity estimates were calculated based on three dietary concentrations of DP and DE. Nutritional carrying capacity estimates that accounted for antinutritional compounds were reduced 50 ± 6%, 28 ± 8%, and 0 ± 0% (mean ± SE) for diets of high, medium, and low DE concentration, respectively, compared to estimates from models that ignored the effects of these compounds. Accounting for effects of plant secondary compounds reduced DP-derived carrying capacity estimates 4 ± 3%, 47 ± 9%, and 9 ± 8% for diets with high, medium, and low concentrations of DP, respectively. High variation in percent reduction in carrying capacity estimates occurred because of site and seasonal variation in plant species composition and biomass, making application of a single correction factor to account for plant secondary compound effects on carrying capacity infeasible. Protein-precipitating capacity of tannins accounted for > 98% of the reductions in carrying capacity estimates based on DP. Our results clearly demonstrate the need to consider effects of tannins on ungulate carrying capacity estimates based on DP and DE. Estimates can be further refined by accounting for nonprotein nitrogen and other antinutritional compounds in all forage items. © 2011 Society for Range Management.

Windels S.K.,Voyageurs National Park | Belant J.L.,Mississippi State University
Wildlife Biology | Year: 2016

Tail-mounted transmitters have been used successfully in temperate regions of North America and Europe but have not been tested in more northern parts of American beaver Castor canadensis range. We deployed 63 tail-mounted transmitters on adult beavers in Voyageurs National Park, Minnesota (USA; 48°30′N, 92°50′W), at the southern edge of the boreal forest. Mean transmitter retention time was 133 days (range = 18-401, SD = 101), with only 7% retained > 12 months. Males and females did not differ in retention times. Retention time was similar for transmitters deployed in fall (n = 38, = 135 days) and spring (n = 21, = 130 days). In 24 cases where we confirmed beavers lost transmitters, 63% tore through the side of the tail, 25% pulled out through a widened attachment hole, and 13% had the lock-nut unscrew. Beavers chewed off or pulled out whip antennas on 50% of transmitters before they were detached from the tail, which reduced VHF signal strength and detection distance. The likelihood that an antenna would be damaged increased 3.8 times for each day of deployment up to 371 days. On average, beavers with transmitters lost 23% of their body mass and 26% of tail thickness over winter, and regained similar percentages over the growing season. Retention rates and retention times of tail transmitters were much lower in Voyageurs National Park relative to more southern areas in the United States where intra-annual variability in body condition is considerably less. Our results reaffirm that methodologies developed for wildlife telemetry or other research and monitoring techniques should be tested under different environmental conditions to ensure objectives can be met in a safe and efficient manner.

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