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An appeal to undergraduate wildlife programs: send scientists to learn statistics

Undergraduate wildlife students taking introductory statistics too often are poorly prepared and insufficiently motivated to learn statistics. We have also encountered too many wildlife professionals, even with graduate degrees, who exhibit an aversion to thinking statistically, either relying too heavily on statisticians or avoiding statistics altogether. We believe part of the reason for these problems is that wildlife majors are insufficiently grounded in the scientific method and analytical thinking before they take statistics. We suggest that a partial solution is to assure wildlife majors are trained in the scientific method at the very beginning of their academic careers.

Wildlife Society Bulletin

Artificial cavities enhance breeding bird densities in managed cottonwood forests

The paucity of natural cavities within short-rotation hardwood agroforests restricts occupancy by cavity-nesting birds. However, providing 1.6 artificial nesting cavities (nest boxes)/ha within 3- to 10-year-old managed cottonwood forests in the Mississippi Alluvial Valley increased territory density of cavity-nesting birds. Differences in territory densities between forests with and without nest boxes increased as stands aged. Seven bird species initiated 38 nests in 173 boxes during 1997 and 39 nests in 172 boxes during 1998. Prothonotary warblers (Protonotaria citrea) and eastern bluebirds (Sialia sialis) accounted for 67% of nests; nearly all warbler nests were in 1.8-L, plastic-coated cardboard (paper) boxes, whereas bluebird nests were divided between paper boxes and 3.5-L wooden boxes. Larger-volume (16.5-L) wooden nest boxes were used by eastern screech owls (Otus asio) and great crested flycatchers (Myiarchus crinitus), but this box type often was usurped by honey bees (Apis mellifera). To enhance territory densities of cavity-nesting birds in cottonwood agroforests, we recommend placement of plastic-coated paper nest boxes, at a density of 0.5/ha, after trees are >4 years old but at least 2 years before anticipated timber harvest.

Wildlife Society Bulletin

Leaf litter bags as an index to populations of northern two-lined salamanders (Eurycea bislineata)

Concern about recent amphibian declines has led to research on amphibian populations, but few statistically tested, standardized methods of counting amphibians exist. We tested whether counts of northern two-lined salamander larvae (Eurycea bislineata) sheltered in leaf litter bags--a relatively new, easily replicable survey technique--had a linear correlation to total number of larvae. Using experimental enclosures placed in streams, we compared number of salamanders found in artificial habitat (leaf litter bags) with total number of salamanders in each enclosure. Low numbers of the animals were found in leaf litter bags, and the relative amount of variation in the index (number of animals in leaf litter bags compared to total number of animals in stream enclosures) was high. The index of salamanders in leaf litter bags was not significantly related to total number of salamanders in enclosures for two-thirds of the replicates or with pooled replicates (P= 0.066). Consequently, we cannot recommend using leaf litter bags to index populations of northern two-lined salamanders.

Wildlife Society Bulletin

A new device to estimate abundance of moist-soil plant seeds

Methods to sample the abundance of moist-soil seeds efficiently and accurately are critical for evaluating management practices and determining food availability. We adapted a portable, gasoline-powered vacuum to estimate abundance of seeds on the surface of a moist-soil wetland in east-central Mississippi and evaluated the sampler by simulating conditions that researchers and managers may experience when sampling moist-soil areas for seeds. We measured the percent recovery of known masses of seeds by the vacuum sampler in relation to 4 experimentally controlled factors (i.e., seed-size class, sample mass, soil moisture class, and vacuum time) with 2-4 levels per factor. We also measured processing time of samples in the laboratory. Across all experimental factors, seed recovery averaged 88.4% and varied little (CV = 0.68%, n = 474). Overall, mean time to process a sample was 30.3 ? 2.5 min (SE, n = 417). Our estimate of seed recovery rate (88%) may be used to adjust estimates for incomplete seed recovery, or project-specific correction factors may be developed by investigators. Our device was effective for estimating surface abundance of moist-soil plant seeds after dehiscence and before habitats were flooded.

Wildlife Society Bulletin

Comparing protein and energy status of winter-fed white-tailed deer

Although nutritional status in response to controlled feeding trials has been extensively studied in captive white-tailed deer (Odocoileus virginianus), there remains a considerable gap in understanding the influence of variable supplemental feeding protocols on free-ranging deer. Consequently, across the northern portion of the white-tailed deer range, numerous property managers are investing substantial resources into winter supplemental-feeding programs without adequate tools to assess the nutritional status of their populations. We studied the influence of a supplemental winter feeding gradient on the protein and energy status of free-ranging white-tailed deer in the Adirondack Mountains of New York. We collected blood and fecal samples from 31 captured fawns across 3 sites that varied considerably in the frequency, quantity, and method of supplemental feed distribution. To facilitate population-wide comparisons, we collected fresh fecal samples off the snow at each of the 3 sites with supplemental feeding and 1 reference site where no feeding occurred. Results indicated that the method of feed distribution, in addition to quantity and frequency, can affect the nutritional status of deer. The least intensively fed population showed considerable overlap in diet quality with the unfed population in a principal components ordination, despite the substantial time and financial resources invested in the feeding program. Data from fecal samples generally denoted a gradient in diet quality and digestibility that corresponded with the availability of supplements. Our results further demonstrated that fecal nitrogen and fecal fiber, indices of dietary protein and digestibility, can be estimated using regressions of fecal pellet mass, enabling a rapid qualitative assessment of diet quality.

Wildlife Society Bulletin

The need for coherence between waterfowl harvest and habitat management

Two of the most significant management efforts affecting waterfowl populations in North America are the North American Waterfowl Management Plan (the Plan) and Federal harvest management programs. Both the Plan and harvest management are continental in scope, involve an extensive group of stakeholders, and rely on adaptive processes of biological planning, implementation, and evaluation. The development of these programs has occurred independently, however, and there has been little explicit recognition that both harvest and habitat effects should be considered for coherent management planning and evaluation. For example, the harvest strategy can affect whether population objectives of the Plan are met, irrespective of the success of the Plan's habitat conservation efforts. Conversely, habitat conservation activities under the Plan can influence harvest potential and, therefore, the amount of hunting opportunity provided. It seems increasingly clear that the Plan's waterfowl population objectives can only be useful for conservation planning and evaluation if they are accompanied by an explicit specification of the harvest strategy and environmental conditions under which they are to be achieved. This clarification also is necessary to ensure that Plan population objectives are not attained solely through the reduction of hunting opportunity. We believe then that it is imperative that these key waterfowl-management programs work to harmonize their objectives. Harvest management programs and the Plan ought to be working toward the same ends, but that is not possible so long as the mutually reinforcing relationship of these programs is obscured by ambiguities in their management objectives.

Wildlife Society Bulletin

Hair of the dog: obtaining samples from coyotes and wolves noninvasively

Canids can be difficult to detect and their populations difficult to monitor. We tested whether hair samples could be collected from coyotes (Canis latrans) in Texas, USA and gray wolves (C. lupus) in Montana, USA using lure to elicit rubbing behavior at both man-made and natural collection devices. We used mitochondrial and nuclear DNA to determine whether collected hair samples were from coyote, wolf, or nontarget species. Both coyotes and wolves rubbed on man-made barbed surfaces but coyotes in Texas seldom rubbed on hanging barbed surfaces. Wolves in Montana showed a tendency to rub at stations where natural-material collection devices (sticks and debris) were present. Time to detection was relatively short (5 nights and 4 nights for coyotes and wolves, respectively) with nontarget and unknown species comprising approximately 26% of the detections in both locations. Eliciting rubbing behavior from coyotes and wolves using lures has advantages over opportunistic genetic sampling methods (e.g., scat transects) because it elicits a behavior that deposits a hair sample at a fixed sampling location, thereby increasing the efficiency of sampling for these canids. Hair samples from rub stations could be used to provide estimates of abundance, measures of genetic diversity and health, and detection-nondetection data useful for cost-effective population monitoring.

Texas;Montana

Evaluation of Canada goose sterilization for population control

We evaluated the vasectomy of 72 male Canada geese as a method to control growing populations of nuisance geese in Westchester County, New York. Thirty-three of the vasectomized males paired with a female and were located during ≥1 breeding seasons; 7 treated males were not seen following surgery. The remaining 32 males were never observed paired with a female during the breeding season. Of 56 nesting attempts by the 33 pairs in ≥1 breeding seasons, 84% of the nests were unsuccessful. Fidelity to nest sites during the second and third breeding seasons occurred for 17 of the 18 vasectomized males and their females that were observed for ≥2 seasons. The results suggest that male sterilization may reduce productivity of nuisance Canada geese providing one carefully selects areas and flocks suitable for this type of control.

New York

Lead exposure in Canada geese of the eastern prairie population

We monitored lead exposure in Eastern Prairie Population Canada geese during summer-winter, 1986-1987 and 1987-1988 at 5 areas. Blood lead concentrations in geese trapped during summer at Cape Churchill Manitoba were below levels indicative of recent lead exposure (0.18 ppm). Geese exposed to lead (&ge;0.18 ppm blood lead) increased to 7.6% at Oak Hammock Wildlife Management Area (WMA), southern Manitoba, where lead shot was still in use, and to 10.0% at Roseau River WMA, northern Minnesota, when fall-staging geese were close to a source of lead shot in Manitoba. Proportion of birds exposed to lead dropped to <2% at Lac Qui Parle WMA, Minnesota, a steel shot zone since 1980. On the wintering grounds at Swan Lake National Wildlife Refuge in Missouri, 4.9% of all geese showed exposure to lead before the hunting season. Lead exposure rose to 10.0% after hunting ended and then decreased to 5.2% in late winter. Incidence of lead shot in gizzards and concentrations of lead in livers supported blood assay data. Soil samples indicated that lead shot continues to be available to geese at Swan Lake, even though the area was established as a non-toxic shot zone in 1978. Steel shot zones have reduced lead exposure in the Eastern Prairie Population, but lead shot persists in the environment and continues to account for lead exposure and mortality in Eastern Prairie Population Canada geese.

Minnesota, Manitoba

Seasonal ingestion of toxic and nontoxic shot by Canada geese

We used rates of ingested shot and elevated blood-lead levels (&ge;0.18 ppm) to estimate the proportion of Canada geese (Branta canadensis) exposed to lead on 3 study areas in Manitoba, Minnesota, and Missouri. Lead exposure was prevalent on all areas and was common after the hunting season closed, when up to 15% of geese could have been exposed to lead shot. However, the proportion of steel shot ingested by geese has increased during the past 2 decades. We suggest that lead exposure is still a source of indirect hunting mortality in Canada geese but project that the prevalence of lead exposure in the Eastern Prairie Population and other waterfowl populations will decrease as nontoxic shot regulations persist and hunters use steel or other nontoxic shot.

Minnesota, Missouri, Manitoba

Tests of wildlife habitat models to evaluate oak-mast production

We measured oak-mast production and forest structure and composition in the Ozark Mountains of Missouri and tested the accuracy of oak-mast prediction variables from 5 Habitat Suitability Index (HSI) species models. Acorn production was positively associated with several measures of abundance and canopy cover of oak trees, and with an index of mast production for all 5 HSI models. We developed 2 modified oak-mast models, based on inputs related to either oak tree density or oak canopy cover and diversity of oak tree species. The revised models accounted for 22-32% of the variance associated with acorn abundance. Future tests of HSI models should consider: (1) the concept of upper limits imposed by habitat and the effects of nonhabitat factors; (2) the benefits of a top-down approach to model development; and (3) testing models across broad geographic regions.

Wildlife Society Bulletin

Testing releasable GPS radiocollars on wolves and white-tailed deer

We tested prototype GPS collars on 8 free-ranging wolves ( Canis lupus ) and 3 white-tailed deer ( Odocoileus virginianus ) for varying periods between February and August 1997. We programmed the 920-gm collars to make a location attempt 6-96 times per day. The collars were designed to be remotely released from the animal and the data were then downloaded to a desktop computer. The collars produced 47-1,549 locations each during 11-41 days; locations were successful in 26-95% of the attempts (x̄ = 70%). Eight collars released successfully. Three collar-release failures were caused by condensation. Two collars had GPS antennas that were improperly attached and did not collect data. Life was as long as, or longer than, expected in 4 collars, less than expected in 5 collars, and unknown in 2 collars. Limitations of this type of collar include brief life if programmed at short location-attempt intervals (≤1 hr) and possible drop-off failure. Nevertheless, the large volume of data we collected with no field telemetry effort demonstrates the potential for this type of GPS collar to answer questions about movements of medium-sized mammals.

Wildlife Society Bulletin

A review of the relationships between visitors and ungulates in national parks

The growth in ungulate populations and the enhanced viewing opportunities they provide in many national parks, a mixed blessing to park managers, has been viewed positively by most park visitors. Visitors, long the major constituency of parks, have played a major role in the way ungulates are managed. I trace the history of the relationships between visitors and ungulates in parks and provide examples of how visitors have influenced ungulate management policies. Today, although public influence on ungulate management seems to be greater than ever, the public has a poor understanding of park management actions. Park interpretive programs can be used to address this problem.

Wildlife Society Bulletin

Black bear depredation on agricultural commodities in Massachusetts

We used response to a mail survey (n = 848) to evaluate the extent and severity of depredation by black bears (Ursus americanus) on agricultural commodities in Massachusetts and to assess producers' attitudes toward and tolerance of bear depredation. Damage abatement techniques were ranked for effectiveness by producers of corn, bees and honey, and livestock and dairy products. Results showed differences in perception of effects of bear depredation among commodity groups. Producers of corn and livestock and dairy products considered bear damage to be low to moderate in severity whereas beekeepers thought their losses were substantial or severe. Most estimates of economic loss were <$1,000 per year. Respondents considered bears to be an inconvenience, but thought they should remain a part of our natural heritage. There was no significant relationship between producers' experience with or economic dependence on their product and their attitude toward bears or their tolerance of bear damage. We conclude that there is need for effective education programs for agricultural producers, strengthened working relationships between producers and state fish and wildlife agencies, incorporation of producers' suggestions into management decisions, and investment in effective, economical, and long-term solutions to bear depredations for each affected commodity group.

Wildlife Society Bulletin

Thunder on the Yellowstone revisited: An assessment of management of native ungulates by natural regulation, 1968-1993

Natural regulation of native ungulates was initiated in 1968 in Yellowstone National Park (YNP) based on the premise that ungulates would reach an equilibrium with their plant resources. The natural-regulation management model stated: density dependence will regulate ungulates (i.e., a dynamic equilibrium will result between ungulates and their food supply, within some bounds of vegetation and soil effects); and no retrogression of soil and vegetation will occur from elk (Cervus elaphus) grazing during this process. The historical record indicated that elk were abundant in the system and elk were primarily food limited before settlement by European man (i.e., wolves [Canis lupus] and Native Americans were only an adjunct to the density dependent population regulation of ungulates). Density dependence was demonstrated in elk, but not in bison (Bison bison). No widespread evidence of overgrazing was observed through 1993 in study sites within vegetation communities that comprised about 97% of the winter range. No evidence of increased exotics, increased sediment yield, warming or drying of the soil, changes in soil nutrients, or differences in aboveground standing-crop biomass of plants was found between grazed and ungrazed plots. Ungulate herbivory apparently stimulated aboveground production of grasses, enhanced nitrogen and macronutrients in grasses, increased nutrient cycling, and enhanced measures of fitness in 6 common plants. However, exposed soil surface (bare ground and pebbles combined) was 11-18% greater on grazed than ungrazed plots, apparently due to a 71% decline in dead and standing litter on grazed plots. Percent live-plant basal cover, however, did not differ on grazed versus ungrazed plots, and there was no difference in soil microclimate or sediment yield. Differences in the abundance of 12% of the herbaceous species were found in grazed versus ungrazed sites (16 of 128 species); 10 were declines and 6 were increases. Willow (Salix spp.) and aspen (Populus tremuloides) declines predated the new management policy, but their slow declines also continued after 1968. Three uncommon plant species (aspen, willow, and Wyoming big sagebrush [Artemisia tridentata tridentata]) and 1 herbivore (moose [Alces alces]) declined under natural-regulation management. Two uncommon species of woody browse (aspen, Wyoming big sagebrush) were overutilized by ungulates (consumption of >2/3 current annual growth occurred). We conclude the natural-regulation model for YNP was flawed in its assumptions of a single, steady state for the park, based on conditions presumed to exist in 1870 prior to establishment of the national park. The period selected as a standard (1870) was an unusual period characterized by frequent large fires and floods, common wolves, few elk, and a cooler, wetter climate. We also conclude there is a high level of uncertainty surrounding what elk densities were in pre-Columbian times (element 3 of the management model) and what effects wolves and Native Americans had in regulating the elk population.

Wildlife Society Bulletin