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Douglas W. Smith, Edward E. Bangs, John K. Oakleaf, Curtis Mack, Joseph Fontaine, Diane Boyd, Michael Jimenez, Daniel H. Pletscher, Carter C. Niemeyer, Thomas J. Meier, Daniel R. Stahler, James Holyan, Valpha J. Asher, Dennis L. Murray
After roughly a 60-year absence, wolves (Canis lupus) immigrated (1979) and were reintroduced (1995–1996) into the northern Rocky Mountains (NRM), USA, where wolves are protected under the Endangered Species Act. The wolf recovery goal is to restore an equitably distributed metapopulation of ≥30 breeding pairs and 300 wolves in Montana, Idaho, and Wyoming, while minimizing damage to livestock; ultimately, the objective is to establish state-managed conservation programs for wolf populations in NRM. Previously, wolves were eradicated from the NRM because of excessive human killing. We used Andersen–Gill hazard models to assess biological, habitat, and anthropogenic factors contributing to current wolf mortality risk and whether federal protection was adequate to provide acceptably low hazards. We radiocollared 711 wolves in Idaho, Montana, and Wyoming (e.g., NRM region of the United States) from 1982 to 2004 and recorded 363 mortalities. Overall, annual survival rate of wolves in the recovery areas was 0.750 (95% CI = 0.728–0.772), which is generally considered adequate for wolf population sustainability and thereby allowed the NRM wolf population to increase. Contrary to our prediction, wolf mortality risk was higher in the northwest Montana (NWMT) recovery area, likely due to less abundant public land being secure wolf habitat compared to other recovery areas. In contrast, lower hazards in the Greater Yellowstone Area (GYA) and central Idaho (CID) likely were due to larger core areas that offered stronger wolf protection. We also found that wolves collared for damage management purposes (targeted sample) had substantially lower survival than those collared for monitoring purposes (representative sample) because most mortality was due to human factors (e.g., illegal take, control). This difference in survival underscores the importance of human-caused mortality in this recovering NRM population. Other factors contributing to increased mortality risk were pup and yearling age class, or dispersing status, which was related to younger age cohorts. When we included habitat variables in our analysis, we found that wolves having abundant agricultural and private land as well as livestock in their territory had higher mortality risk. Wolf survival was higher in areas with increased wolf density, implying that secure core habitat, particularly in GYA and CID, is important for wolf protection. We failed to detect changes in wolf hazards according to either gender or season. Maintaining wolves in NWMT will require greater attention to human harvest, conflict resolution, and illegal mortality than in either CID or GYA; however, if human access increases in the future in either of the latter 2 areas hazards to wolves also may increase. Indeed, because overall suitable habitat is more fragmented and the NRM has higher human access than many places where wolves roam freely and are subject to harvest (e.g., Canada and AK), monitoring of wolf vital rates, along with concomitant conservation and management strategies directed at wolves, their habitat, and humans, will be important for ensuring long-term viability of wolves in the region.
Gray wolf (Canis lupus) populations are recovering in many parts of the world and managers from various jurisdictions will be faced with difficult decisions as wolf populations continue to increase. Wolf management in Alberta, Canada, is achieved mostly through trapping on a registered trapline system. Wolf harvest increased over the last 22 years relative to population increases. Most wolf harvests occurred in the Rocky Mountains and surrounding foothills area and this pattern was consistent over time. On average, trappers only harvested an estimated 9.8% of the provincial population annually despite the lack of bag limits or quotas. Harvests are spatially autocorrelated with peak autocorrelation coinciding with average home-range size for wolves in Alberta. When wolf control actions are deemed necessary, trappers are unlikely to remove a sufficient number of wolves over a large enough area to limit subpopulations under the registered trapline system.
In western Canada it is illegal to trap or snare cougars (Puma concolor), but cougars are sometimes caught accidentally in snares placed near carrion baits, a technique commonly used by trappers to harvest wolves (Canis lupus). We studied cougar foraging ecology and survival in west-central Alberta to estimate the propensity for cougars to scavenge, their susceptibility to snaring at trapper bait stations, and the implications these have for managing cougar populations. During 2005–2008, we used data from visits to 3,407 Global Positioning System (GPS) location clusters and >400 km of snow tracking of 44 cougars to locate foraging events and calculate scavenging rates. We identified 83 instances of scavenging, and 64% of monitored cougars scavenged at least once. Scavenging rates were higher in winter (0.12 events/week) than in summer (0.04 events/week), reflecting seasonal variation in carrion availability. Individual cougars scavenged at different rates, and winter feeding on carrion occupied up to 50% of total carcass handling time for some cougars. Based on these results we conclude that cougars are facultative scavengers. A propensity to scavenge made cougars susceptible to snaring causing high annual mortality in radiocollared cougars (0.11, 95% CI = 0.03–0.21). Provincial cougar mortality data demonstrate that snaring has increased dramatically as a mortality source in Alberta over the last 2 decades. Mortalities of radiocollared cougars during our study were 100% human caused and the addition of snaring mortality to already high hunting mortality resulted in low annual survival (0.67, 95% CI = 0.53–0.81). Our study is one of the first to identify population-level consequences for nontarget animals killed unintentionally by indiscriminate harvest techniques in a terrestrial ecosystem. Maintaining sustainable cougar harvest where snaring at carrion baits is permitted may require flexible hunting quotas capable of accommodating high cougar snaring mortalities in some years.
During the past 2 decades, the grizzly bear (Ursus arctos) population in the Greater Yellowstone Ecosystem (GYE) has increased in numbers and expanded its range. Early efforts to model grizzly bear mortality were principally focused within the United States Fish and Wildlife Service Grizzly Bear Recovery Zone, which currently represents only about 61% of known bear distribution in the GYE. A more recent analysis that explored one spatial covariate that encompassed the entire GYE suggested that grizzly bear survival was highest in Yellowstone National Park, followed by areas in the grizzly bear Recovery Zone outside the park, and lowest outside the Recovery Zone. Although management differences within these areas partially explained differences in grizzly bear survival, these simple spatial covariates did not capture site-specific reasons why bears die at higher rates outside the Recovery Zone. Here, we model annual survival of grizzly bears in the GYE to 1) identify landscape features (i.e., foods, land management policies, or human disturbances factors) that best describe spatial heterogeneity among bear mortalities, 2) spatially depict the differences in grizzly bear survival across the GYE, and 3) demonstrate how our spatially explicit model of survival can be linked with demographic parameters to identify source and sink habitats. We used recent data from radiomarked bears to estimate survival (1983–2003) using the known-fate data type in Program MARK. Our top models suggested that survival of independent (age ≥2 yr) grizzly bears was best explained by the level of human development of the landscape within the home ranges of bears. Survival improved as secure habitat and elevation increased but declined as road density, number of homes, and site developments increased. Bears living in areas open to fall ungulate hunting suffered higher rates of mortality than bears living in areas closed to hunting. Our top model strongly supported previous research that identified roads and developed sites as hazards to grizzly bear survival. We also demonstrated that rural homes and ungulate hunting negatively affected survival, both new findings. We illustrate how our survival model, when linked with estimates of reproduction and survival of dependent young, can be used to identify demographically the source and sink habitats in the GYE. Finally, we discuss how this demographic model constitutes one component of a habitat-based framework for grizzly bear conservation. Such a framework can spatially depict the areas of risk in otherwise good habitat, providing a focus for resource management in the GYE.
Estimating population size in a mark–recapture framework using DNA obtained from remotely collected genetic samples (e.g., feces) has become common in recent years but rarely has been used for ungulates. Using DNA extracted from fecal pellets, we estimated the size of an argali (Ovis ammon) population that was believed to be isolated from others within the Big Pamir Mountains, Afghanistan, an area where access was difficult and expensive. We used closed-capture models to estimate abundance, and Pradel models to examine closure assumptions, both as implemented in Program MARK. We also made visual counts of argali in the Big Pamirs, allowing comparison of count indices of abundance with modeled estimates. Our model-averaged estimate for female argali in the Big Pamir was 172 (95% CI = 117–232), which was about 23% higher than our best assessment using uncorrected visual counts. However, mark–recapture models suggested that males were not a closed population; thus, we were unable to provide a meaningful estimate of overall population size. Males either suffered much higher mortality than females during the sampling period, or, more likely, males moved in and out of the Big Pamir area. Although information from DNA did not provide a clear overall population estimate, it suggested that the Big Pamir was not isolated from other argali populations, which could not have been confirmed with visual observations alone. Estimating argali population size using mark–recapture models and fecal DNA is feasible but may be too expensive for frequent monitoring of large and remote populations. Our study demonstrates the importance of sex identification and separate abundance estimation for each sex, especially if movement ecology differs by sex.
Moose (Alces alces) and roe deer (Capreolus pygargus) are sympatric in the forest region of northeastern China. Using univariate analyses of feeding sign data, we found the 2 species were positively associated, but there were distinctions between their use of forage resources across landscape, patch, and microhabitat scales. We used resource selection function models to predict the influence of environmental covariates on moose and roe deer foraging; we detected covariate effects at the landscape and microhabitat scales but not at the patch scale. Forage resources used by the 2 species were similar, but moose used wetter areas and more low-visibility habitats than did roe deer, which strongly avoided areas with sparse vegetation. Both species were influenced by forage abundance and distribution at the microhabitat scale but exhibited differences in intensity of use of plant species and microhabitats. Moose used areas with deeper snow and avoided hiding cover; roe deer avoided areas with higher total basal areas of tree stems and preferred areas with high plant species richness. For moose, there was a trade-off in the use of concealment cover between the landscape and microhabitat scales. We detected avoidance by moose of roads where roe deer occurred. Roe deer exhibited more capacity for coping with human disturbance and interspecific interaction. In areas similar to our study area, road closures and suppression of roe deer near roads within 3–5 years postlogging may benefit moose. Furthermore, a mosaic of areas with different logging intervals may contribute to spatial separation of moose and roe deer and promote their coexistence.
I investigated local and regional differences in percent moss in the feces of muskoxen (Ovibos moschatus) and reindeer or caribou (Rangifer tarandus) in northwestern Alaska, USA, and related fecal moss to forage availability, snow conditions, animal density, and terrain ruggedness on wintering areas. Reindeer are a partially domesticated form of Rangifer tarandus originating from Europe and Asia and differ physiologically and ecologically from caribou. Percent moss in feces of muskoxen differed locally among individual wintering areas. Because of the large local variation in moss content of muskox feces, regional differences between the 2 study areas were difficult to resolve. Percent of moss in the feces of reindeer–caribou did not differ between wintering areas within the same study area but did differ between study areas. On muskox wintering areas, fecal moss correlated negatively with graminoid cover and snow hardness and positively with moss cover and muskox density, but fecal moss did not correlate with snow depth or terrain ruggedness. On reindeer–caribou wintering areas, fecal moss correlated positively with moss availability but not with lichen cover or snow depth or hardness. Because muskox groups in Alaska are isolated from each other in winter, even groups wintering on neighboring hills may face different foraging availability and might, therefore, exhibit differences in growth or productivity. Reindeer–caribou are more mobile than muskoxen in winter, and fecal samples may not be representative of vegetative and snow conditions at the wintering area where I collected them. I conclude that managers can use fecal moss as an indicator of overgrazed ranges, severe snow conditions, or crowded conditions on muskox wintering areas, but that the association between fecal moss and range conditions has to be drawn with caution for the more mobile reindeer–caribou.
Many studies of interactions between exotic and native ungulates have not had temporal and spatial controls nor have they considered the types of competitive interactions that would allow coexistence. For exotic axis deer (Axis axis) and native white-tailed deer (Odocoileus virginianus) to coexist one species should be superior at interference competition and the other species should be superior at exploitative competition. We generated and tested predictions, based on body size and diet breadth, about habitat selection by white-tailed deer in the presence and absence of axis deer, dominance relationships, and time at sites provisioned with high quality forage. We conducted our study in treatment (axis and white-tailed deer) and control (white-tailed deer only) areas when both species were present and after axis deer were removed. We conducted vehicle surveys to determine habitat use of both species. At provisioned feeding sites we recorded aggressive behaviors and amount of time species spent at feeding sites alone and together. In the treatment area white-tailed deer selection for wooded habitat increased 2.1 times after axis deer were removed, whereas habitat selection by white-tailed deer was constant in the control area over the same time. At feeding sites axis deer were dominant to white-tailed deer; both species spent a significantly greater amount of time alone than at feeders together, but amount of time that individuals of each species spent at feeders did not differ. Axis deer were superior at interference competition, but white-tailed deer were not superior at exploitative competition; thus, species coexistence is unlikely. Whether white-tailed deer are negatively impacted by axis deer at spatial scales larger than our experiment probably depends on abundance of axis deer at larger spatial scales. Experiments of species interactions with temporal and spatial controls that consider types of competitive interactions increase a manager's understanding of when and how native ungulates may be negatively impacted by exotic ungulates.
Condensed tannins (CT) can reduce digestibility of forages for white-tailed deer (Odocoileus virginianus), potentially confounding estimates of diet quality and nutritional carrying capacity. We collected 143 spring and 142 summer samples of 8 important deer forage species from 22 properties in Mississippi, USA, and tested for CT content using a modified butanol-HCl assay. Three species (partridge pea [Chamaecrista fasciculata], southern dewberry [Rubus trivialis], and roundleaf greenbrier [Smilax rotundifolia]) contained CT, ranging from 0.11% to 6.46% dry weight. Summer CT concentration was greater than in spring for 2 species. We ranked soil samples from least to most fertile using 8 chemical characteristics and found a positive correlation between fertility and CT concentration for 1 species and no correlation for 2 species. We tested effects of CT concentration on in vitro dry matter disappearance (IVDMD) and in vitro protein digestibility using samples of partridge pea and roundleaf greenbrier and rumen fluid from 3 free-ranging deer. Average IVDMD was reduced 1.9% for each 1% increase in CT concentration. In vitro protein digestibility was reduced 2.5% for each 1% increase in CT concentration. Assuming that our methods reflect the effects of CT on in vivo digestibility, maximum loss of available crude protein (CP) in our samples was 3.0 g/100 g dry-weight forage, and only 13 of the 112 CT-containing forage samples (12%) would have decreased available CP by >1 g/100 g dry-weight forage. Deer consuming equal portions of sampled forages would lose <1% of dietary CP to CT. Comparisons of foraging area quality using crude protein estimates should be unaffected by CT under reasonable restrictions of similar habitat types, soil fertility, and time. Given the ability of deer to forage selectively and the abundance of alternative forages in Mississippi, the potential for CT to substantially affect spring or summer diet quality of deer appears minimal.
Hunting is the primary tool for managing white-tailed deer (Odocoileus virginianus) populations. Effectiveness of hunting in suburban areas may be reduced due to limited hunter access to small properties, firearms-discharge laws, and public safety concerns. In Connecticut, USA, hunting over bait on private land was recently legalized to increase harvest opportunities. Our objective was to assess bow-hunter willingness to use bait and effects of bait type, hunter disturbance, time spent hunting, and property size on deer-harvest potential in a suburban landscape. We mailed a prebaiting survey in February 2002 and a postbaiting survey in February 2004 to the same group of hunters. Hunters using bait were more successful and harvested more deer than hunters using no bait. Hunters using bait on small properties observed similar numbers of deer within shooting range as hunters using bait on larger properties. Hunters using bait met their venison needs, whereas hunters using no bait did not meet their needs. Resource managers should implement strategies that increase hunter success when developing urban deer-management programs for communities.
We evaluated multiscale habitat selection by threatened Newfoundland (Canada) martens (Martes americana atrata) across landscapes composed of a range of habitat types to test the hypothesis that martens preferred mature (61–80-yr-old) and overmature (>80 yr) conifer stands. At both the landscape and stand scales, adult (≥1 yr) resident martens (n = 58, 92 yr-specific home ranges) selected for, or used in proportion to availability, a broad range of habitat types, including recent cuts ≤5 yr old, regenerating forest <6.5 m, precommercially thinned stands, and mature and overmature forest. Marten home ranges were not dominated by mature and overmature forest; median availability of mature and overmature forest within individual home ranges was only 30% (range = 11–76%). Age distributions were not different among martens with high, intermediate, and low quantity of mature and overmature forest in their home range; our data do not indicate that martens inhabiting ranges with little mature and overmature forest were compromising fitness. Habitat selection by martens in Newfoundland was more generalized than has traditionally been inferred, and we suggest that inherent landscape fragmentation, in combination with absence of many predators and competitors (i.e., ecological release), caused the Newfoundland marten to evolve to use a more generalized habitat niche than many mainland populations of American martens. We recommend that landscapes suitable for marten not exceed >29% younger aged forest. Maintaining resident martens in landscapes where forest harvesting is occurring requires prescriptions that recognize the highly fragmented nature of the natural landscape, the prevalence of mature and overmature forest, younger forests, avoided land-cover types, and human access.
We studied breeding populations of 2 coexisting ground-nesting birds, the red-faced warbler (Cardellina rubrifrons) and yellow-eyed junco (Junco phaeonotus), in high-elevation (>2,000 m) forested drainages of the Santa Catalina Mountains, Arizona, USA. From 2004 to 2005, we 1) estimated density and nesting success of breeding populations of red-faced warblers and yellow-eyed juncos, 2) identified nest-site characteristics for each species (i.e., used sites vs. random plots), 3) compared nest-site characteristics between the 2 species, and 4) examined effects of a recent (2003) wildfire on distribution of nests of both species. In addition, we estimated the areal extent of montane riparian forest (the preferred breeding habitat of both species) within high-elevation forests of the Santa Catalina Mountains. We found that red-faced warblers and yellow-eyed juncos were the 2 most common ground-nesting birds within our study area with an average density of 2.4 and 1.4 singing males/ha, respectively, along drainage bottoms. Compared to random plots, most red-faced warbler and yellow-eyed junco nests were located close (≤30 m) to drainage bottoms within a strip of montane riparian forest characterized by abundant brush, small woody debris, ferns, and forbs (both species), high number and diversity of saplings and small trees (red-faced warblers), and abundant shrubs and downed logs and less canopy cover (yellow-eyed juncos). Although both species nested in close proximity within montane riparian forest, nest-site characteristics differed between the 2 species, especially at finer spatial scales. For example, most yellow-eyed juncos nested adjacent to grass (principally Muhlenbergia spp.), whereas red-faced warblers nested adjacent to a variety of plant species, including grass, bigtooth maple (Acer grandidentatum), white fir (Abies concolor), and Douglas-fir (Pseudotsuga menziesii). Both red-faced warblers and yellow-eyed juncos avoided nesting in areas burned during a recent wildfire. In addition, nesting success was low for red-faced warblers (13%) and yellow-eyed juncos (19%) following the wildfire, suggesting an indirect negative effect of fire on breeding populations in the short-term. Montane riparian forest appears to provide important breeding habitat for red-faced warblers and yellow-eyed juncos. However, little research or conservation planning has been directed toward montane riparian forest in the region, even though this forest type is limited in its areal extent (<11% of high-elevation forest in the Santa Catalina Mountains) and increasingly threatened by disturbance. Results from our study can be used to facilitate the management and conservation of breeding populations of red-faced warblers and yellow-eyed juncos in high-elevation forests of the southwestern United States.
Lowland riparian vegetation in the southwestern United States is critically important for maintaining a high richness and density of breeding birds. Further investigation is needed within riparian corridors, however, to evaluate the relative importance of vegetation type and hydrologic regime for avian density and nest survival as targets for regional conservation or restoration efforts. We estimated the densities of 40 bird species and for species grouped on the basis of nest height and dependence on surface water in gallery cottonwood–willow (Populus spp.–Salix spp.) forests, saltcedar (Tamarix spp.) shrub lands, and terrace vegetation types along a gradient in the hydrologic regime of the San Pedro River, Arizona, USA. We also assessed nest survival for shrub-nesting insectivores and herbivores. Canopy-nesting birds as a group and 14 individual bird species reached their greatest densities in cottonwood forests regardless of the hydrologic regime. Water-dependent birds as a group reached their highest density in both intermittent- and perennial-flow cottonwood stands, but certain species occurred almost exclusively in perennial-flow sites. Two shrub-nesting species and the brown-headed cowbird (Molothrus ater) were most abundant in saltcedar shrub lands, and the brown-headed cowbird was most abundant in saltcedar stands with intermittent flows. Mesquite (Prosopis spp.) and big sacaton (Sporobolus wrightii) grassland each maintained the highest densities of certain species within ≥1 hydrologic regime. Shrub-nesting insectivores had the greatest nest survival in cottonwood, including Arizona Bell's vireo (Vireo bellii arizonae), and also had lower proportions of nests parasitized and preyed upon, although 95% confidence intervals among vegetation types overlapped. Nest survival for both shrub-nesting insectivores and herbivores was lowest in intermittent-flow saltcedar, although, again, confidence intervals overlapped. Nest survival was lower in parasitized than nonparasitized nests in mesquite and across vegetation types for Arizona Bell's vireo and in cottonwood for Abert's towhee (Pipilo aberti). Riparian management that maintains heterogeneous riparian vegetation types, including floodplain vegetation comprising cottonwood–willow gallery riparian forests with some stretches of perennial flow, are important for maintaining the high diversity and abundance of breeding birds on the San Pedro River and probably across the region. Cottonwood stands also appear to maintain highest nest survival for some shrub-nesting birds.
We evaluated 6 years of vegetation response following prescribed fire in Wyoming big sagebrush (Artemisia tridentata spp. wyomingensis) steppe on vegetation cover, productivity, and nutritional quality of forbs preferred by greater sage-grouse (Centrocercus urophasianus), and abundance of common arthropod orders. Habitat cover (shrubs and tall herbaceous cover [>18 cm ht]) was about 50% lower after burning compared to unburned controls because of the loss of sagebrush. Perennial grasses and an invasive annual forb, pale alyssum (Alyssum alyssoides), increased in cover or yield after fire. There were no increases in yield or nutritional quality of forb species important in diets of sage-grouse. Abundance of ants (Hymenoptera), a significant component in the diet of young sage-grouse, decreased after fire. These results suggest that prescribed fire will not improve habitat characteristics for sage-grouse in Wyoming big sagebrush steppe where the community consists of shrubs, native grasses, and native forbs.
Staging areas and migratory stopovers of wetland birds have the potential to function as geographic bottlenecks; entire populations within a flyway may be affected by the quality and quantity of available wetland habitat at stopover sites. Although approximately 90% of playa wetlands in the Rainwater Basin (RWB) region of south-central Nebraska, USA, have been destroyed, the area still provides essential stopover habitat for >10 million waterfowl each spring. We evaluated community patterns and species associations to assess importance of assembly rules in structuring wetland bird communities during migration and to better facilitate multispecies conservation and management strategies. We surveyed 36–40 playas twice weekly in the RWB and observed approximately 2.6 million individual migratory wetland birds representing 72 species during 3 spring migrations 2002–2004. We evaluated spatial and temporal species co-occurrence patterns of geese, dabbling ducks, diving ducks, and shorebirds using null model analysis. Goose species co-occurrence scores did not differ from random in any year of the study, suggesting that goose species frequently use the same habitats during migration. Co-occurrence patterns among dabbling ducks were not different than expected by chance in any year; however, when we evaluated co-occurrence at a weekly scale, dabbling ducks co-occurred less often than expected during weeks of peak migration (high abundance), indicating that dabbling duck species spatially segregated at high densities. Diving duck co-occurrence patterns did not differ from random in any year, suggesting that diving duck species used the same habitats during migration. Shorebird species co-occurred less often than expected in 2002 and 2004, and during weeks of high shorebird abundance, indicating that shorebird communities were distinctly structured during those times. Most association values among lesser snow geese (Chen caerulescens) and dabbling duck species were positive, indicating dabbling ducks did not avoid wetlands with snow geese, a concern for waterfowl managers. However, we frequently observed snow geese and dabbling ducks using different microhabitats within a wetland, which indicate species associations and co-occurrence patterns may have occurred at a finer spatial scale than we measured. This approach of co-occurrence analysis will allow wildlife managers charged with multispecies management at migration stopover sites to make informed conservation and management decisions based on community structure rather than historic single-species approaches.
Unlike other North American prairie-nesting dabbling ducks, northern pintail (Anas acuta) populations have not increased since the early 1990s and remain well below the long-term average for traditional survey areas. Previously reported estimates of annual survival and recovery rates for pintails did not investigate any spatial or temporal factors to explain annual variation of these rates. We used band-recovery data from 1970 to 2003 to test the influence of temporal periods defined by differing harvest regulations and habitat conditions of breeding grounds with spatially delineated regions on survival and recovery rates of northern pintails in North America. We separated regions based on a multiresponse permutation procedure to identify banding blocks with dissimilar recovery distributions based on a cluster analysis. We categorized time by grouping years into temporal periods based on bag limits, season lengths, or overflight versus nonoverflight years. We used the Brownie approach in Program MARK to evaluate 46 a priori models estimating survival and recovery rates. The best approximating model indicated that survival varied with age, sex, and region with additive time and interactive time-by-age and time-by-region effects. Recovery rate was best represented by a fully interactive term comprised of age, sex, region, and year. There were no statistical differences among average annual survival point estimates between age and sex classes within each region, and our estimates were similar to previous unpublished studies. We found the eastern region had decreased survival and increased recovery rates compared to other regions. Trends in pintail survival suggest that variation in annual survival was not the cause of the initial decrease in the northern pintail population and is unlikely the dominant factor preventing the population from increasing. The influence of other population parameters, such as recruitment rate, should be investigated to further evaluate other causes for the population status of northern pintails. Use of the top-ranked model to estimate annual survival and recovery rates for northern pintails in North America, which indicated that annually varying estimates of survival rates were better supported by the data than grouping years into temporal classes (i.e., based on bag limits, season lengths, and overflight yr) can be used by managers and policy makers when considering annual harvest regulations and effects of conservation efforts. Managers should incorporate these estimates into future demographic studies of pintails as well as consider using the top-ranked model for future analyses of band-recovery data.
Food abundance can affect a species' distribution. In many studies of potential food limitation, researchers focus on carrying capacity estimates during the nonbreeding season for temperate species consuming a fixed food source. Estimates of energetic carrying capacity for year-round breeders feeding on a replenishing resource would be more difficult and require much data. To determine whether gathering detailed information on year-round carrying capacity would be an important investment, we conducted an assessment to determine whether there was evidence that energy or protein might limit numbers of the tropical, endangered Hawaiian moorhen (Gallinula chloropus sandvicensis). We compared observed numbers of moorhen at 15 Oahu, Hawaii, USA, wetlands with predicted numbers based on measured energy and protein in food plants and abundance of these food plants in each wetland and on estimates of energy expenditure of moorhen. We made comparisons assuming moorhen are limited by their ability to metabolize food plants, by competition for food, and by estimated costs associated with reproduction. We also compared ranked moorhen abundance and density with ranked energy and protein under different wetland management regimes. Energy values consistently overestimated expected numbers of Hawaiian moorhen at wetlands except for one wetland location (predicted, 3803 ± 4856; observed, 6.2 ± 10.8). In addition, we detected no significant relationship between moorhen abundance and measures of energy (all r2 = 0.02–0.73, all P > 0.1) or protein abundance (all r2 = 0.08–0.50, all P > 0.3). This lack of relationship held once we controlled for wetland area or when we considered whether wetlands were managed for waterbirds. Hawaiian moorhen on Oahu did not appear to be limited by energy, nor did they appear to select sites based on energy or protein, in contrast to many studies relating animal numbers to energy in nonbreeding situations. Consequently, we suggest that researchers and managers explore other potentially limiting factors for Hawaiian moorhen.
Increased raptor and corvid abundance has been documented in landscapes fragmented by man-made structures, such as fence posts and power lines. These vertical structures may enhance raptor and corvid foraging and predation efficiency because of increased availability of perch, nesting, and roosting sites. Concomitantly, vertical structures, in particular power distribution lines, have been identified as a threat to sage-grouse (Centrocercus spp.) conservation. To mitigate potential impacts of power distribution lines on sage-grouse and other avian species, the electrical power industry has retrofitted support poles with perch deterrents to discourage raptor and corvid use. No published information is available regarding efficacy of contemporary perch deterrents on avian predator use of lower-voltage power distribution lines. We evaluated efficacy of 5 perch deterrents mounted on support poles of an 11-km section of a 12.5-kV distribution line that bisected occupied Gunnison sage-grouse (Centrocercus minimus) habitat in southeastern Utah, USA. Perch deterrents were mounted on the line in November–December 2006 following a random replicated block design that included controls. During 168 hours and 84 hours of direct observation in 2007 and 2008, respectively, we recorded 276 and 139 perching events of 7 potential avian predators of sage-grouse. Golden eagles (Aquila chrysaetos) were the dominant species we recorded during both years. We did not detect any difference in perching events by perch deterrent we evaluated and controls (P > 0.05). Perch deterrents we evaluated were not effective because of inherent design and placement flaws. Additionally, previous pole modifications that mitigated avian electrocutions provided alternative perches. We did not record any raptor or corvid electrocutions or direct predation on Gunnison sage-grouse. The conclusions of this study can be applied by conservation groups and power companies to future management of power distribution lines within areas inhabited by species sensitive to man-made vertical structures.
We genotyped 180 captive desert tortoises (Gopherus agassizii) from Kingman (n = 45), Phoenix (n = 113), and Tucson (n = 22), Arizona, USA, to determine if the genetic lineage of captives is associated with that of wild tortoises in the local area (Sonoran Desert). We tested all samples for 16 short tandem repeats and sequenced 1,109 base pairs of mitochondrial DNA (mtDNA). To determine genetic origin, we performed assignment tests against a reference database of 997 desert tortoise samples collected throughout the Mojave and Sonoran Deserts. We found that >40% of our Arizona captive samples were genetically of Mojave Desert or hybrid origin, with the percentage of individuals exhibiting the Mojave genotype increasing as the sample locations approached the California, USA, border. In Phoenix, 11.5% were Sonoran–Mojave crosses, and 8.8% were hybrids between desert tortoise and Texas tortoise (G. berlandieri). Our findings present many potential implications for wild tortoises in the Sonoran Desert of Arizona. Escaped or released captive tortoises with Mojave or hybrid genotypes have the potential to affect the genetic composition of Sonoran wild populations. Genotyping captive desert tortoises could be used to inform the adoption process, and thereby provide additional protection to native desert-tortoise populations in Arizona.
Many aquatic species in the arid southwestern United States are imperiled, persisting primarily in isolated, low-order streams that are increasingly vulnerable to stochastic disturbances. During 2003 and 2004, we surveyed 39 mountain canyons in southeastern Arizona, USA, for lowland leopard frogs (Rana yavapaiensis), a species that has declined in abundance and distribution across its range in the United States. We quantified habitat features at 2 spatial scales, canyon and pool, to identify features that distinguished sites inhabited by frogs from those uninhabited by frogs. Canyons inhabited by frogs had watersheds that averaged 8.1 km2 larger (SE = 2.52), pools that averaged 37.8 m3 greater (9.30) in volume, gradients that averaged 4.1% (1.40%) less steep, and locations that averaged 3.2 km closer (1.06) to the nearest valley stream than did uninhabited canyons. Plunge pools inhabited by frogs averaged 13.5% (5.66%) more perimeter vegetation, 11.2% (5.34%) more canopy cover, and 1.9 (0.60) more refuges than uninhabited pools. In general, canyons that provided more perennial water during dry summer months and plunge pools that provided more bank heterogeneity were more likely to be inhabited by frogs. Conservation of lowland leopard frogs and other aquatic species that inhabit xeric systems in the southwestern United States depends principally on maintaining riparian ecosystems that provide habitat for these species and the adjacent uplands that influence the structure and function of these systems. Therefore, both riparian areas and their adjacent uplands must be managed to maintain habitat for organisms that inhabit these rare and diverse ecosystems.
A previous analysis of the content of articles published in The Wildlife Society (TWS) journals from 1937 to 1989 concluded that TWS should strive to publish more articles on nongame and endangered species, ecosystems, habitat fragmentation, and human dimensions. We revisited this analysis and included the years 1990–2007 to determine whether, and how, TWS journals have addressed previous concerns. We also analyzed changes in subject content for TWS journals from 1937 to 2007 using selected terms that we considered indicative of emerging trends within the wildlife profession and society by documenting patterns of use of these terms as key words. Additionally, we evaluated authorship patterns for all TWS journals during 1937–2007 to determine trends in both numbers of authors per article and author affiliations. Our analysis demonstrated that the content of TWS journals has changed over time, and the changes reflected emerging themes in TWS, the wildlife profession, and society. We documented increases in published studies of nongame species and multiple species and articles with multiple authorships representing diverse affiliations. We argue that these patterns reflect a TWS response to shifts in public opinion, policy developments, advances in technology, and changes in university curricula. Although the number of studies published on human dimensions and conservation education has increased over time, these disciplines remained underrepresented.
Cultural evidence suggests that sooty shearwater (Puffinus griseus) chicks have been harvested by Rakiura Māori on islands in southern New Zealand since prehistoric times. Concerns exist that modern harvests may be impacting sooty shearwater abundance. We modeled human-related and ecological determinants of harvest (total no. of individuals harvested) of sooty shearwater chicks on 11 islands and examined the relationship between shearwater abundance and harvesting rates (chicks/hr) and harvester behavior throughout the harvesting season. Models best explaining variation in harvest between harvesting areas (manu), for both the early and late parts of the harvesting season, included harvester-days (included in all models with change in deviance information criteria [ΔDIC], ΔDIC < 8.36 and ΔDIC < 11.5, for the early and late periods, respectively). Other harvest determinants included shearwater density, size of the manu, and number of people helping harvesters (all included in the top 5 models within ΔDIC = 2.25 for the late period). Areas harvested by several families under a common-property harvesting system had higher harvest intensity for their size (24% points higher, 95% credible interval 11–36%) than those managed as an exclusive resource for one family. The slowest harvesters spent more time harvesting but on average only harvested 36% (95% credible interval 15–65%) and 34% (95% credible interval 12–63%) of the harvest taken by the fastest harvesters during the early and late periods, respectively. Our results highlight the possibility of elevated harvest intensity as the population of harvesters increases. However, our models suggested that a corresponding reduction in harvesting rate at low prey densities during the most productive period could potentially regulate harvest intensity. Future research will integrate these results into prospective shearwater demographic models to assess the utility of a range of harvesting strategies in ensuring harvest sustainability.
OvoControl G is a relatively new product that reduces hatchability of Canada goose (Branta canadensis) eggs, and few data are available on its cost effectiveness. Variables such as presence of nontargets, alternative foods, and public support can affect cost efficacy. We present a model that uses these and other factors to estimate the cost of application of OvoControl G for managing nuisance Canada geese. We found that at low goose densities (<35 pairs of geese), fixed labor was a significant portion of costs. As goose densities increase, OvoControl G becomes more cost effective than other methods, such as egg oiling or addling. Managers can use this model to determine whether OvoControl G will provide a successful and cost-effective treatment for population control of Canada geese in specific management areas.
Genetic profiling using fecal samples collected noninvasively in the wild can provide managers with an alternative to live-trapping. However, before embarking on a large-scale survey, feasibility of this methodology should be assessed for the focal species. Costs associated with fecal genotyping can be high because of the need for multiple amplifications to prevent and detect errors. Assessing the relative amount of target DNA before genotyping means samples can be eliminated where error rates will be high or amplification success will be low, thereby reducing costs. We collected fecal samples from an endangered population of swift fox (Vulpes velox) and employed target-DNA quantification and a screening protocol to assess sample quality before genetic profiling. Quantification was critical in identifying samples of low quality (68%, <0.2 ng/µL). Comparison of the amplification, from a subset of loci in 25 samples that did not meet the screening criteria, confirmed the effectiveness of this method. The protocol, however, used a considerable amount of DNA, and an assessment of the locus and sample variability allowed us to refine it for future population surveys. Although we did not use >50% of the samples we collected, the remaining samples provided 36 unique genotypes, which corresponded to approximately 70% of animals estimated to be present in the study area. Although obtaining fecal DNA from small carnivores is challenging, our protocol, including the quantification and qualification of DNA, the selection of markers, and the use of postgenotyping analyses, such as DROPOUT, CAPWIRE, and geographic information, provides a more cost-effective way to produce reliable results. The method we have developed is an informative approach that wildlife managers can use to conduct population surveys where the collection of feces is possible without the need for live-trapping.
Wildlife managers need reliable estimates of population size, trend, and distribution to make informed decisions about how to recover at-risk populations, yet obtaining these estimates is costly and often imprecise. The grizzly bear (Ursus arctos) population in northwestern Montana, USA, has been managed for recovery since being listed under the United States Endangered Species Act in 1975, yet no rigorous data were available to evaluate the program's success. We used encounter data from 379 grizzly bears identified through bear rub surveys to parameterize a series of Pradel model simulations in Program MARK to assess the ability of noninvasive genetic sampling to estimate population growth rates. We evaluated model performance in terms of 1) power to detect gender-specific and population-wide declines in population abundance, 2) precision and relative bias of growth rate estimates, and 3) sampling effort required to achieve 80% power to detect a decline within 10 years. Simulations indicated that ecosystem-wide, annual bear rub surveys would exceed 80% power to detect a 3% annual decline within 6 years. Robust-design models with 2 simulated surveys per year provided precise and unbiased annual estimates of trend, abundance, and apparent survival. Designs incorporating one survey per year require less sampling effort but only yield trend and apparent survival estimates. Our results suggest that systematic, annual bear rub surveys may provide a viable complement or alternative to telemetry-based methods for monitoring trends in grizzly bear populations.
We used a simple yet powerful method for judging public support for management actions from randomized surveys. We asked respondents to rank choices (representing management regulations under consideration) according to their preference, and we then used discrete choice models to estimate probability of choosing among options (conditional on the set of options presented to respondents). Because choices may share similar unmodeled characteristics, the multinomial logit model, commonly applied to discrete choice data, may not be appropriate. We introduced the nested logit model, which offers a simple approach for incorporating correlation among choices. This forced choice survey approach provides a useful method of gathering public input; it is relatively easy to apply in practice, and the data are likely to be more informative than asking constituents to rate attractiveness of each option separately.
Rachel C. Cook, John G. Cook, Thomas R. Stephenson, Woodrow L. Myers, Scott M. Mccorquodale, David J. Vales, Larry L. Irwin, P. Briggs Hall, Rocky D. Spencer, Shannon L. Murphie, Kathryn A. Schoenecker, Patrick J. Miller
Because they do not require sacrificing animals, body condition scores (BCS), thickness of rump fat (MAXFAT), and other similar predictors of body fat have advanced estimating nutritional condition of ungulates and their use has proliferated in North America in the last decade. However, initial testing of these predictors was too limited to assess their reliability among diverse habitats, ecotypes, subspecies, and populations across the continent. With data collected from mule deer (Odocoileus hemionus), elk (Cervus elaphus), and moose (Alces alces) during initial model development and data collected subsequently from free-ranging mule deer and elk herds across much of the western United States, we evaluated reliability across a broader range of conditions than were initially available. First, to more rigorously test reliability of the MAXFAT index, we evaluated its robustness across the 3 species, using an allometric scaling function to adjust for differences in animal size. We then evaluated MAXFAT, rump body condition score (rBCS), rLIVINDEX (an arithmetic combination of MAXFAT and rBCS), and our new allometrically scaled rump-fat thickness index using data from 815 free-ranging female Roosevelt and Rocky Mountain elk (C. e. roosevelti and C. e. nelsoni) from 19 populations encompassing 4 geographic regions and 250 free-ranging female mule deer from 7 populations and 2 regions. We tested for effects of subspecies, geographic region, and captive versus free-ranging existence. Rump-fat thickness, when scaled allometrically with body mass, was related to ingesta-free body fat over a 38–522-kg range of body mass (r2 = 0.87; P < 0.001), indicating the technique is remarkably robust among at least the 3 cervid species of our analysis. However, we found an underscoring bias with the rBCS for elk that had >12% body fat. This bias translated into a difference between subspecies, because Rocky Mountain elk tended to be fatter than Roosevelt elk in our sample. Effects of observer error with the rBCS also existed for mule deer with moderate to high levels of body fat, and deer body size significantly affected accuracy of the MAXFAT predictor. Our analyses confirm robustness of the rump-fat index for these 3 species but highlight the potential for bias due to differences in body size and to observer error with BCS scoring. We present alternative LIVINDEX equations where potential bias from rBCS and bias due to body size are eliminated or reduced. These modifications improve the accuracy of estimating body fat for projects intended to monitor nutritional status of herds or to evaluate nutrition's influence on population demographics.
Estimates of population size are necessary for effective management of threatened and endangered species, but accurate estimation is often difficult when species are cryptic. We evaluated effectiveness of mark–recapture techniques using the Lincoln–Peterson estimator for predicting true census size of a population of tuatara (Sphenodon punctatus), a burrowing reptile that is a conservation priority in New Zealand. We found that Lincoln–Peterson estimates (N ˆ = 85) were accurate for predicting the census size (N = 87) after only a 3-day mark–recapture survey. We recommend this method as a cost-effective way to accurately estimate population size for isolated, inaccessible tuatara populations, because it requires limited personnel, expertise, and time, and has low environmental impact on fragile sites.
We immobilized elk with either isoflurane to produce general anesthesia (control), 0.01 mg/kg carfentanil plus 0.1 mg/kg xylazine, or 0.25 mg/kg butorphanol plus 0.4 mg/kg azaperone plus 0.15 mg/kg medetomidine (BAM) and measured the bispectral index (BIS). The carfentanil-xylazine BIS (70.4 ± 1.4) and the BAM BIS (60.2 ± 1.5) were higher than the control BIS (47.2 ± 4.1; P ≤ 0.001). These data indicate that opioids produce neuroleptanalgesia and not general anesthesia or sedation, which explains observed elk responses to these drugs.
We designed a reliable and inexpensive universal trap timer that records the time from the moment a single-live-capture trap is triggered by an animal to when the observer checks the trap. Combined with trapping information, the diel activity pattern of a given species or demographic group can then be described or compared between imposed treatments. The universal trap timer is adaptable to operate reliably with most single-capture trap designs, requires no permanent modification of traps, and is easy to construct.
CARLA G. HEISTER, Henry Graves Memorial Library, Yale School of Forestry and Environmental Studies, 195 Prospect Street, New Haven, CT 06511, USA. Telephone: 203-432-5132; FAX: 203-432-5942; e-mail: carla.heister@yale.edu. Material for inclusion on this list should be submitted to the compiler.
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