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Translocations are a common conservation technique; however, the feasibility and success of translocations are evaluated rarely. We translocated 57 trumpeter swans (Cygnus buccinator) from Idaho to previous termUtahnext term during 1996 to encourage migration to more southern wintering areas. We evaluated the feasibility and success of the translocation by studying biological and socio-political criteria prior to and during the translocation. Lack of support from governmental and non-governmental agencies did not allow additional translocations in subsequent years. Additional releases are needed, however, to increase the probability of swan returns to the release area. Our evaluation explores the possibility that...
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The recent discovery of a pathogenic fungus (Batrachochytrium dendrobatidis) associated with declines of frogs in the American and Australian tropics, suggests that at least the proximate cause, may be known for many previously unexplained amphibian declines. We have monitored boreal toads in Colorado since 1991 at four sites using capture?recapture of adults and counts of egg masses to examine the dynamics of this metapopulation. Numbers of male toads declined in 1996 and 1999 with annual survival rate averaging 78% from 1991 to 1994, 45% in 1995 and 3% between 1998 and 1999. Numbers of egg masses also declined. An etiological diagnosis of chytridiomycosis consistent with infections by the genus Batrachochytrium...
Amphibian populations continue to be imperiled by the chytrid fungus (Batrachochytrium dendrobatidis). Understanding where B. dendrobatidis (Bd) occurs and how it may be limited by environmental factors is critical to our ability to effectively conserve the amphibians affected by Bd. We sampled 1247 amphibians (boreal toads and surrogates) at 261 boreal toad (Bufo boreas) breeding sites (97 clusters) along an 11� latitudinal gradient in the Rocky Mountains to determine the distribution of B. dendrobatidis and examine environmental factors, such as temperature and elevation, that might affect its distribution. The fungus was detected at 64% of all clusters and occurred across a range of elevations (1030?3550 m) and...
Recent declines in North American honeybee populations have highlighted the importance of native bee conservation, and the need for research on the ecological requirements of native bees in farmland. In this study, we investigated the value of hedgerows as foraging habitat for native bees in mosaics of small-scale agriculture and natural vegetation in two riparian landscapes in southeast Arizona, USA. In the summers of 2002 and 2003, we surveyed bees and flowers in four habitats: hedgerows, agricultural fields, woodlots, and native woodland. We asked: (1) How do hedgerows compare to other available habitats in bee abundance and species richness? (2) How does bee species composition in hedgerows compare to species...
Like many other species, cutthroat trout (Oncorhynchus clarki) have declined substantially relative to historic conditions, and many existing populations are isolated. To inform conservation and restoration efforts for stream-resident cutthroat trout, I built a stage-structured stochastic simulation model to explore the dynamics of populations in isolation or connected by immigration. Relatively small increases in carrying capacity substantially reduced extinction risk in small, isolated populations. In the sensitivity matrix, the two most important elements affecting population growth rate were the survival of subadults that became reproductively mature the next year and the survival of young-of-the-year fish....
We modeled populations of lynx (Lynx canadensis) and snowshoe hares (Lepus americanus) to determine prey densities required for persistence of lynx translocated to the southern portion of the species' range. The models suggested that a density of 1.1?1.8 hares/h is required for lynx persistence; these densities are higher than those reported for most hare populations across the USA. We found that lynx dispersal and density-independent mortality substantially increased the hare density required for lynx persistence. Reintroduction success was associated with number of release events, total number of animals released, and timing of release relative to the phase of the hare population cycle. However, no release protocol...
Characteristics of previous termbirdnext term and small mammal communities can be valuable in monitoring for impacts on specific plots of land. In previous termUtahnext term (USA), significant differences were found among years, habitats and seasons in previous termbirdnext term and small mammal abundance, species diversity, and species richness; thus, estimates of these characteristics are consistent and repeatable and can be used for detecting change. Also, previous termbirdnext term and small mammal communities are dependent on a wide variety of food resources and habitat characteristics; thus they should reflect a variety of impacts. A comparison is made between two methods of handling previous termbirdnext...
Catostomid fishes are a diverse family of 76+ freshwater species that are distributed across North America in many different habitats. This group of fish is facing a variety of impacts and conservation issues that are somewhat unique relative to more economically valuable and heavily managed fish species. Here, we present a brief series of case studies to highlight the threats such as migration barriers, flow regulation, environmental contamination, habitat degradation, exploitation and impacts from introduced (non-native) species that are facing catostomids in different regions. Collectively, the case studies reveal that individual species usually are not threatened by a single, isolated factor. Instead, species...
Although the five species of prairie dogs (Cynomys spp.) are recognized as important components of grassland ecosystems in western North America, they have experienced major population declines due to poisoning, outbreaks of sylvatic plague, recreational shooting, and habitat conversion. From May 2000 to October 2001, we investigated 270 colonies of Gunnison’s prairie dog (Cynomys gunnisoni) in Arizona. Because these colonies were classified as active in previous surveys (1987, 1990–1994, 1998), we were able to examine their persistence. Most (70%) of the colonies became inactive between the initial and recent surveys, with colony extinctions spanning our study area. Colony persistence was positively associated...
Black-tailed prairie dogs (Cynomys ludovicianus) increasingly compete for available habitat with human development in the Colorado Front Range. Because the effects of increased urbanization on prairie dog colonies are unknown, we studied how landscape context affects prairie dog density in Boulder County, Colorado, USA. We used burrow density as a proxy for prairie dog density because these variables were correlated at our study sites (r=0.60). Using remotely sensed data and a GIS, we quantified percent urbanization, road density, and the percentage of other prairie dog colonies in the surrounding landscape at 200, 1000, and 2000 m from the perimeter of 22 prairie dog colonies, and compared burrow density with each...
We evaluated the effect of three different sampling schemes used to organize spatially explicit biological information had on the spatial placement of conservation reserves in previous termUtah,next term USA. The three sampling schemes consisted of a hexagon representation developed by the EPA/EMAP program (statistical basis), watershed boundaries (ecological), and the current county boundaries of previous termUtahnext term (socio-political). Four decision criteria were used to estimate effects, including amount of area, length of edge, lowest number of contiguous reserves, and greatest number of terrestrial vertebrate species covered. A fifth evaluation criterion was the effect each sampling scheme had on the ability...
The activities of summer visitors to the tundra of Trail Ridge in Rocky Mountain National Park results in the rapid destruction of vegetation in the areas seen by most visitors at close range?especially near parking areas. Ecosystems differ in their reaction to trampling; those with high soil-moisture are most easily damaged. Tall herb ecosystems are next, and then fellfield. Turf types are the most durable. Other activities affecting tundra are rock collecting, littering, crushing by car tyres, and flower picking. Published in Biological Conservation, volume 2, issue 4, on pages 257 - 265, in 1970.
Catostomid fishes are a diverse family of 76+ freshwater species that are distributed across North America in many different habitats. This group of fish is facing a variety of impacts and conservation issues that are somewhat unique relative to more economically valuable and heavily managed fish species. Here, we present a brief series of case studies to highlight the threats such as migration barriers, flow regulation, environmental contamination, habitat degradation, exploitation and impacts from introduced (non-native) species that are facing catostomids in different regions. Collectively, the case studies reveal that individual species usually are not threatened by a single, isolated factor. Instead, species...
The endangered Sonoran topminnow Poeciliopsis occidentalis has steadily declined in distribution and abundance in the past several decades, and currently survives in the United States only in several isolated localities in southern Arizona. This reduction is correlated with, and primarily attributed to, habitat destruction, and introduction and establishment of mosquitofish Gambusia affinis and other exotic fishes. Topminnows have characteristically been reduced in number or replaced within a year or two of introduction of non-native fishes. Other native fishes have experienced similar declines after introduction of exotics, and much of the endemic western ichthyofauna may be vulnerable to extirpation in this manner....
Dramatic declines in the endangered Columbia Basin pygmy rabbit, a genetically unique population of small, burrowing rabbits in Northwestern United States, are likely the combined results of habitat degradation and fragmentation, disease, and predation. A critical component of pygmy rabbit habitat includes big sagebrush (Artemisia tridentata), which constitutes 82–99% of their winter diet and 10–50% of their summer diet. Sagebrush also forms the bulk of hiding cover around burrow sites. Across the range of pygmy rabbits, sagebrush habitat is grazed extensively by cattle. However, grazing has unknown effects on pygmy rabbits inhabiting the remaining, fragmented shrub-steppe habitat. We evaluated the effects of...
The desert tortoise Gopherus agassizii is federally listed as Threatened because of documented declines in some populations, yet the proximate causes of these declines are not well understood. With use of radiotelemetry, I monitored a total of 55 individual tortoises at two Mojave Desert sites over three years. Both populations suffered high adult mortality during an extreme drought period, but the temporal pattern and inferred proximate causes of mortality differed between sites. At the eastern Mojave site, no telemetered tortoises died in 1988 or 1989, but 41% died in 1990. All nine carcasses were found and only one showed any evidence of predation or scavenging. Tortoises that died had symptoms of dehydration...
Assumptions of optimal foraging theory were applied to the feeding ecology of pronghorn Antilocapra americana to address issues of immediate relevance to conservation biology in the Great Basin Desert of North America. The relationships between foraging efficiency and: (1) group size: (2) habitat; and (3) disturbance history were examined in two study sites. Individual foraging efficiency increased with group size to a point in both study sites, but animals in the disturbed area remained in larger groups despite foraging less profitably. The hypothesis that individuals in a disturbed environment remain together for enhanced protection from (human?) predators was supported and interpreted in the light of proposed...
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Populations with small effective sizes are at risk for inbreeding depression and loss of adaptive potential. Variance in reproductive success is one of several factors reducing effective population size (Ne) below the actual population size (N). Here, we investigate the effects of polygynous (skewed) mating and variation in female breeding success on the effective size of a small population of the Gunnison sage-grouse (Centrocercus minimus), a ground nesting bird with a lek mating system. During a two-year field study, we recorded attendance of marked birds at leks, male mating success, the reproductive success of radio-tagged females, and annual survival. We developed simulations to estimate the distribution of...
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Eight study-sites were chosen on road margins in the alpine tundra of Rocky Mountain National Park, Colorado. Seven of the sites were located about the middle of slopes created by filling, below the roads. The remaining site was above the road, and flat on bedrock. Mosaics of pioneer vegetation types are present on roadcut slopes. These appear to be correlated with altitude, exposure, substrate texture, and degree of slope. Forty to fifty years after denudation, succession plays only a minor role on roadcut slopes. Plant coverage after that time is approximately one-half that of cushion-plant communities on natural tundra. The most important pioneer plants under these conditions are ?bunch type? Gramineae, especially...
map background search result map search result map Vegetation of roadcut slopes in the tundra of Rocky Mountain National Park, Colorado Evidence for disease-related amphibian decline in Colorado Polygyny and female breeding failure reduce effective population size in the lekking Gunnison sage-grouse Vegetation of roadcut slopes in the tundra of Rocky Mountain National Park, Colorado Evidence for disease-related amphibian decline in Colorado Polygyny and female breeding failure reduce effective population size in the lekking Gunnison sage-grouse