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We capitalized on a regional-scale, anthropogenic experiment?the reduction of black-tailed prairie dog (Cynomys ludovicianus) towns across the Great Plains of North America?to test the hypothesis that decline of this species has led to declines in diversity of native grassland vertebrates of this region. We compared species richness and species composition of non-volant mammals, reptiles and amphibians at 36 prairie dog towns and 36 paired sites in the Panhandle Region of Oklahoma during the summers and falls of 1997, 1998 and 1999. We detected 30 species of mammals, 18 species of reptiles and seven species of amphibians. Comparisons between communities at prairie dog towns and paired sites in the adjacent landscape...
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Captive breeding is increasingly being used to create supplies of endangered animals for release into natural habitats, but rearing strategies vary and debates arise over which methods are most efficient. We assessed postrelease behaviors and survival of three groups of black-footed ferrets, each with different prerelease experience. Eighteen ferret kits ≤60 days of age were moved with their dams from cages to 80-m2 outdoor pens with prairie dog burrows. These animals were compared to animals reared in standard cages (n=72), some of which were given experience killing prairie dogs (n=32). Ferrets were released onto white-tailed prairie dog (Cynomys leucurus) colonies in Wyoming, USA, in fall, 1992. Radio-tagged...
Visitors to Rocky Mountain National Park are especially attracted to its easily accessible alpine tundra, which widely dominates the landscape above tree-limit. A remarkable summer highway, Trail Ridge Road, traverses more than twelve miles (19 km ) of tundra, rising in its highest tract to elevations of over 12,000 feet (3,658 m). Visitor activities are largely confined to the immediate vicinity of ‘black-top’ parking areas located at points of special interest, but many persons do venture out along the established pathways. Only a few visitors each year are venturesome enough, or take the time, to wander at leisure over the gently rolling land. Trampling by the visitors kills plants and initiates erosion processes...
The alpine tundra region of the southern Rocky Mountains is a dramatic landscape which attracts many visitors seeking the refreshment that urban dwellers often get from a primeval environment. This paper describes the current situation and persisting vegetation of one of the more accessible of these areas, the tundra of Trail Ridge in Rocky Mountain National Park, Colorado. The harsh nature of the environment is illustrated from data of 12 years, and the more important local ecosystems are described. Man's use of this landscape leads to critical management problems, especially in national parks, because no organism similar to Man participated in these systems during the millions of years of evolution which moulded...
We analyzed the conservation status of 73 vegetation cover types distributed across a 1.76 million km2 region in 10 states of the western USA. We found that 25 vegetation cover types had at least 10% of their area in nature reserves. These were generally plant communities located at higher elevations and thus more commonly associated with national parks and wilderness areas. All but three of the remaining 48 cover types occurred with sufficient area on publically owned lands in the region to imply that transforming land management intent on these lands could also increase their protection. We also analyzed the level of protection afforded each cover type across its entire geographic distribution in the region. Most...
The relationships between Mycoplasma agassizii, a causative agent of upper respiratory disease (URTD), and desert tortoise (Gopherus agassizii), generally illustrate the complexities of disease dynamics in wild vertebrate populations. In this review, we summarize current understanding of URTD in Mojave desert tortoise populations, we illustrate how inadequate knowledge of tortoise immune systems may obfuscate assessment of disease, and we suggest approaches to future management of URTD in desert tortoise populations. We challenge the view that M. agassizii causes consistent levels of morbidity and/or mortality across the Mojave desert. Instead, URTD may be described more accurately as a context-dependent disease....
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...
Understanding how altered flow regimes mediate interactions among native and nonnative species is necessary for the conservation of aquatic systems. Anthropogenic alteration of natural flows and establishment of nonnative fishes coincided with near extirpation of Colorado pikeminnow (Ptychocheilus lucius) from the San Juan River, NM, USA. Despite major efforts to re-establish this species, recruitment of young individuals into the adult population has not been documented in several decades. A potential reason for apparent recruitment failure is that modified flow regimes and nonnative species have affected reproductive success of native prey, thus limiting potentially critical resources for young (
Information about geographic distributions is required for species conservation and management. Ultimately, this information is derived from records of occurrence. However, the reliability and availability of occurrence records are variable. A conceptual framework for evaluating the reliability of occurrence records is provided. Only records associated with physical evidence, especially a museum voucher specimen, are considered verified. However, errors in species identification or location are possible even for verified records. In addition, biases exist in occurrence records because they generally are collected haphazardly. Other sources of bias include sampling error associated with small areas or range limits...
Maintaining healthy ecosystems is a prerequisite for conserving biodiversity. The complex nature of ecosystems often necessitates the use of indicator taxa to monitor ecosystem health. However, ambiguous selection criteria and the use of inappropriate taxa have brought the utility of indicator taxa under question. This review compiles existing selection criteria from the literature, evaluates inconsistencies among these criteria, and proposes a step-wise selection process. In addition, 100 vertebrate and 32 invertebrate taxa documented in the conservation science literature as indicators of ecosystem health are examined to assess how well they adhere to the referenced criteria. Few vertebrate taxa fulfill multiple...
Small aspen stands are disappearing from the landscape in the Southwest, so it is important to understand their contribution to the avian community. We sampled birds in 53 small, isolated aspen stands and 53 paired plots within the ponderosa pine forest in northern Arizona, during the 1996 and 1997 breeding seasons. Bird species richness and abundance were higher in aspen than in pine. However, bird species richness and abundance did not vary with size of the aspen patch or isolation index. In addition, direct ordination of species distributions with habitat factors suggested no distinct avian communities. This suggests that aspen stands do not harbor separate populations, but rather are locations where the regional...
The strength of top-down forces in terrestrial food webs is highly debated as there are few examples illustrating the role of largemammalian carnivores in structuring biotic and abiotic systems. Based on the results of this studywe hypothesize that an increase in human visitation within Zion Canyon of Zion National Park ultimately resulted in a catastrophic regime shift through pathways involving trophic cascades and abiotic environmental changes. Increases in human visitors in Zion Canyon apparently reduced cougar (Puma concolor) densities, which subsequently led to higher mule deer (Odocoileus hemionus) densities, higher browsing intensities and reduced recruitment of riparian cottonwood trees (Populus fremontii),...
Large predators potentially can help shape the structure and functioning of terrestrial ecosystems, yet strong evidence of top-down herbivore limitation has not been widely reported in the scientific literature. Herein we synthesize outcomes of recent tri-trophic cascades studies involving the presence and absence of large predators for five national parks in the western United States, including Olympic, Yosemite, Yellowstone, Zion, and Wind Cave. Historical observations by park biologists regarding woody browse species and recently compiled age structure data for deciduous trees indicate major impacts to woody plant communities by ungulates following the extirpation or displacement of large predators. Declines...
Visitors to Rocky Mountain National Park are especially attracted to its easily accessible alpine tundra, which widely dominates the landscape above tree-limit. A remarkable summer highway, Trail Ridge Road, traverses more than twelve miles (19 km ) of tundra, rising in its highest tract to elevations of over 12,000 feet (3,658 m). Visitor activities are largely confined to the immediate vicinity of ?black-top? parking areas located at points of special interest, but many persons do venture out along the established pathways. Only a few visitors each year are venturesome enough, or take the time, to wander at leisure over the gently rolling land. Trampling by the visitors kills plants and initiates erosion processes...
A buffer zone of 30.5 m is commonly used to protect species in riparian and wetland systems. This 30.5 m standard was developed to protect water quality, not biodiversity, and few studies have tested its effectiveness for protecting riparian and wetland species. We tested the standard implementation of 30.5 m buffers to determine if they protect critical habitat for semi-aquatic vertebrate species, using the boreal toad (Bufo boreas) as an example. Using radio telemetry of 84 toads in south-central Utah in 2003 and 2004, we found that the standard implementation of 30.5 m buffers did not protect all critical habitats for boreal toads. Managers should consider the following factors when establishing buffer zones:...
We conducted an analysis of aspen (Populus tremuloides) overstory recruitment on the northern range of Yellowstone National Park (YNP) using information provided in a monograph published by Warren (Warren, E.R., 1926. A study of beaver in the Yaney region of Yellowstone National Park, Roosevelt-Wildl. Ann. 1, 1–191), increment cores collected from riparian aspen stands in 1998, and an extensive random sample of aspen increment cores collected over YNP's entire northern range in 1997 and 1998. We summarized aspen size classes reported by Warren and estimated overstory origination dates of the stands he described using a linear regression based on our riparian aspen diameter/age relationship. Applying our regression...
Widespread degradation of the sagebrush ecosystem in the western United States, including the invasion of cheatgrass, has prompted resource managers to consider a variety of approaches to restore and conserve habitats for sagebrush-associated species. One such approach involves the use of greater sage-grouse, a species of prominent conservation interest, as an umbrella species. This shortcut approach assumes that managing habitats to conserve sage-grouse will simultaneously benefit other species of conservation concern. The efficacy of using sage-grouse as an umbrella species for conservation management, however, has not been fully evaluated. We tested that concept by comparing: (1) commonality in land-cover associations,...
Biological invasions into five nature reserves in arid environments are examined. Vascular plant invasions have not been particularly severe in the four continental reserves except along watercourses, where introduced phreatophytes have established extensively, crowding out native vegetation and often lowering water tables. The invasive genus Tamarix affects dozens of reserves in southwestern USA and would appear to be an outstanding candidate for biological control. Feral ungulate invasions have negatively affected most reserves, but are generally controllable, given the resources and the will to accomplish the task. Alien fish, often casually introduced by sportsmen or aquarists, are a major threat to native fish...
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We utilized nine microsatellite loci and 865 bases from two mtDNA genes to estimate demographic parameters and visualize historic/contemporary connectivity among populations of a sky-island rattlesnake (New Mexico ridge-nosed rattlesnake, Crotalus willardi obscurus). This taxon is listed as threatened under the United States Endangered Species Act (ESA) and is distributed patchily within three borderland mountain ranges [Animas (ANM), Peloncillo (PEL), Sierra San Luis (SSL)] of southeastern Arizona, southwestern New Mexico and north-central M�xico. Molecular data support a hypothesis of northward range expansion from M�xico, with subsequent isolation on sky-islands through vicariant desertification that transformed...
Ground-water and surface flow depletions are altering riparian ecosystems throughout the southwestern United States, and have contributed to the decline of forests of the pioneer trees Populus fremontii (Fremont cottonwood) and Salix gooddingii (Goodding willow). On some rivers, these forests have been replaced by shrublands of Tamarix ramosissima (tamarisk), a drought-tolerant species from Eurasia. The physiological response of these three riparian plant species to decreases in water availability is well studied, but little attention has been given to shifts in community and population structure in response to declines in surface flow and ground-water levels. Based on study of 17 sites spanning a hydrologic gradient,...


map background search result map search result map Influence of prerelease experience on reintroduced black-footed ferrets (Mustela nigripes) Geographic isolation, genetic divergence, and ecological non-exchangeability define ESUs in a threatened sky-island rattlesnake Influence of prerelease experience on reintroduced black-footed ferrets (Mustela nigripes) Geographic isolation, genetic divergence, and ecological non-exchangeability define ESUs in a threatened sky-island rattlesnake