Investigating the distribution of prairie dogs in an urban landscape

Habitat fragmentation is a prevalent threat to biological diversity, and urbanization is a primary agent of fragmentation and a leading cause of species endangerment. Landscape biogeographic and local habitat characteristics can be important determinants of the distribution of species in habitat patches in urban landscapes. However, the specifics of which characteristics are most critical to maintaining biological diversity are not fully known for prairie ecosystems, especially in fragmented urban habitat. This study focuses on black-tailed prairie dogs along an urban gradient in Denver, CO. Prairie dogs have declined precipitously throughout the region and are an essential part of the prairie ecosystem, making them excellent study subjects. We identified a series of habitat fragments along a gradient of urbanization in the fully urbanized areas and south suburbs of Denver, CO, both containing and not containing prairie dogs. Local characteristics, including fragment slope and vegetative cover, and landscape characteristics, including fragment size, age and connectivity, were measured on each fragment. We used likelihood-based methods to explore which variables most accurately predicted prairie dog occurrence within our study area. Multiple factors influenced the distribution of prairie dogs in urban settings, with colony connectivity the strongest predictor of occupancy. Large and recently isolated fragments near other prairie dog colonies, flat areas and those with high graminoid cover were most likely to support prairie dog populations. Our study provides the first attempt to model prairie dog occurrence in highly fragmented urban habitat and has important implications for the management and conservation of prairie dogs.     

Connectivity of prairie dog colonies in an altered landscape: inferences from analysis of microsatellite DNA variation

Connectivity of populations influences the degree to which species maintain genetic diversity and persist despite local extinctions. Natural landscape features are known to influence connectivity, but global anthropogenic landscape change underscores the importance of quantifying how human-modified landscapes disrupt connectivity of natural populations. Grasslands of western North America have experienced extensive habitat alteration, fragmenting populations of species such as black-tailed prairie dogs (Cynomys ludovicianus). Population sizes and the geographic range of prairie dogs have been declining for over a century due to habitat loss, disease, and eradication efforts. In many places, prairie dogs have persisted in the face of emerging urban landscapes that carve habitat into smaller and smaller fragments separated by uninhabitable areas. In extreme cases, prairie dog colonies are completely bounded by urbanization. Connectivity is particularly important for prairie dogs because colonies suffer high probabilities of extirpation by plague, and dispersal permits recolonization. Here we explore connectivity of prairie dog populations using analyses of 11 microsatellite loci for 9 prairie dog colonies spanning the fragmented landscape of Boulder County, Colorado. Isolation-by-resistance modeling suggests that wetlands and high intensity urbanization limit movement of prairie dogs. However, prairie dogs appear to move moderately well through low intensity development (including roads) and freely through cropland and grassland. Additionally, there is a marked decline in gene flow between colonies with increasing geographic distance, indicating isolation by distance even in an altered landscape. Our results suggest that prairie dog colonies retain some connectivity despite fragmentation by urbanization and agricultural development.     

Mark-Resight Methodology for Estimating Population Densities for Prairie Dogs

Abstract: Accurate assessments of local population size of the black-tailed prairie dog (Cynomys ludovicianus) are essential because of their overall decline and importance to prairie ecosystems. We describe the use of mark-resight methodology to estimate black-tailed prairie dog population size and density. Study colonies include isolated urban habitat fragments in Denver, Colorado, USA, and unfragmented control colonies in the Pawnee National Grassland, USA. We compare results from various mark-resight estimators to those derived from linear transformations of visual counts of active prairie dogs. Our results suggest that mark-resight methods are feasible in both urban and rural systems, and reveal extremely high densities for isolated prairie dogs in urban sites. Our methodology can be used to obtain reliable, unbiased estimates of local population size and density.     

Effects of habitat fragmentation and black-tailed prairie dogs on urban avian diversity

Urbanization and habitat fragmentation have the potential to influence bird communities. In addition, these phenomena, as well as ongoing lethal control measures, have also greatly reduced the range of the black-tailed prairie dog (Cynomys ludovicianus) since the beginning of the 20th century. Although prairie dogs are highly interactive species that can influence avian communities, few studies have investigated whether these interactions persist in urban settings. Our goal was to investigate the relative impacts of habitat fragmentation and prairie dogs on bird communities within an urban matrix. We performed bird surveys on 20 habitat fragments (10 colonized by prairie dogs, 10 uncolonized by prairie dogs) distributed throughout the Denver metropolitan area, and calculated Shannon–Weiner diversity and richness of all birds and native species, as well as total counts of grassland birds and raptors. Diversity, richness, and counts of many species increased with increasing fragment connectivity, and decreased on fragments isolated for longer periods of time. Avian diversity and richness did not differ between fragments with and without prairie dogs, suggesting that this element of the ecological role of prairie dogs is not fully retained in urban habitat. Future studies of the role of prairie dogs as keystone species in urban systems should include other taxa as well as consider the influence of the urban matrix surrounding prairie dog habitat. Our results emphasize that conservation of urban avian diversity should focus on landscape connectivity as well as local habitat features.     

Habitat use by Mountain Plovers in prairie dog colonies in northeastern New Mexico

ABSTRACT Mountain Plovers (Charadrius montanus) are grassland birds that often breed in close association with colonies of black‐tailed prairie dogs (Cynomys ludovicianus). However, not all colonies provide plover nesting habitat or habitat of equal quality, and the characteristics of colonies important for plovers remain poorly understood. Over two years, I used plover distribution surveys, territory mapping, and habitat sampling to study habitat use by plovers in prairie dog colonies in shortgrass prairie in northeastern New Mexico. My objective was to document important components of plover breeding habitat in colonies by comparing characteristics of used and unused habitats at three spatial scales: colony, territory, and nest‐site. I found evidence of plover breeding in 14 of 44 colonies in 2009 and 13 of 43 colonies in 2010. Based on logistic regression, the probability of a colony being occupied by plovers was positively associated with colony size, but negatively associated with mean vegetation height. Preference for larger colonies could relate to minimum habitat requirements, or a potential tendency of this species to nest in social clusters. Shorter vegetation height was strongly correlated with greater bare ground and lower forb/subshrub cover, all characteristics that may be related to plover predator avoidance and foraging microhabitat. At both the territory and nest‐site scale, areas used by plovers had shorter vegetation, more bare ground, and less forb/subshrub cover than unused areas. Nest sites were also more sloped, perhaps to reduce risk of flooding, and located further away from the nearest prairie dog burrow, perhaps to reduce risk of disturbance. Overall, my results show that plover use of prairie dog colonies was influenced by landscape and habitat features of colonies, and suggest that large colonies are particularly valuable because they are most likely to contain adequate areas with preferred habitat characteristics.     

Occupancy of Mountain Plover and Burrowing Owl in Colorado

Abstract: Concern over the decline of grassland birds has spurred efforts to increase understanding of grassland bird-habitat relationships. Previous studies have suggested that black-tailed prairie dogs (Cynomys ludovicianus) provide important habitat for shortgrass prairie avifauna, such as mountain plover (Charadrius montanus) and western burrowing owl (Athene cunicularia hypugaea), although such studies are lacking in Colorado (USA). We used methods to estimate occupancy (ψ) of mountain plover and burrowing owl on prairie dog colonies and other shortgrass prairie habitats in eastern Colorado. Mountain plover occupancy was higher on prairie dog colonies (ψ = 0.50, 95% CI = 0.36–0.64) than on grassland (ψ = 0.07, 95% CI = 0.03–0.15) and dryland agriculture (ψ = 0.13, 95% CI = 0.07–0.23). Burrowing owl occupancy was higher on active prairie dog colonies (ψ = 0.80, 95% CI = 0.66–0.89) compared with inactive colonies (ψ = 0.23, 95% CI = 0.07–0.53), which in turn was much higher than on grassland (ψ = 0.01, 95% CI = 0.00–0.07) and dryland agriculture (ψ = 0.00, 95% CI ψ 0.00–0.00). Mountain plover occupancy also was positively correlated with increasing amounts of prairie dog colony in the landscape. Burrowing owl occupancy was negatively correlated with increasing amounts of prairie dog colony in the surrounding landscape. Our results suggest that actions to conserve mountain plovers and burrowing owls should incorporate land management to benefit prairie dogs. Because managing for specific colony attributes is difficult, alternative management that promotes heterogeneity may ensure that suitable habitat is available for the guild of grassland inhabitants.     

Disturbance regimes and mountain plover habitat in shortgrass steppe: Large herbivore grazing does not substitute for prairie dog grazing or fire

Restoring historical disturbance regimes to enhance habitat for grassland birds can conflict with livestock production goals and has been controversial because of uncertainty in the frequency and pattern of different disturbances prior to European settlement. We studied nesting habitat for the mountain plover (Charadrius montanus) in relation to prescribed fire, grazing by large herbivores (cattle), and grazing by black-tailed prairie dogs (Cynomys ludovicianus) in the shortgrass steppe of northeastern Colorado. Breeding mountain plovers primarily occurred on black-tailed prairie dog colonies or areas burned during the previous dormant season. Vegetation surrounding mountain plover nests and foraging locations was characterized by a fine-scale mosaic of prostrate (<4 cm tall) vegetated patches interspersed with >35% bare soil in a given square meter, with this fine-scale pattern distributed over a broad (>100-m radius) area. Mountain plovers rarely occupied grassland lacking prairie dogs or recent fire, but those that did selected sites with similar vegetation height and bare soil exposure as sites on burns and prairie dog colonies. Vegetation structure at mountain plover-occupied sites was also similar to random sites on burns and prairie dog colonies, but differed substantially from sites managed only with cattle. Intensive cattle grazing at twice the recommended stocking rate during spring (Mar–May) or summer (May–Oct) for 6 years produced significantly less bare soil than burns and prairie dog colonies, particularly following years with average or above-average precipitation. Thus, intensive cattle grazing did not substitute for prairie dog grazing or fire in terms of effects on vegetation structure and mountain plover habitat. Both prescribed burning and increased size and distribution of black-tailed prairie dog colonies appear to be effective and complementary means to manage for mountain plover breeding habitat in shortgrass steppe. Provision of mountain plover habitat has tradeoffs with traditional management for livestock production. Thus, managers need to clearly define desired outcomes for management to provide multiple ecosystem goods and services. © 2012 The Wildlife Society.     

High prevalence of <Emphasis Type="Italic">Yersinia pestis</Emphasis> in black-tailed prairie dog colonies during an apparent enzootic phase of sylvatic plague

Sylvatic plague (Yersinia pestis) was introduced into North America over 100 years ago. The disease causes high mortality and extirpations in black-tailed prairie dogs (Cynomys ludovicianus), which is of conservation concern because prairie dogs provide habitat for the critically endangered black-footed ferret (Mustela nigripes). Our goal was to help elucidate the mechanism Y. pestis uses to persist in prairie ecosystems during enzootic and epizootic phases. We used a nested PCR protocol to assay for plague genomes in fleas collected from prairie dog burrows potentially exposed to plague in 1999 and 2000. No active plague epizootic was apparent in the 55 prairie dog colonies sampled in 2002 and 2003. However, 63% of the colonies contained plague-positive burrows in 2002, and 57% contained plague-positive burrows in 2003. Within plague-positive colonies, 23% of sampled burrows contained plague-positive fleas in 2002, and 26% contained plague-positive fleas in 2003. Of 15 intensively sampled colonies, there was no relationship between change in colony area and percentage of plague-positive burrows over the two years of the study. Some seasonality in plague prevalence was apparent because the highest percentages of plague-positive colonies were recorded in May and June. The surprisingly high prevalence of plague on study area colonies without any obvious epizootic suggested that the pathogen existed in an enzootic state in black-tailed prairie dogs. These findings have important implications for the management of prairie dogs and other species that are purported to be enzootic reservoir species.     

The absence of concordant population genetic structure in the black‐tailed prairie dog and the flea,Oropsylla hirsuta,with implications for the spread of Yersinia pestis

The black‐tailed prairie dog (Cynomys ludovicianus) is a keystone species on the mid‐ and short‐grass prairies of North America. The species has suffered extensive colony extirpations and isolation as a result of human activity including the introduction of an exotic pathogen, Yersinia pestis, the causative agent of sylvatic plague. The prairie dog flea, Oropsylla hirsuta, is the most common flea on our study colonies in north‐central Montana and it has been shown to carry Y. pestis. We used microsatellite markers to estimate the level of population genetic concordance between black‐tailed prairie dogs and O. hirsuta in order to determine the extent to which prairie dogs are responsible for dispersing this potential plague vector among prairie dog colonies. We sampled fleas and prairie dogs from six prairie dog colonies in two regions separated by about 46 km. These colonies were extirpated by a plague epizootic that began months after our sampling was completed in 2005. Prairie dogs showed significant isolation‐by‐distance and a tendency toward genetic structure on the regional scale that the fleas did not. Fleas exhibited higher estimated rates of gene flow among prairie dog colonies than the prairie dogs sampled from the same colonies. While the findings suggested black‐tailed prairie dogs may have contributed to flea dispersal, we attributed the lack of concordance between the population genetic structures of host and ectoparasite to additional flea dispersal that was mediated by mammals other than prairie dogs that were present in the prairie system.     

A plague epizootic in the black-tailed prairie dog (Cynomys ludovicianus)

Plague is the primary cause for the rangewide decline in prairie dog (Cynomys spp.) distribution and abundance, yet our knowledge of plague dynamics in prairie dog populations is limited. Our understanding of the effects of plague on the most widespread species, the black-tailed prairie dog (C. ludovicianus), is particularly weak. During a study on the population biology of black-tailed prairie dogs in Wyoming, USA, plague was detected in a colony under intensive monitoring, providing a unique opportunity to quantify various consequences of plague. The epizootic reduced juvenile abundance by 96% and adult abundance by 95%. Of the survivors, eight of nine adults and one of eight juveniles developed antibodies to Yersinia pestis. Demographic groups appeared equally susceptible to infection, and age structure was unaffected. Survivors occupied three small coteries and exhibited improved body condition, but increased flea infestation compared to a neighboring, uninfected colony. Black-tailed prairie dogs are capable of surviving a plague epizootic and reorganizing into apparently functional coteries. Surviving prairie dogs may be critical in the repopulation of plague-decimated colonies and, ultimately, the evolution of plague resistance.     

Interactive disturbance effects of two disparate ecosystem engineers in North American shortgrass steppe

Disturbances such as fire, grazing, and soil mixing by animals interact to shape vegetation in grassland ecosystems. Animal-generated disturbances are unique in that they arise from a suite of behaviors that are themselves subject to modification by external factors. The manner in which co-occurring animal taxa interact to alter vegetation is a function of their respective behaviors, which shape the characteristics (e.g., the magnitude or extent) of their disturbances. To determine whether prairie dogs (Cynomys ludovicianus) and harvester ants (Pogonomyrmex occidentalis) interactively alter vegetation structure and heterogeneity on the Colorado shortgrass steppe, we characterized the size, dispersion, and vegetation of prairie dog burrow mounds and ant nests (located on and off prairie dog colonies) and vegetation growing beyond mound and nest perimeters. Ants located on prairie dog colonies engineered significantly larger nests and disturbed nearly twice as much total soil area as their off-colony counterparts. Ant nests were overdispersed both on and off prairie dog colonies, while prairie dog mounds were randomly dispersed. Where harvester ants and prairie dogs co-occur, the overdispersed pattern of on-colony ant nests is in effect "overlaid" onto the random pattern of prairie dog mounds, resulting in a unique, aggregated pattern of soil disturbance. Ant nests on prairie dog colonies had significantly less vegetation and lower plant species diversity than did prairie dog mounds, while off-colony nests were similar to mounds. These results suggest that ant nests are more highly disturbed when located on prairie dog colonies. Beyond nests proper, ants did not appear to alter vegetation in a manner distinct from prairie dogs. As such, the interactive effects of prairie dogs and ants on vegetation arise mainly from the disturbance characteristics of mounds and nests proper.     

Habitat selection by mountain plovers in shortgrass steppe

Much of the breeding range for the mountain plover (Charadrius montanus) occurs in shortgrass steppe and mixed-grass prairie in the western Great Plains of North America. Studies of mountain plovers in shortgrass steppe during the 1970s and 1990s were focused in Weld County, Colorado, which was considered a key breeding area for the species. These studies, however, did not include habitats influenced by black-tailed prairie dogs (Cynomys ludovicianus) or prescribed fire. The role of these 2 rangeland disturbance processes has increased substantially over the past 15 years. During 2008–2009, I used radial distance point count surveys to estimate mountain plover densities early in the nesting season in 4 habitats on public lands in Weld County, Colorado. All 4 habitats were grazed by cattle during the growing season at moderate stocking rates but had different additional disturbances consisting of 1) dormant-season prescribed burns, 2) active black-tailed prairie dog colonies, 3) black-tailed prairie dog colonies affected by epizootic plague in the past 1–2 years, and 4) rangeland with no recent history of fire or prairie dogs. Mountain plover densities were similar on active black-tailed prairie dog colonies ( = 6.8 birds/km², 95% CI = 4.3–10.6) and prescribed burns ( = 5.6 birds/km², 95% CI = 3.5–9.1). In contrast, no plovers were detected at randomly selected rangeland sites grazed by cattle but lacking recent disturbance by prairie dogs or fire, even though survey effort was highest for this rangeland habitat. Mountain plover densities were intermediate (2.0 birds/km², 95% CI = 0.8–5.0) on sites where black-tailed prairie dogs had recently been extirpated by plague. These findings suggest that prescribed burns and active black-tailed prairie dog colonies may enhance breeding habitat for mountain plovers in shortgrass steppe and illustrate the potential for suppressed or altered disturbance processes to influence habitat availability for declining wildlife species. © 2011 The Wildlife Society.     

Western Burrowing Owls (Athene cunicularia hypugaea) Eavesdrop on Alarm Calls of Black‐Tailed Prairie Dogs (Cynomys ludovicianus)

Animals sharing a common habitat can indirectly receive information about their environment by observing information exchanges between other animals, a process known as eavesdropping. Animals that use an auditory alarm calling system are an important indirect information source for eavesdropping individuals in their environments. We investigated whether Western burrowing owls (Athene cunicularia hypugaea) nesting on black‐tailed prairie dog (Cynomys ludovicianus) colonies responded to broadcasts of prairie dog alarm calls. Western burrowing owls are closely associated with black‐tailed prairie dogs in Colorado and neighboring states on the Great Plains of the United States. Prairie dog burrows in active colonies can serve as nesting sites for Western burrowing owls, and prairie dogs may act as an alternative prey source for predators, potentially decreasing the burrowing owls' risk of predation through the dilution effect. Burrowing owls nesting on prairie dog colonies may also eavesdrop on prairie dog alarm calls, enhancing their survival and nesting success on prairie dog colonies. We performed broadcast experiments with three different sounds: a prairie dog alarm call, a biological control (cattle mooing), and a non‐biological control (an airplane engine), and characterized burrowing owl responses as either alert or relaxed. For each sound stimulus, we recorded the time to first alert response to broadcast sounds (latency) and also how frequently the target burrowing owl exhibited an alert response within the first ten seconds of the broadcast (intensity). Burrowing owls reacted more quickly to the prairie dog alarm than to the biological control. They significantly increased the intensity of alert behaviors in response to broadcasts of the alarm, but did not show an increased reaction to either the biological or the non‐biological control. Our results suggest that burrowing owls nesting on prairie dog colonies eavesdrop on, and increase their alert behaviors in response to, prairie dog alarm calls.     

Ecosystem engineering varies spatially: a test of the vegetation modification paradigm for prairie dogs

Colonial, burrowing herbivores can be engineers of grassland and shrubland ecosystems worldwide. Spatial variation in landscapes suggests caution when extrapolating single‐place studies of single species, but lack of data and the need to generalize often leads to ‘model system’ thinking and application of results beyond appropriate statistical inference. Generalizations about the engineering effects of prairie dogs (Cynomys sp.) developed largely from intensive study at a single complex of black‐tailed prairie dogs C. ludovicianus in northern mixed prairie, but have been extrapolated to other ecoregions and prairie dog species in North America, and other colonial, burrowing herbivores. We tested the paradigm that prairie dogs decrease vegetation volume and the cover of grasses and tall shrubs, and increase bare ground and forb cover. We sampled vegetation on and off 279 colonies at 13 complexes of 3 prairie dog species widely distributed across 5 ecoregions in North America. The paradigm was generally supported at 7 black‐tailed prairie dog complexes in northern mixed prairie, where vegetation volume, grass cover, and tall shrub cover were lower, and bare ground and forb cover were higher, on colonies than at paired off‐colony sites. Outside the northern mixed prairie, all 3 prairie dog species consistently reduced vegetation volume, but their effects on cover of plant functional groups varied with prairie dog species and the grazing tolerance of dominant perennial grasses. White‐tailed prairie dogs C. leucurus in sagebrush steppe did not reduce shrub cover, whereas black‐tailed prairie dogs suppressed shrub cover at all complexes with tall shrubs in the surrounding habitat matrix. Black‐tailed prairie dogs in shortgrass steppe and Gunnison's prairie dogs C. gunnisoni in Colorado Plateau grassland both had relatively minor effects on grass cover, which may reflect the dominance of grazing‐tolerant shortgrasses at both complexes. Variation in modification of vegetation structure may be understood in terms of the responses of different dominant perennial grasses to intense defoliation and differences in foraging behavior among prairie dog species. Spatial variation in the engineering role of prairie dogs suggests spatial variation in their keystone role, and spatial variation in the roles of other ecosystem engineers. Thus, ecosystem engineering can have a spatial component not evident from single‐place studies.     

Rapid Decline of a Grassland System and Its Ecological and Conservation Implications

One of the most important conservation issues in ecology is the imperiled state of grassland ecosystems worldwide due to land conversion, desertification, and the loss of native populations and species. The Janos region of northwestern Mexico maintains one of the largest remaining black-tailed prairie dog (Cynomys ludovicianus) colony complexes in North America and supports a high diversity of threatened and endangered species. Yet, cattle grazing, agriculture, and drought have greatly impacted the region. We evaluated the impact of human activities on the Janos grasslands, comparing changes in the vertebrate community over the last two decades. Our results reveal profound, rapid changes in the Janos grassland community, demonstrating large declines in vertebrate abundance across all taxonomic groups. We also found that the 55,000 ha prairie dog colony complex has declined by 73% since 1988. The prairie dog complex has become increasingly fragmented, and their densities have shown a precipitous decline over the years, from an average density of 25 per ha in 1988 to 2 per ha in 2004. We demonstrated that prairie dogs strongly suppressed woody plant encroachment as well as created open grassland habitat by clearing woody vegetation, and found rapid invasion of shrubland once the prairie dogs disappeared from the grasslands. Comparison of grasslands and shrublands showed markedly different species compositions, with species richness being greatest when both habitats were considered together. Our data demonstrate the rapid decline of a grassland ecosystem, and documents the dramatic loss in biodiversity over a very short time period concomitant with anthropogenic grassland degradation and the decline of a keystone species.     

Plant-herbivore interactions in a North American mixed-grass prairie

Summary Studies were conducted during the 1979 growing season to examine how North American bison (Bison bison) use prairie dog (Cynomys ludovicianus) colonies in Wind Cave National Park, South Dakota. Objectives included (1) determining whether bison selected for prairie dog towns parkwide; (2) characterizing in greater detail bison use patterns of a 36-ha colony in Pringle Valley as a function of time since prairie dog colonization; and (3) relating these bison use patterns to measured changes in structure and nutritional value of vegetation on and off the dog town.During midsummer, prairie dog towns were one of the most frequently used habitats by bison parkwide. Day-long observations at Pringle Valley revealed that bison exerted strong selection (nearly 90% of all habitat use and feeding time) for the dog town, which occupied only 39% of the valley. While there, they partitioned their use of the colony by grazing in moderately affected areas (occupied <8 years by prairie dogs) and by resting in the oldest area (>26 years occupation).Prairie dogs facilitate bison habitat selection for a shortgrass successional stage in this mixed-grass community by causing a broad array of compositional, structural, and nutritional changes in the vegetation.     

Multiscale Habitat Selection by Burrowing Owls in Black-Tailed Prairie Dog Colonies

ABSTRACT Some populations of western burrowing owls (Athene cunicularia hypugaea) have declined in recent decades. To design and implement effective recovery efforts, we need a better understanding of how distribution and demographic traits are influenced by habitat quality. To this end, we measured spatial patterns of burrowing owl breeding habitat selection within black-tailed prairie dog (Cynomys ludovicianus) colonies in northeastern Wyoming, USA. We compared burrow-, site-, colony-, and landscape-scale habitat parameters between burrowing owl nest burrows (n = 105) and unoccupied burrows (n = 85). We sampled 4 types of prairie dog colonies: 1) owl-occupied, active with prairie dogs (n = 16); 2) owl-occupied, inactive (n = 13); 3) owl-unoccupied, active (n = 14); and 4) owl-unoccupied, inactive (n = 14). We used an information-theoretic approach to examine a set of candidate models of burrowing owl nest-site selection. The model with the most support included variables at all 4 spatial scales, and results were consistent among the 4 types of prairie dog colonies. Nest burrows had longer tunnels, more available burrows within 30 m, and less shrub cover within 30 m, more prairie dog activity within 100 m, and were closer to water than unoccupied burrows. The model correctly classified 76% of cases, all model coefficients were stable, and the model had high predictive ability. Based on our results, we recommend actions to ensure persistence of the remaining prairie dog colonies as an important management strategy for burrowing owl conservation in the Great Plains of North America.     

Prairie dog presence affects occurrence patterns of disease vectors on small mammals

Wildlife disease is recognized as a burgeoning threat to imperiled species and aspects of host and vector community ecology have been shown to have significant effects on disease dynamics. The black‐tailed prairie dog is a species of conservation concern that is highly susceptible to plague, a flea‐transmitted disease. Prairie dogs (Cynomys) alter the grassland communities in which they exist and have been shown to affect populations of small rodents, which are purported disease reservoirs. To explore potential ecological effects of black‐tailed prairie dogs on plague dynamics, we quantified flea occurrence patterns on small mammals in the presence and absence of prairie dogs at 8 study areas across their geographic range. Small mammals sampled from prairie dog colonies showed significantly higher flea prevalence, flea abundance, and relative flea species richness than those sampled from off‐colony sites. Successful plague transmission likely is dependent on high prevalence and abundance of fleas that can serve as competent vectors. Prairie dogs may therefore facilitate the maintenance of plague by increasing flea occurrence on potential plague reservoir species. Our data demonstrate the previously unreported ecological influence of prairie dogs on vector species assemblages, which could influence disease dynamics.     

Possible vector dissemination by swift foxes following a plague epizootic in black-tailed prairie dogs in northwestern Texas

To determine whether swift foxes (Vulpes velox) could facilitate transmission of Yersinia pestis to uninfected black-tailed prairie dog (Cynomys ludovicianus) colonies by acquiring infected fleas, ectoparasite and serologic samples were collected from swift foxes living adjacent to prairie dog towns during a 2004 plague epizootic in northwestern Texas, USA. A previous study (1999-2001) indicated that these swift foxes were infested almost exclusively with the flea Pulex irritans. Black-tailed prairie dogs examined from the study area harbored only Pulex simulans and Oropsylla hirsuta. Although P. irritans was most common, P. simulans and O. hirsuta were collected from six swift foxes and a single coyote (Canis latrans) following the plague epizootic. Thus, both of these canids could act as transport hosts (at least temporarily) of prairie dog fleas following the loss of their normal hosts during a plague die-off. All six adult swift foxes tested positive for antibodies to Y. pestis. All 107 fleas from swift foxes tested negative for Y. pestis by mouse inoculation. Although swift foxes could potentially carry Y. pestis to un-infected prairie dog colonies, we believe they play only a minor role in plague epidemiology, considering that they harbored just a few uninfected prairie dog fleas (P. simulans and O. hirsuta).