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.     

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.     

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.     

Bison-prairie dog-plant interactions in a North American mixed-grass prairie

Both bison and prairie dogs have multiple and dramatic effects on grassland landscapes and both are considered by many to be keystone herbivores. Numerous studies have documented their independent or combined impact on grassland ecosystem processes, but there have been few attempts to simultaneously assess the individual and interactive effects of bison and prairie dogs where they co-occur. We began a long-term study in late 1994 in Badlands National Park, South Dakota, USA, to evaluate the ecological consequences of the presence or exclusion of prairie dogs, bison, or both, upon various aspects of plant community dynamics and N cycling. Five different treatments were established at three separate mixed-grass prairie sites in the park: (1) off the prairie dog colony with bison excluded, (2) off colony with continued bison utilization, (3) on colony with bison excluded but continued prairie dog use, (4) on colony with utilization by prairie dogs and bison, and (5) on colony with both excluded. There were few differences in aboveground biomass or plant species composition between the two off-colony treatments or among the three on-colony treatments, even after 3 years of treatment imposition. However, aboveground biomass was >2 times greater in off-colony sites than on-colony sites, primarily due to the near elimination of grasses on prairie dog colonies. Off-colony sites were dominated by a few grass species, resulting in lower plant species diversity, while on-colony sites were dominated by several forb species. Net N mineralization early in the growing season was 4 times greater on prairie dog colonies than at off-colony sites, but all sites exhibited net immobilization by the latter half of the growing season. The results of this study indicate distinct differences in several ecosystem properties between on- and off-colony treatments. Whether these patterns represent relatively stable alternate states or whether distinct changes will emerge in the different herbivore treatments after several additional years is of considerable interest.     

Interactive effects of keystone rodents on the structure of desert grassland arthropod communities

Certain species play particularly large roles in ecosystems, and are often referred to as keystones. However, little is known about the interactive effects of these species where they co-occur. Prairie dogs ( Cynomys spp.) and banner-tailed kangaroo rats Dipodomys spectabilis are commonly considered keystone species of grassland ecosystems, creating a mosaic of unique habitats on the landscape through ecosystem engineering and herbivory. We examined the separate and interactive effects of these species on the structure of grassland arthropod communities. We conducted a cross-site study at two locations in the northern Chihuahuan Desert, and evaluated the impacts of these rodents on ground-dwelling arthropod and grasshopper communities in areas where prairie dogs and kangaroo rats co-occurred compared to areas where each rodent species occurred alone. Our results demonstrate that prairie dogs ( C. gunnisoni and C. ludovicianus ) and banner-tailed kangaroo rats had keystone-level impacts on arthropod communities both separately and interactively. Their burrow systems provided important habitats for multiple trophic and taxonomic groups of arthropods, and increased overall arthropod abundance and species richness. Many arthropods also were attracted to the aboveground habitats around the mounds and across the landscapes where the rodents occurred. Detritivores, predators, ants, grasshoppers, and rare rodent burrow inhabitants were especially associated with prairie dog and kangaroo rat activity. The impacts of prairie dogs and kangaroo rats were unique, and the habitats they created supported different assemblages of arthropods. Where both rodent species co-occurred, there was greater heterogeneity and arthropod diversity on the landscape. Our results suggest that the interaction of multiple keystones, especially those with engineering roles, results in unique and more diverse communities in time and space.     

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.     

Spatial Analysis of Effects of Mowing and Burning on Colony Expansion in Reintroduced Black‐Tailed Prairie Dog (Cynomys ludovicianus)

Factors governing the rate and direction of prairie dog (Cynomys spp.) colony expansion remain poorly understood. However, increased knowledge and ability to control these factors may lead to more effective reintroductions of prairie dogs and restoration of grassland habitats. We present density and directional analyses of the establishment of new burrows on three reintroduced colonies of Black‐tailed prairie dog (Cynomys ludovicianus) in southern New Mexico; the study colonies had been subjected to mow and burn treatments in the second year of the study. Our hypotheses were that prairie dogs will preferentially dig new burrows in the treatment plots versus control plots and that the colonies will expand in the direction of the treatment plots. The results support these hypotheses; analysis of burrow counts by site and treatment shows that prairie dogs preferentially colonized both mow and burn treatments compared to untreated areas at the periphery of the colonies. Directional analysis showed a significant posttreatment orientation of new burrows toward the treatment plots for all colonies. Our results show that the direction of expansion of prairie dog colonies can be manipulated. Effective control of the expansion of prairie dog colonies may lead to more successful reintroductions.     

Reintroducing a keystone burrowing rodent to restore an arid North American grassland: challenges and successes

Prairie dogs (Cynomys spp.) are important ecosystem engineers in North America's central grasslands, and are a key prey base for numerous predators. Prairie dogs have declined dramatically across their former range, prompting reintroduction efforts to restore their populations and ecosystem functions, but the success of these reintroductions is rarely monitored rigorously. Here, we reintroduced 2,400 Gunnison's prairie dogs (C. gunnisoni) over a period of 6 years to the Sevilleta National Wildlife Refuge, in central New Mexico, U.S.A., a semi‐arid grassland ecosystem at the southern edge of their range. We evaluated the population dynamics of prairie dogs following their reintroduction, and their consequent effects on grassland vertebrates. We found postrelease survival of prairie dogs stabilized at levels typical for the species (ca. 50%) after approximately 1 month, while average annual recruitment was ca. 0.35 juveniles per female, well below what was required for a self‐sustaining, stable population. Extreme drought conditions during much of the study period may have contributed to low recruitment. However, recruitment increased steadily over time, indicating that the reintroduced colony may simply need more time to establish in this arid system. We also found well‐known associates of prairie dog colonies, such as American badgers (Taxidea taxus) and burrowing owls (Athene cunicularia), were significantly more common on the colonies than off. After 7 years, we have yet to meet our goal of establishing a self‐sustaining population of Gunnison's prairie dogs in this semi‐arid grassland. But despite the uncertainty and challenges, our work shows that reestablishing keystone species can promote ecosystem restoration.     

Keystone rodent interactions: prairie dogs and kangaroo rats structure the biotic composition of a desertified grassland

Understanding the interactive effects of multiple keystone species where they co-occur may have important consequences for regional biodiversity. Additionally, understanding how the impacts of keystone species vary across different ecosystems is important for effectively guiding conservation and management. We conducted a large-scale field study in northern Mexico where the geographic distributions of black-tailed prairie dogs Cynomys ludovicianus and banner-tailed kangaroo rats Dipodomys spectabilis overlap. These species are considered both keystones and ecosystem engineers of grassland environments, but little is known about their separate and interacting roles in desertified systems where they co-occur. Our research evaluated 1) the independent impacts of black-tailed prairie dogs and banner-tailed kangaroo rats in a desertified annual grassland, and 2) their interactive effects on grassland community structure and biodiversity. Prairie dogs and kangaroo rats differentially affected vegetation structure, plant cover, species composition, and species richness across multiple spatial and temporal scales. The interactive effects of these keystone species resulted in enhanced landscape heterogeneity and biodiversity. Our results demonstrate the importance of prairie dogs and kangaroo rats in desertified grasslands, and have important implications for understanding the interactive effects and context-dependency of keystone species.     

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.     

Geographic variation in rodent-flea relationships in the presence of black-tailed prairie dog colonies

We characterized the relationship between fleas and their rodent hosts in the presence of prairie dog colonies and compared them to adjacent assemblages away from colonies. We evaluated the rodent-flea relationship by quantifying prevalence, probability of infestation, flea load, and intensity of fleas on rodents. As prairie dog burrows provide refugia for fleas, we hypothesized that prevalence, flea load, and intensity would be higher for rodents that are associated with black-tailed prairie dog colonies. Rodents were trapped at off- and on-colony grids, resulting in the collection of 4,509 fleas from 1,430 rodents in six study areas. The rodent community composition varied between these study areas. Flea species richness was not different between prairie dog colonies and the surrounding grasslands (p = 0.883) but was positively correlated with rodent species richness (p = 0.055). Prairie dog colonies did not increase the prevalence of fleas (p > 0.10). Flea loads on rodents did not vary between off- and on-colony grids at three of the study areas (p > 0.10). Based on the prevalence, infestation rates, and flea loads, we identified Peromyscus maniculatus, Onychomys leucogaster, and two Neotoma species as important rodent hosts for fleas and Aetheca wagneri, Orchopeus leucopus, Peromyscopsylla hesperomys, Pleochaetis exilis, and Thrassisfotus as the most important fleas associated with these rodents. Prairie dog colonies did not seem to facilitate transmission of fleas between rodent hosts, and the few rodent-flea associations exhibited significant differences between off- and on-colony grids.     

Prairie dog towns as islands: applications of island biogeography and landscape ecology for conserving nonvolant terrestrial vertebrates

Aim To evaluate the utility of island biogeography theory as a model for understanding and conserving native communities of nonvolant terrestrial vertebrates at prairie dog towns. Location Oklahoma Panhandle, USA. Methods We surveyed mammal, reptile and amphibian communities on 36 black‐tailed prairie dog (Cynomys ludovicianus) towns during the summers and falls of 1997 to 1999. We used a Geographic Information System (GIS) to characterize the landscape within 10 km of each town. We used Principal Components Analysis (PCA), Correlation Analysis, and Linear Regression to test for patterns in species richness relative to area and isolation of towns, local habitat characteristics, and characteristics of the adjacent landscape. Results Species richness was not significantly correlated with town size, town isolation, or local habitat characteristics. On the other hand, species richness was significantly correlated with characteristics of the landscape within 10 km of the focal town. In addition, species richness of mammals at prairie dog towns during the summer increased in a northerly direction, while richness of mammals at towns during fall increased to the west. Main conclusions These results, albeit contrary to traditional island biogeography theory, are consistent with an emerging view that communities on relatively small islands are strongly influenced by characteristics of the adjacent landscape (or seascape). We recommend that to the extent possible, networks of reserves for prairie dogs and their associated species should include clusters of large towns (i.e. larger than those studied here), as well as large but isolated towns, and that conservation efforts should include management of the intervening matrix of anthropogenic habitats.     

Grooming behaviors of black‐tailed prairie dogs are influenced by flea parasitism,conspecifics, and proximity to refuge

Grooming is a common animal behavior that aids in ectoparasite defense. Ectoparasites can stimulate grooming, and natural selection can also favor endogenous mechanisms that evoke periodic bouts of “programmed” grooming to dislodge or kill ectoparasites before they bite or feed. Moreover, grooming can function as a displacement or communication behavior. We compared the grooming behaviors of adult female black‐tailed prairie dogs (Cynomys ludovicianus) on colonies with or without flea control via pulicide dust. Roughly 91% of the prairie dogs sampled on the non‐dusted colony carried at least one flea, whereas we did not find fleas on two dusted colonies. During focal observations, prairie dogs on the non‐dusted colony groomed at higher frequencies and for longer durations than prairie dogs on the dusted colonies, lending support to the hypothesis that fleas stimulated grooming. However, the reduced amount of time spent grooming on the dusted colonies suggested that approximately 25% of grooming might be attributed to factors other than direct stimulation from ectoparasites. Non‐dusted colony prairie dogs rarely autogroomed when near each other. Dusted colony prairie dogs autogroomed for shorter durations when far from a burrow opening (refuge), suggesting a trade‐off between self‐grooming and antipredator defense. Allogrooming was detected only on the non‐dusted colony and was limited to adult females grooming young pups. Grooming appears to serve an antiparasitic function in C. ludovicianus. Antiparasitic grooming might aid in defense against fleas that transmit the plague bacterium Yersinia pestis. Plague was introduced to North America ca. 1900 and now has a strong influence on most prairie dog populations, suggesting a magnified effect of grooming on prairie dog fitness.     

Polymerase chain reaction (PCR) identification of rodent blood meals confirms host sharing by flea vectors of plague

Elucidating feeding relationships between hosts and parasites remains a significant challenge in studies of the ecology of infectious diseases, especially those involving small or cryptic vectors. Black‐tailed prairie dogs (Cynomys ludovicianus) are a species of conservation importance in the North American Great Plains whose populations are extirpated by plague, a flea‐vectored, bacterial disease. Using polymerase chain reaction (PCR) assays, we determined that fleas (Oropsylla hirsuta) associated with prairie dogs feed upon northern grasshopper mice (Onychomys leucogaster), a rodent that has been implicated in the transmission and maintenance of plague in prairie‐dog colonies. Our results definitively show that grasshopper mice not only share fleas with prairie dogs during plague epizootics, but also provide them with blood meals, offering a mechanism by which the pathogen, Yersinia pestis, may be transmitted between host species and maintained between epizootics. The lack of identifiable host DNA in a significant fraction of engorged Oropsylla hirsuta collected from animals (47%) and prairie‐dog burrows (100%) suggests a rapid rate of digestion and feeding that may facilitate disease transmission during epizootics but also complicate efforts to detect feeding on alternative hosts. Combined with other analytical approaches, e.g., stable isotope analysis, molecular genetic techniques can provide novel insights into host‐parasite feeding relationships and improve our understanding of the role of alternative hosts in the transmission and maintenance of disease.     

Black-Tailed Prairie Dogs,Cattle, and the Conservation of North America’s Arid Grasslands

Prairie dogs (Cynomys spp.) have been eliminated from over 95% of their historic range in large part from direct eradication campaigns to reduce their purported competition with cattle for forage. Despite the longstanding importance of this issue to grassland management and conservation, the ecological interactions between cattle and prairie dogs have not been well examined. We address this issue through two complementary experiments to determine if cattle and prairie dogs form a mutualistic grazing association similar to that between prairie dogs and American bison. Our experimental results show that cattle preferentially graze along prairie dog colony edges and use their colony centers for resting, resembling the mutualistic relationship prairie dogs have with American bison. Our results also show that prairie dog colonies are not only an important component of the grassland mosaic for maintaining biodiversity, but also provide benefits to cattle, thereby challenging the long-standing view of prairie dogs as an undesirable pest species in grasslands.     

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.     

Biodiversity and reduced extinction risks in spatially isolated rodent populations

Ecologists have rarely explored the potential influence of local (alpha) biodiversity on the stability and local extinction of spatially isolated populations. Twenty years of annual counts of a small, grazing rodent (Utah prairie dogs, Cynomys parvidens ) from 20 different isolated local populations (colonies) in southern Utah, U.S.A. were analysed. These prairie dogs exhibited large fluctuations and repeated extinctions at individual colonies during the census period. Frequency of extinction at a colony declined dramatically as the number of locally occurring plant species increased. This pattern was not explained by differences among colonies in plant productivity, plant species composition, colony size, or variability in annual counts. Thus, lower extinction risk of consumer populations may be associated with greater resource diversity, and maintaining high local plant diversity may help sustain spatially isolated herbivore populations in fragmented habitats.     

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.     

Colorado animal‐based plague surveillance systems: relationships between targeted animal species and prediction efficacy of areas at risk for humans

Human plague risks (Yersinia pestis infection) are greatest when epizootics cause high mortality among this bacterium's natural rodent hosts. Therefore, health departments in plague‐endemic areas commonly establish animal‐based surveillance programs to monitor Y. pestis infection among plague hosts and vectors. The primary objectives of our study were to determine whether passive animal‐based plague surveillance samples collected in Colorado from 1991 to 2005 were sampled from high human plague risk areas and whether these samples provided information useful for predicting human plague case locations. By comparing locations of plague‐positive animal samples with a previously constructed GIS‐based plague risk model, we determined that the majority of plague‐positive Gunnison's prairie dogs (100%) and non‐prairie dog sciurids (85.82%), and moderately high percentages of sigmodontine rodents (71.4%), domestic cats (69.3%), coyotes (62.9%), and domestic dogs (62.5%) were recovered within 1 km of the nearest area posing high peridomestic risk to humans. In contrast, the majority of white‐tailed prairie dog (66.7%), leporid (cottontailed and jack rabbits) (71.4%), and black‐tailed prairie dog (93.0%) samples originated more than 1 km from the nearest human risk habitat. Plague‐positive animals or their fleas were rarely (one of 19 cases) collected within 2 km of a case exposure site during the 24 months preceding the dates of illness onset for these cases. Low spatial accuracy for identifying epizootic activity prior to human plague cases suggested that other mammalian species or their fleas are likely more important sources of human infection in high plague risk areas. To address this issue, epidemiological observations and multi‐locus variable number tandem repeat analyses (MLVA) were used to preliminarily identify chipmunks as an under‐sampled, but potentially important, species for human plague risk in Colorado.     

Prairie Dog Decline Reduces the Supply of Ecosystem Services and Leads to Desertification of Semiarid Grasslands

Anthropogenic impacts on North American grasslands, a highly endangered ecosystem, have led to declines of prairie dogs, a keystone species, over 98% of their historical range. While impacts of this loss on maintenance of grassland biodiversity have been widely documented, much less is known about the consequences on the supply of ecosystem services. Here we assessed the effect of prairie dogs in the supply of five ecosystem services by comparing grasslands currently occupied by prairie dogs, grasslands devoid of prairie dogs, and areas that used to be occupied by prairie dogs that are currently dominated by mesquite scrub. Groundwater recharge, regulation of soil erosion, regulation of soil productive potential, soil carbon storage and forage availability were consistently quantitatively or qualitatively higher in prairie dog grasslands relative to grasslands or mesquite scrub. Our findings indicate a severe loss of ecosystem services associated to the absence of prairie dogs. These findings suggest that contrary to a much publicize perception, especially in the US, prairie dogs are fundamental in maintaining grasslands and their decline have strong negative impacts in human well – being through the loss of ecosystem services.