Survival,fidelity, and recovery rates of white-winged doves in Texas

Management of migratory birds at the national level has historically relied on regulatory boundaries for definition of harvest restrictions and estimation of demographic parameters. Most species of migratory game birds are not expanding their ranges, so migratory corridors are approximately fixed. White-winged doves (Zenaida asiatica), however, have undergone significant variation in population structure with marked range expansion occurring in Texas, and range contraction in Arizona, during the last 30 years. Because >85% of white-winged dove harvest in the United States (approx. 1.3 million annually) now occurs in Texas, information on vital rates of expanding white-winged dove populations is necessary for informed management. We used band recovery and mark–recapture data to investigate variation in survival and harvest across 3 geographic strata for white-winged doves banded in the pre-hunting season in Texas during 2007–2010. We banded 60,742 white-winged doves, recovered 2,458 bands via harvest reporting, and recaptured 455 known-age birds between 2007 and 2010. The best supporting model found some evidence for geographic differences in survival rates among strata (A–C) in both hatch-year (juvenile; A = 0.205 [SE = 0.0476], B = 0.213 [SE = 0.0278], C = 0.364 [SE = 0.0254]) and after-hatch year (adult; A = 0.483 [SE = 0.0775], B = 0.465 [SE = 0.0366], C = 0.538 [SE = 0.251]) birds. White-winged doves had a low probability of moving among strata (0.009) or being recaptured (0.002) across all strata. Harvest recovery rates were concordant with estimates for other dove species, but were variable across geographic strata. Based on our results, harvest management strategies for white-winged doves in Texas and elsewhere should consider differences in population vital rates among geographic strata. © 2012 The Wildlife Society.     

Genetic variation at the MHC DRB1 locus is similar across Gunnison's prairie dog (Cynomys gunnisoni) colonies regardless of plague history

Yersinia pestis was introduced to North America around 1900 and leads to nearly 100% mortality in prairie dog (Cynomys spp.) colonies during epizootic events, which suggests this pathogen may exert a strong selective force. We characterized genetic diversity at an MHC class II locus (DRB1) in Gunnison's prairie dog (C. gunnisoni) and quantified population genetic structure at the DRB1 versus 12 microsatellite loci in three large Arizona colonies. Two colonies, Seligman (SE) and Espee Ranch (ES), have experienced multiple plague‐related die‐offs in recent years, whereas plague has never been documented at Aubrey Valley (AV). We found fairly low allelic diversity at the DRB1 locus, with one allele (DRB1*01) at high frequency (0.67–0.87) in all colonies. Two other DRB1 alleles appear to be trans‐species polymorphisms shared with the black‐tailed prairie dog (C. ludovicianus), indicating that these alleles have been maintained across evolutionary time frames. Estimates of genetic differentiation were generally lower at the MHC locus (F_ST = 0.033) than at microsatellite markers (F_ST = 0.098). The reduced differentiation at DRB1 may indicate that selection has been important for shaping variation at MHC loci, regardless of the presence or absence of plague in recent decades. However, genetic drift has probably also influenced the DRB1 locus because its level of differentiation was not different from that of microsatellites in an F_ST outlier analysis. We then compared specific MHC alleles to plague survivorship in 60 C. gunnisoni that had been experimentally infected with Y. pestis. We found that survival was greater in individuals that carried at least one copy of the most common allele (DRB1*01) compared to those that did not (60% vs. 20%). Although the sample sizes of these two groups were unbalanced, this result suggests the possibility that this MHC class II locus, or a nearby linked gene, could play a role in plague survival.     

Abundance patterns of two Oropsylla (Ceratophyllidae: Siphonaptera) species on black-tailed prairie dog (Cynomys ludovicianus) hosts.

Behavioral, genetic, and immune variation within a host population may lead to aggregation of parasites whereby a small proportion of hosts harbor a majority of parasites. In situations where two or more parasite species infect the same host population there is the potential for interaction among parasites that could potentially influence patterns of aggregation through either competition or facilitation. We studied the occurrence and abundance patterns of two congeneric flea species on black-tailed prairie dog (Cynomys ludovicianus) hosts to test for interactions among parasite species. We live-trapped prairie dogs on ten sites in Boulder County, CO and collected their fleas. We found a non-random, positive association between the two flea species, Oropsylla hirsuta and O. tuberculata cynomuris; hosts with high loads of one flea species had high loads of the second species. This result suggests that there is no interspecific competition among fleas on prairie dog hosts. Host weight had a weak negative relationship to flea load and host sex did not influence flea load, though there were slight differences in flea prevalence and abundance between male and female C. ludovicianus. While genetic and behavioral variation among hosts may predispose certain individuals to infection, our results indicate apparent facilitation among flea species that may result from immune suppression or other flea-mediated factors.     

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.     

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.     

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.     

Provision of Service Dogs for People With Mobility Disabilities

ABSTRACT

Interactions among domestic dogs (Canis familiaris), black-tailed prairie dogs (Cynomys ludovicianus), and people were studied at Dry Creek, Boulder, Colorado. Our objective was to develop a basic understanding of the nature of dog—prairie dog interactions in this recreational area, because this is an issue that has high visibility and over which there is conflict in Boulder: There are those who want dogs to run free regardless of their impact on the behavior and lives of prairie dogs and those who want to protect prairie dogs and have dogs restrained or go elsewhere. We found that dogs clearly influenced the behavior of prairie dogs, however, no prairie dogs were known to be caught or killed by any dog during the course of study. Prairie dogs disturbed by dogs were more alert (vigilant) and wary of dogs and played less than undisturbed individuals. However, disturbed prairie dogs were less wary of the presence of humans than undisturbed animals. People tried to stop dogs from harassing prairie dogs only 25% of the time. A survey showed that 58% of people polled at Dry Creek (all dog owners) did not believe that prairie dogs should be protected even if dogs are a problem. Increased human responsibility would likely go a long way towards reducing existing conflict among people wanting to protect prairie dogs and those who do not. Boulder city officials have not yet incorporated our data into their immediate management plans. However, by identifying the nature of dog—prairie dog encounters and specific areas of conflict among people who side either with dogs or prairie dogs, in the future, proactive strategies grounded by empirical data can be developed and implemented so that the interests of all parties can be accommodated.     

Prairie Dogs: An Ecological Review and Current Biopolitics

ABSTRACT In recent years, people have interpreted scientific information about the black-tailed prairie dog (Cynomys ludovicianus) in various, and sometimes conflicting, ways. Political complexity around the relationship among black-tailed prairie dogs, agricultural interests, and wildlife has increased in recent years, particularly when prairie dogs occur on publicly owned lands leased to private entities for livestock grazing. Some have proposed that estimates of prairie dog (Cynomys spp.) numbers from 1900 are inflated, that prairie dog grazing is not unique (other grazers have similar affects on vegetation), and that prairie dogs significantly reduce carrying capacity for livestock and wildlife. We address all these issues but concentrate on the degree of competition between prairie dogs and ungulates because this motivates most prairie dog control actions. We conclude that the available information does not justify holding distribution and numbers of prairie dogs at a level that is too low to perform their keystone ecological function. We further conclude that it is especially important that prairie dogs be sufficiently abundant on public lands to perform this function.     

Long-Term Effects of Black-Tailed Prairie Dogs on Livestock Grazing Distribution and Mass Gain

The conservation and management of black-tailed prairie dogs (Cynomys ludovicianus) have been contentious issues in grasslands of central North America for much of the past century, primarily because of the perception that they compete with livestock for forage. Studies quantifying the magnitude of competition between prairie dogs and cattle are difficult to conduct because of the large spatial and long temporal scales needed to quantify how competition varies in response to interannual variation in precipitation and prairie dog abundance. We examined variation in mass gains of yearling steers in shortgrass steppe of northeastern Colorado, USA, with and without prairie dogs from 2008–2019, a period that encompassed a full cycle in prairie dog abundance from a nadir following plague-induced population collapse, to peak abundance following population recovery, to plague-induced population lows again. Analyses of cattle grazing distribution with global positioning system (GPS)-collars revealed preferential grazing on colonies following a period of unusually high vegetation production, and preferential grazing off colonies following a period of rapid vegetation senescence, but these patterns were not clearly related to cattle mass gains. Across all 12 years of the study, average daily mass gain (ADG) during the growing season was 0.97 kg/steer/day in pastures where prairie dogs were controlled annually, and 0.95 kg/steer/day in pastures where they were not. Average daily mass gain was a quadradic function of precipitation and a linear function of prairie dog occupancy within a pasture, with a generalized linear mixed model predicting an 8.0% decrease in ADG as prairie dog occupancy increased from 0 to 60% of a pasture with average growing-season precipitation. We did not detect a significant interaction between precipitation and prairie dog occupancy, but one limitation of our study is that the only drought year (2012) occurred when prairie dogs occupied low percentages (10–25%) of the study pastures. Prairie dogs had a small but detectable negative effect on cattle mass gains during the growing season in shortgrass steppe. The magnitude of this effect can be used by managers in combination with market conditions and the spatial extent of prairie dog colonies to estimate economic effects of prairie dogs on livestock operations. © 2021 The Wildlife Society. This article is a U.S. Government work and is in the public domain in the USA.     

Potential Effects of Environmental Conditions on Prairie Dog Flea Development and Implications for Sylvatic Plague Epizootics

Fleas are common ectoparasites of vertebrates worldwide and vectors of many pathogens causing disease, such as sylvatic plague in prairie dog colonies. Development of fleas is regulated by environmental conditions, especially temperature and relative humidity. Development rates are typically slower at low temperatures and faster at high temperatures, which are bounded by lower and upper thresholds where development is reduced. Prairie dogs and their associated fleas (mostly Oropsylla spp) live in burrows that moderate outside environmental conditions, remaining cooler in summer and warmer in winter. We found burrow microclimates were characterized by stable daily temperatures and high relative humidity, with temperatures increasing from spring through summer. We previously showed temperature increases corresponded with increasing off-host flea abundance. To evaluate how changes in temperature could affect future prairie dog flea development and abundance, we used development rates of O. montana (a species related to prairie dog fleas), determined how prairie dog burrow microclimates are affected by ambient weather, and combined these results to develop a predictive model. Our model predicts burrow temperatures and flea development rates will increase during the twenty-first century, potentially leading to higher flea abundance and an increased probability of plague epizootics if Y. pestis is present.

     

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.     

Tyrosine hydroxylase‐synthesizing cells in the hypothalamus of prairie voles (Microtus ochrogaster): Sex differences in the anteroventral periventricular preoptic area and effects of adult gonadectomy or neonatal gonadal hormones

The vertebrate hypothalamus and surrounding region contain a large population of cells expressing tyrosine hydroxylase (TH), the rate limiting enzyme for synthesis of dopamine and other catecholamines. Some of these populations are sexually dimorphic in rats. We here examined sex differences in TH‐immunoreactive populations in the forebrain of gonadally intact and gonadectomized prairie voles (Microtus ochrogaster), a species that sometimes shows unusual sexual differentiation of brain and behavior. A sex difference was found in the anteroventral periventricular preoptic area (AVPV; likely analogous to the rat rostral A14) only in gonadectomized subjects, which was due to a 50% reduction in the number of TH‐immunoreactive cells after castration in males. There was no significant sex difference or effects of gonadectomy on the number of TH‐immunoreactive cells in the anteroventral preoptic area (AVP), periventricular anterior hypothalamus (caudal A14), arcuate nucleus (A12), zona incerta (A13), or posterodorsal hypothalamus (A11). In a second experiment, testosterone propionate (TP; 500 μg), diethylstilbestrol (DES; 1 μg), or estradiol benzoate (EB; 30 μg) injected daily during the first week after birth each significantly reduced later TH expression in the AVPV of females by approximately 40–65% compared to oil‐treated controls. Unlike rats, therefore, a sex difference in TH expression in the prairie vole AVPV is found only after removal of circulating gonadal hormones in males. Furthermore, unlike our previous findings on the generation of sex differences in extra‐hypothalamic arginine‐vasopressin expression in prairie voles, TH expression in the AVPV of female prairie voles can be highly masculinized by neonatal exposure to either aromatizable androgens or estrogens. © 2005 Wiley Periodicals, Inc. J Neurobiol, 2006     

Deltamethrin flea-control preserves genetic variability of black-tailed prairie dogs during a plague outbreak

Genetic variability and structure of nine black-tailed prairie dog (BTPD, Cynomys ludovicianus) colonies were estimated with 15 unlinked microsatellite markers. A plague epizootic occurred between the first and second years of sampling and our study colonies were nearly extirpated with the exception of three colonies in which prairie dog burrows were previously dusted with an insecticide, deltamethrin, used to control fleas (vectors of the causative agent of plague, Yersinia pestis). This situation provided context to compare genetic variability and structure among dusted and non-dusted colonies pre-epizootic, and among the three dusted colonies pre- and post-epizootic. We found no statistical difference in population genetic structures between dusted and non-dusted colonies pre-epizootic. On dusted colonies, gene flow and recent migration rates increased from the first (pre-epizootic) year to the second (post-epizootic) year which suggested dusted colonies were acting as refugia for prairie dogs from surrounding colonies impacted by plague. Indeed, in the dusted colonies, estimated densities of adult prairie dogs (including dispersers), but not juveniles (non-dispersers), increased from the first year to the second year. In addition to preserving BTPDs and many species that depend on them, protecting colonies with deltamethrin or a plague vaccine could be an effective method to preserve genetic variability of prairie dogs.     

Black-tailed prairie dogs and the structure of avian communities on the shortgrass plains

We tested the hypothesis that black-tailed prairie dogs (Cynomys ludovicianus) influence avian community structure on the shortgrass prairie. We surveyed 36 prairie dog towns and 36 paired sites without prairie dogs during summer and fall of 1997, 1998, and 1999 in the Oklahoma Panhandle. Our surveys totaled 9,040 individual observations for 73 avian species. Significantly distinct avian communities were present on prairie dog towns when compared to sites within four different macrohabitats of the surrounding landscape: open rangeland, scrub/sandsage (Artemisia filifolia) habitats, Conservation Reserve Program (CRP) plots, and fallow crop fields. Relative densities of all bird species combined was higher on prairie dog towns versus paired sites in summer and fall. Mean species richness of birds was significantly higher on prairie dog towns than paired sites during summer, but there were no significant differences in fall. Open rangeland had the highest mean species richness in fall. Assemblages of avian communities differed significantly between prairie dog towns and the four macrohabitat types during summer. Burrowing owls (Athene cunicularia), killdeer (Charadrius vociferous), horned larks (Eremophila alpestris), and meadowlarks (Sturnella spp.) were positively and significantly associated with prairie dog towns during summer, while horned larks and ferruginous hawks (Buteo regalis) were significantly associated with prairie dog towns during fall. Even in their current remnant state, black-tailed prairie dogs continue to play a significant role in the assembly of ecological communities across the Great Plains. Conservation of prairie dogs goes well beyond a single species, and is an important strategy for the preservation of the prairie ecosystem as a whole.     

A Simple Detection Method for Low-Affinity Membrane Protein Interactions by Baculoviral Display

Background

Membrane protein interactions play an important role in cell-to-cell recognition in various biological activities such as in the immune or neural system. Nevertheless, there has remained the major obstacle of expression of the membrane proteins in their active form. Recently, we and other investigators found that functional membrane proteins express on baculovirus particles (budded virus, BV). In this study, we applied this BV display system to detect interaction between membrane proteins important for cell-to-cell interaction in immune system.

Methodology/Principal Findings

We infected Sf9 cells with recombinant baculovirus encoding the T cell membrane protein CD2 or its ligand CD58 and recovered the BV. We detected specific interaction between CD2-displaying BV and CD58-displaying BV by an enzyme-linked immunosorbent assay (ELISA). Using this system, we also detected specific interaction between two other membrane receptor-ligand pairs, CD40-CD40 ligand (CD40L), and glucocorticoid-induced TNFR family-related protein (GITR)-GITR ligand (GITRL). Furthermore, we observed specific binding of BV displaying CD58, CD40L, or GITRL to cells naturally expressing their respective receptors by flowcytometric analysis using anti-baculoviral gp64 antibody. Finally we isolated CD2 cDNA from a cDNA expression library by magnetic separation using CD58-displayng BV and anti-gp64 antibody.

Conclusions

We found the BV display system worked effectively in the detection of the interaction of membrane proteins. Since various membrane proteins and their oligomeric complexes can be displayed on BV in the native form, this BV display system should prove highly useful in the search for natural ligands or to develop screening systems for therapeutic antibodies and/or compounds.     

Identification of the neoplastically transformed cells in Marek's disease herpesvirus-induced lymphomas: recognition by the monoclonal antibody AV37

Understanding the interactions between herpesviruses and their host cells and also the interactions between neoplastically transformed cells and the host immune system is fundamental to understanding the mechanisms of herpesvirus oncology. However, this has been difficult as no animal models of herpesvirus-induced oncogenesis in the natural host exist in which neoplastically transformed cells are also definitively identified and may be studied in vivo. Marek's disease (MD) herpesvirus (MDV) of poultry, although a recognized natural oncogenic virus causing T-cell lymphomas, is no exception. In this work, we identify for the first time the neoplastically transformed cells in MD as the CD4(+) major histocompatibility complex (MHC) class I(hi), MHC class II(hi), interleukin-2 receptor alpha-chain-positive, CD28(lo/-), phosphoprotein 38-negative (pp38(-)), glycoprotein B-negative (gB(-)), alphabeta T-cell-receptor-positive (TCR(+)) cells which uniquely overexpress a novel host-encoded extracellular antigen that is also expressed by MDV-transformed cell lines and recognized by the monoclonal antibody (MAb) AV37. Normal uninfected leukocytes and MD lymphoma cells were isolated directly ex vivo and examined by flow cytometry with MAb recognizing AV37, known leukocyte antigens, and MDV antigens pp38 and gB. CD28 mRNA was examined by PCR. Cell cycle distribution and in vitro survival were compared for each lymphoma cell population. We demonstrate for the first time that the antigen recognized by AV37 is expressed at very low levels by small minorities of uninfected leukocytes, whereas particular MD lymphoma cells uniquely express extremely high levels of the AV37 antigen; the AV37(hi) MD lymphoma cells fulfill the accepted criteria for neoplastic transformation in vivo (protection from cell death despite hyperproliferation, presence in all MD lymphomas, and not supportive of MDV production); the lymphoma environment is essential for AV37(+) MD lymphoma cell survival; pp38 is an antigen expressed during MDV-productive infection and is not expressed by neoplastically transformed cells in vivo; AV37(+) MD lymphoma cells have the putative immune evasion mechanism of CD28 down-regulation; AV37(hi) peripheral blood leukocytes appear early after MDV infection in both MD-resistant and -susceptible chickens; and analysis of TCR variable beta chain gene family expression suggests that MD lymphomas have polyclonal origins. Identification of the neoplastically transformed cells in MD facilitates a detailed understanding of MD pathogenesis and also improves the utility of MD as a general model for herpesvirus oncology.     

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.     

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.     

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.     

Prevalence and abundance of fleas in black-tailed prairie dog burrows: implications for the transmission of plague (Yersinia pestis)

Plague, the disease caused by the bacterium Yersinia pestis, can have devastating impacts on North American wildlife. Epizootics, or die-offs, in prairie dogs (Cynomys ludovicianus) occur sporadically and fleas (Siphonaptera) are probably important in the disease's transmission and possibly as maintenance hosts of Y. pestis between epizootics. We monitored changes in flea abundance in prairie dog burrows in response to precipitation, temperature, and plague activity in shortgrass steppe in northern Colorado. Oropsylla hirsuta was the most commonly found flea, and it increased in abundance with temperature. In contrast, Oropsylla tuberculata cynomuris declined with rising temperature. During plague epizootics, flea abundance in burrows increased and then subsequently declined after the extirpation of their prairie dog hosts.