Prairie Dog Colonies Research Articles

Managing Populations, Diseases, and Landowner Perceptions of Prairie Dogs for Black-Footed Ferret Reintroduction

The black-footed ferret (Mustela nigripes) is one of the rarest mammal species in North America. Captive breeding has prevented extinction of this species, but successful reintroduction of ferrets into their native grassland habitat is a complex endeavor. As specialist predators, ferrets depend almost exclusively on prairie dogs (Cynomys spp.) for both food and shelter, so successful black-footed ferret reintroduction hinges on maintaining large colonies of prairie dogs. However, prairie dogs are also considered agricultural pests and are often subjected to eradication programs. These eradication programs hamper efforts to reintroduce ferrets and disrupt the valuable ecosystem services prairie dogs provide in their role as both keystone and foundation species. Even when agreements are reached to maintain prairie dog colonies, plague (Yersinia pestis), which infects both prairie dogs and ferrets, can threaten the success of a ferret reintroduction program. We describe the research on the complex ecological relationships and socio-environmental challenges of reintroducing endangered black-footed ferrets, with a focus on the most abundant prairie dog species, the black-tailed prairie dog (Cynomys ludovicianus).

Prairie Dog (Cynomys ludovicianus) Influence on Forage Quantity and Quality in a Grazed Grassland-Shrubland Ecotone

Black-tailed prairie dogs (Cynomys ludovicianus) have high dietary overlap with livestock, which can cause forage-centric conflicts between agriculture and conservation. Research suggests prairie dogs can enhance forage quality, but trade-offs between quality and quantity throughout the growing season remain unclear, as well as the degree to which increased forage quality is caused by altered species composition versus altered plant physiology. To assess the effects of prairie dog herbivory on forage in a northern mixed-grass prairie, we collected samples on prairie dog colonies and at sites without prairie dogs during June, July, and August 2016 - 2017 for forage quality, and August 2015 - 2017 for herbaceous biomass. To isolate mechanisms affecting forage quality, we collected both composite samples of all herbaceous species and samples of western wheatgrass (Pascopyrum smithii [Rydb.] Á. Löve). Across years and plant sample types, crude protein, phosphorus, and fat were 12-44% greater and neutral detergent fiber was 6-10% lower on prairie dog colonies than at sites without prairie dogs. The effects of prairie dogs on forage quality persisted throughout the season for western wheatgrass samples (all treatment*time p-values ≥ 0.4). Across years, aboveground herbaceous biomass did not differ significantly between prairie dog colonies and sites without prairie dogs (on-colony: 933 ± 156 kg/ha, off-colony: 982 ± 117 kg/ha). The effects of prairie dogs on herbaceous biomass were significantly influenced by spring precipitation. In years with dry springs, herbaceous biomass was lower on colonies than sites without prairie dogs and this pattern was reversed in years with wet springs. Our results demonstrate season-long enhanced forage quality on prairie dog colonies, indicating that multiple mechanisms are shaping forage quality in this system, including altered species composition, phenological growth stage, and soil condition. Across years, enhanced forage quality may help to offset reductions in forage quantity for agricultural producers.

Plant and Bird Community Dynamics in Mixed-Grass Prairie Grazed by Native and Domestic Herbivores

Native colonial and large ungulate herbivores infrequently coexist on contemporary landscapes but frequently would have in the past, and understanding these interactions is important for conservation in working landscapes—those lands managed for biological and economic objectives. Although many factors contribute to grassland bird declines, consistent and long-term removal of native herbivores from western grasslands promotes homogenous landscapes that are now uniformly grazed by cattle (Bos taurus). This shift in grassland disturbance patterns limits habitat availability for specialized grassland species. We investigated vegetation and bird community dynamics in pastures grazed by domestic cattle and a native colonial herbivore, the black-tailed prairie dog (Cynomys ludovicianus). The study occurred in the northern mixed-grass prairie of the United States on four experimental pastures stratified by the proportion of prairie dog occupancy to create an ecological gradient. Vegetation and bird surveys were conducted from 2012 to 2015 on and off prairie dog colonies. Vegetation and bird communities were not different along the experimental pasture gradient but did differ relative to location on versus off town. Prairie dogs induced changes in the plant community with midstatured grasses like side-oats grama (Bouteloua curtipendula) and green needlegrass (Nassella viridula) being associated with off-colony sites while on-colony sites were associated with disturbance-tolerant species such as fetid marigold (Dyssodia papposa). The bird community responded to changes in vegetation structure resulting from prairie dogs with grasshopper sparrows (Ammodramus savannarum) being more abundant off colonies in areas with greater vegetation structure, while bird species with more complex life histories, such as the upland sandpiper (Bartramia longicauda), were associated with both on− and off−prairie dog colonies. Our findings demonstrate the importance of maintaining spatial heterogeneity in working landscapes and show that native colonial herbivores can help achieve this in the presence of herbivory by domestic cattle.

Climate variability and trends in climate extremes in the priority conservation area El Tokio and adjacent areas in northeastern Mexico

El Tokio, a priority conservation area in Mexico and North America, and its adjacent areas hold the world's last remaining colonies of the Mexican Black-tailed Prairie Dog (Cynomys mexicanus) and serve as home to over 250 bird species, including global wintering grassland birds of high conservation concern, and other rare, endemic and endangered species of flora and fauna. While alarming changes in distribution and migration patterns of species existing in the study area have been reported, studies on the role of climate in these changes are scarce, partly because of the lack of climate information. To fill this gap, this study defined the climate types and eight bioclimatic variables of five ecoregions within and adjacent to El Tokio and analyzed climate indices showing trends of climate extremes, using 30-year climate data and the software RClimDex 1.0 RCs. Results showed climate variability in the study area, with 14 climate types, mostly arid and semi-arid. The analysis of bioclimatic variables showed that the Plains of Zacatecano-Potosino Plateau ecoregion, which contains prairie dog colonies, had the highest annual and mean temperature in the most humid, driest and hottest trimesters of the year; its precipitation had lower seasonality in relation to other ecoregions. Climate indices to detect trends in climate extremes showed greater intensity in precipitation, but also longer dry intervals during the year in the Plains of Zacatecano-Potosno Plateau, while the adjacent Sierra with Forests ecoregion, which borders some colonies, showed trends of warmer winters, summers with fewer days with high minimum temperatures, and precipitation that was less in amount and intensity. The generated climate datasets and analyses contribute essential input for climate change studies and for biological studies and conservation programs for the species and ecosystems present in the biologically rich study area, some of which are greatly threatened and of international concern.

Disturbance shapes avian communities on a grassland–sagebrush ecotone

AbstractEcotones, or transitional zones between ecosystems, are often hotspots for biodiversity and targets for conservation. Where the Great Plains meet the sagebrush (Artemisia spp.) steppe, an opportunity exists to conserve habitat for the two most imperiled avian guilds in North America, grassland and shrub‐steppe birds. This ecotone creates a unique challenge with respect to the management of disturbance processes, such as fire and grazing, because grassland and sagebrush‐shrubland birds respond quite dissimilarly to disturbance. To address this management challenge and maximize conservation opportunities, we examined the responses of grassland and sagebrush bird communities to disturbance at a grassland–sagebrush ecotone in northeast Wyoming, USA. Specifically, we surveyed bird communities on active black‐tailed prairie dog (Cynomys ludovicianus) colonies and burned areas, as well as on paired undisturbed points in 2016 and 2017. Bird community structure varied in response to both the presence and type of disturbance. Although alpha diversity of avian species was highest on undisturbed sites and burned areas, only prairie dog colonies provided breeding habitat for the imperiled shortgrass‐obligate mountain plover (Charadrius montanus), and species turnover (beta diversity) was greatest between on‐colony and off‐colony points. Furthermore, bird communities were shaped by both disturbance‐dependent (e.g., disturbance age) and disturbance‐independent (e.g., topography and soils) landscape features. Managers must balance the benefits of high species diversity in undisturbed sagebrush with habitat requirements of other imperiled species like the mountain plover. This may entail prioritizing the amount and distribution of disturbances in relation to population goals for species of conservation concern while simultaneously maintaining a mosaic of all three patch types in this landscape.

Long-term declines of a highly interactive urban species

Urbanization generates shifts in wildlife communities, with some species increasing their distribution and abundance, while others decline. We used a dataset spanning 15 years to assess trends in distribution and habitat dynamics of the black-tailed prairie dog, a highly interactive species, in urban habitat remnants in Denver, CO, USA. Both available habitat and number of prairie dog colonies declined steeply over the course of the study. However, we did observe new colonization events that correlated with habitat connectivity. Destruction of habitat may be slowing, but the rate of decline of prairie dogs apparently remained unaffected. By using our estimated rates of loss of colonies throughout the study, we projected a 40% probability that prairie dogs will be extirpated from this area by 2067, though that probability could range as high as 50% or as low as 20% depending on the rate of urban development (i.e. habitat loss). Prairie dogs may fulfill important ecological roles in urban landscapes, and could persist in the Denver area with appropriate management and habitat protections.

Local factors associated with on-host flea distributions on prairie dog colonies.

Outbreaks of plague, a flea‐vectored bacterial disease, occur periodically in prairie dog populations in the western United States. In order to understand the conditions that are conducive to plague outbreaks and potentially predict spatial and temporal variations in risk, it is important to understand the factors associated with flea abundance and distribution that may lead to plague outbreaks. We collected and identified 20,041 fleas from 6,542 individual prairie dogs of four different species over a 4‐year period along a latitudinal gradient from Texas to Montana. We assessed local climate and other factors associated with flea prevalence and abundance, as well as the incidence of plague outbreaks. Oropsylla hirsuta, a prairie dog specialist flea, and Pulex simulans, a generalist flea species, were the most common fleas found on our pairs. High elevation pairs in Wyoming and Utah had distinct flea communities compared with the rest of the study pairs. The incidence of prairie dogs with Yersinia pestis detections in fleas was low (n = 64 prairie dogs with positive fleas out of 5,024 samples from 4,218 individual prairie dogs). The results of our regression models indicate that many factors are associated with the presence of fleas. In general, flea abundance (number of fleas on hosts) is higher during plague outbreaks, lower when prairie dogs are more abundant, and reaches peak levels when climate and weather variables are at intermediate levels. Changing climate conditions will likely affect aspects of both flea and host communities, including population densities and species composition, which may lead to changes in plague dynamics. Our results support the hypothesis that local conditions, including host, vector, and environmental factors, influence the likelihood of plague outbreaks, and that predicting changes to plague dynamics under climate change scenarios will have to consider both host and vector responses to local factors.

Prairie dogs and wildfires shape vegetation structure in a sagebrush grassland more than does rest from ungulate grazing

AbstractUnderstanding drivers of vegetation structure has direct implications for wildlife conservation and livestock management, but the relative importance of multiple disturbances interacting within the same system to shape vegetation structure remains unclear. We investigated the separate and interactive effects of multiple disturbance drivers on vegetation structure through a three‐tiered, large‐scale manipulative experiment in northeast Wyoming, USA. We used nested grazing exclosures to isolate the effects of herbivory from livestock, wild ungulates, or small mammals within areas affected by either historical wildfire, black‐tailed prairie dog (Cynomys ludovicianus) colonies, or neither disturbance. We analyzed the interactive effects of disturbance history and contemporary herbivory by either small mammals alone, small mammals + native ungulates, or small mammals + native ungulates + livestock on vegetation structure by quantifying vegetation height, visual obstruction, shrub density, shrub canopy, and shrub leader growth. The exclusion of wild ungulates and lightly to moderately stocked livestock for two years did not significantly affect herbaceous vegetation structure, shrub density, or shrub canopy cover. Maximum vegetation height, visual obstruction, and heights of grasses and forbs were ~50% lower on black‐tailed prairie dog colonies than in undisturbed areas. Prairie dog colonies contained 71% lower shrub densities than undisturbed sites. Sites with wildfire or black‐tailed prairie dogs had 89% lower canopy cover of shrubs and Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis), when compared to undisturbed sites. Shrub leaders experienced over 4.5 times more browsing on prairie dog colonies, when compared to undisturbed areas. For most metrics, disturbance history did not modify the effects of contemporary herbivory on vegetation structure. However, shrubs on prairie dog colonies experienced significantly more leader browsing in the combined presence of livestock, native ungulates, and small mammals than in treatments where livestock were excluded. Our research has direct implications for wildlife conservation and rangeland management by demonstrating that short‐term (1–2 yr) rest from large ungulate grazing may not substantially alter vegetation structure in this system. Instead, structural variation is strongly driven by black‐tailed prairie dog colonization and historical wildfire. Understanding and managing multiple, potentially interacting disturbances is critical for maximizing wildlife conservation and livestock production in heterogeneous landscapes.

Impact of Sylvatic Plague Vaccine on Non-target Small Rodents in Grassland Ecosystems.

Oral vaccination is an emerging management strategy to reduce the prevalence of high impact infectious diseases within wild animal populations. Plague is a flea-borne zoonosis of rodents that often decimates prairie dog (Cynomys spp.) colonies in the western USA. Recently, an oral sylvatic plague vaccine (SPV) was developed to protect prairie dogs from plague and aid recovery of the endangered black-footed ferret (Mustela nigripes). Although oral vaccination programs are targeted toward specific species, field distribution of vaccine-laden baits can result in vaccine uptake by non-target animals and unintended indirect effects. We assessed the impact of SPV on non-target rodents at paired vaccine and placebo-treated prairie dog colonies in four US states from 2013 to 2015. Bait consumption by non-target rodents was high (70.8%, n = 3113), but anti-plague antibody development on vaccine plots was low (23.7%, n = 266). In addition, no significant differences were noted in combined deer mice (Peromyscus maniculatus) and western harvest mouse (Reithrodontomys megalotis) abundance or community evenness and richness of non-target rodents between vaccine-treated and placebo plots. In our 3-year field study, we could not detect a significant positive or negative effect of SPV application on non-target rodents.

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.

Relaciones interespecíficas de forrajeo de gorrión de Worthen (Spizella wortheni) durante la época no reproductiva en Coahuila, México

El gorrión de Worthen (GW) (Spizella wortheni) en México es endémico de Coahuila, Nuevo León y San Luis Potosí, México. Actualmente, GW tiene una distribución restringida, se encuentra en poblaciones pequeñas y está en peligro de extinción. Esta especie se asocia a márgenes de colonias de perrito de las praderas y ha sido estudiada escasamente. Por ello, en la época no reproductiva (otoño-invierno), durante febrero y marzo, así como de septiembre a diciembre de 2015, bandadas mixtas asociadas al GW y monoespecíficas de GW fueron monitoreadas en el Rancho Experimental Los Ángeles, Coahuila, México. En este estudio, las especies asociadas al GW, su composición y tamaño de las bandadas fueron registradas; además, las características del hábitat de forrajeo fueron evaluadas. Trece especies de aves se asociaron al GW y tres tipos de asociaciones de alimentación del GW en bandadas fueron identificadas: 1) bandadas mixtas grandes, 2) bandadas mixtas pequeñas y 3) bandadas monoespecíficas de GW. El 57 % del número total de especies registradas en las bandadas tuvo hábitos alimenticios granívoros similares a los del GW. En las bandadas mixtas dominadas por G W, esta especie fue la líder o especie núcleo, mientras que en las bandadas dominadas por otra especie fue seguidora. Los componentes de hábitat asociados a las bandadas mixtas grandes fueron altura y cobertura de coyonoxtle (Cylindropuntia imbricata Haw.), mientras que los relacionados a las bandadas mixtas pequeñas fueron altura y cobertura de nopal rastrero (Opuntia rastrera Weber). La identificación de sitios no reproductivos de alimentación del GW en pastizales conservados puede representar una herramienta útil en el diseño de estrategias de conservación del GW y especies asociadas.

Plague in a Colony of Gunnison's Prairie Dogs ( Cynomys gunnisoni) Despite Three Years of Infusions of Burrows with 0.05% Deltamethrin to Kill Fleas.

At Valles Caldera National Preserve in New Mexico, US, infusing Gunnison's prairie dog ( Cynomys gunnisoni) burrows with an insecticide dust containing 0.05% deltamethrin killed fleas which transmit bubonic plague. The reduction in the number of fleas per prairie dog was significant and dramatic immediately after infusions, with a suggestion that the reduction persisted for as long as 12 mo. Despite the lower flea counts, however, a plague epizootic killed >95% of prairie dogs after 3 yr of infusions (once per year). More research is necessary for a better understanding of the efficacy of insecticide dusts at lowering flea counts and protecting prairie dogs from plague.

Paltry past‐precipitation: Predisposing prairie dogs to plague?

ABSTRACTThe plague bacterium Yersinia pestis was introduced to California in 1900 and spread rapidly as a sylvatic disease of mammalian hosts and flea vectors, invading the Great Plains in the United States by the 1930s to 1940s. In grassland ecosystems, plague causes periodic, devastating epizootics in colonies of black‐tailed prairie dogs (Cynomys ludovicianus), sciurid rodents that create and maintain subterranean burrows. In doing so, plague inhibits prairie dogs from functioning as keystone species of grassland communities. The rate at which fleas transmit Y. pestis is thought to increase when fleas are abundant. Flea densities can increase during droughts when vegetative production is reduced and herbivorous prairie dogs are malnourished and have weakened defenses against fleas. Epizootics of plague have erupted frequently in prairie dogs during years in which precipitation was plentiful, and the accompanying cool temperatures might have facilitated the rate at which fleas transmitted Y. pestis. Together these observations evoke the hypothesis that transitions from dry‐to‐wet years provide conditions for plague epizootics in prairie dogs. Using generalized linear models, we analyzed a 24‐year dataset on the occurrence of plague epizootics in 42 colonies of prairie dogs from Colorado, USA, 1982–2005. Of the 33 epizootics observed, 52% erupted during years with increased precipitation in summer. For the years with increased summer precipitation, if precipitation in the prior growing season declined from the maximum of 502 mm to the minimum of 200 mm, the prevalence of plague epizootics was predicted to increase 3‐fold. Thus, reduced precipitation may have predisposed prairie dogs to plague epizootics when moisture returned. Biologists sometimes assume dry conditions are detrimental for plague. However, 48% of epizootics occurred during years in which precipitation was scarce in summer. In some cases, an increased abundance of fleas during dry years might compensate for other conditions that become less favorable for plague transmission. Global warming is forecasted to amplify the hydrological cycle in the Great Plains, causing an increased occurrence of prolonged droughts interceded by brief periods of intense precipitation. Results herein suggest these changes might affect plague cycles in prairie dogs. Both negative and positive consequences of dry conditions should be considered when managing plague. © 2017 The Wildlife Society.

Sylvatic Plague Vaccine Partially Protects Prairie Dogs (Cynomys spp.) in Field Trials

Sylvatic plague, caused by Yersinia pestis, frequently afflicts prairie dogs (Cynomys spp.), causing population declines and local extirpations. We tested the effectiveness of bait-delivered sylvatic plague vaccine (SPV) in prairie dog colonies on 29 paired placebo and treatment plots (1–59 ha in size; average 16.9 ha) in 7 western states from 2013 to 2015. We compared relative abundance (using catch per unit effort (CPUE) as an index) and apparent survival of prairie dogs on 26 of the 29 paired plots, 12 with confirmed or suspected plague (Y. pestis positive carcasses or fleas). Even though plague mortality occurred in prairie dogs on vaccine plots, SPV treatment had an overall positive effect on CPUE in all three years, regardless of plague status. Odds of capturing a unique animal were 1.10 (95% confidence interval [C.I.] 1.02–1.19) times higher per trap day on vaccine-treated plots than placebo plots in 2013, 1.47 (95% C.I. 1.41–1.52) times higher in 2014 and 1.19 (95% C.I. 1.13–1.25) times higher in 2015. On pairs where plague occurred, odds of apparent survival were 1.76 (95% Bayesian credible interval [B.C.I.] 1.28–2.43) times higher on vaccine plots than placebo plots for adults and 2.41 (95% B.C.I. 1.72–3.38) times higher for juveniles. Our results provide evidence that consumption of vaccine-laden baits can protect prairie dogs against plague; however, further evaluation and refinement are needed to optimize SPV use as a management tool.

Burrow Dusting or Oral Vaccination Prevents Plague-Associated Prairie Dog Colony Collapse

Plague impacts prairie dogs (Cynomys spp.), the endangered black-footed ferret (Mustela nigripes) and other sensitive wildlife species. We compared efficacy of prophylactic treatments (burrow dusting with deltamethrin or oral vaccination with recombinant “sylvatic plague vaccine” [RCN-F1/V307]) to placebo treatment in black-tailed prairie dog (C. ludovicianus) colonies. Between 2013 and 2015, we measured prairie dog apparent survival, burrow activity and flea abundance on triplicate plots (“blocks”) receiving dust, vaccine or placebo treatment. Epizootic plague affected all three blocks but emerged asynchronously. Dust plots had fewer fleas per burrow (P < 0.0001), and prairie dogs captured on dust plots had fewer fleas (P < 0.0001) than those on vaccine or placebo plots. Burrow activity and prairie dog density declined sharply in placebo plots when epizootic plague emerged. Patterns in corresponding dust and vaccine plots were less consistent and appeared strongly influenced by timing of treatment applications relative to plague emergence. Deltamethrin or oral vaccination enhanced apparent survival within two blocks. Applying insecticide or vaccine prior to epizootic emergence blunted effects of plague on prairie dog survival and abundance, thereby preventing colony collapse. Successful plague mitigation will likely entail strategic combined uses of burrow dusting and oral vaccination within large colonies or colony complexes.

Swabbing Prairie Dog Burrows for Fleas That Transmit Yersinia pestis: Influences on Efficiency.

Scientists and health-care professionals sometimes use a swabbing technique to collect fleas from rodent burrows, and later test the fleas for Yersinia pestis, the causative agent of plague. Detection of Y. pestis is enhanced when large pools of fleas are available. The following study investigated factors that might affect the rate at which fleas are collected from burrows in colonies of black-tailed prairie dogs (Cynomys ludovicianus). Data were collected from 13 colonies in New Mexico during 0600-1000 hours, June-August 2010-2011. Fleas were scarce on swabs inserted into burrows that were not actively used by prairie dogs; fleas are presumably suppressed in burrows that are void of hosts and might have begun to collapse due to a lack of maintenance. Fleas were scarce on swabs inserted into burrows with little sunlight entering the tunnel; many species of fleas use changes in light intensity to locate objects, but if light is limited, it might be difficult to locate a swab. Fleas were scarce on swabs inserted to shallow depths underground, especially during hot mornings, and during the hottest portions of mornings; when conditions are hot above ground, ectothermic fleas might migrate into the deep components of burrows, or become less willing to jump onto hosts, making it difficult to collect the fleas with swabs. If the swabbing technique is used to survey for Y. pestis on colonies of black-tailed prairie dogs, investigators might use the results of this study to modify their methods and increase the number of fleas collected.

Kangaroo rat foraging in proximity to a colony of reintroduced black-tailed prairie dogs

Abstract We examined the indirect effects of reintroduced black-tailed prairie dogs (Cynomys ludovicianus) on resident kangaroo rat (Dipodomys) populations. We used the Giving-up Density theory to quantify kangaroo rat foraging on a black-tailed prairie dog colony vs. foraging near the colony edge or in the surrounding native habitat. This approach allowed us to assess the influence of black-tailed prairie dogs on kangaroo rat foraging activity. Our results showed a greater foraging preference off-colony in most seasons. Kangaroo rats visited off-colony feeding trays more frequently and collected a greater mean mass of seed as well. This indicated that kangaroo rats perceived the area off the prairie dog colony as having a lower foraging cost than the on-colony or colony edge locations. Our data suggest that from the perspective of the seed-eating kangaroo rat, the colony is not viewed as high quality habitat. Both prairie dogs and kangaroo rats have been described as keystone modifiers in grassland ecosy...

Population density of the western burrowing owl (Athene cunicularia hypugaea) in Mexican prairie dog (Cynomys mexicanus) colonies in northeastern Mexico.

BackgroundThe western burrowing owl (Athene cunicularia hypugaea) occurs throughout western North America in various habitats such as desert, short-grass prairie and shrub-steppe, among others, where the main threat for this species is habitat loss. Range-wide declines have prompted a need for reliable estimates of its populations in Mexico, where the size of resident and migratory populations remain unknown.ResultsOur objective was to estimate the abundance and density of breeding western burrowing owl populations in Mexican prairie dog (Cynomys mexicanus) colonies in two sites located within the Chihuahuan Desert ecoregion in the states of Nuevo Leon and San Luis Potosi, Mexico. Line transect surveys were conducted from February to April of 2010 and 2011. Fifty 60 ha transects were analyzed using distance sampling to estimate owl and Mexican prairie dog populations. We estimated a population of 2026 owls (95 % CI 1756–2336) in 2010 and 2015 owls (95 % CI 1573–2317) in 2011 across 50 Mexican prairie dog colonies (20,529 ha).ConclusionsThe results represent the first systematic attempt to provide reliable evidence related to the size of the adult owl populations, within the largest and best preserved Mexican prairie dog colonies in Mexico.

Prey use and productivity of ferruginous hawks in rural and exurban New Mexico

Habitat loss from human development affects native wildlife populations, especially in the western United States where the human population is growing 2–3 times faster than any other part of the country. We analyzed regurgitated pellets, prey remains, and video to describe the diet of ferruginous hawks (Buteo regalis) nesting in rural and exurban grasslands in New Mexico, USA, to better understand the conservation needs of this species. Three mammals—Botta's pocket gopher (Thomomys bottae), Gunnison's prairie dog (Cynomys gunnisoni), and desert cottontail (Sylvilagus audubonii)—comprised the majority of ferruginous hawk diet in percent biomass, whereas Botta's pocket gopher dominated diet in percent frequency. Hawks breeding in the exurban grassland (i.e., exurban hawks) consumed more Gunnison's prairie dogs, whereas hawks in the rural area (i.e., rural hawks) consumed more lagomorphs. From 1998–2005, and during the 2 years of our prey use study, exurban hawks delivered more biomass and prey items and experienced greater nesting success and productivity than rural hawks. The presence of prairie dogs, a colonial mammal whose occurrence theoretically reduces predatory search time, assisted in the maintenance of relatively high productivity levels for exurban hawks in our study. In 2004, the exurban grassland supported 5 times more prairie dog colonies than the rural area, but the number of exurban colonies decreased by 50% from 1999–2004. Extant prairie dog colonies and habitat supporting other medium-sized mammals (e.g., Geomyidae) should be conserved to enable maintenance of ferruginous hawk populations in the western United States, particularly in anthropogenically altered areas. © 2016 The Wildlife Society.

Factors that affect parasitism of black‐tailed prairie dogs by fleas

AbstractFleas (Insecta: Siphonaptera) are hematophagous ectoparasites that feed on vertebrate hosts. Fleas can reduce the fitness of hosts by interfering with immune responses, disrupting adaptive behaviors, and transmitting pathogens. The negative effects of fleas on hosts are usually most pronounced when fleas attain high densities. In lab studies, fleas desiccate and die under dry conditions, suggesting that populations of fleas will tend to decline when precipitation is scarce under natural conditions. To test this hypothesis, we compared precipitation vs. parasitism of black‐tailed prairie dogs (Cynomys ludovicianus) by fleas at a single colony during May and June of 13 consecutive years (1976–1988) at Wind Cave National Park, South Dakota, USA. The number of fleas on prairie dogs decreased with increasing precipitation during both the prior growing season (April through August of the prior year) and the just‐completed winter–spring (January through April of current year). Due to the reduction in available moisture and palatable forage in dry years, herbivorous prairie dogs might have been food‐limited, with weakened behavioral and immunological defenses against fleas. In support of this hypothesis, adult prairie dogs of low mass harbored more fleas than heavier adults. Our results have implications for the spread of plague, an introduced bacterial disease, transmitted by fleas, that devastates prairie dog colonies and, in doing so, can transform grassland ecosystems.