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J.F. Cully

Publications and source records attributed to J.F. Cully.

10 recordsLinked to original sources
USGS2011

Spread of plague among black-tailed prairie dogs is associated with colony spatial characteristics

Sylvatic plague ( Yersinia pestis ) is an exotic pathogen that is highly virulent in black‐tailed prairie dogs ( Cynomys ludovicianus ) and causes widespread colony losses and individual mortality rates >95%. We investigated colony spatial characteristics that may influence inter‐colony transmission of plague at 3 prairie dog colony complexes in the Great Plains. The 4 spatial characteristics we considered include: colony size, Euclidean distance to nearest neighboring colony, colony proximity index, and distance to nearest drainage (dispersal) corridor. We used multi‐state mark–recapture models to determine the relationship between these colony characteristics and probability of plague transmission among prairie dog colonies. Annual mapping of colonies and mark–recapture analyses of disease dynamics in natural colonies led to 4 main results: 1) plague outbreaks exhibited high spatial and temporal variation, 2) the site of initiation of epizootic plague may have substantially influenced the subsequent inter‐colony spread of plague, 3) the long‐term effect of plague on individual colonies differed among sites because of how individuals and colonies were distributed, and 4) colony spatial characteristics were related to the probability of infection at all sites although the relative importance and direction of relationships varied among sites. Our findings suggest that conventional prairie dog conservation management strategies, including promoting large, highly connected colonies, may need to be altered in the presence of plague.

Colorado, Oklahoma, Texas, Kansas, New Mexico↗
USGS2010

Spatial variation in keystone effects: Small mammal diversity associated with black-tailed prairie dog colonies

Species with extensive geographic ranges may interact with different species assemblages at distant locations, with the result that the nature of the interactions may vary spatially. Black-tailed prairie dogs Cynomys ludovicianus occur from Canada to Mexico in grasslands of the western Great Plains of North America. Black-tailed prairie dogs alter vegetation and dig extensive burrow systems that alter grassland habitats for plants and other animal species. These alterations of habitat justify the descriptor " ecological engineer," and the resulting changes in species composition have earned them status as a keystone species. We examined the impact of black-tailed prairie dogs on small mammal assemblages by trapping at on- and off-colony locations at eight study areas across the species' geographic range. We posed 2 nested hypotheses: 1) prairie dogs function as a keystone species for other rodent species; and 2) the keystone role varies spatially. Assuming that it does, we asked what are the sources of the variation? Black-tailed prairie dogs consistently functioned as a keystone species in that there were strong statistically significant differences in community composition on versus off prairie dog colonies across the species range in prairie grassland. Small mammal species composition varied along both latitudinal and longitudinal gradients, and species richness varied from 4 to 11. Assemblages closer together were more similar; such correlations approximately doubled when including only on- or off-colony grids. Black-tailed prairie dogs had a significant effect on associated rodent assemblages that varied regionally, dependent upon the composition of the local rodent species pool. Over the range of the black-tailed prairie dog, on-colony rodent richness and evenness were less variable, and species composition was more consistent than off-colony assemblages. ?? 2010 The Authors.

Ecography↗
USGS2009

Effects of rodent community diversity and composition on prevalence of an endemic bacterial pathogen - Bartonella

By studying Bartonella prevalence in rodent communities from 23 geographic sites in the western United States and one site in northern Mexico, the present study focused on the effects of rodent community diversity (measured by richness and Shannon index) and composition on prevalence of Bartonella infections. The analysis showed negative correlations of Bartonella prevalence with rodent richness and Shannon index. Further, Bartonella prevalence varied among rodent genera/species. Three models were applied to explain the observations. (1) Within-species/genus transmission: Bartonella strains usually are host-specific and adding non-host species would decrease Bartonella prevalence in its principal host through reduction of host contact (encounter reduction); (2) Frequency-dependence: Adding hosts would decrease the proportion of all infected individuals in the community, resulting in a reduction in the number of contacts between susceptible and infected individuals that usually leads to transmission (transmission reduction); and (3) Dominant species effect: Dominant species, if not susceptible to Bartonellae , can constrain the abundance of susceptible hosts (susceptible host regulation). These mechanisms work in concert; and the level of Bartonella prevalence is an outcome of regulation of all of these mechanisms on the entire system.

Biodiversity↗
USGS2007

Spatiotemporal dynamics of black-tailed prairie dog colonies affected by plague

Black-tailed prairie dogs (Cynomys ludovicianus) are a key component of the disturbance regime in semi-arid grasslands of central North America. Many studies have compared community and ecosystem characteristics on prairie dog colonies to grasslands without prairie dogs, but little is known about landscape-scale patterns of disturbance that prairie dog colony complexes may impose on grasslands over long time periods. We examined spatiotemporal dynamics in two prairie dog colony complexes in southeastern Colorado (Comanche) and northcentral Montana (Phillips County) that have been strongly influenced by plague, and compared them to a complex unaffected by plague in northwestern Nebraska (Oglala). Both plague-affected complexes exhibited substantial spatiotemporal variability in the area occupied during a decade, in contrast to the stability of colonies in the Oglala complex. However, the plague-affected complexes differed in spatial patterns of colony movement. Colonies in the Comanche complex in shortgrass steppe shifted locations over a decade. Only 10% of the area occupied in 1995 was still occupied by prairie dogs in 2006. In 2005 and 2006 respectively, 74 and 83% of the total area of the Comanche complex occurred in locations that were not occupied in 1995, and only 1% of the complex was occupied continuously over a decade. In contrast, prairie dogs in the Phillips County complex in mixed-grass prairie and sagebrush steppe primarily recolonized previously occupied areas after plague-induced colony declines. In Phillips County, 62% of the area occupied in 1993 was also occupied by prairie dogs in 2004, and 12% of the complex was occupied continuously over a decade. Our results indicate that plague accelerates spatiotemporal movement of prairie dog colonies, and have significant implications for landscape-scale effects of prairie dog disturbance on grassland composition and productivity. These findings highlight the need to combine landscape-scale measures of habitat suitability with long-term measures of colony locations to understand the role of plague-affected prairie dogs as a grassland disturbance process. ?? 2007 Springer Science+Business Media B.V.

Landscape Ecology↗
USGS2007

Acquisition of nonspecific Bartonella strains by the northern grasshopper mouse (Onychomys leucogaster)

Rodent-associated Bartonella species are generally host-specific parasites in North America. Here evidence that Bartonella species can 'jump' between host species is presented. Northern grasshopper mice and other rodents were trapped in the western USA. A study of Bartonella infection in grasshopper mice demonstrated a high prevalence that varied from 25% to 90% by location. Bartonella infection was detected in other rodent species with a high prevalence as well. Sequence analyses of gltA identified 29 Bartonella variants in rodents, 10 of which were obtained from grasshopper mice. Among these 10, only six variants were specific to grasshopper mice, whereas four were identical to variants specific to deer mice or 13-lined ground squirrels. Fourteen of 90 sequenced isolates obtained from grasshopper mice were strains found more commonly in other rodent species and were apparently acquired from these animals. The ecological behavior of grasshopper mice may explain the occurrence of Bartonella strains in occasional hosts. The observed rate at which Bartonella jumps from a donor host species to the grasshopper mouse was directly proportional to a metric of donor host density and to the prevalence of Bartonella in the donor host, and inversely proportional to the same parameters for the grasshopper mouse. ?? 2007 Federation of European Microbiological Societies.

FEMS Microbiology Ecology↗
USGS2005

Landscape structure and plague occurrence in black-tailed prairie dogs on grasslands of the western USA

Landscape structure influences the abundance and distribution of many species, including pathogens that cause infectious diseases. Black-tailed prairie dogs in the western USA have declined precipitously over the past 100 years, most recently due to grassland conversion and their susceptibility to sylvatic plague. We assembled and analyzed two long-term data sets on plague occurrence in black-tailed prairie dogs to explore the hypotheses that plague occurrence is associated with colony characteristics and landscape context. Our two study areas (Boulder County, Colorado, and Phillips County, Montana) differed markedly in degree of urbanization and other landscape characteristics. In both study areas, we found associations between plague occurrence and landscape and colony characteristics such as the amount of roads, streams and lakes surrounding a prairie dog colony, the area covered by the colony and its neighbors, and the distance to the nearest plague-positive colony. Logistic regression models were similar between the two study areas, with the best models predicting positive effects of proximity to plague-positive colonies and negative effects of road, stream and lake cover on plague occurrence. Taken together, these results suggest that roads, streams and lakes may serve as barriers to plague in black-tailed prairie dog colonies by affecting movement of or habitat quality for plague hosts or for fleas that serve as vectors for the pathogen. The similarity in plague correlates between urban and rural study areas suggests that the correlates of plague are not altered by uniquely urban stressors. ?? Springer 2005.

Landscape Ecology↗
USGS2004

Density-dependent habitat selection by brown-headed cowbirds (Molothrus ater) in tallgrass prairie

Local distributions of avian brood parasites among their host habitats may depend upon conspecific parasite density. We used isodar analysis to test for density-dependent habitat selection in brown-headed cowbirds (Molothrus ater) among tallgrass prairie adjacent to wooded edges, and prairie interior habitat (>100 m from wooded edges) with and without experimental perches. Eight study sites containing these three habitat treatments were established along a geographical gradient in cowbird abundance within the Flint Hills region of Eastern Kansas and Oklahoma, USA. The focal host species of our study, the dickcissel (Spiza americana), is the most abundant and preferred cowbird host in the prairie of this region. Cowbird relative abundance and cowbird:host abundance ratios were used as estimates of female cowbird density, whereas cowbird egg density was measured as parasitism frequency (percent of dickcissel nests parasitized), and parasitism intensity (number of cowbird eggs per parasitized nest). Geographical variation in cowbird abundance was independent of host abundance. Within study sites, host abundance was highest in wooded edge plots, intermediate in the experimental perch plots, and lowest in prairie interior. Cowbirds exhibited a pattern of density-dependent selection of prairie edge versus experimental perch and interior habitats. On sites where measures of cowbird density were lowest, all cowbird density estimates (female cowbirds and their eggs) were highest near (???100 m) wooded edges, where host and perch availability are highest. However, as overall cowbird density increased geographically, these density estimates increased more rapidly in experimental perch plots and prairie interiors. Variation in cowbird abundance and cowbird:host ratios suggested density-dependent cowbird selection of experimental perch over prairie interior habitat, but parasitism levels on dickcissel nests were similar among these two habitats at all levels of local cowbird parasitism. The density-dependent pattern of cowbird distribution among prairie edge and interior suggested that density effects on perceived cowbird fitness are greatest at wooded edges. A positive relationship between daily nest mortality rates of parasitized nests during the nestling period with parasitism intensity levels per nest suggested a density-dependent effect on cowbird reproductive success. However, this relationship was similar among habitats, such that all habitats should have been perceived as being equally suitable to cowbirds at all densities. Other unmeasured effects on cowbird habitat suitability (e.g., reduced cowbird success in edge-dwelling host nests, cowbird despotism at edges) might have affected cowbird habitat selection. Managers attempting to minimize cowbird parasitism on sensitive cowbird hosts should consider that hosts in otherwise less-preferred cowbird habitats (e.g., habitat interiors) are at greater risk of being parasitized where cowbirds become particularly abundant. ?? Springer-Verlag 2004.

Oecologia↗
USGS2001

Interspecific comparisons of sylvatic plague in prairie dogs

Of the 3 major factors (habitat loss, poisoning, and disease) that limit abundance of prairie dogs today, sylvatic plague caused by Yersinia pestis is the 1 factor that is beyond human control. Plague epizootics frequently kill >99% of prairie dogs in infected colonies. Although epizootics of sylvatic plague occur throughout most of the range of prairie dogs in the United States and are well described, long-term maintenance of plague in enzootic rodent species is not well documented or understood. We review dynamics of plague in white-tailed (Cynomys leucurus), Gunnison's (C. gunnisoni), and black-tailed (C. ludovicianus) prairie dogs, and their rodent and flea associates. We use epidemiologic concepts to support an enzootic hypothesis in which the disease is maintained in a dynamic state, which requires transmission of Y. pestis to be slower than recruitment of new susceptible mammal hosts. Major effects of plague are to reduce colony size of black-tailed prairie dogs and increase intercolony distances within colony complexes. In the presence of plague, black-tailed prairie dogs will probably survive in complexes of small colonies that are usually >3 km from their nearest neighbor colonies.

Journal of Mammalogy↗
USGS1999

Lone star tick abundance, fire, and bison grazing in tall-grass prairie

Lone star ticks ( Amblyomma americanum L.) were collected by drag samples of 1 km transects on 12 watersheds at Konza Prairie Research Natural Area near Manhattan, Kans., during summer 1995-1996. Watersheds were treated to 2 experimental treatments: 3 burn intervals (1-year, 4-year, and 20-year) and 2 grazing treatments (grazed by bison ( Bos bison L.) or ungrazed). The objectives were to determine whether fire interval, time since most recent burn, and the presence of large ungulate grazers would cause changes in lone star tick abundance in tallgrass prairie in central Kansas. Watersheds burned at 1-year intervals had fewer larvae and adults than watersheds burned at 4-year or 20-year intervals. Watersheds burned during the year of sampling had fewer ticks than watersheds burned one or more years in the past. For watersheds burned 1 or more years in the past there was no effect from time since burn. The presence of bison did not affect tick abundance. Spring burning is an effective method to reduce tick populations in tallgrass prairie during the year of the burn.

Journal of Range Management↗