Breeding Season Avifauna of Prairie Dog Colonies and Non-Colonized Areas in Shortgrass Prairie

Avian assemblages of black-tailed prairie dog (Cynomys ludovicianus) colonies were compared to those present at two types of non-colonized grassland, during the breeding season, in southwestern Kansas and southeastern Colorado. Relative abundances were quantified in 1996 during a period of drought and in 1997 during a period of above average precipitation. We detected fewer bird species at all sites in 1996 than in 1997, and the total number of bird species detected on prairie dog colonies was lower than that detected on both types of non-colonized areas during both years. Homed larks (Eremophila alpestris) had higher relative abundances on non-colonized sites in 1996, but were more abundant on prairie dog colonies in 1997. Lark buntings (Calamospiza melanocorys) and grasshopper sparrows (Ammodramus savannarum) were not recorded at the study sites in 1996, but appeared in high numbers in 1997. These two species, and western meadowlarks (Sturnella neglecta), had higher relative abundances on non-colonized sites in 1997 than on prairie dog colonies. A comparison of our results with those of other studies suggest that the effects of prairie dogs on associated biota might not be identical in all regions of the Great Plains, or under all environmental conditions

Lack of Brown-Headed Cowbird Nest Parasitism in a Short Grass Region

While conducting field work in Morton County, southwestern Kansas and Baca County, southeastern Colorado, during the period 27 May to 2 July 1997, we found 36 nests of seven bird species. Nests were not searched for systematically, but were found coincidentally as data were collected along transects during research investigating the breeding bird and plant communities of black-tailed prairie dog (Cynomys ludovicianus) colonies and noncolonized shortgrass prairie (Winter 1999). Low densities of the brown-headed cowbird in our study region, which is characterized by a semi-arid climate, might be a consequence of host populations that exhibit extreme temporal and spatial variability in response to the climatic variability of these regions (Wiens 1974, Cody 1985, Winter et al. 2003). As host populations vary greatly in time and space over large areas on the western Great Plains (Wiens 1974, Cody 1985), perhaps the brown-headed cowbird is simply unable to effectively respond to host population changes

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 \u3e95%. 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 longterm 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

Breeding Season Avifauna of Prairie Dog Colonies and Non-Colonized Areas in Shortgrass Prairie

Avian assemblages of black-tailed prairie dog (Cynomys ludovicianus) colonies were compared to those present at two types of non-colonized grassland, during the breeding season, in southwestern Kansas and southeastern Colorado. Relative abundances were quantified in 1996 during a period of drought and in 1997 during a period of above average precipitation. We detected fewer bird species at all sites in 1996 than in 1997, and the total number of bird species detected on prairie dog colonies was lower than that detected on both types of non-colonized areas during both years. Homed larks (Eremophila alpestris) had higher relative abundances on non-colonized sites in 1996, but were more abundant on prairie dog colonies in 1997. Lark buntings (Calamospiza melanocorys) and grasshopper sparrows (Ammodramus savannarum) were not recorded at the study sites in 1996, but appeared in high numbers in 1997. These two species, and western meadowlarks (Sturnella neglecta), had higher relative abundances on non-colonized sites in 1997 than on prairie dog colonies. A comparison of our results with those of other studies suggest that the effects of prairie dogs on associated biota might not be identical in all regions of the Great Plains, or under all environmental conditions

Influence of Prairie Dogs on Vegetation in Kansas Shortgrass Prairie

We quantified plant species richness, frequency, percent cover and percent bare ground on black-tailed prairie dog colonies and non-colonized areas in southwest Kansas in 1996 and 1997. In 1996 field sampling occurred after 12 months of below-average precipitation, while field sampling in 1997 occurred after 10 months of above-average precipitation. In 1996 prairie dog colonies were characterized by lower percentages of grass cover and higher percentages of forb cover than non-colonized sites, but there was no difference in percent bare ground. In 1997 percent grass cover, forb cover and bare ground was similar for prairie dog colonies and non-colonized areas. A preliminary analysis indicates that plant species richness of prairie dog colonies was similar to that of non-colonized areas. In 1996 four perennial grasses, two perennial forbs and one annual forb differed in frequency among the treatments. In 1997 seven perennial grasses, seven perennial forbs, six annual or biennial forbs and one annual grass differed in frequency among the treatments

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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 offcolony assemblages