Plague transforms positive effects of precipitation on prairie dogs to negative effects

Abstract

Rodents characteristically benefit from increased precipitation, especially in typically dry habitats; “good years” of high precipitation improve their forage and water balance. However, Yersinia pestis (plague), a flea-borne pathogen of mammals that was introduced to western North America, has the greatest negative impact on at least some species of rodents during years of above-average precipitation. In the absence of plague mitigation, negative effects of plague in wet years might overwhelm the otherwise beneficial effects of increased moisture. In Montana and Utah, USA, where plague now occurs enzootically, we investigated the influence of precipitation on finite rates of annual population change (2000–2005) for 3 species of prairie dogs ( Cynomys spp.) in replicated plots treated with deltamethrin dust and in non-treated plots for paired comparisons. There was a significant interaction between precipitation and treatment. When we reduced plague vector fleas, prairie dog visual counts tended to increase with increasing precipitation. Simultaneously, there was a negative relationship between counts and precipitation on paired plots where plague was not managed, suggesting that plague transformed and reversed the otherwise beneficial effect of increased precipitation. Are the good years gone for prairie dogs? Even if the good years are not gone, they are perhaps relatively scarce compared to historic times prior to the invasion of plague. This scenario might apply to other ecosystems and may pose broad conservation challenges in western North America.

Oral Sylvatic Plague Vaccine Does Not Adequately Protect Prairie Dogs (Cynomys spp.) for Endangered Black-Footed Ferret (Mustela nigripes) Conservation

“…NDVI values from 16-day Moderate Resolution Imaging Spectroradiometer composites that included the days of trapping for the center point of each plot were extracted for each plot (data available from NASA Earthdata; and ). In much of the BTPD range, plant production correlates positively with precipitation (Biggins et al 2021a ). We calculated annual precipitation ( appt ) and growing season precipitation (March to July, gppt ) from interpolated 4 km PRISM grid cells that intersected each plot for each year (data available from the PRISM Climate Group; ).…”

Prairie dog responses to vector control and vaccination during an initial Yersinia pestis invasion

“…Therein, Y. pestis was (and remains) lethal to a variety of mammals and functions as an ecosystem transformer ( Eads and Biggins, 2015 ). The fate of some mammal species hinges on effective plague mitigation, with accumulating evidence of negative Y. pestis effects on several imperiled species ( Biggins et al, 2010 , 2021a , b ; Matchett et al, 2010 ; Goldberg et al, 2021 , Goldberg et al, 2022 ), raising concern among ecologists and conservation biologists ( Zeppelini et al, 2016 ; Eads et al, 2022a ).…”

“…For the purposes herein, we define plague epizootics within a given species as resulting in the deaths of >90% of individuals over a wide area within weeks to months ( Biggins and Eads, 2019 ). We define enzootic plague as affecting lesser proportions of individuals, while acknowledging that enzootic plague can have strong ecological impacts ( Zeppelini et al, 2016 ) with significant conservation implications ( Biggins et al, 2021b , Biggins et al, 2021a , Biggins et al, 2010 ; Matchett et al, 2010 ; Goldberg et al, 2021 , Goldberg et al, 2022 ; Eads et al, 2022a , Eads et al, 2022b ).…”

“…Plague epizootics among Cynomys seem to have been halted with flea control in many cases ( Seery et al, 2003 ; Hoogland et al, 2004 ), although not always ( Tripp et al, 2017 ; Hoogland et al, 2018 ). Dusting improved annual apparent survival of prairie dogs and their population densities under enzootic and epizootic conditions ( Biggins et al, 2010 , 2021a , b ) and preserved prairie dog genetic variability during an epizootic ( Jones et al, 2012 ).…”

Disease and weather induce rapid shifts in a rangeland ecosystem mediated by a keystone species (Cynomys ludovicianus)

“…However, climate projections for the North American Great Plains consistently predict greater variation in precipitation with increased heavy precipitation events (Conant et al, 2018), which may present a novel degree of variability beyond those experienced historically. Although rangeland fauna co-evolved with, and may be better able to respond positively to variability, than wildlife in more stable or equilibrial ecosystems, the degree of variability predicted under climate change is unprecedented and may interact with other novel drivers such as disease (e.g., Biggins et al, 2021).…”