Photo via Stanford University
Plague, the highly infectious disease caused by the bacterium, Yersinia pestis, has become common problem among prairie dog colonies of the United States and it has devastated populations over the past few decades. It will hit and wipe out a colony, then when a new colony moves in to the abandoned tunnels, the plague reappears and wipes them out as well. The cycles have confounded researchers so far, with mystery surrounding how the plague seems to lay dormant until new victims arrive. But scientists from Standford University have figured it out -- the secret to what is bringing down prairie dog towns is linked to meat-eating mice. Specifically, the grasshopper mouse, a prairie inhabitant that carries the fleas that spread the plague.
Stanford University reports that James Holland Jones, an associate professor of anthropology and a center fellow at the Woods Institute for the Environment at Stanford University and his colleagues have pinned the grasshopper mouse down as the culprit, explaining that when the mouse population density is high enough, the plague break-out occurs and wipes out virtually all of the prairie dogs nearby.
By focusing on black-tailed prairie dogs, the researchers saw that the territoriality that usually protects prairie dog towns from infecting one another is being bridged by these mice. The mice will eat the carcass of a prairie dog that has died of the plague, and the infected fleas will hop aboard the mouse as well. The mouse then travels to another territory and spreads the plague that would otherwise have been isolated.
Photo via Jaymi Heimbuch
"Plague sort of smolders in the prairie dog community for long periods in between epizootics," Jones said. "The mouse is like the spark that allows the pathogen to get carried to a new place where there's more fuel. And then just the right set of events coalesces, where you have the right mouse densities and the right spatial pattern of infected prairie dogs. At that point, the mice trigger the epizootic, and suddenly you get this catastrophic mortality where nearly all the prairie dogs die of the plague, where before only a few animals were dying. The territoriality of prairie dogs and the lack thereof in grasshopper mice is what makes the whole system work."
Back in March we talked about the impact plague is having on both prairie dogs and the more threatened black-footed ferret, and that finding a source for the spreading of the disease would be vital in controlling it. The prairie dogs, once abundant, have felt the pinch of habitat loss and poisonings, just when they and their skill at language is starting to be appreciated. This research could prove to be the important link needed to help prairie dog populations in the future, and when linked with the support the animals are receiving from organizations like WildEarth Guardians, they might make a come-back.
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