FLEA ABUNDANCE, DIVERSITY, AND PLAGUE IN GUNNISON'S PRAIRIE DOGS (CYNOMYS GUNNISONI) AND THEIR BURROWS IN MONTANE GRASSLANDS IN NORTHERN NEW MEXICO

Plague, a flea-transmitted infectious disease caused by the bacterium Yersinia pestis, is a primary threat to the persistence of prairie dog populations (Cynomys spp.). We conducted a 3-yr survey (2004-2006) of fleas from Gunnison's prairie dogs (Cynomys gunnisoni) and their burrows in montane grasslands in Valles Caldera National Preserve in New Mexico. Our objectives were to describe flea communities and identify flea and rodent species important to the maintenance of plague. We live-trapped prairie dogs and conducted burrow sweeps at three colonies in spring and summer of each year. One hundred thirty prairie dogs and 51 golden-mantled ground squirrels (Spermophilus lateralis) were captured over 3,640 trap nights and 320 burrows were swabbed for fleas. Five flea species were identified from prairie dogs and ground squirrels and four were identified from burrow samples. Oropsylla hirsuta was the most abundant species found on prairie dogs and in burrows. Oropsylla idahoensis was most common on ground squirrels. Two colonies experienced plague epizootics in fall 2004. Plague-positive fleas were recovered from burrows (O. hirsuta and Oropsylla tuberculata tuberculata) and a prairie dog (O. hirsuta) in spring 2005 and summer 2006. Three prairie dogs collected in summer 2005 and 2006 had plague antibody. We found a significant surge in flea abundance and prevalence, particularly within burrows, following plague exposure. We noted an increased tendency for flea exchange opportunities in the spring before O. hirsuta reached its peak population. We hypothesize that the role of burrows as a site of flea exchange, particularly between prairie dogs and ground squirrels, may be as important as summer conditions that lead to buildup in O. hirsuta populations for determining plague outbreaks.