Abstract - Black-Tailed Prairie Dog Dispersal and DES Control

Franklin, W.L. and Garrett, M.G. 1983. Black-Tailed Prairie Dog Dispersal and DES Control. Final Report to the National Park Service; Contract CX-1200-1-B023 to Iowa State University. 95 p.

Abstract

This folder contains two separate reports - "Dispersal of black-tailed prairie dogs (Cynomys ludovicianus) in Wind Cave National Park" and "Diethylsitlbestrol as a Temporary Chemosterilant to Control Black-tailed Prairie Dog Populations". First Report: An investigation of black-tailed prairie dogs (Cynomys ludovicianus) was conducted to gather baseline information on dispersal activities and to identify factors responsible for dispersal behavior. Study was conducted in Wind Cave National Park from 1979 to 1981. Dispersing prairie dogs were radiotracked to determine distance of movements and survivorship, and a study colonly was intensively monitored to determine proximate factors that cause dispersal.

Exchange of individuals between coteries (family groups) within the study colony (intracolony dispersal) occurred during all times of the year, while dispersal away from established colonies (intercolonly dispersal) occurred only during a predictable period in late spring. Both males and females dispersed, but males were predominantly yearlings while females also included many older individuals. Intercolonly dispersers appeared to be in good physical condition, moved an average distance of 2.4 km from the point of capture, and survivors immigrated into existing colonies; no new colonies were established by radiocollared animals. The mortality rate of intercolony dispersers was significantly greater compared with residents of the study colony.

Several proximate factors seem to be related to dispersal. Prairie dogs prefer the new vegetative growth at colony peripheries. An inverse relationship exists between animal density relative to this food resource and the relative change in animal numbers during the dispersal season, although this may not be a linear relationship. There was no relationship between absolute coterie density and change in animal numbers. Other factores include the shortage of unrelated females in the coterie, harrassment of females by juveniles, and probably genetic influence.

The initiation of new prairie dog colonies in Wind Cave National Park may be related to factors that disturb the native vegetation. Major differences between newly established colonies and undisturbed prairie seem go be physical characteristics of the site, such as the height of vegetation and the proportion of bare ground. This may be directly influenced by park management practices (e.g., limiting the size of the ungulate herds, controlled burns), and should be an important consideration when implementing management plans.

Second Report: Controling reproduction in pest rodent populations may be preferable to using lethal rodenticides. The effectiveness os diethylstilbestrol (DES), a synthetic estrogen, as a reproductive inhibitor is femail black-tailed prairie dogs (Cynomys ludovicianus) was examined in a 4-year study at Wind Cave National Park, South Dakota. In 1981, the colonly was divided into control and experimental areas. Application of DES-treated oats (.11% active ingredient) during the breeding season resulted in complete curtailment of reproduction in the experimental group while reproduction in the control group was normal. Results were identical in 1982 when treatment was reversed. There were no obvious effects of DES treatment on subsequen reproductive capability of study animals. In 1981, surface expansion of the study colony was 4X less on the DES-treated side compared with the control.