Uiii Lifiiif; Resources — Mammals 



107 



(10(1 iiiillioii acres) of grasslaiuls. hiil hy I960 

 that area had been reduced to about 607, 500 ha 

 (1.5 mdlioii acres; Marsh 1984). Much reduc- 

 tion was attributed to prairie dog control pro- 

 grams, which continue. For example, in South 

 Dakota in the late I980"s. $6.2 million was 

 spent to apply to.xicants to prairie dog coKinies 

 on Pine Ridge Indian Reservation (.Shaips 

 1988). At least two states (Nebraska and South 

 Dakota) have laws prohibiting landowners from 

 allowing prairie dogs to flourish on their prop- 

 erties; if the land manager does not "control" 

 the "infestation." the state can do so and bill 

 expenses to the owner (Clarke 1988). 



Sylvatic plague also has been devastating to 

 prairie dogs and was the likely cause of the dra- 

 matic decline in prairie dogs at Meeteetse. 

 Although the Meeteetse complex recently sup- 

 ported the densest and most vigorous popula- 

 tion of black-footed ferrets ever known, it can- 

 not be considered as fenet habitat now because 

 of plagued-induced losses of prairie dogs. 

 Plague is present in most of the monitored 

 white-tailed prairie dog (Cynomys leuciinis) 

 complexes, including the Shirley Basin tenet 

 reintroduction site (Table). The plague's persis- 

 tence could be responsible for the generally 

 lower densities of white-tailed prairie dogs 

 (averaging fewer than seven prairie dogs per 

 hectare or fewer than three per acre). 



Several prairie dog complexes have been eval- 

 uated as sites for reintroduction of black-footed 

 ferrets (Table). The evaluation involves giouping 

 clusters of colonies separated by fewer than 7 km 

 (4.3 mi) into complexes, based on movement 

 capabilities of ferrets (Biggins et al. 1993); these 

 areas include some of the best prairie dog com- 

 plexes remaining in the states. Nevertheless. 

 other extensive prairie dog complexes were not 

 considered for ferret reintroduction. 



Most of the original range of the black-foot- 



ed feiTct was associated with black-tailed prairie 

 dog {Cynomys linldvlcianiis) complexes, which 

 now exhibit the highest population densities of 

 all prairie dogs (Table). Black-footed ferret rein- 

 troductions recently began al black-tailed prairie 

 dog complexes near Malta, Montana, and 

 Badlands National Park, South Dakota (Table). 

 Al present, the best example of a large complex 

 of black-tailed prairie dogs is near Nuevos Casas 

 Grandes. Chihuahua, Mexico (Table). It supports 

 an impressive associated fauna and is a potential 

 reintroduction site for black-footed feirets. 



Ramifications of a healthy prairie dog 

 ecosystem extend well beyond black-footed fer- 

 rets. The prairie dog is a keystone species of the 

 North American prairies. It is an important pri- 

 mary consumer, converting plants to animal 

 biomass at a higher rate than other vertebrate 

 herbivores of the short-grass prairies, and its 

 burrowing provides homes for many other 

 species of animals and increases nutrients in 

 surface soil. This animal also provides food for 

 many predators. We estimated it takes 700-800 

 prairie dogs to annually support a reproducing 

 pair of black-footed feirets and a similar bio- 

 mass of associated predators (Biggins et al. 

 1993). suggesting that large complexes of 

 prairie dog colonies are necessary to support 

 self-sustaining populations of these second- 

 order consumers. 



The 98% loss of the productive prairie dog 

 ecosystem has not yet motivated legal protec- 

 tion or plans for management. There is no fed- 

 eral legislation directly promoting the welfare 

 of the prairie dog ecosystem (even on public 

 lands), and the only existing state legislation 

 promotes poisoning. 



To develop a plan for remedial action, sever- 

 al immediate research needs are apparent in the 

 prairie dog ecosystem: determine the relative 

 diversity and abundance of invertebrates and 



Ihicc spcLics 111 [Maine d*.)gs make 

 up 90<7c of the black-tooted ferret's 

 diet; prairie dog hurrow.s are also 

 used by the ferrets during the day. 



Table. Prairie dog complexes 

 evaluated for black-footed ferret 

 relntroductions. (Some data from 

 Black-footed Ferret Interstate 

 Coordinating Committee.) 



"Gunnison's prairie dog (Cynomys gunnisoni), v^hite-tailed prairie dog (C. leucurus), and black-lailed prairie dog (C. ludovicianus). 



