184 EXTINCT AND VANISHING MAMMALS 



bellied weasel, Mustela eversmanni, and the bobac marmot in 

 the "towns" of which it lives, preying on these rodents. The 

 black-footed ferret is believed to rely chiefly upon the prairie- 

 dogs for sustenance as an abundant and dependable source of 

 food, yet it doubtless captures other small animals, and 

 Roosevelt has even recorded a case of one killed in the act of 

 attacking a small antelope fawn. It is surprising that in view 

 of the abundance and accessibility of its natural prey, the 

 prairie-dogs, this ferret should be nevertheless relatively rare, 

 for specimens are rather uncommon in collections, and indi- 

 viduals are seldom seen in life even by those living in its habitat. 

 Bailey (1926) has even suggested "that this very abundance 

 [of the prairie-dogs] has in some way pauperized the species 

 until reproduction is restricted," but adds that "apparently 

 nothing is known of the breeding habits or of the number of 

 young at a birth. " Since there are three pairs of mammae the 

 size of a litter probably does not exceed this number and may 

 normally be less. It is obvious that in a case of such specialized 

 food preference it would be disastrous for the species to become 

 so common as seriously to deplete the numbers of its host, so 

 that undoubtedly some sort of adjustment has been evolved, 

 but its nature remains uncertain. Possibly enemies as yet un- 

 recognized are a factor, such as rattlesnakes that might devour 

 the young, or the hibernating habits of the prairie-dogs, al- 

 though not well marked in the southern parts of the range, may 

 affect the ferret's abundance. In its habits it is believed to be 

 in large part nocturnal, but it has been seen active by day. 



In view of the damage done to range vegetation or to culti- 

 vated crops, the hand of the agriculturist is against the prairie- 

 dog, and of late years poisoning campaigns on a large scale 

 have been carried on that in some localities have largely 

 exterminated these rodents. Undoubtedly a further result of 

 these activities will be to eliminate or at least to reduce con- 

 siderably the numbers of the weasel so that the reason for its 

 inclusion among the vanishing mammals is clear. 



Writing of North Dakota, the eastward extension of its 

 range, Bailey (1926) says that a few have been taken in the 

 western part of the State and adduces four instances in the 

 years 1910 to 1915; he quotes Jewett, who killed a specimen 

 near Quinion in 1913, that none of the old residents to whom he 

 showed it were acquainted with the species. Coues (1877) in 



