BUREAU or BIOLOGICAL SUKVEY. 



345 



Oregon. Pennsylvania, South Dakota, Texas, Vermont, Washin<!;ton, 

 and Wisconsin. 



Tiie imperfect I'eturns furnish the foHowino; data regardin<i; ani- 

 mals noAv heing reared in caj)iivity and the number of persons 



engaged in the business : 



Judging from these figures and from observations made in the 

 field by representatives of the Biological Surve}', it is estimated that 

 500 ranchers are raising silver foxes in the United States; that they 

 have between 12,000 and 15,000 foxes in captivity ; and that the value 

 of the investment is about $8,000,000. 



Studies of fur bearers have been continued at the experimental fur 

 farm at Ivcc>.e\ille, N. Y. The animals confined there are red and 

 cross foxes, skunks, and martens. Experiments have been made in 

 the feeding, housing, and management of these animals. The major 

 part of the work, liowever, consisted of a study of the diseases and 

 parasites which afi'ect fur bearers and methods of control. 



Progress was made in studies of the prevalence of internal and 

 external parasites of foxes, in determining effective agents for their 

 removal from infested animals, and in improving methods of admin- 

 istering remedie:s. Extended studies have been made regarding the 

 tolerance of foxes to varied remedial drugs in order to determine 

 safe and effective dosage at various ages and under varied states of 

 health: 



Examination of 446 fecal samples from 43 different fox ranches 

 indicates that internal parasites are very prevalent. The most im- 

 portant parasites found are hookworms, roundworms, lung worms, 

 fiukes, tapeworms, and coccidia. Valuable information has been ob- 

 tained regarding the occurrence of such parasites among wild foxes. 

 Investigations of the relative susceptibility of fox pups at various 

 ages to infestation with internal parasites, as compared with the 

 adults, and of the seasonal variability in the abundance and the 

 symptoms of parasitic infestation have yielded important informa- 

 tion. 



Studies have been continued of the physiology^ of foxes both in 

 liealth and disease for the purpose of obtaining information regard- 

 ing pulse, respiration, and temperature, and the variations of these 

 at different ages and under differing conditions of excitement and 

 health. Sucli information is required for a proper understanding of 

 conditions existins: in healthy animals and for the detection, diag- 

 nosis, and treatment of disease among them. 



Experiments have been made regarding types of pens with im- 

 jjro^ed sanitary features to ascertain tlieir value in reducing disease, 

 |);!rasitic infestation, and mortality among young and adult foxes. 

 Other experiments have been conducted to determine the effective- 



