96 STOCK-POISONING PLANTS OF MONTANA. 



locoed sheep to remain with the band. The loco habit seems to be 

 learned by imitation, and as long as locoed sheep are allowed to 

 remain with other sheep the number of cases of locoed animals rapidly 

 increases. Stockmen have frequently suggested the possibility of 

 animals inheriting the tendency to -eat loco weeds. There seems, how- 

 ever, to be no support for such a theor3^ When once started, the 

 spread of the disease seems to depend almost entirely upon imitation, 

 one sheep learning the habit from another. On one range in Montana 

 we found 500 locoed sheep in one band. The owner of this band stated 

 that the number of locoed sheep in the band was constantly increasing, 

 and at the same time the worst cases were dying from day to day. 

 During the previous winter he had lost 700 sheep from loco disease. 

 With the sheep on this ranch the habit of eating loco weeds had pre- 

 vailed for two years. Previous to that time no cases of locoed sheep 

 had been observed, although sheep had been raised upon the range for 

 fifteen years. The habit had not been acquired in consequence of any 

 increased abundance of the loco weed. This plant had been observed 

 in great quantities on the range as far back as could be remembered. 

 Another band of sheep, belonging to a neighboring sheep man, acci- 

 dentall}" came in contact with the band containing the 500 locoed sheep 

 during the earl}^ spring of 1900. In the earl}^ part of Ma}^ the herder 

 of this second band reported that he noticed two or three cases of 

 locoed sheep in his band. By June 25, when this band of sheep was 

 brought to the shearing shed, the number of locoed sheep in it was 

 found to have increased to 150. This one instance will serve to illus- 

 trate how rapidly the habit of eating loco spreads among sheep, and 

 should furnish a forcible argument for removing all cases from the 

 band as soon as discovered. In another part of the State an experi- 

 enced sheep raiser became nearly ruined financially through his sheep 

 acquiring the loco habit. By adopting the method of immediately 

 isolating the affected sheep, feeding them for mutton, and replacing 

 them with sheep which are free from the loco habit, he has entirel}' 

 eradicated this trouble on his ranch, although the loco weeds grow there 

 as abundantl}^ as ever. 



The fact has generally been observed b}^ sheep raisers that the habit 

 of eating loco weed is usually acquired by young sheep from the age of 

 4 to 18 months. Old sheep seldom acquire it. The loco habit has 

 frequently been compared to the morphine and chloral habits in man, 

 and in some respects the two habits seem to be comparable. In sheep 

 which have never before eaten the loco weed, large quantities of it 

 frequently cause death within from one to three da3^s. In chronic 

 cases of the loco habit the animal seems to acquire a sort of immunity 

 or increased resisting power against the action of the loco weed. In 

 such cases the first effect of eating seems to be that of a stimulant. 

 This is more easily observed in animals afflicted with the chronic loco 



