XXVIII 



METHODS OF INVESTIGATION IN ECONOMIC 

 MAMMALOGY 



As in the much more highly developed science of economic or- 

 nithology, in economic mammalogy there are three different lines of 

 evidence, of unequal importance, upon which to base conclusions: 

 Purely circumstantial evidence, direct observation or the testimony of 

 eye witnesses, and the examination of the contents of stomachs. In 

 a general way, circumstantial evidence is the least reliable and most 

 likely to be misleading of the three. A mountain lion may kill a calf. 

 After it has fed, a rain may descend and obliterate the tracks of the 

 big cat. Then a bear comes along and feeds upon the carcass, leaving 

 his tracks to prove his guilt to the satisfaction of the owner of the 

 calf, who promptly begins a round-up of the bears of the vicinity, and 

 the guilty party escapes punishment because of the lack of evidence 

 against him. However, as in human courts of justice, some kinds of 

 circumstantial evidence, under some circumstances, may be the very 

 strongest sort, conclusive and incontrovertible. 



Direct observation, though usually more satisfactory, is not always 

 so. It depends upon several things, such as the powers of observation 

 of the observer, his opportunity for accurate observation, his com- 

 plete freedom from prejudice or pre-conceived notions, and so on. 

 In observations of this sort one is likely to be influenced by what he 

 expects to see, and thus to reach a very definite conclusion based upon 

 a very flimsy foundation of real fact. Many mistakes have been made 

 in exactly this way in both ornithology and mammalogy. Yet in some 

 instances careful observation by competent, unprejudiced observers, 

 under favorable conditions, may afford as definite and conclusive proof 

 as any other possible means. 



The well-preserved contents of the stomach is conclusive as to at 

 least that portion of the last meal eaten by the individual. Therefore, 

 if a sufficient number of stomachs be examined and their contents are 

 well enough preserved to be recognized with certainty, they would 

 be the most reliable evidence of the diet of the species in the particu- 

 lar locality at the particular season of the year. If enough stomachs 



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