334 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 30 



basic principle is that an area can sustain up to and not beyond 

 a certain abundance. If the stock is increased above the carryini; 

 capacity of the area its productive capacity is lessened, and this 

 naturally leads to ultimate reduction of numbers. If the area is 

 not fully stocked it will not produce as large a crop as it might 

 under best utilization. 



If more than the normal surplus produced by the basic breeding 

 stock is taken, the breeding supply will be reduced and production 

 can not be sustained. If all the surplus is not used it is not only 

 wasted but it also becomes a source of danger through overstocking. 



This is intended to make clear the fact that there is a definite 

 critical point which, if passed in the case of any valuable animal 

 or plant, leads to reduced production and threatened extermination. 



It can be shown that by building up the wild stock a surplus can 

 be provided that may be harvested at a profit, and indeed it must be 

 removed to prevent overstocking. The work of the biologist is to 



6 M. year — 76 



jz-Zi. yea/- - 51 



4M.year- 3A- 



1^^-10 In'ifral Stock 



FIGUBB 2 



determine the dividing line which is not always clearly defined and 

 varies as conditions change. 



Reliable statistics applied to the graph in Figure 1 will show 

 the trend of the wild life population. Appropriate action then be- 

 comes obvious. 



The steps in increasing the wild-life supply may be graphically 

 illustrated by the inverted pyramid. 



The problem is one of arithmetical progression and by application 

 of the proper figures appropriate to the species, region, and condi- 

 tions of life it is possible to illustrate the case quite clearly. The 

 method is applicable in illustrating the increase of injurious forms 

 as well as beneficial ones. 



With the foundation idea established of maintaining a definite 

 maximum breeding stock and harvesting only the surplus, we next 

 have for consideration factors that must guide us in harvesting the 

 surplus. Different factors, of course, are operative in different 

 animals. 



