238 



L. B. SLOBODKIN 



The yield from any real population is typically mixed. The population 

 efficiency associated with a mixed yield is given by: 



Ep = 



Yi 



C ^pi^ ^i 



(8) 



For a given population the estimate of J5p from equation (8) ought to be 

 identical with that from equation (3). The relation between the two estimates 

 is shown in Fig. 9. 1 believe the spread is due to weakness in the estimates of J. 



0.20 



Fig. 9.— Population efficiency estimated for the same population from equation (8) (B) and from 

 equation (3) {A). The line is drawn on the assumption A = B. 



The value of c, from equation (7) was i-68 calories per four calorie days. 

 Five control populations consumed 8 • i calories per four days.The expected 

 steady state standing crop, from equation (5), was therefore 4-7 calories. 

 The observed mean standing crop of these populations was 4-5 calories. 



Population efficiency depends on life expectancy and growth efficiency of 

 the animals removed and on the interaction between these animals and the 

 other members of the population. 



