6 Viewpoint of Modern Ecology 



These values show that mortahty was high throughout development 

 and that a particularly critical period occurred during the transition 

 to the post-larval stage. Out of each million mackerel eggs spawned 

 in the area of this investigation only four survived on the average to 

 reach a size at which the young fish could forage for themselves 

 eflFectively. Others would, of course, succumb before they grew to 

 spawning size. 



The U. S. Fish and Wildlife Service estimated that early in 1944 

 there were roughly 125 million ducks in North America. These ducks 

 ordinarily produce 10 to 16 eggs per pair. If all the adults and all the 

 eggs produced in 1944 had survived, there would have been about 

 900 million ducks inhabiting the continent in 1945. Actually the 

 population was not significantly larger at the next census, early in 

 1945, with again about 125 million ducks present. This means that 

 something like 775 million ducks had died during the year. The 

 sportsman's kill, which is estimated from licenses and bag reports, was 

 about 20 million during 1944, or less than 3 per cent of the total 

 mortality ( Griscom, 1947 ) . Again it is obvious that a very large por- 

 tion of this bird population died during the year, and most died of 

 "natural causes"— not by the hand of man. 



One process developed during the course of evolution that acts to 

 insure the survival of species in the face of this high mortality is the 

 production of huge numbers of young. The prodigious fertility of 

 nature is a measure of the destructive action that is received from the 

 environment. In species in which each pair produces thousands or 

 millions of eggs or seeds, only two survive on the average to reach 

 the adult condition as long as the population is not continually in- 

 creasing. Many examples could be given of the huge excess number 

 of young that are produced and the small number that survive 

 (Fig. 1.3). Insects are notoriously prolific. The queen termite in an 

 African species after only one mating is reported to lay eggs at the 

 rate of one every few seconds and to continue egg laying at this 

 terrific pace for the rest of her life. A calculation shows that at this 

 rate each termite queen would lay approximately 30,000 eggs per day 

 or 100 milhon in her lifetime (Wheeler, 1923). According to esti- 

 mates, an oyster may discharge 500 million ripe eggs in one spawning. 

 If all these eggs developed into mature oysters and all subsequent 

 progeny survived, after only four generations we would have a pile of 

 oysters about eight times the size of the earth! 



Plants also have the capacity to reproduce at very high rates, and, 

 if all spores or seeds grew to maturity, plant populations would in- 

 crease with tremendous rapidity. Pine trees liberate such quantities 



