312 MAN --AN ADAPTIVE MECHANISM 



In certain species of animals, the maximum of con- 

 sciousness and minimum of sleep is established promptly 

 at birth, owing to the requirements for nutrition and 

 the necessity for an immediate motor adaptation 

 against constantly menacing enemies. Only in those 

 species in which the parents are able to defend their 

 young against enemies and to supply them with food is 

 there a period of prolonged unconsciousness after 

 birth. Birds which nest in the branches of trees and 

 are hidden from their enemies sleep much of the time 

 during the first days after they are hatched ; but 

 birds which nest on the ground, and depend for safety 

 upon their ability to run and hide from prowling ene- 

 mies, are conscious and able to run almost as soon as 

 they are hatched. For example, young quail are 

 sometimes seen running about with pieces of shell still 

 on their backs. Aquatic birds are awake and active 

 as soon as they are hatched. The eaglet, on the con- 

 trary, which spends its early days on the inaccessible 

 peaks of rocky promontories, develops slowly. The 

 offspring of the herbivora are wide awake and able to 

 walk, even to run, on the first day after birth. The 

 herbivora are dependent upon flight for their safety ; 

 while the young of the carnivora, which are able to 

 defend their offspring, sleep for days after their birth. 

 This, and the quality of food, may explain why the 

 hunted herbivora eat more, and oftener, and sleep less 

 than do the pursuing carnivora. The herbivora, need- 

 ing to be constantly on guard, use more fuel and 

 hence need to replenish their resources more constantly 

 and abundantly ; while the carnivora, secure from 

 attack, divide their time between hunting and sleep- 



