24 ANIMAL LIFE AND SOCIAL GROWTH 



at least eight different strata can easily be rec- 

 ognized by a naturalist. In Panama these have 

 been found to be divided as follows: 



8. The air above the forest. 



7. The trees, 125 feet or more in height, that 

 extend above the main forest roof. 



6. The upper forest canopy. 



5. The lower tree tops, 40-60 feet high. 



4. The small trees, 20-30 feet high. 



3. The higher shrubs, 10 feet high. 

 2. The forest floor. 



1. The subterranean stratum. 



This is an excellent statement of the facts that a 

 zoologist observes and careful work would doubt- 

 less show that some of the animals living within 

 the tropical rain-forest are limited to these differ- 

 ent levels of the forest, but in general in Panama 

 the majority of the animals themselves appear to 

 recognize only the following : 



6. The air above the forest which can be occu- 

 pied only by flying animals such as birds, bats, 

 and insects. 



5. The tree tops which have a distinct bird 

 population. 



4. The mid-forest, again distinguished by its 

 birds. 



Many animals do not recognize the distinction 

 between these two strata and are known as the 



