512 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 64 



tremendous psychological advantages in whatever competition takes 

 place. Proper consideration of this factor calls for some modification 

 of conventional views as to the struggle for existence, the ruthlessness 

 of natural testings, and the nature of predation. The favored parts of 

 a territorial population that live in relative social peace and are well 

 adjusted to their environmental resources may, in fact, have fairly 

 easy lives. They may not have to do much more than to conduct them- 

 selves according to their ordinary endowments to live securely with 

 respect to their ancient predatory enemies. In contrast, life can be 

 anything but benign for the wastage parts of a territorial population, 

 and these are characteristically vulnerable to such predators as have 

 aptitudes for preying upon them. 



Species having weak if any territoriality may show much more vio- 

 lent fluctuations. It is quite understandable that the less a population 

 is self -limited, the more it must be limited by something else : by preda- 

 tion, parasitism, disease, emigration, malnutrition or exhaustion of 

 food, exposure to climatic emergencies, and the miscellaneous troubles 

 that become compounded whenever populations get out of bounds. 



THE ROLE OF TERRITORY 



Surely, one of the principal differences to be seen in predator-prey 

 relationships of higher vertebrates and invertebrates is linked with the 

 relative importance of territoriality in these phylogenetically differing 

 groups. Between the extremes represented by the most socially ex- 

 clusive of the mammals and birds and, let us say, oysters growing on top 

 of one another, many forms have developed territorial behavior to 

 some degree. 



Lizards and fishes — among them chameleons, sunfishes, and stickle- 

 backs — include territory holders at least during their breeding seasons. 

 Although territoriality in lizards and fishes may allow great numerical 

 abundance, populations of these forms may still show distinct tenden- 

 cies to level off with increased crowding and, often, with apparent inde- 

 pendence of predatory enemies. Phylogenetically down-scale a little 

 more, we also have insects and crustaceans that are capable of display- 

 ing effective antagonism toward possible competitors ; and their popu- 

 lations may have at least some of the features of thresholds of security 

 and vulnerable overflows. I think of dragonflies perched on tips of 

 cattail stalks and patrolling their holdings, and, if their behavior is 

 not truly territorial in so doing, it looks like the next thing to it. 



J. H. Pepper published, in the mid-fifties, a most informative com- 

 parison of the population dynamics of Montana grasshoppers and 

 Iowa muskrats. As far apart in their taxonomic relationships and 

 as diverse in their living requirements as grasshoppers and muskrats 

 are, they may show social intolerances and habitat responsiveness that 



