280 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1949 
ized saliva accelerates digestion. Little is known regarding the 
poisonous bite of these little creatures, but it is apparently similar 
to that of a slightly larger close relative, the short-tailed shrew 
(Blarina) whose saliva is definitely known to be poisonous to many 
small creatures and whose bite on a man’s finger is sufficiently 
poisonous to produce pain extending halfway up the arm with resultant 
irritation lasting as much as a week. Such bites are somewhat com- 
parable to the bites of snakes in which a secretion from specialized 
glands is introduced under the skin of the victim, although these 
shrews do not have specialized teeth or glands that are primarily 
poison producers. 
Among the reptiles, the chamaeleon (Chamaeleonidae) has the 
interesting habit of obtaining the insects on which it feeds almost 
exclusively by suddenly extending its tongue to a distance almost as 
great as the length of its head and body and catching the unwary 
insect with it. The tongue is attached near the front of the mouth 
and folds back into the mouth like that of the frogs and toads, which 
also capture their prey in a similar manner (pl. 10, fig. 2). 
Emil Liers’ study of otters (Zutra) in North America have shown 
that these remarkably intelligent and playful animals feed largely on 
crayfish and numerous small invertebrates instead of fish, which they 
have generally been supposed to eat. It is strange that this was not 
discovered long ago, emphasizing the fact that there is still a fertile 
field for research on animal life. 
Through the long period of development of each species, animals 
have learned that in general each individual or pair requires a cer- 
tain amount of territory in which to sustain itself. Other species 
that do not conflict with it will be tolerated in this territory, while 
those that would be competitors may be driven out. Forms of life 
that constitute the food supply are rarely devoured to the point of 
extermination, and animals can therefore ordinarily obtain sufficient 
food within a rather definite territory. Some require but a small 
range for this purpose; others must have an extensive territory and 
move to various parts of it at frequent intervals to obtain the necessary 
food. For example, the wolf (Canis nubilus and related forms), an 
animal that preys on other animal life, usually has a range about 20 
miles in diameter and, except when the female is living at the den 
caring for the young, it traverses this range, generally in large circuits, 
returning to any given portion of the range about once every 2 weeks. 
Seasonal fluctuation in the food supply, such as the migration of 
fishes or the dying off of insects, results in the migration of forms that 
prey upon them to locations in which food can be found. For example, 
insect-eating birds have an abundant supply of food in the Northern 
Hemisphere during the summer but, with the approach of winter, 
