Olfactorry Signals

The importance of the olfactory sense for most mammals may be inferred from a superficial study of their behavior and of the relations of the olfactory organs to the brain. The part played by smell in feeding and exploration has already been mentioned. Rats sniff all food and all objects that they encounter; but they also sniff other rats, especially strangers and potential mates. They not only respond to odors, but also produce them; like other mammals, they have an elaborate equipment of glands which secrete olfactory signals. These substance are called pheronomes.

Two groups of signals determine the manner in which one animal responds to another; both are concerned with recognition.

1. Hardly anything is known of species odors, but we may guess that they exist among rodents. We must not, however, also assume that response to specific odors are irrevocably fixed for each individual of each species. 
2. The evidence of distinctive group or colony odors is more convincing when a strange wild rat is introduced into a colony, there is a marked increase in "recognition sniffing" among the residents. When an adult resident male meets adult male intruder; fellow residents are not attacked.