Environmental odors for communication

Mammals often damage plants or the substrate before or during marking, such as when deer thrash a sapling or tree branch with the head or antlers, or scrape the ground before urinating on it. Odors from the plant or soil may become part of the active signal. 

Environmental odors can also play a role in interspecific interactions such as preying. The domestic dog uses cues from disturbed soil and crushed plants when tracking and they can be trained to follow tracks that lack scent. When following a scent, such as a human track, they can be diverted by another scent crossing the first pathway. The choice made by the dog is influenced by the odors and cues available at any point (Most and Bruckner, 1936 see p. 414). 

The environmental odors used for homing in fish, amphibia, and birds, or possibly for long-range navigation, are not yet understood and will be discussed in Chapter 4. 

---