To date, most studies of communication center on interactions among members of CAB the same species. However, animals have much to gain from being able to interpret the signals of other species, and in some cases, communication may facilitate true mutualistic relationships. Chapter 1 of my dissertation puts forward the theoretical underpinnings of mutualistic interspecific communication and presents a four-stage model for the development of interspecific communication in a cooperative context. Each stage of the model is described, along with examples of each stage found in nature. I also make predictions for the conditions under which mutualistic interspecific communication is most likely to develop.

Cooperative livestock herding is an especially complex interaction that makes use of mutualistic interspecific communication. Chapters 2 and 3 of my dissertation directly explore this study system. Training sessions of human/dog hobby herding teams were recorded and these data were used to analyze both the language used by the herder and the behavior of the dog in a cooperative working context. Chapter 2 focuses on the acoustic signals used by the human herding partner. Herders' language is a more truncated version of dog-directed language that has been previously described in pet, rather than working, contexts. Herding language had even shorter utterance lengths, higher levels of repetition, and fewer questions directed to the dog. During the herding training sessions, more praise was used than scolding. The more skilled the herders were, the more commands they gave per minute. A higher level of praise, more questions, more general statements and a wider vocabulary were all negatively correlated with skill level.

Both the human herder and the dog are communicative agents in the system of livestock herding, so chapter 3 focuses on the role of the dog in livestock herding, examining differences based on the breed and the skill level in canine herding motor patterns. I found differences in the number of undesirable behaviors used, spacing between dog and sheep, and locomotion. Specifically, Border collies and more highly skilled dogs worked further off the sheep. When in motion, small dogs were more likely to run and less likely to walk than other dogs. Border collies were more likely than upright herding breeds to circle the sheep, while upright breeds were more likely to split the group of sheep. German shepherds were more likely than other breeds to grab sheep. The application of these findings on behavioral conformation should aid herders and trainers in planning their training schedules, and a more thorough understanding of breed differences based on previous human requirements will help dog owners understand their own companion animals.