Animal psychology is the study of behavior in animals. Wikipedia draws a distinction between the term "animal psychology" from comparative psychology, and as humans are animals, this branch of psychology often makes comparisons between animal behavior and human behavior. Distinct from an animal trainer, the animal psychologist or comparative psychologist analyzes and studies the behavior in a clinical and controlled setting.

Jane Goodall, for example, in her work with chimps in their natural habitat went on to write extensively about their behavior, and one of her published books with Mark Bekoff Pd.D. directly addresses animal psychology: "The Emotional Lives of Animals: A Leading Scientist Explores Animal Joy, Sorrow, and Empathy - and Why They Matter" (May 28, 2008).

Animal trainers are experts in animal behavior and therefore in animal psychology, and employ their understanding and observation of animal psychology in their training approaches. Any number of animal training books and studies addresses behavior modification techniques and understandings in order to accomplish a desired trait or behavior

While there are few degrees in "animal psychology", Breyer State does offer one (see link below). Most people interested in advanced study and theory of animal psychology might pursue degrees in zoology] or marine biology to name a couple examples, as the study of the animal science in integrated with animal behavior.

Other animal psychologists are working with the "psychic" abilities of animals, and there are multiple sources and books about the healing nature of animals offered through a lens of animal psychology.

For further reference:

http://en.wikipedia.org/wiki/Animal_psychology

http://www.amazon.com/Emotional-Lives-Animals-Scientist-Explores/dp/1577316290/ref=sr_1_1?s=books&ie=UTF8&qid=1294535275&sr=1-1

http://www.breyerstate.com/masters-animal-psychology.htm

http://www.psychwww.com/resource/bytopic/animal.html