The type of psychologist who would be most likely to study the communication patterns of chimpanzees and porpoises would be an ethologist.
Step-by-step explanation:
The scientific study of the psychology of animals is called 'ethology'. One who is an expert in animal psychology is thus called an ethologist. The discipline of animal psychology is to a great extent different from that of human psychology. Thus, it requires a person to be specialized in ethology to understand animal psychology.
Comparative Psychology is a sub-discipline of psychology and ethology. This would be most likely to study the communication patterns of chimpanzees and porpoises.