A researcher wants to study monkeys in their natural habitat, out in the wild. What type of qualitative research method is best to use?

The researcher best use the qualitative research method of using a case study of a group of monkeys in their wild habitat and observe them, making notes on observations and developing trends in their behaviour to determine research clues as to the activity of the monkeys and how they act in their habitat with one another and in response to the environment itself.