Answer:
naturalistic observation
Step-by-step explanation:
Naturalistic observation -
It is the method of observation in the research field , where the method used is observing the object of study in their particular natural environment , is referred to as naturalistic observation.
This helps to get a pure and proper source of knowledge for the research work , and helps to understand the subject is the best possible way.
Hence, from the given scenario of the question,
Chan Lee observe the gorillas in their natural habitat , i.e. ,in the subtropical forests , to get the best information , showcasing naturalistic observation.