Lee, G. H., Coe, J. C. 1988. Greenspace for primates. International Zoo News 35(3), 19-21.

Against most expectations, after 11 years, the Seattle gorilla exhibit is still lushly landscaped. The animals climb trees to favorite perches to get a better view and browse among certain favourite plants. All of these normal behaviours are reducing the stress usually associated with primates kept in small concrete enclosures.