Factors influencing orangutan (Pongo pygmaeus abelii) behavior in indoor holding facilities and outdoor exhibits (1993)

Forthman, D. L., Brown, M. T., Perkins, L. A. et al.

Abstract

Restriction of data collection to three weeks .... severely limits these results. ... What is interesting is the similarity in behavior in the two locations [indoors vs outdoors], despite marked differences in density and hours of the day observed. ... Members of the high density indoor group spread out considerably more in the outdoor exhibit. ... 'Rare' behaviors were ameliorated outdoors in 7 of the 9 animals which displayed them.