Photos 98 & 99*: More important than a toy, a gnawing stick, a mirror or television is a perch for caged macaques. It no longer restricts the animals to a terrestrial life style - to which they are biologically not adapted - but opens up the vertical dimension thereby increasing the usable cage space and promoting species-typical arboreal activities such as climbing, leaping, balancing, bouncing, perching and looking-out (photo 98). Serving as a prop for exercise the perch has therapeutic value for animals suffering from cage paralysis [authors' own unpublished observation]. The perch also allows for species-typical vertical flight responses in alarming situations [Lindburg, 1971; Chopra et al., 1992] and for retreat to a dry place during the daily cage cleaning (photo 99). Access to elevated, 'safe' sites has survival value for macaques. This explains why caged animals never lose interest in a perch.
In a study with 25 adult single-caged rhesus males who were exposed to a perch for 12 months, individuals sat on their perch on average 28% of the time [Reinhardt, 1989b].
Inexpensive perches can readily be made from branches of dead deciduous trees (photo 98; Reinhardt et al., 1987c) - preferably from read oaks to forestall clogging problems of sewer drains [Reinhardt, 1992e] - or sections of polyvinyl chloride (PCV) pipes (photo 99; Reinhardt & Smith, 1988).
The diameter of a perch must be large enough so that an animal can comfortably sit on it over extended periods of time.
Rhesus monkeys are inquisitive animals who want to know what's going on outside of their cage, and they show a strong preference for sitting in the front rather in the middle or rear of the cage [Reinhardt, 1989c; Woodbeck & Reinhardt, 1991]. Therefore, perches should always be installed in such a way that they enable the occupant to sit right in front of the cage (photos 98 & 99); probably, this fosters a sense of security by giving the animal visual control over the environment outside of the cage [cf. van Wagenen, 1950; Niemeyer et al., 1998].
Swings are less suitable than perches to enhance cage space complexity. When given the choice, rhesus monkeys clearly prefer perches over swings, presumably because perches - unlike swings - are fixed structures permitting relaxed posturing rather than unstable balancing in a cage that is too small for accurate adjustments of body movements [Kopecky & Reinhardt, 1991; cf. Dexter & Bayne, 1994; Phillippi-Falkenstein, 1998].