Bercovitch, F. B., Tena-Betancourt, E., Kessler, M. J. et al. 1990. A multi-functional environmental enrichment device for primate enclosures. Laboratory Primate Newsletter 29(1), 16-17.

We describe an extremely cost-effective procedure for modifying captive enclosures that does not interfere with research procedures and that provides the monkeys with a multi-functional device that probably enhances the captive environment. ... [Telephone spools] have become a favored play areas, with immature monkeys darting around, through, and over them. .... [They] are used by the macaques for grooming episodes and for protection from conspecifics. ... Spool deployment has not been accompanied by any adverse consequences. ... However, they have become specialized locations, with monkeys supplanting others over access to them.