Reinhardt, V. 1992. Environmental enrichment branches that do not clog drains. Laboratory Primate Newsletter 31(2), 8.

More than 700 caged rhesus and stump-tailed macaques housed in 29 rooms have been exposed to red oak perches and/or loose branch segments for a period of six months. Drains did not clog in any of the 29 rooms during this time although the animals gnawed the wood extensively.