Anonymous. 1992. Annual Reports: Howletts and Port Lympne Zoo Parks, UK. International Zoo News 39(1), 30-41.
Several structural enrichment enhancers are described. When a barrel with an opening in the front was hung from the roof of the siamang enclosure, our then solitary male, Mitch, spent much of his time looking out at the world from within it. We have found that cargo nets make high-level nest sites for the chimpanzees and gorillas which, when filled with hay, provide a wonderful springy bed.