Miller, P. 1994. Lion-tamarin and marmoset enrichment at the National Zoo. In Touch 1(4), 5.

As always, the key to successful enrichment is variety. Use a different device each day. Load it with different foods each time. Sometimes don't load it with anything at all! (It keeps them guessing.) Before you start, get a quantitative idea of how your animal spatially and temporally partitions its enclosure. Your goal should be to expand both to every possible limit.