Krebs, B. L., & Watters, J. V. (2017). Simple but temporally unpredictable puzzles are cognitive enrichment. Animal Behavior and Cognition, 4(1), 119–134. https://doi.org/10.12966/abc.09.02.2017

Provision of problem solving opportunities as enrichment for animals considered highly intelligent has increased over the last twenty years, but this emphasis on animals considered intelligent may overlook the need for cognitive challenge in species not typified as problem solving animals. Commonly used foraging challenges, such as puzzle feeders, may occupy more of an animal’s day with food gathering, but interest in the feeder may wane as animals learn to extract food more efficiently. We tested the hypothesis that making a simple puzzle available at variable intervals can maintain an animal’s motivation and be cognitively enriching for species not typically considered “thinking animals.” We built and tested a time-delay puzzle feeder with a black rhinoceros (hereafter “rhino”) at the San Francisco Zoo. The feeder required the rhino to push a ball to get treats, however food was not always available. An audio cue signaled the availability of food. We assessed the rhino’s behavior before and after he learned to use the feeder. The rhino’s interest in all enrichment items increased with the feeder, and we found no evidence for habituation to the feeder over time. We also found evidence that the positive behavioral impacts of the puzzle feeder carried over into weeks during which the feeder was not available. Our results highlight the positive impact of providing problem solving opportunities as enrichment for captive animals, and suggest a method for maintaining animal interest in simple puzzle devices by varying reward schedules.