Harris, L. D., Custer, L. B., Soranaka, E. T. et al. 2001. Evaluation of objects and food for environmental enrichment of NZW rabbits. Contemporary Topics in Laboratory Animal Science 40(1), 27-30.

Male and female 6-week old New Zealand White rabbits were divided into three groups: food-enriched (Bunny Stix, Bunny Blocks, or celery), non-food enriched (Jingle Ball, Kong toy, or Nylabone), and not enriched. ... Rabbits spent significantly more time interacting with the Bunny Stix than any other food item or non-food object. In addition, total activity time was significantly greater for all rabbits enriched with food versus any of the non-food items.