Sullivan is helping to lead what he calls a paradigm shift at Brookfield, a revolution in the way its residents eat that is proving to have benefits for guests and animals alike. Instead of the old regimen of keepers delivering food two or three times a day on a set schedule, the zoo is working to propagate semirandom feeding devices throughout its 216-acre property in the near western suburbs. It's being used in 15 to 20 percent of exhibits now, but the goal is to get to near-blanket coverage within five years.