Chicago: Scientists are learning more about how zoo animals feel and how a toy or a little training can sometimes help cut the endless pacing and other repetitive behaviors that are often assumed to be signs of distress. Some big cats want a high perch from which to view visitors, polar bears want to scratch for hidden caches of food, and male barn swallows could use a tail extension to appeal to potential mates, according to experts from zoos and universities meeting on Friday at Chicago's Brookfield Zoo.