This two-stage skill is used by animal trainers who want their pets to come to them. It comes in handy if you are seperated from a beast of burden, for as long as they can hear you, they will respond to your whistle and arrive. To start this skill, try:
use heel at <tamed animal in the room> This will give you a special ID which you use in the second part of the skill, which is:use heel at <animal ID> Note that the animal still has to travel the distance from you to it, and may arrive tired or hungry. Also note that the sound of your whistle works better outdoors. You have to use this skill again every reboot and every time the animal is stabled.