It is not unusual for some animals to play with toys. An example of this is a dolphin being trained to nudge a ball through a hoop. Young chimpanzees use sticks as dolls - the social aspect is seen by the fact, that young females more often use a stick this way than young male chimpanzees.[21][22] They carry their chosen stick and put it in their nest. Such behaviour is also seen in some adult female chimpanzees, but never after they have become mothers.