имя ошибки Python не определено

У меня проблемы с выяснением, почему я получаю эту ошибку. Мой код это

#define the Animal Class

class Animal:
    def __init__ (self, animal_type, age, color):
        self.animal_type = animal_type
        self.age = age
        self.color = color

    def makeNoise():
        pass

    def __str__(self):
        print ("% is % years old and is %" % animal_type,age, color)


#define child classes of Animal 
class Wolves(Animal):
    def __init__(self, animal_type, age, color, wild):

        Animal.__init__(self, animal_type, age, color)
        self.wild = wild
    def __str__(self):
        print ("% is % years old and is % and is %" % (animal_type, age, color, wild))

class Bear(Animal):
    def __init__ (self, animal_type, age, color, sex):
        self.sex = sex
        Animal.__init__(self,animal_type, age, color)

class Moose(Animal):
    def __init__(self, animal_type, age, color, antlers):
        self.antlers = antlers
        Animal.__init__(self, animal_type, age, color)

#add items to each class

wally = Wolves("wolf", 4, "grey","wild")
sally = Wolves("wolf", 3, "white", "tame")

print (str(sally))
print (str(wally))

И полный обратный след

Traceback (most recent call last):
  File "//mgroupnet.com/RedirectedFolders/SBT/Documents/bear51.py", line 41, in <module>
    print (str(sally))
  File "//mgroupnet.com/RedirectedFolders/SBT/Documents/bear51.py", line 24, in __str__
    print ("% is % years old and is % and is %" % (animal_type, age, color, wild))
NameError: name 'animal_type' is not defined

Что я делаю не так?