Should I unittest private/protected method

This is actually language agnostic. But I'll give you context in python.

I have this parent class

class Mamal(object):
    def __init__(self):
        """ do some work """

    def eat(self, food):
        """Eat the food"""
        way_to_eat = self._eating_method()
        self._consume(food)

    def _eating_method(self):
        """Template method"""

    def _consume(self, food):
        """Template method"""

Here eat is the only public method and _consume, _eating_method are actually protected method which will be implemented by child classes.

What will you test when you have written only the Mamal class?

Obviously all 4 methods.

Now lets introduce a child

class Whale(Mamal):    
    def _eating_method(self):
        """Template method"""

    def _consume(self, food):
        """Template method"""

Look at this class. it has only 2 protected method.

Should I test all 4 methods of Whale (including 2 inherited) or just test the changes introduced (only overrided 2 methods)?

What is the ideal case?