Determining Django Model Instance Types after a Query on a Base-class

Is there a way to determine what the 'real' class of a Django database object is, after it has been returned from a query for on a base class?

For instance, if I have these models...

class Animal(models.Model):
    name= models.CharField(max_length=128)

class Person(Animal):
    pants_size = models.IntegerField(null=True)

class Dog(Animal):
    panting_rate = models.IntegerField(null=True)

And create these instances...

Person(name='Dave').save()
Dog(name='Mr. Rufflesworth').save()

If I do a query like Animal.objects.all(), I end up with two Animal instances, not an instance of Person and an instance of Dog. Is there any way to determine which instance is of which type?

FYI: I already tried doing this...

isinstance(Animal.objects.get(name='Dave'),Person) # <-- Returns false!

But that doesn't seem to work.