Isaac has divided animals into four groups.  1.  He calls all birds 'ducks' (or 'gucks').  For example, a raven is a 'guck'.  2.  He calls all insects 'bees'.  For example, a lady bird is a 'bee'.  3.  He calls dogs 'dogs' (or 'gaaaaa') - describing the same group in the same way that most people use.  4.  Finally, he calls all non-dog mammals 'cat'.  For example, horses and sheep are 'cats'.  He is quite consistent.