Possum up a native tree

What is it about the hierachy of animals that if someone tortures a dog there are calls for higher prison sentences for animal cruelty and yet the state poisons (read slow, agonising death) hundreds of thousands of animals (mostly the Australian possum which is eating our native forests but also birds and fish that get caught up in the cycle) with the blanket use of 1080.
Interestingly enough when the gypsy moth (a threat to our agriculture industry) was found in Auckland they actually sprayed poison on parts of the city with a plane.
Go figure!