Ethical principles guide decisions about what we consider to be right or wrong proposals and actions, so that when value judgements are made these engage us in ethics. Ethical thinking is clearly relevant to decisions about the way we treat animals, and such thinking has led to the
commonly held view that animal use by people is acceptable provided that such use is humane. The ethical requirement that we treat animals humanely means that we must minimise the harms we do to all animals in our care or under our control. Accordingly, we must assess what harms are done to
the animals, how bad each harm is in terms of its intensity and duration, what methods are available or can be developed to minimise each harm, and the relative effectiveness of those methods of harm minimisation. We must also seek to use the most humane methods currently available that can
be practically applied. Ethically driven scientific evaluations of this sort have improved the humaneness of livestock slaughter and vertebrate pest control. For instance, detailed studies of different pre-slaughter stunning methods have validated their use to pre-empt the pain and distress
that otherwise conscious animals would experience during the fatal neck cut and the short period of consciousness (sensibility) that follows it. Likewise, reducing injuries caused by restraint traps has improved the humaneness of this vertebrate pest control method, and comparing the effects
of different poisons has allowed the least humane ones to be identified. Difficult questions nevertheless remain at the problematic interface between quantitative scientific observations and their interpretation regarding the suffering that animals may experience, as well as questions about
the relativities of different types of suffering.