One theme in The Island of Dr. Moreau is ‘nature fights back’. Moreau cruelly vivisects animals in an attempt to make them humanoid. He is selfishly motivated by renown, as his work does not have any practical use. Moreau justifies his work to Prendick by stating that “this extraordinary branch of knowledge has never been sought as an end, and systematically, by modern investigators until I took it up!” (Wells 59). He only wishes to prove himself to the scientific community by doing something that has never been done before. However, he does not stop to consider why that may be. Moreau ignorantly states that he is “puzzled why the things I have done here have not been done before” as if the unnecessary pain inflicted on the animals isn’t enough of a deterrent (Wells 57). And although Moreau has justified his actions in his own mind, the following events suggest he is at fault. Moreau physically and mentally alters these creatures to resemble humans, but they always revert to their original animal forms over time. He attempts to counteract this by introducing the Law to scare the beast-men away from animalistic behaviors, but he is ultimately unsuccessful. This can be seen in the Leopard-man ‘sucking his drink’ and killing rabbits. When his puma escapes and Moreau attempts to recapture it, they both end up dead. After Moreau dies, Montgomery follows. They both had to die to restore the balance of nature. Moreau died for his experimentation, and Montgomery because he supported him, or at least turned a blind eye. Prendick survives because he saw the wrong in Moreau’s experiments and even works against him, like when he shot the Leopard-man instead of letting him be recaptured. When Prendick eventually leaves the island, the beast-men have lost most of their human characteristics. They can no longer speak and live wild in the forest. So although the animals had to suffer through Moreau’s vivisection, they fight back and ultimately outlive him. This restores nature to equilibrium, how it should have been. 

Another theme is the exploitation of animals. In his explanation of his work, Moreau denies the importance of the animals’ pain. Prendick asks him, “Where is your justification for inflicting all this pain?”, to which Moreau responds with:

"Oh, but it is such a little thing! A mind truly opened to what science has to teach much see that it is a little thing. It may be that save in this little planet, this speck of cosmic dust, invisible long before the nearest star could be attained–it may be, I say, that nowhere else does this thing called pain occur. But the laws we feel our way towards–Why, even on this earth, even among living things, what pain is there?” (Wells 60).

He denies the importance of all pain, not just animals’, and tries to prove his point by driving a penknife into his thigh. Moreau downplays his cruelty by putting it in the perspective of the universe. But if we have such little impact, doesn’t that make the actions we do have control over more important? And doesn’t that make each person/creature’s experience more significant to themselves? In attempting to discount their suffering, Moreau effectively supports a moral argument against his own work. This theme is commonly used in ecohorror because it explores the idea that animals may be justified in fighting back against people. In the case that they do, we may deserve it by our own moral standards. The beast-men’s victory at the end suggests that Wells supports the idea of animal sentience and how it should be considered when deciding if an experiment is worth the consequences. Wells’s opinions are valid to this day, as genetic engineering fields continue to grow and scientists must determine what it means to go ‘too far’.