"I never pity animals in captivity because I have seen too many wild animals suffering from starvation and other things. I remember polar bears emaciated to extreme weakness because the ice had gone and with it every chance for them to hunt food. I have seen caribou exhausted by fear, and around them howling wolves forcing them to run and run until they lost sense and strength and became an easy prey. In nature, every animal is merciless toward every other."
January 1, 1970
https://en.wikiquote.org/wiki/Wild_animal_suffering