Before arriving at the island, what is Rainsford's position on hunting?
In the exposition of the story, Rainsford asks Whitney what the best game is, to which Whitney replies, "hunting...for the hunter, not the jaguar." Rainsford says, "Don't talk rot Whitney. You're a big game hunter, not a philosopher, who cares what the jaguar feels!"
Rainsford is alpha-male here. He shows no empathy toward his prey. He has not been desensitized in the way modern males have to the feelings of animals. In those days, and in that part of the world, there were few zoos, no animals rights organizations, no dog and cat-lovers culture.
As a note, this scene is parodied in The Simpsons Treehouse of Horror XVI in which Lisa exclaims, "Hunting is cruel!" Homer replies, "Lisa, animals don't feel death. That was proven by the scientists at Black Angus!" Then, Bart chimes in, "No fair! Dad gets to kill wild animals..."
So, it seems there's been a shift in how we view the feelings of animals. Historically, even biblically, man has been a big game hunter, trusting his instincts, free to exert dominion over the animal kingdom. But lately, there's been some apologies made. Males in particular have been made for feel guilty for hunting, but not eating (yet!) animals. Now, our meat is butchered and pre-packaged. Our mercies, as Ian McEwan would say, are selective. We still eat animals, but we don't want to watch them die. In his novel Saturday, McEwan says his protagonist would never throw a lobster into a boiling pot, but he would never refuse a lobster dinner. Such equivocation is unsettling, even hypocritical.