Environmental changes make a difference with humans as well as with animals. Both were meant to be biological successes and they would be if their natural habitats remained undisturbed. But time changes everything and some animals adapt more easily than others. Every need that they have or would have in the future was carefully built into their DNA. What happens to upset that has more to do with the invasion of humans on their natural rhythm than it does with their failure as a valid member of nature.
In nature every creature resides somewhere on the food chain and that takes care of overpopulation naturally. To a small creature, success is one meal at a time. A hungry cat catching mice in the barn is successful if she catches her dinner quietly and without fanfare. She simply waits in the shadows somewhere until the little mice come out for their dinner and she, quick as a lightening bolt will pounce. With one paw she will have him nailed. If she is not too hungry she may play with the poor little frightened creature before she eats him alive.
Whether or not a field cat is more successful than a well groomed house cat that doesn’t have to work for her food but is given it at regular intervals depend on the circumstances and who is comparing successes. Cats were not meant to be human and treated as such and domestication was not a built in longing.
Probably, deep down every cat in their dream world is a master hunter and while sleep believe they are galloping in tall grass chasing after their breakfast. They wake to find themselves in baskets with all the doors locked and they must wait until their mistress with the key gets up before they have their nice and tidy but boring breakfast.
After that the grooming session is nearing and the long claws must be file down. This would not be necessary had they been out chasing over gravel and running and skipping through briars and sand piles. This would have been a natural manicure. No matter how you look at it, there's little adventure in sitting alone in an empty house all day chasing a ball of yarn. The spirit of freedom never goes away completely. There's nothing better than hunting and running wild in the big and adventure beckoning world, at least at times.
Yet, after living lives of luxury with every need take care of who can blame the cats for wanting to run back inside and snooze by an open fire with an adoring keeper sitting nearby ready to be at their beck and call? Success means different things to different animals. There are those who are not sure it was a good thing when man began turning wild animals into four legged humans. For safety it may have seemed okay, but strictly for amusement, questions do remain. Each group of animal, and yes, humans are in this category, do best at survival if they are allowed to roam free and are not confined to small cells.