It is estimated that domestic cats kill millions of small animals and birds every year, and that's in the U.S. alone! The world-wide kill rates between domestic and stray cats could be up in the billions. It's not just rodents or birds they go after either. Anything from mice to frogs and snakes is on the list when it comes to prey for a cat. Cats, the biggest huntersAs impressive as this may seem, cat's can also be of harm the ecology around them. Especially when it comes to endangered species of birds or other creatures. According to statistics from national parks, parks that contained cats had up to 50% fewer birds in them than parks without.A ban on cats?A conservation organisation in New Zealand even suggested evoking a ban on cats in order to preserve certain species of endangered animals. Cats are natural-born killers, perfectly designed to hunt and have incredible instincts that drive them to do. If your cat spends a decent amount of time outdoors its likely that it's left you a 'gift' or two on the porch much to our dismay. Cats tend to hunt better in open areas much like fields as their prey have fewer places to hide. A cat can have a success rate of to 70% in some cases which blows its other predatory competition out of the water. Tigers only have a 1 in 20 successes rate when it comes to hunting and even leopards have only a 1 in 7 success rate. However when it comes to house cats, usually they do not hunt to kill, which is why some conservationists believe they are bad when it comes to the environment. As they are fed by their owner's cats tend to kill needlessly and can eradicate species for no reason whatsoever. So if you own a cat, perhaps its better to keep it indoors, not only for its own safety but the safety of all those little critters out there too.