When it comes to hunting, cats take that very seriously. For indoor cats, they'd go after any small critters that somehow have crawled or flown into the house. A fruit fly for instance is purr-fect prey for cats. Cats can hear sounds that even dogs fail to hear. With 2 satellite dish shaped ears, cats’ range of hearing goes up to ultrasonic which is superbly high. When you notice your cat staring at something on the wall, you know there is probably a bug in the house.
Here is a video of my cats Flip and Shadow :):
Cats are also very determined hunters. They will not give up until they have learned that there is no way to catch their prey. However, for some, failure is simply not an option. You may find them chattering in their mouth, a reaction that some cats do to imitate biting the prey.
"Studies have shown that it is this unusual jaw movement that brings about almost instantaneous death, as it is vital for the cat to reduce any risk of injury to itself . So unable to control itself at the site of a tasty bird outside, the cat will sometimes involuntarily enact this special jaw movement" according to Paw Online.
A video from a YouTuber: