Final answer:
Cats are naturally more active at night due to their nocturnal instincts. They may hunt, play, explore, or mark their territory while their human companions are asleep.
Step-by-step explanation:
When humans are asleep, cats continue with their nocturnal habits. As natural predators, cats have instincts that lead them to be more active during the night. While we are sleeping, cats may engage in activities like hunting for prey, which can be simulated by playing with toys if they are indoors. They might also explore their environment, looking for new stimuli or marking their territory.
Cats have an acute sense of smell, which they use to communicate with other cats or to hunt. If you notice a smell of cats in the night air, it could be due to your feline friend investigating or marking their territory. Cats are independent creatures and are perfectly content doing their own thing, whether that's lounging in a cozy spot or silently observing the world around them.