Kept in barred cages, wolves, lions, bears and apes became listless and troubled. Today, zoos know better. They create interesting habitats and activities for their animals. Polar bears usually have a pool stocked with live trout, to stimulate their hunting skills. Leopard have tall trees to climb and eat in.
Wolves follow invisible scent trails laid down by zookeepers, to stimulate their sense of smell.
These additions excite and give purpose. Domestic dogs and cats need to feel that way too. Unfortunately, most of them spend their days in home environments that are lonely and lack stimulation. While left alone, their instincts to hunt, explore, play or socialize are rarely engaged. Instead, most dogs and cats spend their days eating, sleeping, pacing, or getting into trouble.