Enrichment first came onto my radar when I saw it used in zoos, keepers creating challenging ways for the captive animals in their care to find and eat their regular rations and treat items. I remember being fascinated by polar bears playing with giant ice cubes with meat frozen inside and black bears climbing into trees to find sealed boxes with melons in them. On the other end of the spectrum, when I lived in Anchorage, there was an elephant who truly seemed to enjoy painting!
Acquiring food is the basic one but even in that realm, there are nuances. Boxes seem to love Kong Wobblers, that they can knock around. My sensitive Border Collie mix Gusto is prone to over self-grooming when he feels stressed, which in the past often results in hot spots on his forelegs. If he is provided with a Licki Mat a couple of times a week, it seems to give a harmless outlet for the behavior and allows him to self-soothe in his own way.
For shelter dogs, I’ve had great success in engaging them with sniff-tubes (PVC tubes with screw cap ends and holes drilled along the sides) filled with a variety of outside of their kennel odors (old horse blankets, chicken feathers, branches from local trails).
As uncomfortable as it makes me, there is truth in our pets being captive animals. We as their keepers/guardians/friends-with-thumbs and need to puzzle out and provide them with what enrichment we can provide to help keep them happy, healthy, and mentally well.