Cats are crepuscular — most active at dawn and dusk — and can sleep 12–16 hours a day in short bouts. Dogs sleep around 12–14 hours, often syncing more to their humans' routines.
Both species cycle through light sleep and REM rapidly. You'll see twitching paws and whiskers during REM dreaming, just like people.
Puppies and kittens spend extra time in REM to support brain development. Senior pets often sleep more but more lightly, waking for comfort or bathroom needs.
A sudden change in sleep — restlessness, waking at night, or sleeping far more — can signal pain, anxiety, or illness worth a vet visit.