Caring for a Pet has its good and bad points. While pets have much simpler needs compared to human Sims, you cannot control pets directly. For that matter, you can't click on them to bring up their Need Meters or select them. In the interface you can right-click a pet's portrait to lock the camera to them, or left-click a pet's portrait to jump the camera to them, but either way your currently selected human Sim will remain the active Sim.
infographic by: www.animalfriends.co.uk