I know that G+ learns what you like/see, and even though I have never, ever, clicked (given focus) on an animal post (90% cats, 9% dogs, 1% other animals) shown on my timeline, most of the time I wait for the animation to load, so the harm is equally done.
I have never joined an animals group or anything similar, but they show on my timeline more often every week. Same with super cars, and lately with road bikes.
How can I stop G+ suggesting (it does well!!) and inserting on my timeline subjects I have not explicitly joined or subscribed?