I bury lots of dogs. Only one stone, goes to the last thing burried. (reminds me where not to dig). It is winter here now. I have one open hole dug in the fall, just in case something goes bad in the winter.
My back yard is the family pet cemetery. Probably 20 dogs and a hundred cats over my time. The kids like the stone when I bury a rat or dog or whatever animal they lose.
I tell the little ones I am not burying a loved pet, I am planting a soul seed back to the earth.
Someone has to do it.