Responses
Tails are spinal vertebrae after the sacrum. On your pets have a feel of their tail base. Its after the pelvis still.
Us humans have reminants of a tail called the coccyx and you can feel it (kinda) too, you just have to get deep into between the butt cheeks
My issue is they get drawn above the pelvis. Looks better to give animal traits, but not anatomically.

Ok, i know youre not actually supose to think while reading these types of stories
But i always get annoyed at beastmen when the artist cant put the tails in the right place
Tails dont come out halfway down your lumbar back!!!
Nearly as annoying as when the prostate is drawn in the wrong place (¬_ ´¬ )