Mine is 142 days today, first pregnancy. There is movement in both sides. And it is violent. I am telling you some days it looks like they're trying to rip out her back, it is unbelievable how much they jerk around in there. Seems different times of the day they are completely still, can look for 10 minutes straight and not see anything, other times only one of the sides is moving, other times both sides have steady movement for like an hour. Since I'd say 100-110 days it is unmistakable, i swear sometime I see the tails trailing, maybe I'm crazy. I don't think there is 1 day I don't see it.