Shouldn't it be easy to attach a sensor at the belly of the turtle that alarms staff when it happens. Sounds like an actual no-brainer use for modern technology.
That would probably really piss the tortoise off. Imagine if your ass was made out of bone, and someone glued a lego to it. Sitting down would be a nightmare.
I raised market-sheep when I was younger and during breeding the ram wears a harness with colored chalk on the underside. You then have visual cues for which ewes are likely to become pregnant.