Black mark around tortoise month

[Gijoux]

I believe rabbits also recycle their poop for maximum nutrition.
Not as revolting as dogs who not only eat their own poop but that from any other animals too.

Both rabbits and tortoises are hind gut fermenter. Lots of good bacteria in their poop. You might try sprinkling NutriBAC for Reptiles & Amphibians, on your greens to increase the good bacteria so the tort doesn't have to eat their poop.