we used to have a tortoise in my parent's backyard for 10 years (before someone stole it)
it was such a cool animal, it would completely disappear during winter and reappear in spring walking across the patio and stuff. even with the dog laying there.
they both got real used to each other (initially the tortoise was scared of the dog and never moved while the dog engaged it and barked at it constantly) and the tortoise would walk right in front of the dog who did not care at all.
those tortoises have tremendously strong jaws and teeth, dang, i got bit by it once feeding it strawberries and he pierced my finger.