The tortoise is not attacking, he’s attempting to breed. Male tortoises have a high sex drive. In the wild, they encounter females so infrequently, that they usually try to breed anything that does not try to eat them or does not run away. Imagine a captive male that has never seen a female, that is tame and has never known an attack by any animal. The open mouth gesture that you see in one shot, is common when a male tortoise vocalizes while courting. But what does any of this have to do with draft animals?