The way i see it, with tactics involving trapping of an animal. The animal should not limit itself to going after the target that aggrod it alone, but instead if it is already aggresive, it should aggro onto other hearthlings that come close too. This would prevent them from blocking the animal with logs/boats/their body. An animal that gets cornered is one that generaly should be watched out for, predator or not, and this might mean that it lashes out at anyone around it. So it's a matter of more aggroing or changing targets really that can stop non aggrod targets from just walking up to them.
The AOE attacks that have been suggested to counter alt ganking seem perfect for stopping them against bears, and from what i've noticed mammoths already have these.