An elephant has great mass , thus it also has very high inertia, which we know is the resistance toacceleration. Acceleration can also be a change in direction of motion as it is equal to change in velocity/time taken, where velocity is a vector. So when an elephant has to change direction it will have to accelerate and as it has high inertia, this acceleration would require a lot of force, which either the elephant would not be able to supply , or would be able to supple but it would get tired faster and lose interest in chasing you. or Inertia.. the heavier an object, the more inertia it has. and what i mean by inertia is the reluctance to change direction during motion, so it's tough for elephant to change its direction to chase after you given it's really heavy mass