It makes the animal characters function like people in animal suits. Unfortunately in most movies this is the norm, Lets look at an example from earlier Disney animation. The jungle book, Baloo's charm and persona was very human, and as in many of the Disney movies animators used the actors voice to sculpt the character.
Logical motives suffer when the people in suits theory rears it's head.
No instinctive reason would make them take care of Mowgli, the wolves acceptance of him was suspicion but could be waived for simplicity sake. I will get into their possible justification next. Even though the apes are far more animal than the Jungle book cast they still are blessed with the powers of speech. Now we can examine the decisions of her life from an animals vantage point. The next assumed action is the slaying of Tarzan's parents with an intent to devour young Tarzan, more than likely Sabor heard Tarzan cry or scream and went to investigate, waiting till his parents left, he moved in for the kill, unfortunately one or both of Tarzan's parents returned before Sabor could make the final pounce on young Tarzan, and struggled against the leopard, calling the other parent if not already present.