Look at the overall picture. Cherry Plum can help when terror leads to aggression. Though this is most commonly experienced by cats, any animal who displays this behavior can be helped by Water Violet. Cats are especially place-conscious and extremely aware of new smells and sensations, but Beech can be helpful to any animal who is reacting negatively to a new environment or household member. Walnut, which is for transitions, is recommended for any kind of change.
Olive can help in cases of physical exhaustion.
Crab Apple can be helpful, and can also accelerate healing. If the fear escalates to terror Rock Rose can be valuable. Aspen is helpful for unknown fears. What this means in terms of animals is often fears which they are picking up from others. If you are having a fearful time your animal will pick absorb and express this.