As a veterinarian, which animals are hard to treat?

In the world of veterinary medicine, some animals pose more of a challenge than others. Exotic pets like reptiles and birds often require specialized knowledge and care, making them a tough group to treat. Also, larger animals like horses can be difficult due to their size and unique physiology. Wildlife animals can be particularly hard due to their natural fear of humans and unfamiliarity with captivity. Regardless, every animal, big or small, tame or wild, brings its own set of challenges and rewards in treatment.