Any animal. Horses, dogs, cats, dolphins, wild animals, mice, etc.
I've noticed many people say they are good dog trainers or have a lot of horse sense, but I see something else in their training that makes me think otherwise. Myself, I adopted one of the most unwieldy, obnoxious dogs that I saw at the animal shelter, and trained her to be a therapy dog. This Border Collie/Pit Bull mix was not aggressive, but would jump on people constantly, mouth too hard, jump on tables and eat what she wanted, chew up things, bark and whine nearly constantly, and so on. She was almost ready to be euthanized probably because no one wanted a dog like that. Because of this and my past successes, I consider myself to have a talent for working with and training dogs.
Some people think that being kind, showing lots of love, feeding them, and taking them to a vet in a timely manner is having a talent for animals, but these reasons alone do not mean a person does have a true talent with an animal.
A talent could include competent training (obedience, tracking, flyball, etc.), competently diagnosing health problems, quality breeding, a strong empathy and understanding of the animal, etc. What is your special talent, if any?