Service animal Service animals can be of many species and come in many sizes. Dogs, cats, dolphins, miniature horses, monkeys, ducks, ferrets, and parrots have all been trained to perform specific duties of a service animal, though the type of animal that may be registered as a "service animal" may vary depending on legal definitions. The people that can qualify for a service animal can have a range of physical and/or mental disabilities. A "guide animal" is an animal specifically trained to assist visually impaired persons to navigate in public. These animals may be trained to open doors, recognize traffic signals, guide
Animal communication teaching these animals a gestural (human made) American Sign Language-like language, the animals have been found to use the new signs on their own to get what they need. The recent experiments on animal language are perhaps the most sophisticated attempt yet to establish human/animal communication, though their relation to natural animal communication is uncertain. The importance of communication is evident from the highly elaborate morphology, behaviour and physiology that some animals have evolved to facilitate this. These include some of the most striking structures in the animal kingdom, such as the peacock's tail, the antlers of a stag and