What animal lives in solitary only?

It's difficult to say definitively which animal lives *only* in solitary. Many animals have solitary phases in their lives, but some are considered mostly solitary. Here are some examples:

Mammals:

* Tigers: While they occasionally interact, they are primarily solitary animals, especially females.

* Leopards: Similar to tigers, leopards are largely solitary, especially outside of mating season.

* Mountain lions: These big cats are very solitary, except when mothers are raising cubs.

* Badgers: Badgers live in burrows, but they are solitary and don't typically interact outside of breeding season.

Birds:

* Owls: Many owl species are solitary, especially during nesting season.

* Hawks: Many hawk species are solitary hunters.

* Herons: Herons are solitary birds except during mating season.

Reptiles:

* Snakes: Many snake species are solitary, except during mating season.

* Lizards: Some lizard species, like the Gila Monster, are solitary.

Fish:

* Sharks: While some sharks live in small groups, many species are solitary.

Insects:

* Praying mantis: These insects are solitary and often cannibalistic.

Keep in mind:

* Even animals considered solitary often interact with others for specific reasons, like breeding, raising young, or defending territory.

* There are many exceptions to these generalizations, and the social structure of any species can vary depending on location, resources, and other factors.

To get a better understanding of any specific animal's social habits, it's best to research their specific species and behavior.