The Ocampa are a humanoid species native to the planet Ocampa V, located in the Delta Quadrant. They resembled humans except for a few folds of skin around their ears. They are born without them, which grow when the infants grow older. The Ocampa have a capacity for great mental skills and telepathy, but their lives on the planet means that these mental powers go unused. Strangely for a humanoid species, their natural life-spans are only around nine years.
In the 14th century, the Ocampa first moved to a subterranean city created by the Nacene after they accidentally removed all nucleogenic particles from the planets atmosphere. For the next 1,000 years the Ocampa were provided for by the Caretaker, who provided power to the city from his array. However, this support ended in 2371 when the Caretaker died, leaving enough energy to support them until 2376. (VOY episode: "Caretaker")
The female Nacene, known as Suspiria, left the Ocampa system in 2072, and took a group of Ocampa with her. She helped these Ocampa extend their lifespans - some living as long as two decades. Suspiria also helped this group develop their mental abilities. (VOY episode: "Cold Fire")
No formal relations existed between the Ocampa and the United Federation of Planets, however, following the USS Voyager's return to Earth in 2377, Starfleet became aware of their existence. In fact, some in Starfleet considered the advantages of utilizing the Ocampa as a possible emergency pool of personnel as the short Ocampan lifespan made them fast learners. (Decipher RPG module: Worlds)