Lurkers were a non-sentient amphibian species found primarily on the planet Belsavis

Belsavis Planet

. They were carrion eaters that preferred to live in tropical environments. They never got too near to settlements or to anything that could be a threat for a single specimen, in fact, they usually traveled and hunted in packs, striking with amazing ferocity, downing their preys for later consumption.
It was believed by biologists serving the Hutt Cartel

Hutt Cartel Organization Galaxy-Wide Organizations

that lurkers originated on an unnamed jungle world on the edges of the Torch Nebula. They were first spotted in the galaxy on Belsavis, about two hundred years before the Cold War, and then they began appearing on more and more worlds. These creatures' existence left a great mystery, since no convincing explanation was given for their wide spread.
A massive lurker known as Subject Alpha roamed the shallow waters of Lake Brell the Brell Sediment near the ruins of the Fellwater Labs on the planet Taris

Taris Planet

, during the Republic

Galactic Republic Organization Galaxy-Wide Organizations

's initiative to resettle

Taris Resettlement Initiative Event Cold War (3653BBY - 3642BBY)

the planet.