[1][2] The first evidence of the sharks in the western tropical Pacific emerged from a National Geographic video taken near the Solomon Islands in 2015.

They are also known to feed on bottom-dwelling teleost fishes, as well as soles, flounders, Alaska pollock, rockfishes, shrimps, hermit crabs, and even marine snails.

A recent study in the Gulf of Alaska suggests that sleeper sharks may prey on juvenile Steller sea lions.

They are believed to produce eggs that hatch inside the female's body (reproduction is ovoviviparous), but gestation time is unknown and litter sizes are thought to be about 10 pups.

[2][9] In 1989, an enormous Pacific sleeper shark was attracted to a bait in deep water outside Tokyo Bay, Japan, and filmed.

[8] A single unconfirmed account exists of an enormous Pacific sleeper shark that potentially measured more than 9.2 m (30 ft) long.

Due to living in frigid depths, the sleeper shark's liver oil does not contain squalene, which would solidify into a dense, nonbuoyant mass.