Horn Shark

The Horn Shark (Heterodontus francisci) is a small, slow-moving bottom-dwelling shark in the family Heterodontidae, named for the prominent spines preceding each dorsal fin. It is found along the eastern Pacific coast from central California to the Gulf of California. Despite its blunt, pig-like head and heavy brow ridges, it is harmless to humans and spends daylight hours resting in rocky crevices or kelp holdfasts. It is one of the most frequently encountered sharks by divers in Southern California. Populations are considered stable, and it holds little commercial significance, making it a low-conservation-concern species notable mainly for its distinctive spiral egg cases and unusual dentition combining sharp front teeth with flattened, crushing rear teeth.

Key field marks:

• Blunt, pig-like snout with heavy ridges above each eye
• Two high dorsal fins, each preceded by a stout spine
• Body brownish-gray with scattered dark spots or blotches
• Small size, rarely exceeding 1.2 m
• Anal fin present, unlike spine-bearing dogfish sharks which lack one

Its spiral, corkscrew-shaped egg cases wedged into rock crevices are a distinctive sign of the species' presence, useful for confirming identification even without seeing the shark itself.

Found in temperate to subtropical coastal waters of the northeastern Pacific, from Monterey Bay, California to the Gulf of California, Mexico. Inhabits rocky reefs, kelp forests, and sandy areas adjacent to reefs from the intertidal zone down to about 150 m, though most common in shallower water under 30 m. Prefers crevices, caves, and dense kelp holdfasts for daytime shelter, and tolerates the moderate temperature range typical of the California Current system.

Horn sharks are nocturnal, resting motionless in rocky crevices or under ledges by day and emerging at night to forage on the bottom. They use powerful jaw muscles and flattened rear teeth to crush hard-shelled prey such as sea urchins, crabs, and mollusks, while sharper front teeth grip softer prey. They are solitary and site-faithful, often returning to the same shelter repeatedly. Reproduction is oviparous; females lay distinctive spiral-flanged egg cases, wedging them into rock crevices to prevent predation, with hatching occurring after several months.