The horn shark is a small, common, bottom-dweller in the warm waters off western North America. It belongs to the bullhead shark family (Heterodontidae). Its name comes from its short, blunt head with high ridges above the eyes. It has large spines on its two high dorsal fins, and many small dark spots on brownish gray skin. Most adults measure about 1 m, and the maximum length of this species is 1.2 m (3.3 ft).
Horn sharks have a small home range, usually no larger than 1,000 m². They like to stay put in the same general area, remaining there year after year. The longest distance a horn shark is known to have traveled is 16.3 km (10 miles)!
Environmental light levels control their daily activity, with horn sharks being most active at night. And they definitely don’t like the cold: their abundance is linked to water temperature, preferably over 21°C (70°F).
Horn sharks can end up with purple stained teeth from eating so many sea urchins!
Habitat and Range
The horn shark is native to the Pacific coast of North America, off California Mexico, and possibly Ecuador and Peru. It likes to stay at the sea bottom in shallow waters, mostly from 2 to 11 m (6.5 to 35 ft), moving to deeper waters in winter.
The habitat of these sluggish fish depends on their age. Young sharks prefer deeper sandy flats, and as they mature they migrate back to relatively shallow water. As adults they prefer shallower areas with plenty of hiding places, such as rocky reefs or beds of thick algae.
This difference means there is less competition for food and habitat between younger and older sharks. But you may wonder how the young sharks hide are able to hide in such flat areas – well, they use feeding pits made by rays (another type of cartilaginous fish) for shelter and hunting areas.
Horn sharks are slow predators who typically hunt alone, at night. Then they spend the days inside a shelter that they use again and again.
The diet of adult sharks is made up of mainly hard-shelled molluscs (like clams and snails), crustaceans (like crabs and shrimp), star fish, and sea urchins. Other prey includes octopus and squid, some smaller invertebrates, and bony fish. Crushing all those shells requires a powerful bite: this fish has the highest known bite force relative to its size of any shark. Young sharks prefer softer prey like worms, small clams, and sea anemones.
These sharks have two types of teeth (hence the Latin genus name Heterodontus, meaning “different teeth”). The small front teeth have a hook, and they are for grabbing prey. The larger side teeth are more like molars, and they are for grinding.
Horn sharks are typically solitary creatures. Sharks and other large fish are their predators.
Horn shark mating happens in December and January. A few weeks later, the female will deposit her fertilized eggs. Females lay two eggs, every 11 to 14 days from about February to April, laying up to 24 eggs in a single breeding season. The cone-shaped egg cases are usually laid in shallow water. Females then wedge the cases into crevices as protection from predators.
Embryos take 6 to 10 months to develop, depending on temperature. The newly hatched sharks are 15 to 17 cm (6 to 7″) long, and they begin to feed about a month later. Aging and growth rates of this species are not well known. Growth is thought to be generally slow.
Humans and Conservation
Horn sharks pose no threat to humans if left alone, but may bite when bothered by divers. They are a hardy species that can survive capture if returned to the water, and they will breed in captivity – they are kept in many public aquaria in the United States.
They have no commercial value and so are not a target of fisheries. Small numbers are caught accidentally and usually discarded, but they may be used. For example in Mexico this species is used for food and fishmeal when caught as a “Bycatch” of fish-trawling. In California the larger horn shark spines are made into jewelry. The International Union for Conservation of Nature (IUCN) does not have enough information to determine the conservation status of this species, so it has no special conservation status.
However, lower horn shark numbers have been observed in popular diving areas in Southern California.
Page Created By: Mike Rogers