Heterodontus francisci
FAMILY
Heterodontidae
TAXONOMY
Cestracion francisci Girard, 1854, California (Monterey Bay).
OTHER COMMON NAMES
English: Bullhead shark, horn shark; Spanish: Dormilón cornudo.
PHYSICAL CHARACTERISTICS
Background gray or light brown with smaller darker brown spots (smaller than eyes) scattered over body, head, fins, and tail. The young have more intense coloration, sometimes with darker bands in between eyes and on fins. The supraorbital ridges are moderately high; finspines relatively tall, but dorsal fins are not as tall as in H. zebra and H. japonicus.
DISTRIBUTION
California bullhead sharks occur off central and southern California and Mexico (Baja California and Gulf of California), extending south possibly to Ecuador and Peru. During warm water influxes, they may reach as far north as San Francisco Bay.
HABITAT
These sharks commonly inhabit from 6.6 to 33 ft (2–10 m), even though they can be found from the intertidal zone down to about 490 ft (150 m). Juveniles are usually in shallower waters, over sandy surfaces. These fishes occur on rocky and sandy bottoms, kelp forests, and in caves and crevices.
BEHAVIOR
These sharks are nocturnal, sluggish, and mostly solitary, preferring the protection of caves and shelters during the day, and
hunting mostly at night. They can remain in a relatively small home range for much of the summer, moving into deeper waters in the winter, at least in some regions. Experiments demonstrate that their diel (24 hours, including one day and night) activity patterns appear to be regulated by light.
FEEDING ECOLOGY AND DIET
California bullhead sharks eat many different invertebrates, including sea urchins, crabs, shrimp, isopods, octopuses, anemones, bivalves, gastropods, polychaetes, and occasionally fishes (at least pipefishes [Syngnathidae] and blacksmiths [Pomacentridae]). Specimens have been filmed devouring purple-colored urchins, turning their teeth and spines into a strong shade of purple. Recently born pups take about one month to begin feeding. Adults in aquaria have been observed consuming their own egg cases.
REPRODUCTIVE BIOLOGY
The mating ritual of California bullhead sharks has been observed in captivity, particularly at the Steinhart Aquarium in San Francisco. Males pursue larger females until obtaining consent, and mating occurs on the bottom of the tank. The male grasps the female's pectoral fin with his teeth, and subsequently one clasper is inserted into the female after coiling around her. Copulation may last between 30 to 40 minutes, and in captivity the eggs are expelled one or two weeks later. In the wild, eggs can be expelled even after one to three months of copulation, as females can produce eggs for extended periods, and sperm is stored and utilized in stages. The young develop for between seven and nine months before hatching.
CONSERVATION STATUS
A decrease in numbers of individuals has been noticed in regions of southern California where there is substantial diving activity, but the species is not listed by the IUCN as Threatened.
SIGNIFICANCE TO HUMANS
These sharks are very common in public aquaria, where mating, egg-laying, and hatching have been observed. In the wild, they are not considered a threat to humans. However, despite their apparent calm demeanor, H. francisci have been known to infrequently swim after and bite divers after being harassed by them.
