other species. For most of the year, horn sharks are most common at a depth of . At the onset of winter, they migrate to water deeper than . This species has been found in caves as deep as . Juvenile horn sharks between long prefer sandy flats with low vertical relief, in water deep. They often take advantage of large feeding pits excavated by the bat ray (Myliobatis californica) for shelter and food. As they mature, horn sharks shift into shallower water and their preferred habitat becomes structurally complex rocky reefs or algae beds. This strongly benthic species seldom ventures more than above the substrate. The relative abundances of the horn shark and the swellshark (Centroscyllim ventriosum), which shares the same habitat, are negatively correlated because horn sharks prefer temperatures warmer than while swellsharks are more cold-tolerant. At Santa Catalina Island, a 20-year warming trend has resulted in an increase in the horn shark population and a decrease in the swellshark population. Horn sharks are less common than swellsharks in the northern Channel Islands, where the water is cooler. Biology and ecology The horn shark is a sporadic swimmer that prefers to use its flexible, muscular pectoral fins to push itself along the bottom. It is usually solitary, though small groups have been recorded. During the day, horn sharks rest motionless, hidden inside caves or crevices, or within thick mats of algae, though they remain relatively alert and will swim away quickly if disturbed. After dusk, they roam actively above the reef in search of food. Horn sharks maintain small home ranges of around , which they may remain faithful to for over a decade, returning to the same shelter every day. The shelter is usually located at the edge of the resident shark's foraging area. The longest documented movement for an individual horn shark is . The daily activity pattern of the horn shark is under exogenous control, meaning that it is regulated by environmental factors rather than by an internal physiological cycle. Observations of captive horn sharks show that the relevant cue is light intensity: the sharks become active immediately after the lights are turned off, and stop as soon as they are turned back on. In one experiment where the sharks were kept in darkness, they remained continuously active for 11 days before slowing, possibly from fatigue. In nature, horn sharks exposed to a bright light