horn shark horn shark species shark family endemic coastal waters western coast north_america california young sharks segregated adults preferring deeper sandy flats preferring shallower rocky reefs beds small species typically measuring length horn shark recognized short blunt head ridges eyes high dorsal fins large spines brown gray coloration small dark spots slow moving generally solitary predators horn sharks hunt night inside small home ranges retreat favored shelter day daily activity cycles controlled environmental light levels adult sharks prey mainly hard shelled crustaceans crush powerful jaws like teeth feeding wide variety invertebrates small bony fishes juveniles prefer softer bodied prey worms sea shark extracts prey substrate necessary motions body reproduction females laying eggs february april laying female picks shaped egg cases protect predators horn sharks harmless harassed readily maintained captivity targeted commercial recreational fisheries small numbers caught mexico species food california spines jewelry information determine horn shark conservation status faces threats coast united_states taxonomy french biologist published scientific description horn shark proceedings species later placed genus eventually genus specific epithet reference san_francisco range horn shark extend far north type specimen bay lost scientific species given erroneously description like sharks horn shark short wide head blunt snout prominent ridges eyes horn shark ridges low terminate abruptly space head deeply concave eye lacks membrane followed tiny nostrils split outflow openings long reaches mouth openings encircled groove groove connects outflow openings mouth mouth small curved prominent furrows corners tooth rows upper jaw tooth rows lower jaw teeth jaws small pointed central flanked pair lateral sides jaws larger elongated like body cylindrical high somewhat shaped dorsal fins bearing stout spines fin spines reef dwelling horn sharks shorter living habitats spines worn rocks sharks movements dorsal fin originates bases large pectoral fins second dorsal fin originates slightly anterior free rear tips pelvic fins caudal fin short lower lobe long broad upper lobe strong notch near tip horn shark dermal denticles small smooth numbering cm2 adults dorsal coloration consists shades gray brown small dark spots absent older sharks underside yellowish dark patch small spots eye species reach length individuals exceed distribution habitat horn shark inhabits continental shelf occurring coasts california baja california southward uncommon warm water northward bring far unconfirmed reports species ecuador peru species year horn sharks common depth onset winter migrate water deeper species found caves deep juvenile horn sharks long prefer sandy flats low vertical relief water deep advantage large feeding pits excavated bat ray shelter food mature horn sharks shift shallower water preferred habitat structurally complex rocky reefs algae beds strongly benthic species seldom ventures substrate relative horn shark shares habitat negatively horn sharks prefer temperatures warmer cold tolerant year warming trend resulted increase horn shark population decrease population horn sharks common northern water cooler biology ecology horn shark clumsy sporadic swimmer prefers use flexible muscular pectoral fins push usually solitary small groups recorded day horn sharks rest hidden inside caves thick algae remain relatively alert swim away quickly disturbed dusk actively reef search food horn sharks maintain small home ranges remain faithful decade returning shelter day shelter usually located edge resident shark foraging area longest documented movement individual horn shark unlike fishes daily activity pattern horn shark control meaning regulated environmental factors internal cycle observations captive horn sharks relevant cue light intensity sharks active immediately lights turned stop soon turned experiment sharks kept darkness remained continuously active days slowing possibly fatigue nature horn sharks exposed bright light night stop swimming sink horn shark preyed larger fishes northern elephant seal adults juveniles egg cases addition captured eaten bald eagles large marine able drill egg cases extract yolk tough skin spines species protection filmed juvenile horn shark spit spines known parasites species include spends stage inside potential prey sea feeding adult horn shark diet consists hard shelled sea crustaceans crabs shrimp crack shells horn shark generates highest known bite force relative size shark excess measured species shark study found average bite force species wild maximum experimental conditions sharks induced bite force large horn sharks feed mainly sea particularly short purple teeth fin spines stained purple prey items adults include worms sea stars cephalopods small bony fishes juveniles feed primarily worms sea small known bite retracted southern california horn sharks known advantage seasonal opportunities summer active fishes particular especially abundant easily captured night lie dormant winter sharks market squid die tens thousands mass spawning event horn sharks hunt mainly sense smell certainly plays role locating prey species fewer sharks like sharks horn shark teeth regularly replaced takes weeks dropped tooth replaced horn shark captures prey created expanding cavity modified mouth form tube force prey drawn mouth secured sharp teeth ground pieces flat lateral teeth extract buried prey horn shark adopts vertical posture head pectoral fins substrate tail arched shark acts pectoral fins downward stroke tail forces head upwards pulls prey loose mode feeding observed shark horn shark capable protruding upper jaw length head motion takes accomplish allows shark use upper jaw like firmly attached prey life history mating horn shark occurs december january possibly annual reproductive cycle male chases female indicate interest ready sharks settle male female pectoral fin teeth minutes pair female spins snout sand minutes february april females lay maximum eggs time days water deep egg case female hours deposit case soft light brown days color including case measures long wide sharks produce longer egg cases mainland california suggesting separate populations sharks exhibit parental care female horn sharks wild pick eggs mouths wedge captivity eggs simply dropped later eggs hatch months emergence young measure long newly hatched sharks internal yolk sac feed month old capable feeding accept food period horn sharks grow slowly highly variable rate correspond size frustrated attempts determine aging process males mature length females length individual sharks lived years old captivity exists unconfirmed report shark reaching years age human interactions normal circumstances horn sharks harmless humans readily approached underwater provoked biting individuals known chase bite divers harassed sharks handled care fin spines inflict painful wound horn shark captivity maintained bred public united_states horn shark commercial value california captured unintentionally traps recreational shark ensures returned water alive species benefits general restrictions placed coastal fishing gear average annual california historically varied divers kill sport jewelry fin spines cause decline numbers horn sharks intensely areas southern california mexico species caught incidentally shrimp human consumption expansion mexican fisheries pose conservation concern future present sufficient information assess overall conservation status species status united_states waters likely concern
Horn shark