Male elk bugling during the fall rut. Large male elk are known as bulls. Male elk have large antlers which are shed each year. Male elk engage in competitive mating behaviors during the rut, including posturing, antler wrestling and bugling, a loud series of screams which is intended to establish dominance over other males and attract females.
Species: Elk, Cervus canadensis
Location: Madison River, Yellowstone National Park, Wyoming
Image ID: 19700
Bull elk in sage brush with large rack of antlers during the fall rut (mating season). This bull elk has sparred with other bulls to establish his harem of females with which he hopes to mate.
Species: Elk, Cervus canadensis
Location: Mammoth Hot Springs, Yellowstone National Park, Wyoming
Image ID: 19718
A great white shark bearing a white plastic researcher's identification ID tag near its dorsal fin swims through the clear waters of Isla Guadalupe, far offshore of the Pacific Coast of Baja California. Guadalupe Island is host to a concentration of large great white sharks, which visit the island to feed on pinnipeds and tuna.
Species: Great white shark, Carcharodon carcharias
Location: Guadalupe Island (Isla Guadalupe), Baja California, Mexico
Image ID: 07739
Male elephant seals (bulls) rear up on their foreflippers and fight for territory and harems of females. Bull elephant seals will haul out and fight from December through March, nearly fasting the entire time as they maintain their territory and harem. They bite and tear at each other on the neck and shoulders, drawing blood and creating scars on the tough hides. Sandy beach rookery, winter, Central California.
Species: Elephant seal, Mirounga angustirostris
Location: Piedras Blancas, San Simeon, California
Image ID: 15394
Scalloped hammerhead shark swims underwater at Cocos Island. The hammerheads eyes and other sensor organs are placed far apart on its wide head to give the shark greater ability to sense the location of prey.
Species: Scalloped hammerhead shark, Sphyrna lewini
Location: Cocos Island, Costa Rica
Image ID: 03192
A bull elephant seal forceably mates (copulates) with a much smaller female, often biting her into submission and using his weight to keep her from fleeing. Males may up to 5000 lbs, triple the size of females. Sandy beach rookery, winter, Central California.
Species: Elephant seal, Mirounga angustirostris
Location: Piedras Blancas, San Simeon, California
Image ID: 35133
Tiger shark close up view, including nictating membrane covering the eye, nostrils and ampullae of Lorenzini.
Species: Tiger shark, Galeocerdo cuvier
Location: Bahamas
Image ID: 31925
A great white shark is countershaded, with a dark gray dorsal color and light gray to white underside, making it more difficult for the shark's prey to see it as approaches from above or below in the water column. The particular undulations of the countershading line along its side, where gray meets white, is unique to each shark and helps researchers to identify individual sharks in capture-recapture studies. Guadalupe Island is host to a relatively large population of great white sharks who, through a history of video and photographs showing their countershading lines, are the subject of an ongoing study of shark behaviour, migration and population size.
Species: Great white shark, Carcharodon carcharias
Location: Guadalupe Island (Isla Guadalupe), Baja California, Mexico
Image ID: 19468