Alex Hyde / Southern Elephant Seal bull (Mirounga leonina) close up portrait, King Haakon Bay, South Georgia. November.

Ingo Arndt / Antarctic Fur Seal (Arctocephalus gazella) bull on land, Stromness Bay, South Georgia Island, Southern Ocean, Antarctic Convergence, November 2008

Wim van den Heever / South African fur seal (Arctocephalus pusillus pusillus) bull breaking apart octopus. False Bay, Cape Town, South Africa.

Steven Kazlowski / Killer WHale / Orca (Orcinus orca) bull and cow in Resurrection Bay, Kenai Fjords National Park, outside Seward, Alaska, May.

Michael Pitts / Bull Elephant seal (Mirounga sp) portrait with penguin walking along beach, St Andrews Bay, South Georgia

Yva Momatiuk & John Eastcott / Pacific Walrus (Odobenus rosmarus divergens) bull portrait on coastal rocks in haul-out cove, summer, Round Island, Bering Sea, Bristol Bay, Alaska

Peter Bassett / Aggressive bull elephant seal and penguins on beach at St Andrews Bay, South Georgia

Heather Angel / Southern magnolia / Bull bay (Magnolia grandiflora) flower. The opening and closing of petals controls the time beetle pollinators enter and leave the flower. Cultivated in garden, Surrey, England, UK...

Alex Hyde / Southern Elephant Seal bull (Mirounga leonina). This dominant bull or 'Beachmaster' fights off rival males to keep his harem of females. King Haakon Bay, South Georgia. November.

Alex Hyde / Front flipper of Southern Elephant Seal bull (Mirounga leonina) showing the five nails and webbing between each digit. King Haakon Bay, South Georgia. November.

Alex Hyde / Southern Elephant Seal bull (Mirounga leonina) swimming. King Haakon Bay, South Georgia. November.

Alex Hyde / Southern Elephant Seal bull (Mirounga leonina) challenging a rival male. King Haakon Bay, South Georgia. November.