Mark Carwardine / California sealions (Zalophus californianus), one in water with other sitting on rock, Baja California, Sea of Cortez (Gulf of California), Mexico

Suzi Eszterhas / California Sea Lion (Zalophus californianus) mother and pup, Monterey Bay, California, USA, April

Alex Mustard / A young California sealion (Zalophus californianus) swims in a shallow pool. Los Isotes, La Paz, Mexico. Sea of Cortez, East Pacific Ocean.

Alex Mustard / A split level view of a bull California sealion (Zalophus californianus) swimming beneath Los Islotes sealion colony. La Paz, Mexico. Sea of Cortez, East Pacific Ocean.

Alex Mustard / A young California sealion (Zalophus californianus) portrait, inside an underwater cave. Los Isotes, La Paz, Mexico. Sea of Cortez, East Pacific Ocean.

Alex Mustard / A young California sealion (Zalophus californianus) playing with a starfish, inside an underwater cave. The pups will pick up a variety of objects (such as starfish, lumps of coral, shells and feather...

Alex Mustard / A young California sealion (Zalophus californianus) playing with a starfish, inside an underwater cave. The pups will pick up a variety of objects (such as starfish, lumps of coral, shells and feather...

Alex Mustard / A bull California sealion (Zalophus californianus) bursting through a school of baitfish in the shallows. Los Isotes, La Paz, Mexico. Sea of Cortez, East Pacific Ocean.

Alex Mustard / A young California sealion (Zalophus californianus) head portrait, Los Isotes, La Paz, Mexico. Sea of Cortez, East Pacific Ocean.

Alex Mustard / A silhouette of a California sealion pup (Zalophus californianus) next to cliffs. Los Isotes, La Paz, Mexico. Sea of Cortez, East Pacific Ocean.

Alex Mustard / A silhouette of a young California sealion (Zalophus californianus) swimming just below the surface, close to shore. Los Isotes, La Paz, Mexico. Sea of Cortez, East Pacific Ocean.

Alex Mustard / An adult California sealion (Zalophus californianus) makes a sharp turn at high speed. Los Islotes, La Paz, Baja California, Mexico. Sea of Cortez, East Pacific Ocean.

Alex Mustard / California sea lion pup (Zalophus californianus) portrait in a rocky underwater cave. La Paz, Baja California Mexico. Sea of Cortez, East Pacific Ocean. October

Alex Mustard / An adult female California sea lion (Zalophus californianus) head portrait, in a rocky underwater cave. La Paz, Baja California Mexico. Sea of Cortez, East Pacific Ocean. October

Doc White / Californian sealion (Zalophus californianus) amongst kelp, Eastern pacific

Alex Mustard / Split level of female California sea lions (Zalophus californianus) basking in the sun on the surface. La Paz, Baja California Mexico. Sea of Cortez, East Pacific Ocean. October

Jeff Rotman / Large group of Californian sealions (Zalophus californianus) swimming underwater, Anacapa Island, California, Pacific Ocean

Jeff Rotman / Free diver swimming amongst Californian sealions (Zalophus californianus) Anacapa Island, California, Pacific Ocean Model released

Tim Laman / Californian sealions (Zalophus californianus), one with fishing wire caught round its neck. Monterey Bay, California.

Peter Scoones / Californian sealions swimming underwater {Zalophus californianus} Baja, Mexico.

Georgette Douwma / Galapagos sealion underwater (Zalophus californianus wollebacki)

Pete Oxford / Galapagos sealion (Zalophua californianus). Galapagos Islands, Ecuador

Mark Carwardine / Californian sea lion (Zalophus californianus) at sea surface, Baja California, Sea of Cortez (Gulf of California), Mexico

Mark Carwardine / Great white shark (Carcharodon carcharias) and Californian sealion (Zalophus californianus) Guadalupe Island, Mexico (North Pacific)

Mark Carwardine / Californian sealion on rock {Zalophus californianus} Baja California, Mexico

Mark Carwardine / Californian sealions in water {Zalophus californianus} Baja California, Mexico

Mark Carwardine / Californian sealions in water {Zalophus californianus} Baja California, Mexico

Mark Carwardine / California Sea Lions (Zalophus californianus) playing underwater as a snorkeller looks on. Sea of Cortez, Baja California, Mexico.

Brent Stephenson / California Sea Lions (Zalophus californianus) sleeping on rocks at the waters edge. Los Islotes, Baja California, Mexico, September.

Matthew Maran / California Sea Lion (Zalophus californianus) barking at the water surface. Barkley Sound, Vancouver Island, Canada, September.

Matthew Maran / California Sea Lions (Zalophus californianus) fighting in shallow waters. Barkley Sound, Vancouver Island, Canada, September.

Matthew Maran / A group of California Sea Lion (Zalophus californianus) raising their heads and barking. Barkley Sound, Vancouver Island, Canada, September.

Alex Mustard / Two young California sealions (Zalophus californianus) swimming in a shallow pool. Los Isotes, La Paz, Mexico. Sea of Cortez, East Pacific Ocean.

Alex Mustard / A young California sealion (Zalophus californianus) swims in a shallow pool. Los Isotes, La Paz, Mexico. Sea of Cortez, East Pacific Ocean.

Alex Mustard / A pair of shy young California sealions (Zalophus californianus) peer out from against a colourful, coral encrusted wall, inside an underwater cave. Los Isotes, La Paz, Mexico. Sea of Cortez, East Pac...

Alex Mustard / A young California sealion (Zalophus californianus) playing with a starfish, inside an underwater cave. The pups will pick up a variety of objects (such as starfish, lumps of coral, shells and feather...

Alex Mustard / A young California sealion (Zalophus californianus) playing with a starfish, inside an underwater cave. The pups will pick up a variety of objects (such as starfish, lumps of coral, shells and feather...

Alex Mustard / A young California sealion (Zalophus californianus) playing with a starfish, inside an underwater cave. The pups will pick up a variety of objects (such as starfish, lumps of coral, shells and feather...

Alex Mustard / A large bull California sealion (Zalophus californianus) patrolling his territory, blowing bubbles as he marks the boundary by vocalising. Los Islotes, La Paz, Baja California, Mexico. Sea Of Cortez,...

Alex Mustard / A young California sealion (Zalophus californianus) uses a starfish as a toy. The playful pups pick up a variety of objects as toys, including starfish, shells, and feathers, often dropping them and c...

Alex Mustard / A silhouette of a young California sealion (Zalophus californianus) swimming just below the surface, close to shore. Los Isotes, La Paz, Mexico. Sea of Cortez, East Pacific Ocean.

Alex Mustard / A young California sealion (Zalophus californianus) playing with a shell (white object in its mouth) in a shallow pool. Los Isotes, La Paz, Mexico. Sea of Cortez, East Pacific Ocean.

Alex Mustard / A school of baitfish parting as a large bull California sealion (Zalophus californianus) swims through as he patrols his territory. Los Islotes, La Paz, Baja California, Mexico. Sea Of Cortez, East Pa...

Alex Mustard / A portrait of an adult California sealion (Zalophus californianus) near the surface. Los Islotes, La Paz, Baja California, Mexico. Sea of Cortez, East Pacific Ocean.

Alex Mustard / An adult California sealion (Zalophus californianus) dives down from the surface on its back after taking a breath of air. Los Islotes, La Paz, Baja California, Mexico. Sea of Cortez, East Pacific Oce...

Alex Mustard / An adult California sealion (Zalophus californianus) looks down from the surface. Los Islotes, La Paz, Baja California, Mexico. Sea of Cortez, East Pacific Ocean.

Alex Mustard / An adult California sealion (Zalophus californianus) in an acrobatic pose under cliffs. Los Islotes, La Paz, Baja California, Mexico. Sea of Cortez, East Pacific Ocean.

Alex Mustard / A large bull California sealion (Zalophus californianus) patrols his territory, blowing bubbles as he marks the boundary by vocalising. Los Islotes, La Paz, Baja California, Mexico. Sea Of Cortez, Eas...

Alex Mustard / A group of adult female California sealions (Zalophus californianus) bask in the sun at the surface. Los Isotes, La Paz, Mexico. Sea of Cortez, East Pacific Ocean.

Alex Mustard / An adult California sealion (Zalophus californianus) makes a fast pass. Los Isotes, La Paz, Mexico. Sea of Cortez, East Pacific Ocean.

Alex Mustard / A young California sealion (Zalophus californianus) swims in the rocky shallows. Los Isotes, La Paz, Mexico. Sea of Cortez, East Pacific Ocean.

Alex Mustard / California Sea lion (Zalophus californianus) swimming in open water. La Paz, Baja California Mexico. Sea of Cortez, East Pacific Ocean. October

Alex Mustard / California sea lion pup (Zalophus californianus) portrait, in a rocky underwater cave. La Paz, Baja California Mexico. Sea of Cortez, East Pacific Ocean. October

Alex Mustard / A playful California sea lion pup (Zalophus californianus) barking and blowing bubbles. La Paz, Baja California Mexico. Sea of Cortez, East Pacific Ocean. October

Alex Mustard / Californian sealion (Zalophus californianus), Guadalupe Island, Mexico. East Pacific Ocean.

Jeff Rotman / Silhouette of Californian sealion (Zalophus californianus) swimming underwater, Anacapa Island, California, Pacific Ocean

Jeff Rotman / Large group of Californian sealions (Zalophus californianus) swimming and playing underwater, Anacapa Island, California, Pacific Ocean

Jeff Rotman / Californian sealions (Zalophus californianus) group swimming and playing underwater, Anacapa Island, California, Pacific Ocean Model released.

Jeff Rotman / Californian sealions (Zalophus californianus) resting on seabed underwater, Anacapa Island, California, Pacific Ocean Model released.

Jeff Rotman / Terry Maas filming Californian sealion (Zalophus californianus) swimming underwater, Anacapa Island, California, Pacific Ocean Model released Model released.

Jeff Rotman / Terry Maas filming Californian sealion (Zalophus californianus) swimming underwater, Anacapa Island, California, Pacific Ocean Model released Model released.

Jeff Rotman / Silhouette of two free divers swimming beside a Californian sealion (Zalophus californianus) Anacapa Island, California, Pacific Ocean Model released Model released.

John Cancalosi / Californian sealion (Zalophus californianus) head portrait, Oregon, USA

John Cancalosi / Californian sealion (Zalophus californianus) portrait, Oregon, USA

John Cancalosi / Californian sealion (Zalophus californianus) head portrait, Oregon, USA

Claudio Contreras / Californian sealion (Zalophus californianus) at waters edge, Asuncion Island, Vizcaino Biosphere Reserve, Baja California Peninsula, Mexico, March

Claudio Contreras / Californian sea lion (Zalophus californianus) with pup, Asuncion Island, Vizcaino Biosphere Reserve, Baja California Peninsula, Mexico, March

Claudio Contreras / Male Californian sealion (Zalophus californianus) Espiritu Santo Island National Park, Sea of Cortez (Gulf of California) Mexico, February

Claudio Contreras / Male Californian sealion (Zalophus californianus) Espiritu Santo Island National Park, Sea of Cortez (Gulf of California) Mexico, February

Claudio Contreras / Californian sea lions (Zalophus californianus) looking over rock, Espiritu Santo Island National Park, Sea of Cortez (Gulf of California) Mexico, February

Claudio Contreras / Californian sea lions (Zalophus californianus) on rocks, one yawning, Espiritu Santo Island National Park, Sea of Cortez (Gulf of California) Mexico, February

Matthew Maran / Californian sealion (Zalophus californianus) barking, Barkley Sound, Vancouver Island, British Columbia, Canada

Matthew Maran / Californian sealion (Zalophus californianus) tagged for research, Barkley Sound, Vancouver Island, Canada

Matthew Maran / Two Californian sealions (Zalophus californianus) Barkley Sound, Vancouver Island, Canada

Matthew Maran / Californian sealion (Zalophus californianus) in water barking, Barkley Sound, Vancouver Island, Canada

Doug Perrine / California sea lions {Zalophus californianus} feeding on baitball of Sardines / Pilchards {Sardinops sagax} off Baja California, Mexico

Doug Perrine / California sea lions {Zalophus californianus} feeding on baitball of Sardines / Pilchards {Sardinops sagax} off Baja California, Mexico

Tim Laman / Californian sealion (Zalophus californianus) sleeping at sunset. La Jolla, California.

Tim Laman / Californian sealions (Zalophus californianus) sleeping at sunset. La Jolla, California.

Suzi Eszterhas / Staff and volunteers from the Marine Mammal Centre move a crated male Californian sea lion {Zalophus californianus} across the beach prior to release, Rodeo Beach, Fort Crokhite, California, USA

Suzi Eszterhas / Newborn pup resting on top of female Californian sea lion {Zalophus californianus} Channel Islands NP, San Miguel Is, California, USA

Suzi Eszterhas / Female Californian sea lion {Zalophus californianus} giving birth, Channel Islands NP, San Miguel Is, California, USA

Suzi Eszterhas / Female Californian sea lion {Zalophus californianus} giving birth, Channel Islands NP, San Miguel Is, California, USA

Suzi Eszterhas / Satellite tag attached with glue to male Californian sea lion {Zalophus californianus} Marine Mammal Centre, California, USA

Suzi Eszterhas / Marine biologist using glue to attach satellite tag to male Californian sea lion {Zalophus californianus} Marine Mammal Centre, California, USA

Suzi Eszterhas / Female Californian sea lion {Zalophus californianus} carrying young pup up cliff, Channel Islands NP, San Miguel Is, California, USA

Suzi Eszterhas / Staff and volunteers from the Marine Mammal Centre release a male Californian sea lion {Zalophus californianus} with radio tag on Rodeo Beach, Fort Crokhite, California, USA

Suzi Eszterhas / Californian sea lion {Zalophus californianus} undergoes an ultrasound guided cystocentesis at Rehabilitation centre, Marine Mammal Center, California, USA

Suzi Eszterhas / Californian sealion {Zalophus californianus} being tested with an EEG for the effects of domoic acid poisoning on the brain, Marine Mammal Center, California, USA

Suzi Eszterhas / Californian sealions {Zalophus californianus} colony with pups on rocky coast, Little Cove, Channel Islands NP, San Miguel Is, California, USA

Suzi Eszterhas / Californian sealions {Zalophus californianus} colony with pups on beach at Point Bennett, Channel Islands NP, San Miguel Is, California, USA

Matthew Maran / Raft of California sealion {Zalophus californianus} regulating the temperature of their bodies through their flippers, Vancouver Island, BC, Canada

Matthew Maran / California sealion {Zalophus californianus} regulating the temperature of their bodies through their flippers, Vancouver Island, BC, Canada

Matthew Maran / California sealion {Zalophus californianus} portrait, Barkley Sound, Vancouver Island, BC, Canada

Tim Laman / Californian sea lion {Zalophus californianus} exhaling air bubbles, amongst Giant kelp forest, off Santa Barbara, California, USA, July