Each year, up to 200 elephant seals that have been separated from their mothers end up in the Marine Mammal Center, an animal hospital in Sausalito, US. Injured, sick and much too small for their age, most of them wouldn't stand a chance of surviving without human help.

Most elephant seal pups are too young to even know what a fish is — and what to do with it. Instead of whole fish, they get "fish smoothies." Volunteers grind up herrings in a blender, and mix them with water and salmon oil. The mash is then filled into huge plastic syringes to be fed to the pups.

While one volunteer restrains the animal, another one inserts a long plastic tube into the animal's stomach. Fish mash from a syringe will then be pressed directly into the pup's digestive system. The procedure is called tube feeding and is used to ensure the animal gets enough calories to grow strong and healthy.

Ultimately, elephant seals have to learn how to eat whole fish to be able to survive in the wild. At the Marine Mammal Center, this process is called "fish school". Initially, volunteers put a fish into the seal's mouth and make it swallow it against its will. Later, the pups will start to take the fish voluntarily or even pick them up from the bottom of their pool.

When the elephant seals are big and healthy enough, they are released into the wild. Unlike sea lions, elephant seals don't become attached to people. After their release, they usually dive off into the ocean, traveling north towards the Pacific Ocean around Alaska and the Aleutian Islands.

While young sea lions are usually quite quick to grasp how to feed themselves, there's another marine mammal species that takes longer to learn how to cope in the wild: the sea otter. They forage for clams, mussels and other food on the ocean floor. Usually, their mothers teach them how to dive, find and pick up food, as well as how to open shellfish.

Monterey Bay Aquarium in California rescues sea otter pups that have been found along the coast. As sea otters have sharp teeth and long claws, employees at the center usually have to wear Kevlar gloves to protect themselves while dealing with the young animals.

When orphaned sea otter pups come in, volunteers at Monterey Bay Aquarium bottle feed them with a milk formula which are based on those that are commercially available for puppies. After a while, the sea otter pups are introduced to the same kinds of solid food they will come across in the ocean: clams, squid, shrimp and so on.

Just like sea lions, sea otters can easily become attached to humans. That's why everyone handling a sea otter pup at Monterey Bay Aquarium wears a disguise. It works both ways: the pup does not see human faces and the human is constantly reminded that they are not allowed to pet the pups – no matter how cute they are.

Because sea otters are ultimately the only ones that can teach a pup how to survive, the Monterery Bay Aqiarium launched a surrogate mother program. Adult female sea otters are put with young orphans. The females take care of the pups and show them everything they need to know. Surprisingly, it works — even though the pup is not the biological offspring of the female.

When a pup is strong enough and has learned everything a sea otter needs to know, it is released along the coast of California. Some sea otters still can't cope and need to be taken back into captivity. But the majority of those rescued and brought up at Monterey Bay Aquarium will live a proper sea otter life in the wild.