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Northern elephant seals once teetered on the brink of extinction. Now the population is bouncing back - but some need a helping hand to survive.
We went behind the scenes at the biggest marine mammal hospital in the world to meet some of their latest arrivals.
When you walk into The Marine Mammal Center near San Fransisco, the first thing that you notice is the smell. More than 1,000lbs of fish can be processed in its kitchens every morning, ready to feed some very hungry young patients.
The centre is home to California sea lions, northern elephant seals, harbour seals and sea otters that need a helping hand. These patients come from up and down the California coastline, and are taken in by the biggest marine mammal hospital in the world for rest and rehabilitation. With that range of patients, breakfast can be a smelly business.
The next thing you notice is the noise. Northern elephant seal pups have a lot to say for themselves, and during peak pupping season, the air rings with their squeals.
'They can sound like they are distressed', says Dr Cara Field, the staff veterinarian at the center. 'But it's OK, they just have lots they want to say.'
At its busiest, the centre can hold hundreds of seal pups, all in specially designed pool areas where they can learn and grow.
By late Spring, nearly every spot in the pool is full of young pups.
Dr Field leads a team of vets, scientists and volunteers who look after them, and her ultimate goal is getting every animal back to health and released into the wild.
The animals are usually found by the public, who can call a team of trained rescuers that transport them straight to hospital.
For the northern elephant seal pups, putting on weight is their big challenge. Their mums leave them on beaches to fend for themselves when they are just 28 days old. It makes them vulnerable to dehydration, malnourishment and injury.
The trouble is, seal pups don't know how to eat a fish, and their mothers never teach them. So it's down to the volunteers at the hospital to fatten the youngsters up, and then get them ready for fish school.
Dr Field says, 'When the animal comes in, we take blood samples from them, and run them the same day. We can get all the animals medical care and a plan for their recovery very quickly.
'On admission, we also check their blood cell count, organ function and electrolyte levels, and give them flipper tags so we can identify individuals easily.'
Northern elephant seals are a conservation success story. In 1884 the subspecies was declared extinct, as so many were hunted for their blubber.
The little pups might look adorable now, but they can grow phenomenally large, with the males reaching up to 2,000 kilogrammes (roughly the same weight as an Indian rhino). All that blubber was once used as fuel for lamps, and demand for it nearly wiped out every elephant seal on the North American coastline.
In 1892, a tiny population of northern elephant seals was rediscovered near Mexico, and from those the population bounced back. The animals were protected by law in America and Mexico in the early twentieth century, and now the population numbers 150,000, proving that it is possible for nature to thrive if given space and a helping hand.
And some pups need a bigger helping hand than others. Most do well in the wild by themselves, but others can struggle. That's where Dr Field steps in.
'Typically, the pups need antibiotics when they come in, and they can be susceptible to parasites and parasitic worms,' she says. 'We also give them all vitamin B and Pepto-Bismol, the same thing we would take for nausea and diarrhoea, to settle their stomachs.
'Most of these seals are simply suffering from dehydration and malnutrition, so they are more straightforward cases for rehabilitation and release.'
When the pups first come in, they are given regular fish mixtures to help them pile on the pounds. The Center dubs these cocktails of herring, vitamins and salmon oil 'fish mash smoothies'. Once they are bigger, the pups must learn how to find, chew and swallow fish by themselves.
When they are healthy, fat and able to feed, they are taken back to the ocean to live out their days in the wild.
The Marine Mammal Center is also an important teaching hospital.
'We have a huge variety of patients on site, and students and scientists from all over the world come to study here. Elephant seals are a useful species for volunteers and scientists to learn from, and they can teach us about the needs of more endangered species like monk seals,' says Dr Field.
'Our care has direct conservation implications for more threatened species.'
More complex patients than seal pups come through the doors too. California sea lions are often in need of some serious TLC, frequently arriving at the hospital with either cancer or a condition called domoic acid toxicosis.
Domoic acid is a harmful neurotoxin produced by blooming algae, which are eaten by fish and shellfish. When the sea lions in turn eat the fish, they are exposed to the toxin too. It can result in seizures, blindness and death.
It was first diagnosed in marine mammals by experts at the Center in 1998.
Even humans can be affected by the toxin. The first reported human poisoning from domoic acid was in Canada in 1987, after people ate infected mussels.
Effective seafood monitoring programs have ensured there have been no other documented cases since 1987, but it goes to show that the gap between us and the ocean ecosystem is not as wide as it can sometimes feel.
Dr Field adds, 'These animals are a window into the health of our oceans. What is impacting them can easily impact us too, and we should be worried about it because we can also be exposed to these pollutants. These animals are telling us a bigger story.'