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Na'au: Today's Challenges May Lead to Tomorrow's Discoveries

The story of Na'au, a California sea lion, is a story of a marine mammal that faced many obstacles. Yet at the same time, the tale of Na'au holds both hope and inspiration for the future.


Na'au, a California sea lion, at The Marine Mammal Center, is prepped for an EEG by veterinary technician Lauren Campbell (left) and veterinary intern Dr. Vanessa Fravel. Results from studying brainwave activity showed Na'au suffered from numerous seizures as a result of chronic domoic acid poisoning causing her to become disoriented in the wild.
© The Marine Mammal Center




Na'au was first rescued in May 2010 when she appeared at the main beach near the Santa Cruz wharf. Na'au had given birth to a pup in view of large crowds.  Mom and pup were brought to the Center when it became apparent that Na'au was not exhibiting typical behavior toward nursing her pup. 

At the Center, she was diagnosed with an acute case of domoic acid poisoning, meaning permanent damage had not been done. After rehabilitation at the Center that included controlling a seizure she had, Na'au was released back into the wild.  She was re-admitted to the Center on July 11 after she was spotted back in Santa Cruz County with a fish hook entanglement. She was in a poor location and was being harassed by both dogs and people.  Again, she was cared for by the Center and returned to her ocean home in July.

Over the weekend of December 4, Na'au was spotted in the middle of the intersection of Delta and Hotchkiss roads in Contra Costa County.  Rescuers nudged Na'au out of the road and into an enclosed area at an elementary school in Knightsen.  Eventually, Na'au was taken to the Center in Sausalito where veterinary staff worked diligently to care for her.  Veterinary Technician Lauren Campbell and Veterinary Intern Dr. Vanessa Fravel carefully obtained blood samples and checked her heart.

After a thorough work-up involving a detailed EEG (electroencephalogram) of her brain waves, Na'au's diagnosis became clear.  She was suffering from a classic case of chronic domoic acid poisoning; she had sustained permanent brain damage due to the consequences of previous sub-lethal exposure to the toxin. On December 7, 2010, she was humanely euthanized by veterinarians.  Through Na’au’s death is sad, there is so much to learn about her situation.  Stanford researchers are conducting a study focused on temporal lobe epilepsy, which is the most common form of epilepsy in adults.  By studying the hippocampus (part of the brain), researchers hope to learn how the brain circuit re-organizes when affected by domoic acid poisoning. Na'au's tissue samples will become part of this study by the Center's colleagues in research that may one day hold the answers to some of science's larger questions about brain disease. It is discoveries from these studies that could make a difficult ending to one animal's life the beginning of something that may benefit future lives.

About Domoic Acid Toxicosis

Domoic acid is produced by toxic algae which accumulates up the food chain, particularly in mussels, sardines and anchovies, that are then eaten by sea lions.  Exposure to the biotoxins can result in brain damage in marine mammals and humans.  This brain damage causes sea lions to become lethargic, disoriented and even to have seizures that can result in death. We refer to "acute" and "chronic" aspects of the disease. Acute cases can possibly be treated, but in chronic cases the animal's brain has sustained severe, permanent damage.

Unfortunately, the Center sees many cases of domoic acid poisoning.  In fact, in 2009, over 200 of the 1,371 California sea lions admitted to the Center were diagnosed with domoic acid poisoning.  In 2010, over 50 of the 614 California sea lions suffered from this condition.

Tragically, this diagnosis of chronic domoic acid poisoning means Na'au would not be able to return to the wild.  Na'au has shown through repeated behaviors that she is likely to endanger herself if returned to her ocean habitat.  She, for instance, could suffer another seizure while at sea and drown.  She also becomes easily disoriented and confused, which explains why she was miles from a water source when she was most recently rescued.


Commonly asked questions about euthanizing marine mammals:

Why couldn't Na'au be returned to the wild to let nature take its course?

A: Our hope with each and every patient is to be able to treat and release them. Sadly, that is not always possible and sometimes placement in a zoo or an aquarium is an appropriate alternative. You’re not the first to suggest long-term placement at a zoo or an aquarium for an animal like Na’au. However, these animals have very significant brain damage, aren’t able to be trained, and their seizure disorders puts them at great risk of drowning, so placement at a facility would not be responsible and would actually perpetuate suffering. These things considered, the most responsible action for us to take is the humane euthanasia of animals with chronic domoic acid toxicity.

 Why couldn't she stay at the Center indefinitely instead? 

A: The Center is not licensed as a long-term nursing care facility.  Additionally, the type of 24-hour care she would require in order to prevent her from having a seizure and drowning in a pool is just not possible here, or even at a zoo or an aquarium. 

Why couldn't she be placed at a zoo or an aquarium?

A: Animals that the Center places at zoos and aquariums are generally healthy, but need extra care due to becoming habituated to people or due to a permanent injury that prevents them from living in the wild. These animals must be able to respond to humans for the purposes of animal care and public education. Because Na’au is not acting like a normal marine mammal (her seizures lead to unpredictable behavior and make it unsafe for humans to be around her), she would not be able to learn the newly daily routines required to live in such a facility.  There is a silver lining in all of this. Each animal that dies in our care presents an opportunity for us to learn more. And thus is the case with Na’au. A team of specialists will be working to learn everything we can from her case, as we do with all such cases, and bit by bit we’ll better understand this disease and apply what we learn to other seizure disorders in marine mammals, and even in people.






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