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Hawaiian monk seal RW22
Press Release

Endangered Hawaiian Monk Seal Dies After Fighting Deadly Disease in Care

November 22, 2021

Endangered Hawaiian monk seal dies after fighting deadly disease in care at dedicated hospital for monk seals on Hawai‘i Island

The Marine Mammal Center is deeply saddened to confirm that adult male monk seal RW22 died in care on November 17, 2021, after a more than five-week battle with a parasitic disease known as toxoplasmosis. RW22 was also suffering from the effects of ingested fishing gear and malnutrition.

“Toxoplasmosis is a complex and deadly disease that requires intensive daily treatment and management for an affected Hawaiian monk seal like RW22,” says Dr. Sophie Whoriskey, Hawaiian Monk Seal Conservation at The Marine Mammal Center. 

All of us are deeply saddened about this unfortunate outcome but we find hope in knowing the valuable insights gained about how this deadly disease affects monk seals will have a positive impact on future patients.

For the past four weeks, experts at The Marine Mammal Center administered a series of intensive medical treatments to RW22 to try to slow the rate of infection. During that time, RW22 regained some stamina and movement but continued to lose weight and deteriorate in body condition due to a minimal appetite.

Following the animal’s death Wednesday, the Center’s experts plan to conduct a post-mortem examination. The team will send tissue and blood samples to NOAA Fisheries for further examination to confirm an exact cause of death. Those results could take weeks to months to process.

“Toxoplasmosis is the number one disease threat to recovery of these endangered animals. The more partners and local communities can work to address this issue, the better for monk seals and other native species in Hawaii affected by this disease,” says Angela Amlin, Hawaiian Monk Seal Recovery Coordinator at NOAA Fisheries. “We applaud our partners at the Center for their incredible efforts and are very grateful for their partnership and dedication to RW22 and the species.”

With no vaccine available for toxoplasmosis, preventative measures must be taken by the general public. This disease is spread into the environment exclusively via cat feces. To help protect endangered Hawaiian monk seals like RW22 from toxoplasmosis, simply dispose of cat litter in the trash, keep your cats safe indoors and tell your community about how they too can prevent this disease from harming more marine mammals.

Toxoplasmosis is one of the main threats facing the endangered Hawaiian monk seal population on the Main Hawaiian Islands, in part due to the infection being difficult to detect. Other main threats to monk seals include negative human interaction and fisheries interaction via hooking and entanglements.

Only three other seals impacted by toxoplasmosis have been rescued prior to death. This is the second patient the Center has admitted to its Kona hospital with the disease.

Learn More About Hawaiian Monk Seals

On October 4, NOAA received a report of RW22 with a fishing line in his mouth off the Oʻahu coast, via the NOAA marine wildlife hotline. NOAA’s trained experts worked with Hawaii Marine Animal Response and community members to locate the seal and were able to successfully rescue RW22 on October 6. The team initially transported the seal to NOAA’s Inouye Regional Center where an x-ray revealed the ingested fishing gear.

Due to RW22’s deteriorated condition, NOAA determined additional care was necessary and initiated travel plans. RW22 was airlifted and transferred to the Center’s Kailua-Kona based hospital for Hawaiian monk seals, Ke Kai Ola, via the U.S. Coast Guard the same day.

After suffering partial facial nerve paralysis and a corneal ulcer to his left eye, a suspected symptom of toxoplasmosis, RW22 underwent a successful eye procedure on November 11, 2021, to provide short-term comfort in hopes of increasing his appetite and general well-being.

Previously in rehabilitation, RW22 regurgitated the ingested fishing gear avoiding surgery. Examination of the gear suggests that he swallowed multiple lines with hooks that appears to be part of a lay net.

The Center’s partnership with NOAA and other cooperating agencies is more important than ever to prevent this endangered species from becoming extinct. Approximately 30 percent of monk seals that are alive today are due to conservation efforts led by NOAA Fisheries and partners like The Marine Mammal Center.

For more information or to set up an interview on this topic, please contact us at


Header image: photo by Sophie Whoriskey © The Marine Mammal Center / NOAA permit #18786

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