Four healthy Hawaiian monk seals were successfully released on the Midway Atoll National Wildlife Refuge after staff at Ke Kai Ola, The Marine Mammal Center’s monk seal hospital on Hawaii island, cared for the endangered mammals for more than 10 months.

Scientists had rescued the malnourished seals from the Northwestern Hawaiian Islands.

“To return four female Hawaiian monk seals back to their ocean home is an incredible success story and a significant boost to an endangered population where the survival of every individual is critical,” said Dr. Cara Field, medical director of The Marine Mammal Center, in a statement. “This success story highlights the importance of our ongoing partnerships to help save this species.”

Scientists of the National Oceanic and Atmospheric Administration’s Hawaiian Monk Seal Research Program rescued the four malnourished monk seal pups from the Northwestern Hawaiian Islands in the fall of 2019.

Two of the seals were rescued from Pearl and Hermes Reef and the other two were rescued from Lisianski Island. All were initially referred to by their flipper tags, DL32, DL36, LL00 and LL34.

Scientists aboard the research vessel Oscar Elton Sette transported them to Honolulu. From there, the U.S. Coast Guard flew them to Ke Kai Ola in Kailua-Kona. The monk seal pups weighed an estimated 55 to 65 pounds when they first arrived.

Animal programs manager Megan McGinnis said the pups were too weak to catch fish on their own. She estimated their chance of surviving on their own at less than 1%.

Staff and volunteers initially tube-fed them “fish milkshakes” that contained a mix of herring and electrolytes three times a day. As the health of the monk seal pups improved, staff fed them live fish to help them practice their foraging skills.

McGinnis said each of the monk seals gained between 110 and 175 pounds while under their care for more than 10 months. “Some of them more than tripled their weight in their time with us.”

A cultural adviser at Ke Kai Ola named the seals Maka Kilo (LL00), Ka‘ena (LL34), Leimana (DL36) and Hilina‘i (DL32).

On Aug. 5, the U.S. Coast Guard transported the healthy monk seals via HC-130 plane from Hawaii Island to the Midway Atoll National Wildlife Refuge, part of the Papa­ha­nau­mo­kua­kea Marine National Monument. “This is a protected area where they are able to be safe and thrive, McGinnis said.

Three of the four seals were fitted with temporary satellite tags to allow scientists to monitor their progress. The fourth seal was not fitted with a tag because she was molting.

According to NOAA, the Hawaiian monk seal population is approximately 1,400 seals — about 1,100 seals in the Northwestern Hawaiian Islands and 300 seals in the main Hawaiian islands.

Since 2014, Ke Kai Ola has rehabilitated and released 33 monk seals, most of which have been rescued from the Northwestern Hawaiian Islands.

The Marine Mammal Center and NOAA remind the public to maintain a safe distance from monk seals. To report a sighting, call the National Oceanic and Atmospheric Administration’s statewide toll-free hotline at 1-888-256-9840.