A rare pair of critically endangered Hawaiian monk seal twins — only the fourth set of twins ever documented — was brought to Honolulu from Midway Atoll National Wildlife Refuge aboard a U.S. Coast Guard C-130 Hercules aircraft early yesterday.

The U.S. Fish and Wildlife Service and the National Oceanic and Atmospheric Administration Fisheries Service are working to ensure the pups are given the best chance for survival and hope to return them to Midway Atoll, where they were born, in the fall, officials said.

The young seals, both females, appear to be healthy and were together on Spit Islet, the smallest island in the atoll. Both were undersized at weaning.

Wildlife officials said the pups were in need of more food, and taking them into captivity and feeding them will increase their chances.

"Past observations indicate that twins have a high probability of mortality and it will be a first if these twins survived and were successfully reintroduced back into the wild," said Dr. Robert Braun, contract marine mammal veterinarian for the Pacific Islands Fisheries Science Center.

The mother of the Midway twins was first identified on Kure Atoll in 1987. The twins were first observed on April 4 and appeared to be only a day or two old. Monk seal mothers stay with their pups for about six weeks, never leaving them to feed. During that period, mothers may lose as much as 300 pounds, while the pups may triple their birth weight. After the mother leaves, the pups are left to fend for themselves.

Volunteers, staff and other personnel at Midway Atoll National Wildlife Refuge built a holding pen for the seal pups.

The transport plane that brought the seals to Honolulu was scheduled to go to Midway to drop off crew members from the Coast Guard Cutter Kukui and NOAA Fisheries Service personnel, where they will begin a week of marine debris cleanup on and around Midway Atoll, said Bud Antonelis, of the NOAA Pacific Islands Fisheries Science Center.

The Hawaiian monk seal is in a crisis situation and its population is at its lowest level ever. Now numbering about 1,200, their numbers are expected to fall below 1,000 within the next five years. Midway Atoll National Wildlife Refuge is home to about 55 monk seals.

"Every monk seal pup is important to us," said Leona Laniawe, the NOAA biologist stationed on Midway Atoll.