Rare twin Hawaiian monk seal pups likely seen at Lisianski Island

Could a Hawaiian monk seal mom have given birth to twin pups at Papahanaumokuakea Marine National Monument this year?

National Oceanic and Atmospheric Administration researchers believe this is a possibility after observing Hawaiian monk seal mom, GV18, nursing two similarly sized pups at Lisianski Island.

The researchers have been at Papahanaumokuakea since May, where they spend five months at field camps, measuring and tagging seal pups, monitoring sea turtles and cleaning up marine debris, along with other tasks.

While monk seal moms occasionally adopt a second pup, says NOAA, this usually lasts for a short period of time. Either the mom or larger pup will drive the adopted pup away. In this case, researchers have not found other seal mothers missing a pup.

GV18, a 14-year-old Hawaiian monk seal mom, nursed both pups together and weaned them at a slightly smaller than normal size.

The birth of twin monk seal pups is extremely rare, according to NOAA.

A previous review of nearly 5,000 monk seal births over a 26-year period between 1983 and 2008 revealed only seven sets of twin pups. Thus, monk seal twinning occurs in only 0.1%of all births. A DNA analysis on these sets of twin pups confirmed they were all fraternal, not identical, twins.

This year’s “twins” are not identical, either, as one pup is a girl and the other a boy.

Researchers tagging weaned pups at Papahanaumokuakea also collect snips of tissue that hold the key to each seal’s genetic makeup. Researchers are eagerly awaiting DNA results from these snips of tissue to confirm whether these pups are indeed twins.

Researchers also noted another maternal milestone at Lisianski Island. A 29-year-old Hawaiian monk seal, TG28, gave birth to her 17th pup this year. She is one of the oldest monk seal moms to have given birth at a late age. The oldest monk seal mom on record is 32 years old.

Hawaiian monk seals are a critically endangered species protected by state and federal laws. Only an estimated 1,400 Hawaiian monk seals remain in the wild, with roughly 1,100 in the Northwestern Hawaiian Islands at Papahanaumokuakea, one of the largest, protected marine conservation areas in the world.