Federal authorities plan to euthanize as many as two adult male Hawaiian monk seals that have attacked pups at Kure Atoll in an effort to prevent the population of the critically endangered species from further declining.

Resources managers believe the action is necessary because the aggressive behavior is injuring, and in some cases, killing the immature seals. The attacks are leaving the already decimated species — the most critically endangered marine mammal in U.S. waters — with even fewer animals around to reproduce. 

There are only about 1,100 Hawaiian monk seals left in the world and the population is declining about 4 percent per year. Scientists say the species could disappear in 50 to 100 years if the trend isn’t reversed.

“The reason we’re doing this as much as anything is because this is an endangered species,” said Sam Pooley, the director of the Pacific Islands Fisheries Science Center. “We’re at the point in its population where every — every particularly female pup — counts for the future of the population.”  

The adult males have been scratching, biting, and mounting the pups. In some cases, they’ve been corralling the small seals into the ocean and then holding them under water. 

Ten of the 13 pups that weaned at Kure Atoll this year have been injured in these attacks over the past two months. Two are missing and feared dead. 

About 100 monk seals live at Kure, which is 1,200 miles northwest of Honolulu inside the Papahanaumokuakea Marine National Monument. 

Kathleen Gobush, a research ecologist at the center, said the males are both “subordinate males.” This means, unlike the dominant males at Kure, they don’t have mating partners and breeding opportunities. 

Gobush said the animals may be displaying what she called “misplaced breeding aggression.”

The priority will be to put down a seal that attacked one pup last year and stepped up his assaults this year to attack nine pups on seven occasions. The two missing pups are ones he assaulted. 

Resource managers may also euthanize a second adult male that began acting aggressively this year, attacking five pups on four occasions. 

The animals would be put down in the next few days, either with a gun or by lethal injection. The task would fall to a team that just arrived by boat at Kure, to bring back researchers who have been studying the animals there for several months. 

“Our folks have spent their careers trying to keep monk seals alive,” Pooley said. “It’s not something we’re looking forward to doing, and I know they’re not looking forward to it.”

Whether officials are able to follow through with the plan will depend on whether they’re able to find the seals and euthanize them without threatening the staff’s safety.

The federal permit the scientists have to study and protect the monk seal population allows euthanasia under limited circumstances like this one. 

Monk seal scientists have had to take similar action because of aggressive male seals twice before in past decades. 

They euthanized one seal in 1991, and moved two seals away from pups in 1998. 

Moving the seals was eliminated as an option this time because doing so would just give the seals an opportunity to attack pups in their new location. Officials searched for an aquarium or research facility to take them in, but none was available.