Endangered Hawaiian duck's comeback is a 'beacon of hope' for conservationists

November 20, 2019, 9:56 a.m.

Just when scientists had about given up hope, the little duck that could emerged. The endangered, endemic koloa maoli (aka the Hawaiian duck) was thought to be threatened with genetic extinction, due to its interbreeding with feral mallards.

But new research published in the Molecular Ecology journal reveals that conservation efforts to save the koloa on the island of Kauai have been successful.

The study was two decades in the making, with research led by scientists from University of California, Davis; U.S. Fish and Wildlife Service; University of Texas, El Paso; Wright State University; Oregon State University; and the state of Hawaii’s Division of Forestry and Wildlife. The team analyzed 425 koloa, mallards and hybrids from populations across the islands, collecting blood and tissue samples to analyze their genetic data.

What they found surprised them.

“The fact that the koloa on Kauai are pure and have a lot of genetic variation are two really positive things that came out of this study,” Caitlin Wells, a wildlife ecologist in the Department of Fish, Wildlife and Conservation Biology at Colorado State University, says in a statement.

Koloa vs. feral mallards

a Hawaiian duck snacks on a mango A koloa munches on a mango at Hawaii's Moanalua Gardens. (Photo: Eric Tessmer [CC by 3.0]/Wikimedia Commons)

Koloa used to thrive throughout all eight islands, but predators, habitat loss and unregulated hunting led to their disappearance from every island, except Kauai and Niihau, by the late 1960s. Conservationists attempted captive breeding and release programs to revive the koloa population, but with feral mallards still running loose, the interbreeding continued.

Domestic mallards were originally brought to the islands for farming, hunting and pond beautification, but many of them escaped — and are now thriving due to people's penchant for feeding stray ducks. Since mallards are infamous for their breeding effectiveness (they are able to crossbreed with ducks even distantly related to them), efforts are now underway to remove all mallards from the Aloha State.

Scientists had also hoped that by simply leaving the koloa hybrids alone, they'd eventually return to a pure koala state on their own. That kind of wishful thinking, however, didn't work out.

“That’s not what we found,” explains Wells. “If you don’t have pure koloa parents that outnumber the feral mallards, you’re not going to get any decreases in those hybrid proportions.”

Though crossbreeding can sometimes be a positive, like adding genetic diversity to an inbred population, it can also threaten the unique gene pool of animals that are already well-adapted to their environment.

“But here’s a case where we have enough individuals with enough genetic variation in the koloa, and we’ve also genetically identified the hybridizing species,” Wells says. “It seems very clear that we can separate those going forward.”

Andy Engilis, study co-author, has been involved in conservation efforts of Hawaiian ducks since the late 1980s. He believes this research is a breakthrough in attempting to save a species from extinction.

“This study lays the foundation for a new chapter in the recovery of the koloa, a new trajectory towards recovery and delisting as an endangered species,” Engilis says.