As virtually anyone who has spent much time in our state knows, Hawaii has a free-roaming cat problem. Growing concern over the impact of the animals on endangered and threatened species as well as their predation of native birds is leading some to call for an aggressive new strategy in dealing with the cats before it’s too late.

How big is the problem? On Oahu alone, research from 2012 suggested at least 300,000 cats may be running free across the island; hundreds of thousands more are believed to live on neighbor islands.

All cats in Hawaii are invasive, having been brought to the islands many generations ago. As their numbers grew, strategies to contain them were put in place, most notably the Hawaiian Humane Society’s ambitious Trap-Neuter-Return management program in 1993.

These free roaming cats in Hawaii Kai are part of colonies that include tens of thousands of animals.
These free-roaming cats in Hawaii Kai are just one colony. Tens of thousands of cats run loose in the islands. Anthony Quintano/Civil Beat

Yet, despite the best efforts of the Humane Society and others with sincere interests in the cats’ well-being, the animals’ cumulative impact is becoming more than our singular ecosystem and some of its most embattled indigenous species can bear.

Cats are the only animals in which the parasites that cause the disease toxoplasmosis can reproduce, which they do in staggering quantities. Cats pass the parasite in their feces by the millions and it moves lethally into the environment.

Scientists are now finding that toxoplasmosis caused by the cats is killing highly endangered Hawaiian monk seals — at least eight so far — spinner dolphins, nene geese and native birds. Because many infected animals die in the wild, far away from scientists, the numbers being tracked so far are thought to be the tip of the iceberg.

Given that only about 1,100 Hawaiian monk seals exist and only about 200 of them live around the main Hawaiian islands, the threat posed by feral cats must be seen as urgent. The threat to the nene, the world’s rarest goose, with an estimated wild population of about 2,500, is also urgent. Spinner dolphins also are protected under federal law.

Significantly culling Hawaii’s feral cat population or eliminating it entirely may well be the only solution. Now may be too soon to make that determination. But some species can’t wait much longer.

There may be other effects, too. Studies of sea lions and rodents show that infection with toxoplasmosis results in behavior that makes them more vulnerable to predation. Locally, that could create a higher propensity for monk seals and spinner dolphins to be taken by sharks.

Beyond toxoplasmosis, there is also the difficulty of native birds being hunted and their numbers driven down by free-roaming cats.

In the face of such challenges, what is being done? The admirable Trap-Neuter-Return effort results in about 10,000 cats being sterilized each year, according to the Hawaiian Humane Society. But that’s hardly a dent when the population remains steady in the hundreds of thousands.

Officials with federal and state agencies have joined forces to form a local toxoplasmosis working group to study and strategize on the topic. The National Oceanic and Atmospheric Administration, the U.S. Fish and Wildlife Service, U.S. Geological Survey and other departments are taking part. The group had its second meeting just last week.

Already, some are calling for elimination of feral cats around Hawaii as the only realistic solution.

While the idea of killing hundreds of thousands of cats sounds gruesome, to put it mildly, Hawaii isn’t the only place considering drastic measures to protect indigenous species against invasive threats. Just last month, the New Zealand government announced a program to eliminate rats, opossums and short-tailed weasels by 2050.

Those animals have devastated the country’s native bird populations, including the iconic New Zealand kiwi. “This is the most ambitious conservation project attempted anywhere in the world, but we believe if we all work together as a country we can achieve it,” said Prime Minister John Key in a statement.

But such a strategy is highly troubling to local animal rights activists, particularly the Hawaiian Humane Society. In a commentary published earlier this week, the group’s President and CEO Pamela Burns decried “a value system in which animals are classified as native, introduced, injurious or invasive” as leading to “a hierarchy in which the protection of certain animals comes at the suffering of others.”

Still, isn’t treating cats the same as seals really choosing cats over seals? That approach means monk seals and birds will continue to decline to the point of possible extinction while the cat population continues to thrive.

Burns has a good point when she says “any policies that involve cats in our communities must be tempered with high-quality information and experts from a cross-section of viewpoints.”

“Before any solutions or policies are proposed, more data-driven research is needed, and more experts need to be involved in the discussion,” she argues.

To that end, the working group of federal and state agencies should move forward and it should include representation from the Humane Society and other reasonable voices with an interest in animals, a commitment to conservation of endangered and threatened species and a dedication to following the best approaches science can provide.

But significantly culling Hawaii’s feral cat population or eliminating it entirely may well be the only way to keep our ecosystem in balance.

Now may be too soon to make that determination. But some of the species being impacted by toxoplasmosis or hunted by feral cats can’t wait much longer.

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