On a Thursday evening last month, two kittens in a cardboard box were left on a stone wall behind a Hawaii Kai bus stop as the sun started to set.

More than 150 older cats were already there, milling around the well-established colony of stray and feral felines in East Honolulu. The stench greeted the nostrils like a truckload of litter boxes, but that hasn’t deterred a team of volunteers from regularly providing the cats food and water.

One of those caregivers found the box of kittens, brought it to a nearby bench and began trying to contact nonprofits and veterinary clinics for help. The middle-aged local man declined to provide his name, noting how “controversial” such cat colonies have become in the community.

Colonies of feral cats are thriving in neighborhoods all over Oahu, from the University of Hawaii’s Manoa campus to Waianae’s homeless encampment, in alleys behind hotels and along trails in the mountains.

But it’s not the smells or caterwauling that is of primary concern to scientists. 

The biggest issue, federal and state scientists said, is the cats’ unique ability to spread toxoplasmosis, a parasitic disease that has killed at least eight critically endangered Hawaiian monk seals, two spinner dolphins, nene geese and native birds over the past 15 years. 

The problem is pitting scientists trying to save threatened marine mammals and other creatures against animal rights activists trying to save abandoned cats.

“You need to stop it at the source and that means preventing cats from defecating in the environment, whether it’s in the hills or on the beaches,” said Michelle Barbieri, a wildlife veterinary medical officer with the National Oceanic and Atmospheric Administration’s Hawaiian Monk Seal Research Program.

Felines are the only animals in which the parasites that cause toxoplasmosis can reproduce, the scientists said. They pass it on through their feces, which other animals then contract by ingesting contaminated food or water. 

“This is a mauka-to-makai issue — the feces can enter the watershed anywhere,” said Angela Amlin, NOAA’s protected species policy analyst who has become an expert on toxoplasmosis.

There are hundreds of thousands of homeless cats on Oahu alone. A 2012 study by Ward Research that the Hawaiian Humane Society commissioned found that 17 percent of Oahu residents feed cats they don’t consider their own, resulting in 300,000 free-roaming cats.

Hundreds of thousands more are estimated to be roaming the Big Island, Kauai and Maui.

With so many cats and so few resources, it’s been a tough problem to solve over the years.

Scientists and animal-rights activists disagree about the most effective strategy to deal with the issue. But there’s a new effort to try to change that — particularly in light of the dwindling population of species found nowhere else in the world.

Veterinarians and some animal-rights advocates agree with state and federal officials that toxoplasmosis is a serious problem and that cats are the inadvertent culprits. But there’s a fundamental disagreement over what approach they should take to effectively tackle it before more damage is done to the recovery efforts of other animals.

The Hawaiian Humane Society backs an approach called TNRM, which stands for Trap, Neuter, Release and Manage. The nonprofit touts it as a compassionate way to maintain colonies in safe environments while limiting the spread of the disease and proliferation of feral cats.

But scientists with NOAA and the Hawaii Department of Land and Natural Resources want a more aggressive strategy — one that may entail a certain level of culling to reduce the population.

“Nobody wants to euthanize cats,” Amlin, NOAA’s toxoplasmosis expert, said. “It’s not something you desire to do. It’s just an understanding that this is something that’s not part of our natural environment here and it’s destroying our ecosystem.” 

Cats have evolved to become the “definitive host,” Barbieri said. They’re the only animal in which the toxoplasma parasite can sexually reproduce, which happens in their guts, and then millions of eggs hitch a ride out of the cat through the feces.

It’s usually kittens that shed the “toxo,” and only for a week or two. But it’s a hardy parasite that can live 18 months or longer in the soil, fresh water or even salt water, according to scientists and veterinarians.

“It’s not the kitten’s fault,” Barbieri siad. “But to reduce the risk to monk seals we have to get their poop out of the environment.”

The animals, just like humans, can have toxoplasmosis their whole lives without showing any symptoms or dying from it. That was part of the challenge in determining whether the monk seals and spinner dolphins were dying from toxoplasmosis or just happened to have it.

“We are being very conservative with how we classify these,” Barbieri said. “These are spinner dolphins and monk seals that have died from toxoplasmosis. We distinguish that very specifically because we are looking for a very specific suite of things to even classify it as a mortality. We do recognize that animals can die and have toxo, but that’s not what we’re talking about.”

The number of fatalities also may be low because often, scientists said, they never find a body, especially with marine mammals. The number of dolphins known to have died from toxo could rise, however, based on work being done at Hawaii Pacific University.

NOAA recently gave $15,000 to HPU to look back at tissue samples it had collected from dolphins to see if toxo may have been the cause of death, said David Schofield, NOAA marine mammal health and response program coordinator.

Humans generally avoid toxoplasmosis by keeping their cats indoors and changing the litter box daily. It can cause flu-like symptoms and pregnant women are advised to take special care because they are more at risk and can pass it on to their unborn child.

Scientists have inferred that it’s similar for animals, which may harbor the disease for years before showing any symptoms. But when an infection does occur, it can get serious in a hurry and there’s no cure.

“The toxo is zooming through their body,” Barbieri said. “They’re attacking the tissues and they’re causing those organs to have a massive inflammatory response and the cells in those organs stop working.”

How Do You Manage Feral Cat Colonies?

Of the estimated 300,000 feral and stray cats on Oahu, only about 10,000 are sterilized each year, Hawaiian Humane Society spokeswoman Jacque Vaughn said.

“It’s just a very expensive, huge resource undertaking,” she said.

Spaying a cat involves trapping it, bringing it to the Humane Society, finding a vet with time to spay the animal, keeping the cat in a cage to make sure there are no complications, returning it to the wild and then monitoring it along with the rest of the colony.

But it’s still the best strategy the nonprofit has found.

“There’s definitely no question that feral cats are a big problem,” said Dr. Erika Sox, co-owner and director of specialty medicine at the Veterinary Emergency and Referral Center of Hawaii.

“The question is how do you actually manage these colonies of cats,” she said. “What I haven’t heard is a reasonable alternative to TNR.”

She said the trap-neuter-release approach improves the health of the colonies, reduces the shedding of toxo and makes the cats more likely to stay in a confined area.

Some studies have found that low-level culling, or euthanasia, of cats actually increased the traffic of cats in the area because other cats would just move in when dominant ones were killed.

“It’s not really clear what the right answer is and how to go about fixing the problem,” Sox said. “The Humane Society and I want to advocate for the humane treatment of cats but we also don’t want to see our endangered species harmed. We definitely need more resources to be effective.”

Short of a massive infusion of cash to drastically expand the trap-neuter-release program, scientists said much more needs to be done.

“The number is not getting lowered,” Amlin said of the feral cat population.

She said culling has become almost unavoidable since there are 300,000 or more cats on Oahu.

“It is a tool that has to be used at least to some degree if we’re going to make progress,” Amlin said.

That tool is a nonstarter for the Humane Society.

“We don’t believe that any one species has a right to life more than another,” Vaughn said, adding that there’s been a bit of a “witch hunt” with cats.

“Cats have become the scapegoat,” she said.

Josh Atwood, Hawaii Invasive Species Council coordinator, said it’s a false assumption that the status quo isn’t hurting other animals.

“You are making a choice. If you’re supporting a community of feral cats, that does place a negative impact on another species,” he said, adding that DLNR is required to treat certain species differently.

“We can’t look at a nene or a Hawaiian monk seal and say it must be treated the same way as a feral cat,” Atwood said. “We have to make sure they are there for the future.”

He noted that some studies that trap-neuter-release proponents have touted actually show reduced colony sizes because of aggressive adoption programs, not the trap-neuter-release program.

In May, the DLNR cohosted an interagency workshop that aimed to better understand the threat of toxoplasmosis. Officials formed a working group to identify action items and develop strategies to address the issue, said Afsheen Siddiqi of the state Division of Forestry and Wildlife.

He said the group provides a good starting point, and includes other state agencies, such as the Division of Aquatic Resources, Office of Hawaiian Affairs and Department of Agriculture, as well as federal entities including NOAA, Fish and Wildlife Service, National Park Service, the Navy and U.S. Geological Survey.

Part of the strategy may mean working to create state laws when the next legislative session starts in January.

“We are not interested in coming after people’s pets,” Atwood said. “We just want to find a way to balance the interest of private pet ownership and our mandate to protect public resources for the public good.”

Officials are discussing options but haven’t determined a strategy yet, he said, adding that they were a bit surprised by the pushback last year in their effort to ban feeding cats on state lands. The bill died after an outpouring of testimony against it.

Humane Society leaders and vets said starving the cats isn’t the answer, noting that they’ll just search for food elsewhere which could broaden their range and exacerbate the problem.

“They’re survivalists,” Sox said.

One of the major challenges is that there is no statewide legal distinction between a pet cat and a feral cat.

“It creates a really confusing landscape in trying to work on policy with cats,” Atwood said.

Attitudes Need To Change

There are a lot of areas where the scientists and Humane Society agree though.

Both sides strongly support educating the public to stop abandoning their pets and to spay them. They also agree that it’s important to encourage pet owners to keep their animals indoors as much as possible to reduce the spread of toxoplasmosis.

Some community members have learned firsthand about the issue, prompting them to stop feeding feral cats.

The most recent monk seal to die of toxoplasmosis was RN36, named Uilani by a canoe-paddling club and others who saw her regularly swimming in Keehi Harbor.

Volunteers noticed Uilani just kind of floating at the surface in the Ala Wai Harbor. This “logging” behavior worries biologists if it goes on for more than a few days. 

NOAA sent a team to rescue the seal after she was spotted in front of the Hilton Hawaiian Village hotel. But with no known cures for toxoplasmosis, the seal died less than 96 hours later.

A necropsy determined Uilani had toxoplasmosis and that it had aggressively attacked her organs.

The New Hope Canoe Club, which named one of its canoes after Uilani, later held a ceremony to scatter the seal’s ashes.

Schofield said the impacts of these feral cat colonies are hitting the community, not just scientists and natural-resource managers.

“There tends to be a perception that it’s scientists versus kittens,” said Amlin, who like many of her colleagues has pet cats.

“This is a huge, longterm thing,” she said. “The attitudes and culture around the way people treat their cats has to change.”