The number of feral cats in Hawaii is staggering, with over 300,000 on Oahu alone. Unfortunately, an oft-proposed solution to this problem, a method known as Trap Neuter Release (TNR; sometimes called Trap, Neuter, Release, Manage or TNRM), is itself problematic.

While the short-term goals of TNR practitioners to provide care to feral cats are well-intentioned, data show that TNR does not work toward the long-term goal of reducing numbers of feral cats. A 2009 review by Travis Longcore et al. in Conservation Biology compiles the results of many studies regarding TNR and concludes that the practice does not result in decreased colony sizes over time, and in some instances has increased the size of cat colonies due to increased abandonment of unwanted pets left in someone else’s care.

TNR is not a tool for colony reduction, but rather colony maintenance.

With over 300,000 cats on Oahu, this is a problem for cats, native wildlife, and people alike.

There are many reasons why people in Hawaii should care about this problem, including one that the Department of Land and Natural Resources (DLNR) deals with daily: Hawaii has the sad distinction of being home to 28 percent of the threatened and endangered species in the U.S., and is the site of 78 percent of the country’s species extinctions. In Hawaii, cats (including those from “managed” colonies) have been documented countless times killing threatened and endangered species, including Hawaiian coots, koloa maoli, nene, palila, stilts, shearwaters and others. In June 2016, researchers on Kauai captured footage of cats killing endangered Hawaiian petrels, which are particularly vulnerable as they nest on the ground.

Cats also threaten native wildlife as the host of the toxoplasmosis parasite. A single cat can excrete 145 billion toxoplasmosis eggs per year in its feces, which can persist in soil or be carried by runoff into our oceans. The National Oceanographic and Atmospheric Administration has recorded at least eight endangered Hawaiian monk seal deaths attributable to toxoplasmosis, as well as the death of a spinner dolphin. Toxoplasmosis can also infect Hawaii’s birds, including nene and alala.

Humans are also at risk from toxoplasmosis, which can damage the immune system and has been linked to mental illness. Toxoplasmosis is of particular concern during pregnancy, as infection can result in miscarriage or birth defects.

If wildlife and human beings aren’t reason enough to be concerned about the maintenance of feral cat colonies, consider the welfare of cats themselves. Researchers estimate the lifespan of outdoor cats at just three years, compared to 12-18 years for indoor cats. The American Humane Association notes that outdoor cats have more diseases and parasites, including feline leukemia, feline AIDS, and intestinal worms. People for the Ethical Treatment of Animals (PETA) recently released a statement opposing TNR as an inhumane method of cat management.

A survey by University of Hawaii researchers Cheryl Lohr and Christopher Lepczyk found that 87 percent of Hawaii residents want to see the number of feral cats on the landscape decrease, and with good reason: it is the best and most humane outcome for native wildlife, people, and cats alike. TNR, however, is not the answer to this problem.

DLNR recently supported legislation to deter animal abandonment, and is supportive of finding a multipronged approach to this complex issue that includes adoption wherever possible, humane euthanasia where necessary, and strict control of cats in areas housing our threatened and endangered species. Relying on a system that maintains the presence of feral cat colonies will only ensure that the threats to cats, people, and wildlife are here for years to come.

Suzanne Case is director of the state Department of Land and Natural Resources.