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A feral cat kills a Newell’s Shearwater on the Hawaiian island of Kauai, photograph by André Raine
First a disclaimer. I have lived with domestic cats nearly all my life. The current pair have completed a decade; I am approaching my ninth. So, it can be said we are growing old together, mostly companionably. An aphorism I occasionally use is “A house is not a home without a cat”. I guess dog lovers might say much the same about their pets.
But not all cats are pets, as are my two and all those who came (and sadly left) before them. Some can be neglected, abandoned, or left to roam and become lost. They can then be called strays. By one definition, a stray cat is one which once lived indoors and was socialized to people at some point in its life, but has left or lost its home, or was abandoned, and no longer has regular human contact. Of course, not all these discarded or wandering moggies have been neutered, so as is normal, they will find a mate and the females will give birth to kittens. Without human contact from a young age the kittens will not become socialized and will grow to be wild animals. These are described as feral cats, that will in turn breed, leading to populations that can become of serious conservation concern, especially on islands with breeding seabirds. As a retired marine ornithologist who has worked on seabird islands my whole career, I have no love for feral cats, as I do for my current pair Annabelle and Oliver at home. I do not see this as a dichotomy.
I started my seabird career in 1971 on 220-ha Dassen Island, off South Africa’s Western Province where I studied the now Critically Endangered African Penguin Spheniscus demersus, along with a suite of cormorants, two gulls and a pelican. The island supported feral cats that I showed killed penguin and cornorant chicks and migratory terns. My control efforts taking potshots with a .22 caliber rifle likely did little to the population and it took many more years before the cats were eradicated by a more concerted hunting effort.
A feral cat on Marion Island, photograph by Valdon Smith
Jump forward a decade or so and I became peripherally involved with the successful cat eradication programme on sub-Antarctic Marion Island. At 32 000 ha and with inhospitable terrain and mostly poor weather, it took some years before the cats were finally removed, using a variety of techniques, Indeed, for many years, Marion was the largest island from which feral cats had been eliminated, only recently pipped by now cat-free Dirk Hartog Island off Western Australia – at 63 000 ha nearly twice as large as South Africa’s Marion Island.
One thing Dassen, Marion and Dirk Hartog have in common is that they have no permanent human populations and are managed as nature reserves where introduced mammals are not welcome. The situation becomes more complex on islands where feral cats coexist with permanent human populations, of whom some inhabitants will be cat lovers and keep them as cherished pets. For some, their affection for their pets extends to the feral animals and they may place food, such as opened cans of tuna, in localities where stray and wild cats congregate, and may even erect feeding stations on poles as advertised for sale online, above the reach of dogs and other predators. With the bonus of free food, the feral cats will breed copiously; their offspring will be able to disperse to areas where they come into contact with native fauna, including seabirds. Some advocates support TNR (Trap, Neuter, Release) programmes for feral cat communities. Unfortunately, there seems to be no good evidence these will lead to an overall reduction in the numbers of feral cats present, nor in their depredations of the local fauna.
Black Petrel chick on Great Barrier Island by Maureen Bennetts of Artists and Biologists Unite for Nature (ABUN) for ACAP, after a photograph by ‘Biz’ Bell
In 2017 while in New Zealand for an ACAP meeting I flew to Great Barrier Island to undertake a three-day hike so as to visit the site of a breeding population of ACAP-listed and Vulnerable Black Petrels Procellaria parkinsoni. Feral cats are present on the island, and indeed, my host on arrival told me that he put out food for two that regularly came to his back door. He did not appear to be overly concerned with (or that knowledgeable of?) the environmental damage feral cats are causing over much of New Zealand. But since then there is the intention to make 28 000-ha Great Barrier cat (and rat) free. Here’s hoping!
The problem: a feral cat gets a handout of cans of tuna
The latest positive news come from “The Big Island” (Hawaii) in the North Pacific, with the Hawaiʻi County Council passing Bill 51 that prohibits the feeding of feral and stray animals such as cats, pigs, goats, and chickens on all County-owned or managed properties. “Bill 51 focuses on public spaces, including County parks, beaches, and facilities where populations of introduced species often congregate due to people feeding them and other inviting conditions”. The bill, assigned as Ordinance No. 25-63, will take effect from 01 January 2026.
The new ordinance should give some increased protection to burrow-nesting seabirds on the island, notably the Endangered Hawaiian Petrel Pterodroma sandwichensis and Critically Endangered Newell’s Shearwater Puffinus newelli, both endemic to the inhabited Hawaiian Islands.
“The issue of feral cat management is especially pressing in Hawai‘i, because outdoor cats are known predators of many imperiled Hawaiian bird species. They have also significantly contributed to the decline of the Nēnē [Hawaiian Goose Branta sandvicensis – Near Threatened] through exposure to toxoplasmosis, an infectious disease that affects a wide variety of species, including the Hawaiian Monk Seal, other wildlife, domestic animals, and people. Feeding not only supports feral cats but also other invasive animals, including rats and pigs, that damage park infrastructure and pose serious risks to public health. Cutting off food sources on County lands is essential to reducing feral populations and safeguarding wildlife.”
However, there is clearly opposition to the Bill, with for example the Alley Cats Allies website considering it “cruel”. It only passed after “after fierce debate and passionate testimony from the public and council members.”. One does wonder if it will be properly enforced, as those determined to feed stray and feral cats in public places may well continue to do so, likely surreptitiously. Threatened endemic seabirds breed on other Hawaiian islands inhabited by people and cats (with Kauai being the main stronghold for the Newell’s Shearwater) – and landowners are not restricted to feeding cats on their private properties.
It seems a major mind change is required before Hawaii’s threatened sea and landbirds can be considered safe from feral cats. A start would be continuing to point out that a feral cat and a pet cat are really two different animals, despite them looking alike and belonging to the same species.
Read more on the Hawaii bill here.
John Cooper, Emeritus Information Officer, Agreement on the Conservation of Albatrosses and Petrels, 15 September 2025