Cat Deterrents for NZ Gardens: What Works, What's Unsafe & the Law

Start with the cat's owner and what's attracting it

SPCA NZ's advice is to talk to the cat's owner first, so they know their cat is coming onto your property. If you don't know whose cat it is, SPCA suggests releasing it with a paper collar carrying a note asking the owner to get in touch.

Next, remove whatever is drawing the cat in. SPCA lists the common attractants as food left outside, sandpits or freshly turned soil, rubbish bins that aren't properly secured, rodents, and cats that aren't desexed. Its overall advice is to start with exclusion and removing attractants, combine several methods, and not give up too soon.

Physical barriers: the approach with the best evidence

Fences. A standard fence won't stop a cat, but you can make one cat-resistant. SPCA NZ suggests adding cat rollers to the top of an existing fence, attaching netting or plastic or metal sheeting that slopes outwards so the cat can't climb over, or running a thin wire about 5 cm above the fence along its whole length so a cat can't balance on top.

Beds and vegetable gardens. Cats prefer to dig in loose soil. SPCA NZ suggests placing objects on top of or pushed into the soil, such as pebbles, pine cones, crushed eggshells, plant stakes or wooden chopsticks. Oregon State University Extension says chicken wire laid flat and pinned down lets plants grow through while stopping cats digging, and bird netting can be set just above the soil (about 2.5–5 cm). The RHS says netting can work for small areas, and densely planted borders with no bare soil are less appealing to cats as a toilet.

Because netting works best over small areas, a raised bed or an edged bed is easier to cover than an open border.

Ultrasonic deterrents: some effect, not a cure

The evidence on ultrasonic cat deterrents is mixed:

• A 2018 field trial in 18 suburban gardens in Perth, Australia, found ultrasonic devices cut the frequency of visits by resident cats by 46% and the length of visits by 78%. The researchers noted the devices will not prevent all incursions, and cats that only visited occasionally showed no clear drop.
• SPCA NZ is more cautious. It points to a study that found minimal effect on behaviour, with cats actually spending more time within the device's reported range.
• The RHS notes some cats flee while others hold their ground, and that the devices work best in open gardens where shrubs or fences don't block the sound.

If you try one, SPCA NZ's general advice applies: combine several methods rather than relying on one.

Motion-activated sprinklers

SPCA NZ says motion-activated sprinklers can be effective at deterring cats, and UK charities Cats Protection and the RSPCA also suggest them. We couldn't find a published field trial, so treat them as practical advice rather than a proven method. Cats Protection notes a light spray is enough.

Scent and chemical repellents

SPCA NZ says scent and chemical repellents have largely shown mixed results and have not been well studied. The RHS adds that commercial repellents can wash off in rain and often give only short-term protection, so they need frequent reapplying.

DIY repellents that can poison cats

Some of the most common home remedies are the unsafe ones:

• Mothballs. SPCA NZ says mothballs are toxic to cats and may even attract them. Pet Poison Helpline says cats are more sensitive to the toxic effects of mothballs, though dogs are more likely to eat them.
• Citrus peels. SPCA NZ says citrus peels are toxic to cats and may attract them. (Some overseas guides recommend citrus peel; SPCA NZ advises against it.)
• Essential oils. Pet Poison Helpline guidance (published by VCA Animal Hospitals) lists essential oils including citrus, peppermint, pine, tea tree (melaleuca), wintergreen and ylang ylang as poisonous to cats, through both ingestion and skin contact. The Merck Veterinary Manual says tea tree oil has been the most commonly reported essential oil poisoning in pets, and cats' grooming puts them at extra risk.
• Slug and snail bait. Pet Poison Helpline says metaldehyde baits are significantly toxic to household pets, with no readily available antidote.
• Cocoa bean mulch (if you also have a dog). Poison Control says cocoa bean mulch contains theobromine and caffeine, which are poisonous to dogs.

If you're unsure about a plant or product in your garden, you can look it up in our toxic plant checker.

What the law says

Cats are protected by the Animal Welfare Act 1999. It is an offence to ill-treat an animal, which the Act defines as causing it pain or distress that is unreasonable or unnecessary. Maximum penalties for an individual are:

• up to 12 months' imprisonment or a $50,000 fine (or both) for ill-treating an animal (section 29);
• up to 3 years or $75,000 for reckless ill-treatment, and up to 5 years or $100,000 for wilful ill-treatment, where the animal dies, is permanently disabled or seriously injured (sections 28A and 28).

SPCA NZ warns that companion cats are considered property under New Zealand law, so you could be held criminally or civilly liable for harming someone's cat. It does not recommend killing cats caught on private property, because it is hard to tell whether a cat is owned. If you do set a live trap, you legally become the person in charge of any cat you catch: SPCA says you must check the trap within 12 hours after sunrise each day, and that hosing a trapped cat, or taking it somewhere unfamiliar to release it, can be an offence.

SPCA also notes that most councils do not have bylaws controlling cat ownership or cat movement. Some do: Wellington City Council requires cats aged 12 weeks or older to be microchipped and registered on the NZ Companion Animal Register, and cats over 6 months to be desexed unless exempt. See our cat curfew guide for local rules in the main cities.

Cats, birds and native wildlife

DOC says cats can kill native birds, lizards, insects, bats and wētā. Its advice to cat owners is to keep cats inside as much as possible, only let them out in an enclosed area or catio, keep them in at night, and fit a collar with a bell. If you're protecting a garden with native lizards, see our guide to New Zealand's native lizards.

If the cat is your own, SPCA NZ supports keeping cats at home, using a catio or a cat-proof fence with a rolling bar on top.

Gardening where cats have been

Healthify NZ says the parasite that causes toxoplasmosis can be present in soil contaminated by infected cat poo. Its advice for people who are pregnant or have a weakened immune system is to wear gloves while gardening, wash your hands before preparing food, and wash fruit and vegetables thoroughly.

Sources

• SPCA New Zealand, How should I deter cats from entering my property?: https://spca.nz/advice-and-welfare/article/how-should-i-deter-cats-from-entering-my-property
• SPCA New Zealand, Animal deterrents and exclusion methods (position statement): https://www.spca.nz/advocacy/position-statements/article/animal-deterrents-and-exclusion-methods
• SPCA New Zealand, Know your obligations before you set a cat trap: https://www.spca.nz/advice-and-welfare/article/know-your-obligations-before-you-set-a-cat-trap
• SPCA New Zealand, Keeping your cat safe and happy at home: https://www.spca.nz/advice-and-welfare/article/keeping-your-cat-safe-and-happy-at-home
• Crawford, Fontaine & Calver (2018), ultrasonic cat deterrents field trial, Global Ecology and Conservation 15: https://www.wellbeingintlstudiesrepository.org/aw_comp_globalcats_predation/5
• Royal Horticultural Society, Cats: https://www.rhs.org.uk/biodiversity/cats
• Oregon State University Extension, Protecting your garden from cats: https://extension.oregonstate.edu/es/node/252396/printable/print
• Cats Protection, Keeping cats out of your garden: https://www.cats.org.uk/keeping-cats-out-of-your-garden
• Pet Poison Helpline, Mothballs: https://www.petpoisonhelpline.com/poison/mothballs/
• VCA Animal Hospitals (for Pet Poison Helpline), Essential oil and liquid potpourri poisoning in cats: https://vcahospitals.com/know-your-pet/essential-oil-and-liquid-potpourri-poisoning-in-cats
• Merck Veterinary Manual, Toxicoses from essential oils in animals: https://www.msdvetmanual.com/toxicology/toxicoses-from-household-hazards/toxicoses-from-essential-oils-in-animals
• Pet Poison Helpline, Dangers of slug and snail bait for pets: https://www.petpoisonhelpline.com/uncategorized/dangers-of-slug-and-snail-bait-for-pets/
• Poison Control, Cocoa bean mulch can poison dogs: https://www.poison.org/articles/cocoa-bean-mulch-can-poison-dogs
• Animal Welfare Act 1999 (sections 2, 28, 28A, 29, 37): https://www.legislation.govt.nz/act/public/1999/0142/latest/DLM51372.html
• Wellington City Council, Cat microchipping: https://wellington.govt.nz/dogs-and-other-animals/cats/cat-microchipping
• Department of Conservation, Make your cat conservation-friendly: https://www.doc.govt.nz/get-involved/conservation-activities/make-your-cat-conservation-friendly/
• Healthify NZ, Toxoplasmosis: https://healthify.nz/health-a-z/t/toxoplasmosis