Pet dogs severely harm wildlife, even when leashed

They sleep at our feet, wag their tails when we return, and bring joy to our lives. Dogs have earned the title of “man’s best friend” for good reason. Across the globe, over a billion domestic dogs share our homes, parks, and neighborhoods. But this growing presence brings with it a hidden toll on the wildlife and the environment.

A new study by Professor Bill Bateman and Dr. Lauren Gilson from Curtin University sheds light on a neglected problem: the environmental impact of pet dogs. While cats have long been studied for their destructive effect on biodiversity, dogs have largely escaped scrutiny. That is starting to change.

The research, published in the journal Pacific Conservation Biology, makes a clear argument. The presence of pet dogs – even the most pampered, leashed ones – can disturb ecosystems, spread disease, and accelerate environmental degradation. In many cases, the harm begins before we even notice.

Pet dogs instinctively harm wildlife

Dogs are the world’s most common large carnivores. Despite centuries of domestication, they retain instincts from their wolf ancestors. This means many still chase, harass, or kill other animals when given the chance. Owners often assume their dog is harmless, especially if it stays on a leash. The research, however, reveals otherwise.

“Dogs are incredibly important to people’s lives and their roles range from providing companionship to contributing to conservation efforts as detection dogs,” said Professor Bateman.

But dogs’ impact on nature can be vast. A study in Queensland found that 9.2% of wildlife admissions to rehabilitation centers were due to dog attacks, with nearly three-quarters of those animals dying.

In Tasmania, modeling shows that off-leash dogs have caused repeated collapses of Little Penguin colonies. Between 1980 and 2020, dog attacks accounted for 91% of all reported penguin deaths in these colonies.

These are not isolated incidents. Across the globe, from South Africa to the Galápagos Islands, owned dogs have attacked penguins, plovers, and other vulnerable species. Even the most playful dog can have deadly consequences in the wrong place.

Wild animals avoid dogs

Disturbance doesn’t require physical contact. Wildlife often perceives dogs as predators, regardless of their behavior. Just the presence – or the scent – of a dog can disrupt nesting, feeding, and movement patterns in birds and mammals.

“Studies have found that animals like deer, foxes and bobcats in the US are less active or completely avoid areas where dogs are regularly walked, even in the absence of the dogs,” said Professor Bateman.

A single dog walking through a beach can cause shorebirds to abandon their nests. In Western Australia, endangered Fairy Tern chicks have been trampled or scattered by off-leash dogs.

Breeding Kentish Plovers in Spain were flushed from their nests nearly every time a dog appeared. Plovers responded far more strongly to humans with dogs than to humans alone.

In northern Australia, migratory birds like Sand Plovers and Knots spend their winters resting. When disturbed by dogs, their energy use jumps by 7.5% a day. These birds travel thousands of kilometers every year. Even a few extra energy costs can mean the difference between survival and death.

Dog owners ignore protection rules

One might assume the solution is simple – leash your dog. Yet, compliance remains alarmingly low. Studies from Australia, the United States, and Europe show that fewer than a quarter of owners leash their dogs in sensitive areas. Even when signs are posted or rules enforced, many dog owners flout them.

“Many owners simply don’t realise the environmental damage dogs can cause, from disturbing wildlife to polluting ecosystems,” said Professor Bateman.

In some cases, this disregard turns confrontational. One researcher was threatened with violence when asking beachgoers not to walk dogs in a protected wetland. Elsewhere, online footage shows dogs chasing birds from mudflats or damaging dune vegetation.

Owners often believe their personal actions won’t matter. This mindset, known as the “tragedy of the commons,” leads to shared spaces – like beaches and forests – being slowly damaged by many small actions. Without a sense of shared responsibility, even the best rules fail.

Dogs threaten wildlife health

Dogs also pollute their environment in less visible ways. Each dog produces about 0.2 kilograms of feces and 0.4 liters of urine daily.

Over a 13-year lifespan, that adds up to over a tonne of waste per dog. When left in parks or natural spaces, it alters soil chemistry, spreads disease, and contaminates waterways.

“Dog waste also contributes to pollution in waterways and inhibits plant growth, while wash-off from chemical treatments used to clean and guard dogs from parasites can add toxic compounds to aquatic environments,” noted Professor Bateman.

Flea and tick medications often contain fipronil and other chemicals. When dogs swim or are washed, these toxins enter streams and rivers. They poison aquatic insects and disrupt entire food chains. In some areas, dog urine has become a leading source of nitrogen in water systems.

The danger extends to wildlife health. Dogs can spread parasites such as roundworms and whipworms through their faeces. Zoonotic diseases like rabies and distemper have jumped from pet dogs to lions, hyenas, and wild canids, causing population declines.

In Italy’s national parks, working dogs have been found carrying parasites harmful to endangered species.

Feeding dogs affects wildlife ecosystems

The environmental toll of dogs goes beyond behavior and waste. Feeding over a billion dogs every day requires vast resources. Pet food production consumes land, water, and energy, adding to global emissions.

“In addition, the pet food industry, driven by a vast global dog population, has a substantial carbon, land and water footprint,” said Professor Bateman.

Studies estimate that 13.5% of wild forage fish – normally eaten by other marine animals – now goes to pet food. The industry uses the equivalent of nearly twice the UK’s land area and emits greenhouse gases equal to a mid-sized nation.

Despite these costs, few owners are willing to change. Only 12 to 16 percent say they would pay more for sustainable dog food, even as prices continue to rise. This resistance blocks one of the few industry-level solutions available today.

The need for awareness and cooperation

Dog ownership is not going away. These animals provide emotional support, companionship, and even serve vital roles in conservation. Detection dogs, for example, help find endangered species and monitor ecosystems.

But their rising numbers and poor owner habits threaten the very wildlife we aim to protect.

“Restrictive measures such as banning dogs from sensitive areas are necessary for protecting vulnerable species but they are not a complete solution. We are calling for a collaborative effort between dog owners, conservation groups and policymakers to develop strategies that balance pet ownership with environmental care,” said Professor Bateman.

Solutions must include better education, improved waste management, responsible food choices, and stronger enforcement of leash laws. Dogs can still share our lives, but their presence in nature must be managed with care and awareness.

We owe it to the wild animals who cannot flee forever – and to our own future on a shared planet.

The study is published in the journal Pacific Conservation Biology.

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