Is your family pet bad for the environment? It depends.

Whether it’s a dog, cat, chicken, goldfish, or tarantula, kids love their pets. In fact, the vast majority of dog and cat owners in the United States consider their animals members of the family.

But pets consume resources, from food and water to medicine, toys, and special furniture. They also produce waste. And this has many pet families wondering just exactly how bad their critters may be for the environment.

A squeaky toy here and a can of tuna there might not seem like a big concern for the planet’s health, especially with the climate rising and one million wildlife species at risk of extinction. But with one-third of all households on Earth owning at least one dog and almost one-quarter of households owning at least one cat, any cost is going to add up.

“If you take small numbers and multiply them by really big numbers, you still end up with really big numbers,” says Gregory Okin, a professor at UCLA’s Institute of Environment and Sustainability.

Waste created by pets—poop, used kitty litter, pet food packaging, used toys, and yes, even Halloween costumes—can push the overall sustainability of owning pets into the red. And of course, some of these issues are unsolvable side effects of the decision to own animals. (There’s no way to make your pets poo less, for example.)

From the kind of pet you choose and the food you feed it, to the way you play with and clean up after that animal, you and your children have plenty of ways to reduce the toll your pets take on the planet. And though not everyone agrees on the best way to minimize your pet’s paw print, we’ve got some basic ideas for your family keep in mind.

The scoop on poop

In a study published in 2017, Okin calculated that all the feces produced by pet dogs and cats living in the United States adds up to 5.1 million tons each year. That’s about how much trash the state of Massachusetts produces annually—which means even more climate-change-inducing methane gas as all those poos break down. 

“Dog and cat poops aren’t big, but there are a lot of them,” he says.

There’s not much to do about a pet’s methane emissions, so the trick is teaching kids about sustainable methods of disposing of said poop. For instance, you might choose compostable doggy bags over plastic, take the trouble to flush your dog’s waste, or buy kitty litter made out of bamboo, corn, or other biodegradable products rather than clay.

Just don’t flush your cat’s messes. Although it might seem like an eco-friendly solution, scientists have found that cat feces can pass deadly parasites on to endangered wildlife.

The problem with pet food

Whether it’s dry kibble or pâté with gravy, pet food ingredients have to come from somewhere—and some are more sustainable than others. Foods that contain high levels of protein are particularly burdensome, especially if those proteins come from high-impact animals, such as cows.

There’s also a lot of confusion about how much protein pets require, with many pet food companies advertising ever-higher levels of whole-muscle proteins, like white meat chicken and salmon fillets, while also disparaging “fillers.”  

“Some use the term ‘filler’ to refer to grains or fibers, but that is basically negative marketing lingo,” says Kelly Swanson, a nutritionist in the Department of Animal Sciences at the University of Illinois. “Grains provide starch useful for diet structure and [are] a readily available energy source, and fiber provides many benefits to gut health.”

In general, Swanson says the pet food industry is already pretty sustainable, since they contain products leftover from the human food industry. But families can do several things to make their pet’s food consumption even more so.

“One is to feed to a healthy body weight,” Swanson says. “There are so many overweight pets.” Not only will this cut down on the amount of food consumed, but it will help you avoid costly vet bills down the road. 

Another suggestion is to adjust your pet’s food based on its age. When they’re young, both puppies and kittens require more protein and overall calories, Swanson says. In fact, he recommends scaling back the protein content fed to pets in general as they age, so long as your veterinarian says it’s OK.

“Cats are carnivores, but they don’t need 50 percent protein,” Swanson says, referring to levels found in some commonly available products.

Instead, he recommends looking for cat foods with protein ratios in the high 20s and low 30s. Dogs can likely get away with even less protein, given that they’ve evolved omnivorous diets that more closely mirror our own.

Doing so will also save you cash at the register, as high-protein foods tend to be more expensive, Swanson notes.

Play with your pets

No, really. According to a study published in Current Biology this March, engaging house cats in just five to 10 minutes of play each day significantly reduced their desire to hunt wild animals.

And that’s good news, because outdoor cats kill billions of wild animals every year, making them an enormous strain on native species.

The study also found a correlation between reduced killings and eating grain-free food with meat-derived proteins. The food tested was only around 30 percent protein, says Martina Cecchetti, the study’s lead author and an ecologist at the University of Exeter in the United Kingdom. That’s in line with Swanson’s recommendations above.

The trickier part, says Cecchetti, is that it did seem to matter that the protein came from animals, instead of plants like corn or soy. This hints at the possibility that the less murderous cats are reacting to a micronutrient such as a certain amino acid, she says. And if future studies could identify what that magic ingredient is, then perhaps we could reduce their paw print even further.

Until then, one thing that intrigues Cecchetti is the effort to include more insects in pet food. Insects are highly nutritious, packed with protein, and can be produced en masse with far fewer resources.

Best of all? Cats regularly hunt and eat insects already. “So it will be quite natural, and probably it can be like a good compromise in some way,” she says.

Cecchetti’s study also found that collars designed to make outdoor cats more conspicuous to their prey reduced the number of birds killed by 42 percent. However, the colorful accessories had no effect on the number of small mammals captured. Interestingly, collars with bells on them showed no effect for either birds or mammals, though other research has found that jingling cats might kill as many as 50 percent fewer animals. (Note: Some contend that bells make cats more likely to become prey themselves.)

Of course, Cecchetti says the best thing you and your kid can do to reduce wildlife losses is to keep your cats indoors.

Small choices, big changes

Another way to contribute to the overall sustainability of pets is to pick the right one. A smaller dog has less of an impact than a large one, Okin says. (Though he also notes because cats need more protein, selecting a cat over a larger, medium-size dog “would still actually be a wash.”)

According to one analysis of pet species and the relative costs they inflict on the environment, small animals like rabbits, guinea pigs, hamsters, mice, and rats were among the most sustainable pets to own. Spiders, such as tarantulas, also garnered a top spot. (They’re also easier for kids to care for, as well.)

But the analysis’s most eco-friendly pet may surprise you—tortoises. This is thanks to the reptile’s vegetarian diet, slow metabolism, and low water and exercise requirements.

Even this recommendation comes with some caveats, however. Tortoises can live for 50 or even 100 years, so though they might seem like a kid-friendly starter pet, your kid might not be caring for it for long. And buyers must take extreme caution to make sure the species they select isn’t sourced from the wild, or—worse yet—endangered. (Read this article on the illegal turtle trade network.)

Hermit crabs are also popular with kids, but the animals don’t breed well in captivity and therefore must be taken from the wild at unsustainable levels. Parrots and many other colorful bird species are similarly threatened. (Check out this read on the negative impacts of parrots’ popularity.)

Whatever you do, Swanson reminds pet owners that it’s not all-or-nothing. Whatever steps your family takes, remember that every choice contributes to the greater good.

Says Swanson, “There are small changes you can make that do add up quite a bit.”