The Biggest Myths About Pet Behavior That People Still Believe

These Common Pet Myths Are Still Fooling People—And It’s Time to Set the Record Straight.

Pet owners love their furry friends, but even the most dedicated animal lovers can fall for common myths about pet behavior. You might think you know your dog or cat inside and out, but some of the things people believe about pets are just plain wrong. These misconceptions can lead to confusion, miscommunication, and even unintended harm. The truth is, understanding your pet’s behavior requires cutting through these old myths and learning what science actually says. Getting it right can improve your relationship with your pet and help them live a happier, healthier life. It’s surprising how much misinformation is still floating around—and chances are, you’ve believed at least one of these myths without realizing it. Here’s what you really need to know about how your pets think and behave.

1. Dogs eat grass because they’re sick.

One of the oldest misconceptions about dogs is the idea that they only eat grass when they’re feeling unwell. According to PetMD, this belief doesn’t hold up. Many dogs chew on grass simply because they enjoy the texture or find it entertaining. Some experts also suggest that it could be a natural instinct inherited from their wild ancestors.

Just because your dog is munching on grass doesn’t mean you need to rush to the vet. Of course, if the behavior becomes excessive or is accompanied by vomiting, it’s worth consulting a professional. Otherwise, occasional grass eating is completely normal and often harmless. Offering safe alternatives like chew toys or treats can help satisfy their craving for something to nibble on.

2. Cats always purr when they’re happy.

It’s easy to assume that a purring cat is a content cat, but that’s not always true. According to OVRS, cats also purr when they’re scared, stressed, or in pain. This soothing vibration can actually serve as a self-soothing mechanism, helping them stay calm during moments of distress.

You might notice your cat purring at the vet, after getting injured, or even when they’re frightened. This doesn’t mean they’re relaxed—instead, it could be their way of coping with an uncomfortable situation. Paying attention to body language, such as flattened ears or a tense posture, can give you a clearer picture of how your cat is feeling. Understanding this can help you provide comfort and support when your feline friend needs it most.

3. A dog wagging its tail is always happy.

Many people believe that a wagging tail automatically signals joy, but that’s only part of the story. According to SG Smart Paw, tail wagging can indicate a variety of emotions—including anxiety, fear, or even aggression. The position and speed of the wag can provide important clues about what your dog is really feeling.

For example, a slow, stiff wag might mean your dog is feeling uncomfortable or unsure. A high, fast wag could signal excitement, while a low wag often indicates submission or fear. Observing the context and overall body language—like ear position and facial expressions—can help you interpret your dog’s mood more accurately. Recognizing these signals helps foster better communication and strengthens your bond with your pet.

4. Dogs have clean mouths.

The belief that a dog’s mouth is cleaner than a human’s is one of the most persistent pet myths out there. According to OVRS, dogs’ mouths are actually teeming with bacteria—many of which can be harmful to humans. While it’s true that dogs have different bacteria than humans, that doesn’t mean their mouths are hygienic.

Allowing your dog to lick your face, especially near your mouth or eyes, can expose you to bacteria and parasites. While most pet owners love those affectionate slobbery kisses, it’s important to practice good hygiene afterward. Regular dental care for your dog, including brushing their teeth and providing dental chews, can help reduce the bacteria in their mouth. Just remember, their mouths are far from clean, and it’s better to play it safe when it comes to sharing smooches.

5. Cats can see in complete darkness.

It’s easy to think that cats have superpowered night vision, but the truth is a little different. While cats can see better in low light than humans, they cannot see in total darkness. Their eyes need at least some light to function effectively, so they aren’t capable of navigating pitch-black spaces any better than humans can.

The secret to their impressive night vision lies in a special layer of cells called the tapetum lucidum, which reflects light and enhances their ability to see in dim environments. This evolutionary advantage allows them to hunt effectively at dawn and dusk. However, in complete darkness, they’re just as blind as we are. Leaving a small nightlight on can help your cat move around safely at night, particularly if they’re older or have vision problems.

6. Dogs look guilty when they’ve done something wrong.

That classic “guilty look” many dog owners recognize—ears back, eyes wide, head lowered—isn’t actually a sign of remorse. This expression is a form of appeasement behavior, meant to reduce tension when dogs sense anger or disappointment from their owners. Dogs don’t process guilt in the same way humans do, but they’re highly attuned to body language and emotional cues.

What you’re seeing is a sign of submission, not an admission of guilt. Your dog is responding to your mood and trying to avoid conflict. Punishing them for this behavior can create fear and confusion rather than teaching them anything constructive. Focusing on positive reinforcement and patience will help create a stronger bond and a more trusting relationship with your furry friend.

7. You can’t teach an old dog new tricks.

The idea that older dogs are untrainable is just plain wrong. Dogs of any age are capable of learning new behaviors, especially when training methods are consistent and gentle. Older dogs can actually be easier to train in some cases, as they tend to be more focused and less distracted than their younger counterparts.

Mental stimulation is essential for older dogs and can even help slow cognitive decline. Engaging activities like puzzle toys, basic obedience training, or teaching new tricks can keep their minds sharp. With patience and encouragement, older dogs can learn just as effectively as puppies. Training can also strengthen your bond, giving your senior dog a renewed sense of purpose and joy.

8. Dogs and cats are natural enemies.

The idea that dogs and cats are destined to be rivals is a misconception. While their instincts and communication styles are different, many dogs and cats can live together peacefully with proper introductions and socialization. In fact, plenty of dogs and cats become inseparable companions over time.

It all comes down to patience, supervision, and understanding each pet’s comfort level. Allow them to adjust gradually and respect each other’s space. Positive reinforcement when they interact calmly can help establish trust between them. Over time, many dogs and cats learn to coexist harmoniously—and some even form deep friendships that defy the old stereotype.

9. Rubbing a dog’s nose in accidents helps with housetraining.

This outdated training method can actually do more harm than good. Rubbing a dog’s nose in their mess doesn’t teach them anything about where they should go—it just instills fear and anxiety. Dogs learn through positive reinforcement, not punishment, and associating accidents with fear can lead to more behavioral issues.

Instead, reward your dog for going in the right place with treats and praise. Consistency, patience, and understanding your dog’s cues are the keys to successful housetraining. Accidents happen, especially with young puppies, so it’s important to stay calm and offer encouragement. A supportive, stress-free environment will help your dog learn faster and feel more secure.

10. Shaving pets keeps them cool in hot weather.

Shaving your pet during hot weather might seem logical, but it can actually make it harder for them to regulate their body temperature. A pet’s coat acts as natural insulation, keeping them cool by protecting their skin from direct sunlight. Shaving their fur can increase the risk of sunburn and heat-related issues.

Instead of shaving, focus on regular grooming and brushing to remove excess fur and prevent matting. Providing plenty of shade, access to water, and avoiding outdoor activities during peak heat hours are much more effective ways to keep your pet comfortable. If you’re unsure about how to care for your pet during hot weather, a veterinarian can provide advice tailored to your pet’s specific needs.