While some old wives’ tales and urban myths are entertaining, there are a few persistent ones exchanged over the backyard fence or the Internet that would be laughable if they didn’t pose a potential threat for pets.

In the spirit of “out with the old and in with the new,” here are some of the most popular dog myths and truths.

One dog year is equal to seven human years

There is no exact formula for canine aging – it’s highly individual. Pets do age much faster than people. On average, the first year of a dog’s life equals about 16 human years, according to PetPlace.com. At 2, they are like 24-year-old humans. At 3, 30-year-olds.

Size and breed are significant factors because most large dogs age faster than smaller dogs. For example a 10-year-old giant breed dog (90 pounds plus such as Great Dane, Mastiff, St. Bernard, Newfoundland) is the equivalent of 78 human years whereas a 10-year-old small breed (under 25 pounds such as Chihuahua, Pug, Shih Tzu, Pomeranian, Bichon Frise) would be 56 human years.

The important thing to remember is that most dogs have already reached adulthood at the age of 2, and by age 7, many pets are entering their senior years. Today, the average life span for dogs is about 13 years and cats can live much longer.

Dogs are color blind

Dogs do see colors, but the colors that they see are neither as rich nor do they see as wide a spectrum as humans. Dogs can’t tell the difference between yellow, red or green but they can detect the difference between closely related shades of blue, gray and violet better than people, according to PetPlace.com. “How Dogs Think” by Stanley Coren points out that when you’re throwing a yellow tennis ball for a dog to fetch, the color makes it easier for people to find the slobber-slick ball in the tall grass, not the dog. Dogs would see a blue tennis ball better.

A dog’s mouth is cleaner than a human’s

“Dog saliva was once considered to be antiseptic and some people still believe it has healing properties,” according to PetPlace.com.

Whoever thought this one up has never observed where our dogs lick or what they put in their mouths! Though it can kill some bacteria, dog saliva contains its own exotic cornucopia of bacteria that can cause serious infections, especially in people with weak immune systems (HIV, chemotherapy, elderly or sick).

If a dog scoots on his rear, he has worms

A dog scoots across the carpet or grass on his rear to, ahem, relieve an itch or irritation in the No. 2 region. “Dogs For Dummies” explains that worms (external parasites like tapeworms, roundworms, etc.) can be one source of that irritation along with impacted anal sacks, fecal material that is clinging to the hair around the anus, even constipation. While some super-diligent pet owners keep the anal glands checked-and-cleaned and give the pet what some appropriately call a “potty path trim,” the job is typically better left to professionals, veterinarians or groomers.

If you think you see evidence of external parasites around the rectum or in the dog’s stool, take a small, fresh sample of the feces to the veterinarian right away for an accurate diagnosis.

Dogs eat grass when their stomachs are upset

The theory goes that grass makes dogs vomit, so when they have the urge to purge (ate something bad, or have an upset tummy) they graze like cows in the backyard. But many dogs graze without any ill effects.

Some theorize that dogs seek grass as it fulfills some nutritional deficiency or that they may do it just because they like the texture on their tongue’s or taste in their mouths. Truth is, no one really knows.

A hot, dry nose means a dog has a fever

You can tell a dog has a fever when you stick a thermometer where the sun doesn’t shine or by utilizing one of the new instant ear thermometers (www.pet-temp.com) and find the dog’s temperature is above 102.5 degrees Fahrenheit. According to the book “Why Do Dogs Have Wet Noses and Other Imponderables,” most healthy dogs have wet noses most of the time, but a dry nose doesn’t mean a dog is sick. The wet nose aides the dog in collecting scent particles for its incredibly sensitive scent-detecting system. A dry-nosed dog may have slept in a heated room, buried its nose under the blankets overnight, or it may be dehydrated.

Dogs feel guilty when they do something wrong

While we all think we’ve witnessed this, it’s not true. The “hang-dog” look of canine culpability is nothing more than fear and submission.

Because he perceives you, the pet owner, as the leader of the pack, he will act submissive if he senses you are displeased, according to PetPlace.com, even if he has no idea what has made you displeased. In fact, if you come home from work and get red-eyed with rage in finding Sparky has disemboweled the sofa, he won’t have a clue what he did to make you angry; he just wants to be a canine-conciliator.

Dogs understand what humans are saying

Well, this one may be true. New research in the Journal of Science shows that dogs have a remarkable capacity to comprehend human speech. Their test subject: Rico, a Border collie, who knows the names of more than 200 toys and fetches them on command.

Veterinary Economics magazine points out that Rico demonstrates the verbal understanding that’s about the level of a 3-year-old toddler. Dogs now join bonobos, chimpanzees, gorillas, orangutans, African grey parrots and dolphins in the list of animals eroding the belief that only humans have the capacity for language.

Dr. Marty Becker is the coauthor of the book “Chicken Soup For The Horse Lover’s Soul.”

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