Q: When dogs yawn, are they sleepy or bored?

A: Neither, really. Think of yawning as a kind of switching gears. A yawn increases the flow of oxygen and boosts the heart rate -- actions that give the brain a good goosing. A yawn can prepare the body for action -- as in the yawning of a keynote speaker waiting for her introduction or a quarterback waiting to get back onto the field. Yawning can also be a way to relax.

Dogs yawn both to charge themselves up and to calm themselves down. It depends on the situation. If you go to a canine agility competition, you'll often spot dogs yawning at the starting line while waiting for the signal to explode across the line to the first obstacle. They're ready to run, and the yawn expresses that stress and excitement. In the waiting room of a veterinary hospital, you'll often see dogs yawning, too -- a sure sign that they're stressed and trying to calm themselves.

In training classes, dogs will often yawn -- and owners will often interpret this as a sign that the dog is bored. Not so. The dog who's yawning in obedience class is more likely stressed than bored, either from nervousness or from wanting to please you but not yet understanding how.

Just as in humans, yawning can be contagious in dogs. If you catch your dog's attention and yawn, you may well get a yawn back. Some experienced dog handlers actually use this to their advantage, encouraging their dogs to yawn as a way to get them either focused or relaxed.

Q: Is it true dogs can't see in colour?

A: Dogs do see colours, but not as many as we can see. And the colours they see aren't as rich, either. This may be a relief to some of us, who are tired of hearing how dogs smell better, hear better, and are faster and stronger than we are.

The bottom line, though, is that dogs don't have great colour vision because they don't need it. If you throw a tennis ball in the grass, the yellow colour makes it easier for you to find, not your dog, who could find a blue tennis ball much more easily. Your dog doesn't care; she's going to find it with her nose.

Dog vision is exactly what you'd expect from an animal whose life depends on her ability to spot prey. We humans developed with the ability to see in rich colour and detail, while a dog's vision is more closely attuned to catching movement. The better to eat you with, my dear!

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Excerpted from Why Do Dogs Drink out of the Toilet? by Marty Becker, DVM, and Gina Spadafori. Copyright 2006 by Marty Becker and Gina Spadafori. Excerpted by permission of Health Communications, Inc. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.

Q: Do dogs get depressed?

A: The emotional range of a dog is not all that wide or deep, to be honest. That's one reason why a dog who seems to show what, in humans, might be signs of depression -- lethargy, loss of appetite, changes in normal sleep patterns -- is more likely to have a physical problem than a mental one.

Still, there's no denying that many dog lovers have observed what looks a lot like grief in pets who have lost a family member, either four-legged or two-legged. Perhaps the most well-known example or canine grief is that of Greyfriars Boby, the Skye terrier who visited his owner's grave in Scotland every day for 14 years, until the dog's own death in 1872. The fact that people noticed and rewarded the dog with food and shelter for his loyalty might have played a factor in his behaviour, but we'd hate to ruin such a good story.

So, yes, it seems some dogs do have an emotional response to the loss of a beloved human or pet companion. But dogs are also amazingly resilient when it comes to joining a new family. Think of shelter dogs. Can you imagine how much time people would have to spend in therapy if they were suddenly removed from one family and placed with another -- in some cases, again and again? Although some newly adopted dogs go through an adjustment period that may include being anxious and destructive when left alone, most bounce back and become happy-go-lucky new family members.

"Love the one you're with," seems to be the motto of many a dog.

Q: Do dogs get Alzheimer's disease?

A: Dogs are living longer and are prone to many of the same age-related health problems as their human companions. One of the most devastating is Canine Cognitive Dysfunction, which is very similar to human Alzheimer's. This condition affects millions or dogs and leads to reduced brain function and, often, behavioural changes.

Like the human Alzheimer's patient, the dog often seems to forget her surroundings and not recognize loved ones. Or she may act confused or disoriented, may sleep more during the day and less at night or even have frequent housetraining lapses.

Imagine going from a world of colour and surround sound to black-and-white images with the sound coming from an AM radio. That's what it's like for your beloved senior dog with Canine Cognitive Dysfunction.

In some cases, a change of diet may help. Others need the addition of a drug specifically developed to treat Canine Cognitive Dysfunction, which can help your pal feel more like herself again. Check with your veterinarian about the diet and medications.

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Excerpted from Why Do Dogs Drink out of the Toilet? by Marty Becker, DVM, and Gina Spadafori. Copyright 2006 by Marty Becker and Gina Spadafori. Excerpted by permission of Health Communications, Inc. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.