We asked a friend of ours recently if she would be willing to contribute a photo of her two dogs, who are 7 and 9 years old, to our Senior Dogs Project. She bristled a little and then said, "My dogs aren't senior! They don't act old. They run and jump and play just as they always have."

Like people, dogs are individual in the way they age. Certain breeds, mixed breeds, and, in general, smaller dogs tend to live longer. A small dog of less than 20 pounds might not seem to show any signs of age until she is 12 or so. A 50-pound dog won't seem old until about 10. Larger dogs begin to show their age at 8 or 9.

It's encouraging that the average lifespan for dogs has increased from 7 years in the 1930's to more than 12 years today. With the right care, it's not uncommon for dogs to live to 14 or 15 these days. Using established guidelines to determine when your dog might qualify as a senior will help you to understand changes in behavior or to anticipate a change in health status. On the basis of your knowledge, you will be better able to identify and approach health problems in an early stage, when they may be more easily treated. Following is a table to give you an idea of the relationship between a dog's age and a human's. Note that the weight of the dog is related to his age in human years:

Tufts University published the following guidelines for defining a senior dog: "The point at which a dog qualifies as 'aged' varies. Veterinarians generally consider small dogs to be senior citizens at about 12 years of age, while large dogs reach the senior stage at 6 to 8 years of age. This roughly corresponds to the 55-plus category in people."

What are the signs of aging and what should you do about them? One of the first signs of aging is slowing down. It will take your dog longer to get up and get started from a lying position, longer to climb stairs (one at a time, rather than two). Some of these changes are natural, but it is important not to overlook changes that may be symptoms of a condition needing treatment.

Never assume that a change in behavior or habits is simply due to old age; it may be due to a treatable condition. An excellent example is that cited by Dr. Robin Downing, DVM, who reports: "Molly wasn't leaping on and off the beds anymore, and she didn't want to go for long walks. Her family was worried that this dog had just suddenly succumbed to old age, but when I did a geriatric workup on her, we discovered Molly had a thyroid condition and arthritic back pain. A maintenance prescription of thyroid replacement hormone, pain and anti-inflammatory medication for the osteo-arthritis in her back, and Molly was back in business. In fact, three years later, her owners tell me Molly is more active than she's been in years!" (Healthy Pet magazine, Spring/Summer 2000, p. 13.)

Diseases occur in older dogs that are not usually seen in young dogs, such as arthritis, diabetes, Cushing's disease, cancer, and kidney, heart, and liver diseases. Blood tests done by a veterinarian will screen for many of these diseases, which is the reason that your veterinarian will do such tests during an annual visit. However, you can also be instrumental in keeping your older dog healthy by:

• keeping his weight down (through good nutrition and regular exercise)
• keeping his teeth clean (next to obesity, periodontal disease is the one most commonly seen in the vet's office)
• getting him to the vet for regular check-ups