The average lifespan of a healthy, well-bred Yorkshire Terrier is approximately 12 to 15 years. If you've adopted a new Yorkie without knowing his exact date of birth, there is no way to be 100 per cent sure how old your dog is. However, by taking a good look at certain aspects of your new pet's teeth, face, and habits, there are many signs that can give you a good general idea of his age.
Check your dog's upper and lower incisors, which are the teeth at the very front of the jaw. When a dog is very young, each these teeth will have three rounded projections, called cusps. The cusps on the lower front teeth begin showing wear generally around the age of 15 months. If they still look fairly fresh and new, it's likely that your Yorkie is younger than that. If the cusps are gone altogether, the dog is probably older than 18 months. Cusp wear is a slower process on the upper incisors and those cusps generally stick around until 2 1/2 to 3 years of age.
Look for tartar or yellowing of the dog's teeth. Tartar deposits are most often seen at the base of the canines (the long, fang-like teeth next to the incisors) beginning at about four years old.
Inspect the hair around your Yorkie's nose and lips. Just like humans, dogs begin to develop grey hair as they age. A Yorkshire Terrier is considered a senior beginning at about 8 years old, so greying of hair on the face can be a sign that you have an older dog.
Observe your dog's mobility. An older Yorkie will be slow to stand up from a sitting or laying position and may be hesitant to jump onto and off furniture, whereas a young dog will seem much quicker and more fearless. If you have an older dog, you can purchase ramps and steps to place near your furniture to make it easier for him to get up and down and minimise the chances of hip injury caused by jumping.
Check the eyes for a cloudy appearance, which often occurs in geriatric dogs. A Yorkie is considered to be geriatric at approximately 12 years of age. The cloudiness is caused by a hardening of lens protein in the eyes and occurs in many old dogs. In most cases, the dog can still see just fine despite the cloudiness but you may want to check with your veterinarian to make sure that it isn't cataracts.
If you have a female Yorkie, she will enter her first heat around the age of six months to one year. If you don't plan on breeding her, having her spayed will vastly cut her chances of developing health problems later in life.