Aging in dogs

Aging in dogs (Canis lupus familiaris) varies from breed to breed, and affects the dog's health, physical ability and life expectancy.

As with humans, advanced years often bring changes in a dog's ability to hear, see and move about easily. Skin condition, appetite and energy levels often degrade with geriatric age, and medical conditions such as cancer, renal failure, arthritis and joint conditions, and other signs of old age, may appear.

The changes in care often required by an older dog may lead a non-experienced owner to release the animal to a shelter or rescue organization. Non-profit groups have sprung up in response to the growing need for senior dog rescue.

The aging profile of dogs varies according to their adult size (often determined by their breed): smaller dogs often live over 15–16 years, medium and large size dogs typically 10 to 13 years, and some giant dog breeds such as mastiffs, often only 7 to 8 years. The latter also mature slightly older than smaller breeds—giant breeds becoming adult around two years old compared to the norm of around 12–15 months for other breeds.

The terms "dog years" and "human years" are frequently used when describing the age of a dog. However, there are two diametrically opposed ways in which the terms are defined:

However, regardless of which set of terminology is used, the relationship between dog years and human years is not linear, as the following section explains.

They can be summarized into three types:

No one formula for dog-to-human age conversion is scientifically agreed on, although within fairly close limits they show great similarities.

As a rough approximation, the human equivalent of a one-year-old dog is between about 10 and 15 years—a one-year-old dog or cat has generally reached its full growth and is sexually mature, although it might still be lanky and need to fill in a more mature musculature, similar to human teenagers. The second year is equivalent to about another 3 to 8 years in terms of physical and mental maturity, and each year thereafter is equivalent to only about 4 or 5 human years.

Emotional maturity occurs, as with humans, over an extended period of time and in stages. As in other areas, development of giant breeds is slightly delayed compared to other breeds, and, as with humans, there is a difference between adulthood and full maturity (compare humans age 20 and age 40 for example). In all but large breeds, sociosexual interest arises around 6–9 months, becoming emotionally adult around 15–18 months and fully mature around 3–4 years, although as with humans learning and refinement continue thereafter.

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