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Aging in Dogs  

As dogs age their temperament, hearing, and skin condition often change, and medical conditions such as cancer, renal failure, arthritis and other joint conditions may appear.

There's an urban legend that a human's (homo sapien) year is equivalent to seven dog (Canis lupus familiaris) years, but it is a misconception, the first year or two years of a dog's life represents 18-25 years of a human, and different breeds and sizes of dogs age differently. For example, giant breeds mature later, becoming adult around two years old compared to the norm of around 12 - 15 months for other breeds.

No one formula for dog to human age conversion is scientifically agreed, 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, and some dogs, like humans, never seem to manage it. Yet again the development of giant breeds is slightly delayed compared to other breeds, and as with humans there is a difference between adulthood and full maturity. In all but large breeds, socio-sexual interest arises at around 6-9 months, and dogs generally become emotionally adult around 15-18 months, they reach full maturity at around 3-4 years, although as with humans learning and refinement continues thereafter.

According to the UC Davis Book of Dogs, small-breed dogs (such as small terriers) become geriatric at about 11 years; medium-breed dogs (such as larger spaniels) at 10 years; large-breed dogs (such as German Shepherd Dogs) at 8 years; and giant-breed dogs (such as Great Danes) at 7 years.

The most common effects of aging are:

  • Loss of hearing
  • Loss of vision (cataracts)
  • Decreased activity, more sleeping, and reduced energy (in part due to reduced lung function)
  • Weight gain (calorie needs can be 30-40% lower in older dogs)
  • Weakening of the immune system leading to infections
  • Skin changes (thickening or darkening of skin, dryness leading to reduced elasticity, loss or whitening of hair)
  • Change in feet and nails (thicker and more brittle nails makes trimming harder)
  • Arthritis and other joint problems
  • Loss of teeth
  • Gastrointestinal upset (stomach lining, diseases of the pancreas, constipation)
  • Urinary issues (incontinence in both genders, and prostatitis/straining to urinate in males)
  • Mammary cysts and tumors in females
  • Senility
  • Heart murmurs
  • Diabetes