For first two years:
- 12.5 years per human year for the first two years for small dogs
- 10.5 years per human year for the first two years for medium-sized dogs
- 9 years per human year for the first two years for large dogs
For years 3+:
- Small: Dachshund (Miniature) 4.32, Border Terrier 4.47, Lhasa Apso 4.49, Shih Tzu 4.78, Whippet Medium 5.30, Chihuahua 4.87, West Highland White Terrier 4.96, Beagle 5.20, Miniature Schnauzer 5.46, Spaniel (Cocker) 5.55, Cavalier King Charles 5.77, Pug 5.95, French Bulldog 7.65
- Medium: Spaniel 5.46, Retriever (Labrador) 5.74, Golden Retriever 5.74, Staffordshire Bull Terrier 5.33, Bulldog 13.42
- Large: German Shepherd 7.84, Boxer 8.90
Large dogs, on the other hand, may take two years to get to their fully mature skeletal body size and then they may only live another four or five years.
The Bulldog for example only lives on average until it’s six years old whereas a Border Terrier lives on average to the age of 14.
What this means is that small dogs age more quickly than big dogs in their first couple of human years but slower than big dogs once they hit adulthood.
So, bizarrely, a small dog is older than a big dog at two human years – but younger at five.
“It doesn’t happen in any other animal,” says Kate Creevy. “There isn’t any other species which has within a single species the same degree of size diversity that dogs have. It’s possible that by creating all of these diversely sized dogs that we unmasked this ageing phenomenon.”