If you've ever been the lucky parent to man’s best friend, you know how fast they grow. It seems like one day, your dog is still a tiny puppy, and the next, he is a fully grown woofer. Bored Panda reached out to Somya Anand, dog behavior specialist at Monkoo Dog online community aimed at building a sustainable life for pets, to find out more about just why dogs grow up so fast until their hair turns grey.

Somya said that how fast your dog grows largely depends on its breed. “It is generally observed that smaller breeds reach full growth faster than larger breeds. It also varies with mixed breeds and the growth milestones are usually closer to the dominant breed variety.”

Having said that, she added that “a pup has become an adult dog as it completes one year; while this may not be accurate, most breeds reach full growth in this time frame—12-18 months—and hence it has become a general rule of thumb.”

Meanwhile, in most cases, dogs are considered senior when they turn anywhere between 5 and 10 years old. As a general rule, large dogs will typically age faster than smaller dogs. Therefore, it’s not uncommon to see a senior Great Dane at age 7 or a Chihuahua in his 20s.

Somya also explained that while your dog is still a puppy, “the rapid growth spurt lasts generally till six months and then becomes more gradual. So don’t be surprised when your tiny little puppies become big overnight!”

At around 2 years of age, most middle-sized dog breeds stop growing altogether, and at the age of 7 years old, dogs exhibit the first signs of "retirement." Many of the signs are similar to that of humans: changed sleeping and eating patterns, weight gain, lumps and bumps, and general slowdown.

For most dog owners, the real headache starts around when the dog reaches 7 to 9 years old. But there are some things to know about raising a senior dog which can help their longevity.

First, brushing your dog's teeth regularly can prevent oral diseases that can shorten your furry friend’s life. Secondly, make sure you give your old boy enough physical activity to keep him in shape and prevent weight gain. And third, one should always provide your woofer with a healthy and nutritious diet.

Most importantly, leaving your dog unattended for long periods of time, especially at a senior age, can lead to severe dog depression and anxiety. Even if your woofer is slower than he ever was before, it doesn’t mean he doesn’t need a stroll in the park and some goofing around!