How Old is Your Dog Really?
Today, I sat outside in the warm breeze and watched one of my four, furry little rays of joy pounce around the yard. As I watched her chase bugs and bark at the deer, it dawned on me just how impressive she was. My little Daisy is nearly twelve years old and is just as spry as any dog half her age. Twelve is pretty old for a dog, as almost everyone knows, but just how old is it really? As humans age, we arrive at these various milestones of bodily failure. In our thirties, we begin to complain that our livers don’t process our all-nighters like they used to in college. In our forties, we go for the “just to be safe” checkups that often make us very uncomfortable. In our fifties, we’ve all got something wrong and are actively working to slow or alleviate its progression. Our sixties are pills and lifestyle changes and anything beyond them is gravy, though not literally, because we aren’t allowed to have gravy anymore. The real question is, why can’t we see these defining moments of health change as easily in our pets? Is my dog really “old” if she runs freely about the yard chasing animals ten times her size? What about her rescue friend, Zoie? They’re roughly the same age, but the level of their activity is drastically different. So, how old is my dog really?
A Dog’s Human Age
We’ve all heard the wives’ tale, “Each human year is equivalent to seven dog years,” but it’s not even remotely that simple. A year of time is, in truth, no different to a dog than it is to us. There is no alternate set of sensations to a year. Dogs are not self-aware and tracking their remaining years. So, how can we reasonably ask how many dog years are in one human year? In reality, you can’t. A year is a year. What you’re really asking is, “how does the rate of aging in dogs compare to the rate of aging in humans?” While not entirely accurate, the chart below is a good ball park: From WebMD
The Rate of Living Theory
The chart is really illustrating the rate of maturation in small, medium, and large dog breeds. Dogs are similar to humans and other mammals in that each individual can vary greatly from another. Much of the modern science of aging is based on The Rate of Living Theory. This theory, proposed by Max Rubner in 1908, suggested that length of mammalian life was directly related to metabolism. He came to this conclusion by observing that larger mammals tended to outlive smaller ones. The oddity in the theory is that small dogs tend to outlive larger dogs. The reasons for this are a lot deeper than the scope of this article and involve more than one metabolic rate in calculations of calorie usage. For our purposes, we will assume a broader understanding. Nonetheless, this theory plays a big part in the understanding of a dog’s maturation cycle.
Maturation Stages of Dogs
The first stage of maturation in dogs is, of course, puppyhood. This is often the cutest stage in a dog’s life, while also being one of the most influential in training. Due to the rapid growth experienced in this stage, the first year of a dog’s life is comparative to our first fifteen. This stage lasts between six to eighteen months. The second stage in maturation is Adolescence, which lasts more or less time based on when puppyhood ends. Think of these months as the difficult teenage years of a human child. Most agree that the third stage, adulthood, begins anywhere between one and three years of age. When this stage occurs is very important to interpreting your dog’s human age. The first three years of a dog’s life is a time of exponential growth as it relates to human age. By reaching full adulthood, a dog can be seen as twenty four years old. As early as six years, and as late as ten, the dog will enter the senior stage. Ultimately, though, the rate of increase per human year, at this point, is anywhere from 3-7 years. As mentioned before, this greatly depends on the size of the dog and individual genetics.
Size as it Relates to Aging
Most resources on oxidative science, or Redox Biology, are fairly limited on concrete facts. However, cell oxidation is why organisms age and die. Typically, as mentioned above, larger mammal species tend to have longer life spans than their smaller counterparts. In the case of dogs, this is less true. Often, the larger the dog breed, the less time it has on this earth. There are several theories regarding why this is, but the most popular right now relates to the levels of a certain growth hormone found in larger breeds. This hormone, IGF-1, is responsible for the increase in size. It is believed that the hormone has a direct correlation with the effects of aging in these breeds. Small to medium sized dogs tend to have much lower levels of this hormone in their blood at all times in life. The general debate around this find, though, revolves around whether or not big dogs age faster, or earlier. It is unclear if the aging process simply begins at earlier stages of a large dogs life or if, once it begins, completes very rapidly. There is evidence to support that both could be simultaneously affecting the dogs, so it is hard to determine which plays the bigger role. One thing is for certain, the experiments necessary to discover the truth behind it would potentially be considered cruel and unusual. So, maybe we’re better off not knowing!
The Bottom Line
Unfortunately, the best calculation for your dog’s human age will only be available after you say goodbye forever. That’s too depressing, so let’s use the chart! My little Daisy may be sixty-four years old in human years, but she’s as healthy as she was in her twenties. Here’s to ripe old age for all our furry friends.