How Old Is My Rescue Dog? A Comprehensive Guide

How old is my rescue dog? You may never know for sure. Determining a rescue dog’s age is challenging. Even seasoned veterinarians and rescuers often misjudge dogs’ ages. The most accurate method, a pricey DNA test, is usually beyond most rescuers’ budgets. 

That’s too bad because I’ve seen firsthand how much age matters when adopting a rescue. When fostering in college, Justin and I fostered a Rat Terrier named Iris (maybe my all-time favorite foster, definitely Justin’s). The rescue told us she was 2-3 years old and, while we sensed she had an old soul, we didn’t think to question them.

An older gentleman met and fell in love with Iris. He was lonely and wanted a friend to watch the sun set on his life with (he told us a few times that Iris would be his last dog). It was lovely and seemed perfect.

But when he took Iris to his own vet, her age was estimated to be at least 7, robbing him of 5 years of time with Iris. It was heartbreaking to see him realize that he was likely to outlive her.

They were still a great fit and he of course kept her, but our experience with Iris gave us a reason to learn all we could about how to estimate a rescue dog’s age, information we are sharing with you here.

Have you recently adopted a dog? Make sure to learn how to crate train a rescue dog for their safety and the sake of your furniture.

You may be anxious about walking your new rescue dog. Many of the volunteers, fosters, and adopters that I work with struggle with leash walking, so I made a foolproof guide to walking a rescue dog.

How Can I Tell How Old My Rescue Dog Is?

The best way to estimate a rescue dog’s age is to look at their teeth, eyes, behavior, and mobility. Other indicators like activity level, hearing, weight, muscles, skin, coat, feet, nails, and pads can be examined to gauge the age of your rescue dog.

Here’s a breakdown of how to determine a rescue dog’s age. It’s best to consider as many factors as possible to arrive at an accurate estimate.

Pro Tip: Did you adopt your rescue dog as an adult? If they haven’t changed very much in the first year of getting them, medium to large breeds were probably aged 2-4 at adoption, while small breeds were likely between 1-5 years old.

What Are The Canine Life Stages?

Canine Life Stage	Small Dogs	Medium Dogs	Large Dogs	Giant Dogs
Puppy	0-4 months	0-4 months	0-6 months	0-6 months
Adolescent	4 months – 1 year	4 months – 1 year	6 months – 2 years	6 months – 3 years
Adult	1 – 11 years	1 – 8 years	2 – 8 years	3 – 6 years
Senior	11 years and up	10 years and up	8 years and up	6 years and up

At What Age Is My Dog Considered a Senior?

Dogs are considered to be seniors when they enter the last 25% of their expected lifespan. That lifespan is largely, but not entirely, dependent on their size.

For example, a Great Dane’s average life expectancy is between 8-10 years, so they are considered senior at 6. On the other hand, Chihuahuas live 15-16 years, so they aren’t considered senior until they are about 11.

How To Tell How Old Your Rescue Dog Is

Teeth

Teeth are typically the most common way that professionals gauge a dog’s age, so that’s where we’ll begin.

Wait: How Big Is Your Rescue Dog?

Before you begin considering your dog’s age based on the teeth, think about whether your dog is considered a small or large breed dog. 

Small dogs may appear older or younger than they are if you’re primarily using the teeth as your gauge.

• Teeth may erupt later or shed later in small dogs, which can confuse an age estimate even in puppies.
• Small dogs are more likely to retain baby teeth, often causing crowding and misalignment unless corrected.
• Small dogs are also more likely to have dental crowding and malocclusion due to the overall small mouth. This can lead to misaligned teeth and bite issues that wear teeth down quickly.
• They are more likely to get periodontal disease since crowded teeth easily trap food and plaque. Additionally, teeth don’t rub in natural patterns that would otherwise clean tartar. This can result in lost teeth and gum disease.

Puppies

The timeline for tooth development in puppies is pretty consistent. Therefore, it’s pretty easy to accurately estimate a young puppy’s age by a few weeks by looking at their teeth:

• Newborn: Typically toothless.
• 1 month: Teeth start to emerge.
• 2 months: Full set of 28 milk (baby) teeth.
• 12-16 weeks: Adult incisors begin replacing puppy incisors.
• 5-6 months: Permanent canine teeth appear.
• 4-7 months: Adult canines, premolars, molars come in.
• By 7 months: Complete set of 42 permanent teeth

Adolescents

By the time a dog is 6 or 7 months old, all of the adult teeth are typically present, and estimating age gets a little bit more challenging. 

When a dog is between 6 months and a year, the teeth will go from spotless pearly whites to showing small amounts of wear and tartar. 

By the time the dog is a year old, there will be noticeable ridges on the four front incisors. The tips of the back molars will still be sharp. 

Between a year and two years, you’ll see some tartar buildup and wear on the incisors, particularly in dogs who enjoy chewing. Some tartar will likely be visible on the gum line of the back molars.

Adults

By the time a dog is between 3 and 5 years old, they will show moderate tartar buildup, particularly if they have not had dental care.Those pearly whites are going to look a little bit more yellow as well. 

You won’t have to look hard to see the wear on the incisors, and in dogs that are primarily fed kibble and given plenty of chew toys, the back molars will start to wear down. 

The ridges on the front incisors, so evident in a year-old dog, are beginning to be worn down by the time the dog is three or four. 

Between the ages of 5 and 10, the wear, tartar buildup, and yellowing continue.

By the time a dog is 7 years old, expect to see the incisors completely smooth. 

Past 7 years, significant wear and declamation, and thicker tartar buildup are more common. 

Seniors

Once a dog is over 10 years old, expect to see some significant wear on the teeth. It is common for incisors to be ground down or broken. 

Dental diseases like gum recession, gingivitis, and lost teeth are very common. 

Even in dogs with generally healthy mouths, there will be a lot of tartar buildup if they haven’t received dental care.

Age Estimate	Dental Characteristics
Newborn	Typically toothless.
1 month	Teeth start to emerge.
2 months	Notice a full set of 28 milk (baby) teeth.
12-16 weeks	Adult incisors are emerging, replacing puppy incisors.
5-6 months	Permanent canine teeth are appearing.
4-7 months	Adult canines, premolars, molars are coming in. You should see a full set of 42 permanent teeth by the end of this period.
6-7 months	All adult teeth are present and look clean and sharp, especially the back molars (primarily in kibble-fed dogs).
1 year	The 4 front incisors show noticeable ridges. The teeth overall appear white and clean.
1-2 years	The teeth might show slight wear, with tartar starting to form, especially at the gum line of the back molars.
3-5 years	Moderate tartar build-up is evident. The incisors display noticeable wear, and the points on the back molars might be starting to wear down.
3-4 years	The ridges on the front incisors are about halfway worn, and you might see the onset of yellowing due to tartar buildup.
5-10 years	Teeth, especially incisors, show significant wear. You may observe gum recession, signs of gingivitis, or even missing teeth. Tartar build-up is likely more pronounced.
Over 10 years	The teeth are considerably worn down. Many teeth may be missing, and signs of advanced dental disease can be evident.
Around 7 years & older	The front incisors might be completely smooth, with the teeth showing significant wear, discoloration, and potentially decay or periodontal disease.

Don’t Confuse Dental Disease and Age

The size of the dog, its bite, and dental care history can influence the speed of dental decay. This decay can lead to gum recession, gingivitis, and even tooth loss. A dog’s diet – whether it’s kibble or soft foods – and access to teething toys also play roles.

Symptoms like bad breath, dental calculus, and swollen gums aren’t exclusive to older dogs. Some young dogs might show these signs due to severe dental issues. 

This is why it’s important to use other factors besides teeth to help determine a dog’s age.

Eyes

Understanding age-related changes in a dog’s eyes can provide clues about their age, though these changes typically give a general indication rather than a precise age. 

However, the following guide is a good indication of how old a dog is by looking into their eyes.

Puppies

Puppies have bright, clear, shiny eyes that are not clouded or blue in the pupil. They react quickly to light and darkness, and the pupils move about alertly.

Adolescents

While still clear, you may see a slight bluish tint at the center. This blue tint isn’t the same as cataracts but is a natural hue change as the dog gets older.

Adults

As dogs get older, that blue-gray appearance spreading out from the center of the eye intensifies. This is due to a natural aging process known as lenticular or nuclear sclerosis. 

At the same time, cloudiness at the iris tends to expand outward towards the lens center. This is benign cloudiness, not harmful cataracts that affect your dog’s vision.

The older your dog gets, the more pronounced the cloudiness is likely to become.

Seniors

The cloudiness that was present when the dog was an adult increases noticeably as they get older. While you may have only noticed it in a certain light when the dog was an adult, by their senior years, it will always be visible. 

Cataracts are quite common in senior dogs and are distinct from the cloudiness of regular old age because they are milky white formations in the lens, clearly identified by a veterinarian. 

As dogs get older, the iris thins, which makes the dog’s eyes seem less colorful. It also makes your dog more sensitive to light.

Age-related conditions like dry eye (keratoconjunctivitis) may make the eyes seem duller and less shiny. 

As an older dog loses muscle tone and fat, the eyes may appear to sink deeper into the skull.

Coat

A dog’s coat is one of the less predictable indications of age, as it could be affected by many other factors, particularly in rescue dogs.

Rescue dogs are often stressed and on a poor diet, both of which result in excessive shedding and poor coat quality. Conditions like allergies, mange, and parasitic infestations affect the coat quality in dogs that are not being cared for properly, regardless of their age. 

That said, the coat CAN give clues to a rescue dog’s age.

Puppies

Puppy fur is soft and silky, typically a bit thinner than it will be as an adult dog. Their coat is often shinier and softer to the touch than it will be when they grow up.

In dogs that will have a curly coat as adults, the coat tends to be wavier in puppies.

Adolescents

During adolescence, dogs transition from their soft puppy fur to an adult coat. 

Many dogs shed their puppy coat at this time, which may lead to shedding even in breeds that don’t typically shed like Poodles or Doodles.

The coat starts to get coarser, particularly on the body, while the fur on the head takes longer to coarse and may remain silky. Breeds that show fading genes or color changes over time will begin to show those age-related changes.

Adults

The coat will meet the breed’s expectations by the time the dog is an adult. It should be relatively consistent from the tip of the nose to the tip of the tail, depending on breed expectations. 

As early as two, some dogs will begin to show signs of graying or fading. In breeds like poodles that have a fading gene, the color is likely to change across the entire body, whereas other breeds, like Labradors, are more likely to show graying on the face or muzzle early. 

White and gray hair around the face or muzzle is common in dogs between 5 and 10 years of age. As dogs get older, their coat may become less shiny, and it may thin in places that receive lots of wear, like the elbows. 

Keep in mind that rescue dogs who have not had proper care may show this kind of hair loss earlier. 

You may notice that when you groom your rescue dog, the coat takes longer to grow back than it did when they were younger.

Seniors

The thinning and graying continue as a rescue dog gets older. Senior dogs typically have thin hair or bald spots on the belly and on places that rub, like the elbows and forearms. 

Graying is generally pronounced on the face, muzzle, and sometimes on the paws. 

As the skin loses elasticity, the coat may appear to lay differently or have a different texture. 

Skin

Puppies

Puppies have pliable, stretchy skin, enabling their mothers to pick them up. 

It feels soft and smooth, and there’s often a very particular smell, even right after a bath. 

Puppies haven’t had much time to acquire knocks and scratches, even if they’ve had a rough start, so there are fewer imperfections on their skin.

Adolescents

In young dogs, the skin is still stretchy and easy to grab, but it is starting to firm into shape (depending on the breed). Floppy-skin breeds like Bulldogs or hound dogs remain flexible throughout their lives.

The skin color itself may change in some breeds like the Chinese Crested. You may notice more dark coloration, or the dog’s skin may go from white to dark entirely.

Some breeds like German Shepherds are born with floppy ears that will begin to prick during their adolescence.

Adults

By the time a dog enters adulthood, the skin sets into its final level of elasticity. It’s common for adult dogs to begin experiencing some skin issues they didn’t have before. Increased dandruff, scaling, or dry patches are more likely. 

Dogs at this age may also begin to express more serious dermatological issues like allergies or skin infections. 

Some dogs keep showing changes in the pigmentation of their skin through adulthood, typically resulting in darker skin areas, especially on the belly.

Seniors

As dogs get older, their skin becomes less elastic and more likely to hang where it’s squeezed. It’s common for older dogs to develop benign lumps and tags. 

While they’re usually harmless, always get these kinds of lumps and bumps checked by a veterinarian.

It’s common for older dogs to have sagging skin on the neck, belly, legs and base of tail and develop fatty deposits, even in a dog that has always been in good shape. 

Some senior dogs lose weight, so their skin seems to hang on them. Liver spots, typically small, flat, black, or brown spots, often appear all over the skin, similar to how they do in humans as they age.

Issues like dryness, flaking, and allergic reactions often worsen as dogs get older.

This sweet old lady is a great example of skin aging. Notice the lumps on her side and the hair loss on her neck and chest. You can also see a fat roll at the base of the tail, despite her being in good physical condition.

This dog hasn’t had somewhere soft to sleep so there are also callouses on places that get a lot of wear, like the elbows. A lack of flea control has resulted in hair loss on places the dog chews, like the tail.

Activity Level

Rescue dogs’ activity levels can vary greatly based on breed, personality, and past experiences. Energetic dogs might appear subdued in shelters and may take weeks or months in a new home to show their true energy. 

By contrast, naturally calm dogs may exhibit a temporary energy spike when they’re first adopted or fostered.

However, after a few months with you, most shelter dogs will settle into their natural activity levels. Even in the shelter, observing their energy patterns can offer clues into their real activity levels.

Puppies

Puppies have two speeds: hyperactive and asleep.

They typically display intense, excited play for a brief period, followed by deep sleep. 

They play hard, but not for long, and are quick to tire on walks or during longer, steady kinds of exercise. 

Any dog may nap throughout the day, but puppies seem to fall asleep against their will periodically.

Adolescents

In general, dogs are most energetic as adolescents. They have escaped the need for frequent sleep of puppyhood but have not yet settled down into the self-control and routine of adulthood. 

Adolescent dogs often find themselves overwhelmed by their energy and may test boundaries or get into scuffles with other dogs. 

Between about eight months and three years are the most common ages for dogs to end up in a shelter, based on my experience. Dogs that haven’t had proper training act out at the same time as they get bigger and stronger. This is one reason there are so many powerful breeds like Pitbulls, German Shepherds, and Huskies at shelters.

While adolescents have more endurance than puppies, their bodies are still growing. They shouldn’t exercise for long periods without rest. 

Also, it’s still typical to see them suddenly fall asleep after a lot of exercise but the periods of exercise and sleep are more extended than with puppies.

Adults

By the time a dog is an adult, they have an understanding of their own need for exercise and how they can expend their energy without getting into trouble. 

Adult dogs often have go-to strategies for activity, like immediately finding a ball or toy for you to play with. 

While all dogs get zoomies, you won’t see the kind of crazy bursts of energy in adult dogs as much as you see them in puppies. Some adult dogs settle into a relatively low-energy level, content with a brief run around the yard and a leisurely stroll.

Seniors

As dogs get older, they slow down. They sleep more during the day, often deep, long naps from which they’ll be very startled if awoken. While they still enjoy the activities they did as adults, they enjoy them for shorter periods.

Senior dogs often show signs of discomfort when they exercise due to problems like luxating patella or hip or elbow dysplasia. 

Older dogs may be more likely to enjoy lower-impact games like chewing on food-dispensing toys and gentle play in the household.

Mobility

Depending on a rescue dog’s past experiences, they may have health issues affecting their mobility. A veterinarian, even one at a shelter, should be able to distinguish between mobility issues stemming from diseases versus those from aging. Here’s what to anticipate regarding dog mobility at various ages.

Puppies

Like any baby, puppies are clumsy and working on their coordination skills. Their movements tend to be rapid and sporadic.

Puppies are prone to tripping or misjudging a distance when trying to jump or run. When they are excited about exploring or playing, they may be even clumsier. However, most puppies take their spills in stride and keep going.

Adolescents

As dogs get older, they get better at coordinating themselves and love testing their limits. 

Breed-specific characteristics like pointing, herding, or retrieving may become more pronounced. An adolescent dog may stop and lift its paw when it sees a squirrel, where it would have simply chased it as a puppy. 

That said, adolescents still haven’t completely gotten their feet under them. Their long legs can still trip them up, and they’re more prone to clumsiness than adults. 

They’re also a little more likely to be embarrassed by these spills than a puppy and may take a moment longer to get back into play.

Adults

Adult dogs move deliberately, even when they’re excitable. They have likely solidified breed-specific behaviors without the sometimes bounding, over-the-top enthusiasm of adolescents. 

Adult dogs are most likely to take offense at a failure of mobility, seeming to be legitimately embarrassed if they trip or fall.

Seniors

Senior dogs seem to be more thoughtful about where they put their energy. 

Their movements become slower and more deliberate. Stiffness and signs of joint pain become much more common, especially when they haven’t moved around for a while or the weather is colder. 

Older dogs are likely to move with halting steps, especially in the hind limbs. They tend to be particular about where they walk, steering clear of slick surfaces and preferring something they can grip.

Signs of Arthritis in Older Dogs

Arthritis, a degenerative joint disease, is prevalent in senior dogs. It results from the wear and tear of cartilage in joints, leading to inflammation and discomfort. Here are the signs:

• Limping:
  • One of the most visible signs.
  • May be more pronounced after resting or sleeping.
• Stiffness:
  • Less fluid movement in joints.
  • Often noticeable in the morning or in colder weather.
• Difficulty Moving:
  • Trouble climbing stairs, jumping, or getting into and out of vehicles.
  • Might hesitate before performing actions that were previously effortless.
• Reduced Activity:
  • Decreased interest in walks or play.
  • Prefers to lie down or rest more than usual.
• Pain:
  • Vocalizing or yelping when touched or while moving.
  • Possible signs of discomfort when certain areas are touched.
• Muscle Mass Loss:
  • Atrophy, especially around the affected joints due to reduced usage.
  • Might lead to a more pronounced bone structure.
• Behavioral Changes:
  • May become irritable or depressed.
  • Reduced interaction with family members or other pets.

Weight and Muscles

Puppies

Puppies have a soft and pudgy appearance due to their growing bodies. Their bellies may seem particularly large after meals, and their bodies are characterized by a mixture of fat and wrinkles. 

As they grow, puppies go through rapid changes, and you’ll likely notice shifts in their weight and body shape even within a week. As they age, muscle tone gradually develops. 

Puppies often have voracious appetites and seem to be always hungry, but it’s important not to overfeed them. While they shouldn’t be free-fed, the recommended amount of food for puppies might surprise you due to their growth rate.

Adolescents

Adolescent dogs have a leaner physique than puppies, with more visible muscles underneath their skin. 

Due to their high activity levels and metabolism, adolescents can sometimes struggle to maintain their weight appropriately, leading to a slightly undernourished appearance despite consuming enough food.

Adults

As dogs transition into adulthood, they fill out their body shape according to their breed standards. 

With a decrease in activity level and metabolism, adult dogs can be prone to weight gain, even if they’re eating the same amount of food as they did as adolescents.

Unlike puppies, weight gain in adult dogs tends to be distributed all over the body, with rolls of fat often visible around the neck and the base of the tail. Adult dogs may also begin to show signs of stiffness or arthritis if they are overweight.

Seniors

Muscle tone and mass tend to decrease as dogs get older, resulting in noticeable hollows in areas like the face, legs, and back. 

The spine of senior dogs can become swaybacked, especially in larger or overweight dogs, as the reduced muscle along the spine can lead to a loss of straight posture. 

Fat distribution changes in older dogs, and even dogs of appropriate weight may develop some fat pads on the lower back and other areas. 

Behavior

Puppies

Puppies are curious, open, and excited about the world around them. They are eager to explore, interact, and play with everything. 

Training sessions with puppies may be short due to their limited attention spans.

Puppies often have accidents in the house as they are still learning to control their bodily functions. They tend to react strongly to various stimuli, but their reactions are short-lived.

Adolescents

Adolescent dogs may test boundaries and behave unpredictably.

They can go through phases where they don’t follow commands they previously mastered. Adolescents seek more stimulation, both physical and mental, and may engage in destructive behavior if not properly engaged.

Sexual maturity can also influence their behavior, leading to behaviors like marking, increased interest in other dogs, and changes in personality like new aggression or reactivity.

Adults

Adult dogs have a stable temperament that has developed over time. 

Their behavior is more predictable, and they are less likely to engage in boundary-pushing behavior. Many adult dogs thrive on routine and may be unsettled by unexpected changes. 

Adult dogs have generally established ways of interacting with other dogs and people, influenced by their socialization and training.

Seniors

As dogs age, their behavior tends to mellow. Dogs that were once highly reactive may become calmer.

The desire for routine and predictability intensifies in seniors. Cognitive changes associated with aging, similar to dementia in humans, can also impact their behavior.

Hearing

Puppies

Newborn puppies are born deaf, but they begin developing their hearing within a few weeks. 

Their sensitive hearing allows them to startle easily at loud or unexpected noises. Puppies’ heightened hearing sensitivity makes them responsive to both verbal and hand commands.

Adolescents

As puppies mature, their hearing improves further. Adolescents become better at distinguishing between different sounds, enhancing their ability to respond to verbal commands. 

Their hearing is typically at its peak during this stage.

Adults

The hearing of most adult dogs gradually declines from their adolescent years.

Dogs exposed to loud environments or those living in noisy surroundings may experience quicker hearing loss.

Years of ear infections can also impact hearing, especially in breeds with floppy ears like Beagles and hounds.

Seniors

Older dogs often experience hearing loss. While some senior dogs lose certain tones or frequencies first, others may lose their hearing entirely. 

Dogs may startle more easily due to diminished hearing, and it’s important to be aware of these changes when interacting with them.

Feet, Nails, and Pads

Puppies

Puppy paw pads are soft and sensitive, and their nails are thin and sharp. 

Their paw pads might be lighter in color, and they might be prone to sensitivity when walking on various surfaces.

Adolescents

With increased activity, paw pads may become calloused and hardened. 

Active adolescents may develop sores or minor injuries on their still-sensitive paw pads.

Adults

Adult dogs have thicker and more matte-looking nails compared to adolescents. 

Paw pads have further hardened and calloused based on their activity level. Cracking or flaking of paw pads might occur, especially at the edges. 

Some adult dogs may have long, hard nails that contact the ground or even force the toes upright if not regularly trimmed.

Seniors

As dogs age, paw pads become darker and drier.

Nails become more brittle in older dogs and are more prone to breaking or splitting. Some seniors might develop growths or warts on their feet as well.

Factors Affecting Age Estimation

While the above factors are great tools to help gauge a shelter dog’s age, there are a lot of other factors to consider:

Size and Breed

Smaller dogs generally live longer than larger dogs, and different breeds have varying lifespans. Some breeds show signs of aging earlier than others.

Physical Health

Dogs with health issues may appear older than their actual age. Certain health conditions can accelerate the aging process, while a well-maintained health can keep a dog looking youthful.

Lifestyle and Diet

Stressful lives or poor diets can make dogs seem older than they are, while an active lifestyle and a balanced diet can have the opposite effect.

At first glance, this may seem like a broken old dog. However, a closer look at her eyes and teeth (and an encouragement to play) show she may be much younger than she seems. She’s just had a hard few years and needs a fresh start.

Genetics

Some breeds naturally age slower than others. Genetic factors can also lead to early development of certain aging signs.

Spay/Neuter

Early spaying/neutering might result in a more adolescent appearance for a longer period. Delaying these procedures might have effects on weight and overall health.

Consulting with a veterinarian or a canine expert can provide valuable insights based on the dog’s overall health, behavior, and physical characteristics.

Conclusion

Determining a rescue dog’s age is far from an exact science. Even the experienced experts are only guessing, and often get it wrong.

However, the more traits you take into account, the more likely you are to make an accurate guess. By looking a dog over from the tip of their nose to their tail and considering behavior, mobility, and activity levels, you can make a pretty good guess at a dog’s age.