The most important senses a dog possesses are sight, touch, and smell, and a dog uses all three senses to perceive their world. However, the sense of smell is their primary sense, and through their highly developed sense of smell, dogs learn about each other, potential threats, and tasty treats. This raises the question, “Can dogs tell how old other dogs are?”
Dogs can tell how old another dog is by using their noses. Dog’s greet one another by sniffing each other’s bums, establishing communication through chemicals. These chemicals enable a dog to gather information such as gender, age, health status, and even what the other dog ate last. They also have a Jacobson’s organ that is responsible solely for detecting pheromones.
This article will discuss what information your dog learns through their olfactory sense, such as the other dog’s age and gender. You will learn that dogs, like a few other animals, possess a second olfactory organ often referred to as the Jacobson’s organ.
Determining Age: Pheromone and Hormone Levels
Smelling and sniffing may look the same to us, but there is a difference between smelling and sniffing, and that difference lies in your dog’s brain. Smelling is involuntary; your dog cannot choose to smell something. On the other hand, sniffing is voluntary. It is the method through which your dog perceives his world.
Your dog can detect, discriminate, and identify the world around them by searching, trailing, and tracking scents. They do not even need the other dog in front of them. They can learn about the other dog from their urine’s scent, such as if the other dog is a puppy. Dog’s know more about their neighborhood than we ever will.
Pheromones and Jacobson’s Organ
Pheromones are defined as chemical substances produced by an animal that serves as a stimulus to others of the same species and elicits one or more behavioral responses (source).
Dogs have an additional organ — the vomeronasal organ, also called Jacobson’s organ, located between the roof of the mouth and bottom of the nasal passages. In an article published in PetMD, Dr. Tyne stated that pheromones, thanks to years of evolution, enable animals to communicate within and with other species (source).
The Jacobson’s organ functions as a second nose but communicates directly with the brain to coordinate mating and other emotional messages. While detecting scent, the Jacobson’s organ bypasses the olfactory system.
Dogs spend a good deal of time urinating on a walk around the block, in what may seem to us an excessive amount. Still, they are talking to the other dogs and learning what is going on around them.
What humans perceive as impolite is proper dog etiquette. With a simple bum sniff, a dog learns the other dog’s age, gender, mood, health, diet, size of their pack, and their pack rank (source).
Hormones and the Olfactory System
Hormones, like estrogen and testosterone, are particularly strong in males and females when they are of age to mate. These are especially useful for dogs to determine the age of other dogs.
In a study published in the February 2012 issue of Theriogenology, Dr. N. Pathirana and colleagues measured the changes in concentrations of an insulin-like peptide (INSL3) and testosterone in dogs’ plasma with age (source).
In general, the level of testosterone was lowest from 0 to 4 months of age, surged between the ages of 5 to 12 months, with a plateau between the ages of 1 to 5 and a marked decrease each year once the dogs were in their sixth year.
How a Dog’s Nose Works
A dog’s nose contains over 100 million scent receptors, and some breeds, such as bloodhounds, have over 300 million. Humans have a paltry five to six million scent receptors. We may know there is a cake baking, but a dog is able to discern each ingredient separately.
Based on the number of scent receptors, a dog’s sense of smell is 100,000 times more sensitive than humans.
When a dog sniffs, they use both their nose and mouth. A dog’s nostrils independently move, which makes them so adept at pinpointing a particular smell.
A dog’s nose has two chambers lined with mucus. The mucus present both inside and outside the nose traps the scent particles to give the scent receptors time to process the scent (source).
Just as the nostrils must be lined with mucus, the outside of the nose must be wet. The mucus on the outside of the nose is part of the reason they have such a fantastic sense of smell.
When your dog inhales, scent particles in the air become trapped in the mucus on the way into the nostrils. When they touch their tongue to the olfactory gland located in their mouth known as the Jacobson’s organ, even the slightest smell is detectable (source).
Think of your dog’s sense of smell as being like your sense of sight. A dog’s nose sends signals to their brain, which they process into a picture of sorts, and this allows them to perceive their world.
The Canine Brain
Humans and dogs both process smell in the olfactory bulb located in the fore-brain. The difference lies in size — a dog’s olfactory lobe is 40 times larger than humans.
The human brain has a large visual cortex because we see the world around us. Dogs have a large olfactory cortex as they smell the world around them (source).
A dog’s ability to smell is far superior to ours and plays a vital role in a dog’s ability to determine age and other factors about another dog. Dog’s love to smell and sniff their way through life. Sniffing is not just an enjoyable pastime, but how they see their world.
Next time you and your dog are out for a walk, give your dog time to smell and sniff. You will have a very happy dog. After all, who is not happy after receiving all the neighborhood gossip?