DOG SENSE

UNDERSTANDING THE FIVE SENSES

Dogs have 18 muscles in each ear, vision based on muted colours and a nose so sensitive that it can pick up scents 500m deep; essentially, our dog's senses are very powerful. As humans, we may share the same five senses, but a dog's five senses are in a different league to ours in terms of sensitivity. This is worth considering, particularly when looking to understand our dog's responses to the world around him. In this article, we look at our dogs' five senses and how they differ from ours.

TOUCH

Touch is the first sense to develop in a puppy, and it is extremely sensitive. We all need to remember this when interacting with dogs of all ages. Whilst it may be human instinct to reach for a dog's head when we greet them, this is generally one of the areas in which dogs least like being touched. Instead, the best place to touch a dog and introduce ourselves is along his sides. Ears and paws are also very sensitive, so unless you know the dog well, these are best left alone.

Whiskers are generally associated with the sensation of touch but also play a role in complementing the visual system. Whiskers are located above the eyes, on both sides of the muzzle, under the chin and sometimes on the upper lip. These whiskers, or vibrissae, are packed with nerve fibres that send sensory information to the brain. They are the most sensitive touch receptors in a dog's body and even respond to air currents as the dog moves. In fact, they are so important that they are among the first hair to develop in a puppy. They serve many different functions, but one of the key ones is helping our dogs navigate the world, especially as they lack clear vision of objects closer to them.

FUN FACT

It is debatable whether touch or proprioception allows our dogs to react to barometric pressure. Regardless, it is established without doubt that a drop in barometric pressure, such as occurs before a storm, is picked up by dogs long before humans can detect it.

VISION

Dogs don't see in full colour like humans. Instead, their vision is far more muted. Their descent from wolves is a significant reason for this, as wolves evolved to hunt during dusk and dawn, so they did not need to see bright colours. In fact, dogs can see almost as well as cats in low light due to an area called the tapetum at the back of the retina. This is also why both dogs' and cats' eyes seem to glow in the dark when light is shone on them.

The colours our dogs see are a combination of blues, yellows and sepia tones, and shapes are not as sharp as they are for us. However, dogs have a wider vision field at 240 degrees (compared to our 180 degrees). This field of vision does vary slightly from breed to breed; for example, sighthounds have a 290-degree field of vision due to the long narrow shape of the skull, and generally, the longer the nose the breed has, the greater the field of vision is.

TASTE

Taste is not highly specialized in dogs. This should come as no surprise when we consider some of the things our dogs seem to find tasty. Dogs have far fewer taste buds than humans, but they do have Jacobson's organ, which assists by helping to enable smell and taste to occur simultaneously. The sense of smell is far more developed in dogs, and scents are much more attractive to dogs than tastes.

DID YOU KNOW?

Dogs have particular taste buds on the tip of their tongues, specially made for water. These become more sensitive after a dog has eaten sweet or salty foods, and it is surmised that this mechanism has developed due to a dog's need to increase water intake after eating sweet or salty foods.

HEARING

The shape and mobility of a dog's ears can help to accentuate their hearing. A dog can tilt and rotate their ears to funnel sound into the inner ear, and some breeds have specially shaped ears that help to amplify sounds. The canine ear canal is much longer than ours, and muscles allow fine-tuning so that the inner ear can localise sounds even when they are far away. This all combines to make a dog's hearing far more sensitive than ours, and they are able to hear sounds four times farther away than we can. Humans can hear a range of between 20Hz to 20,000Hz, whereas dogs have a range of approximately 40Hz to 60,000Hz. This helps dogs to differentiate sounds, like that of your car, when you arrive home. It also means that they can hear very high-pitched noises!

This does, of course, have a downside when it comes to dogs living with humans. Being so much more sensitive to sound makes many household noises absolutely intolerable for our canine companions. Vacuum cleaners, for instance, can be unbearable for dogs, which is why many dogs react when these appliances are in use.

DID YOU KNOW?

Jacobson's organ (also known as the vomeronasal area) helps puppies locate their mother's milk

SMELL

As we've discussed before, a dog's sense of smell is truly remarkable and highly specialised. Scientists estimate that a dog's sense of smell is somewhere between 10,000 and 100,000 times more accurate than ours. One of the main reasons for this is the sheer number of scent (olfactory) receptors dogs possess – for every human olfactory receptor, dogs have around 50. As might be anticipated, with all of this information about scent coming in through the nose, the area of the brain that processes this information is also 40 times bigger than ours.

Dogs' noses also function quite differently from ours. When we inhale, we smell and breathe through the same passages within our noses. When dogs inhale, on the other hand, a fold of tissue just inside their nostrils helps them to separate the functions of smelling and breathing, which refines the whole process.

Similarly, we force out any incoming odours when we exhale through our nose. When dogs exhale, on the other hand, the used air exits through the slits on the side of the nose, and this helps to bring new scents into the nose. This division of functions means that a dog can sniff and take in new odours almost constantly.

All of this means that dogs can identify individual humans by odour and can know exactly what we have been doing. Did we go running, eat something or perhaps fraternize with some other dogs?! They can also detect our emotional states. As we become fearful or excited, our bodies release chemicals, and we undergo changes in our physiological state, such as a raised heart rate and sweat production. This allows dogs to read our 'mood' and often triggers a change in their behaviour.

In essence, dogs take in a huge amount of information when they sniff. As humans, we just can't compete with this ability!

FINAL THOUGHTS

Our dogs' senses are hugely sensitized compared to ours in so many respects, and we need to be aware of how this affects them so as to make their lives as comfortable as possible.