as one teaspoonful in thirteen gallons of water.
SUPER SCENTING
One of the first things a dog will do in a new environment is to put his nose to the floor and sniff. A human in the same situation would look around. A dog when meeting another dog or a person will, characteristically, sniff them, sometimes in the most embarrassing, but smelliest, places. A human (fortunately!) will just look. Both are gathering information about their world, but the way in which they do it illustrates one of the most important differences between them. We live in a very visual world, whereas dogs live in a very smelly one.
Their sense of smell is incredible by our standards. Not only do they have many more cells in their nose for detecting different smells (the area used for smell detection is fourteen times the size of ours), but these cells are of better quality and the part of their brain that receives the information is considerably more developed. This allows dogs to detect and identify a much wider variety of scents at much lower concentrations.
Dogs gather a lot of information by sniffing at places in a territory which have been marked by other dogs.
Smells on the ground need careful investigation.
Using this ability enables them to acquire much more information in one sniff than we can ever imagine. Going for a walk and sniffing the scents left behind by other dogs must be like watching a video of all those who have passed by in the past few days. Information such as sex, health and social standing may be passed on through urine and faeces. This allows most male dogs, and some females, to advertise their presence and status by marking every available lamppost and clump of grass.
Although we cannot even begin to understand what it is like to be able to detect odours in the same way as our dogs do, knowing that they live in a different sensory world can help us to understand them better. It helps to explain some of their peculiar habits, such as sniffing everything they come into contact with, kicking up earth with their back hind legs after going to the toilet (they have scent glands in between their pads), and rolling in substances that we would rather they did not.
SCENT CAMOUFLAGE
Rolling in substances with a very strong scent has never been fully explained. It is likely that it is a remnant of the days when dogs’ ancestors needed to camouflage their own scent to be more like that of their environment in order to be more successful when out hunting.
EMPLOYING A DOG’S SUPERIOR SENSES
Man has utilized the dog’s incredible sense of smell in a variety of ways. To detect drugs, explosives, to find lost people, to track criminals, to find buried survivors after earthquakes or avalanches, to track animals to be hunted, or, more recently, to sniff out dry rot and termites in buildings, to find human bodies lost in water or to detect skin cancers and other diseases. In such exercises, dogs are better than any machine, having a better publicity value, being more accurate, more reliable, cheaper, and more fun!
SEEING THINGS DIFFERENTLY
Dogs have a greater field of vision than humans. This enables them to see things to the rear and sides. The amount of overlap (shaded area) will determine how well the animal can judge distances.
A human has a field of vision of about 100 degrees.
A whippet’s field of vision is about 200 degrees.
Dogs that have been bred to look more like us, such as the King Charles Spaniel, with forward-facing eyes, have a reduced field of vision.
Long-coated breeds with hair that hangs over their eyes will have their field of vision greatly reduced. It is best to clip it or tie it back so that they can see properly.
SENSITIVE SIGHT
Dogs can see less well than humans. They can see colours but not as well as we can, and they cannot differentiate easily between certain colours, such as red and green. A dog looking for a red ball, for example, on green grass is more likely to be using his nose than his eyes.
They do, however, see better than us when less light is available. A reflective layer at the back of their eyes allows them to make better use of the light entering the eyes by trapping and reusing it. This is why their eyes shine eerily when they are caught in car headlights or a torch beam.
While we are able to make out static shapes easily and can quickly differentiate between two objects, dogs see things better as soon as they move. They can detect movement on a very small scale, helping them to be efficient hunters. In our world, it enables them to notice subtle body movements, which allow them to detect, a fraction of a second before we have said anything, that we are about to take them for a walk.
IMPRESSIVE HEARING
Dogs can hear better than we can. Firstly, they hear sounds more acutely. For example, a sound that can just be heard by a person 100 metres away, can be heard by a dog for up to 450 metres. Secondly, dogs can hear sounds of a higher frequency. Our range is up to about 20 kHz whereas dogs can hear sounds up to at least 35 kHz, allowing them to hear in the ultrasonic range. They also seem to be able to discriminate between two sounds that appear the same to us. It is probably this sense more than any other that has led people to believe that dogs have a ‘sixth’ sense. Because of their superior hearing, for example, dogs may become aware of the arrival of their owner long before a person sitting in the same room. A dog can hear things that we cannot, such as a ‘silent’ dog whistle, and may alert us to the presence of intruders or other noises in the environment long before we have heard anything.
SOUND SENSITIVITY
Dogs that were once used for herding, such as Collies, have very sensitive hearing and, as a result, are more likely to find it difficult to live in very noisy environments and are more prone than other dogs to developing noise phobias.
Dogs with long, fluffy ears, such as Cocker Spaniels, are likely to be less good at sound detection and location.
MOVABLE EARS
Dogs are able to pinpoint the location of a sound source more accurately than us. This is achieved by having ears that can be manoeuvred into a position that allows them to catch sound more efficiently.
DIFFERENT METHODS OF COMMUNICATION
Everyday communication between adult dogs relies mostly on body posture and scent exchange with very little in the way of vocalization. In comparison, we rely very heavily on the spoken (or written) word and only use body signals and scent in very subtle and secondary ways.