The dog is one of the most popular animals in the world. It was among the first
animals to be domesticated, or trained for use by humans. It is characterized
by loyalty, friendship, protectiveness, and affection. Therefore, dogs are also
known as man's best friend. Domestic dogs vary in size depending on their breeds.
Their sense of smell is very sharp. A dog has a tendency to continually sniff
the air, the ground, and nearby objects to learn what is happening around it.
Different breeds of dogs have different eye shapes and dimensions, and they
also have different retina.
The eyesight of a dog is not as keen as its sense of smelling and hearing.
Dogs detect sounds as low as the 16 to 20 Hz frequency range (compared to 20
to 70 Hz for humans) and above 45 kHz [18] (compared to 13 to 20 kHz for humans).
The dog is a social creature. It prefers the company of people and of other
dogs. The average life span of a small - and a medium-sized dog is 15 years.
A large dog lives only up to the age of 10. Dogs exist in a wide range of
sizes, colors, and temperaments. Dogs are able to healthily digest a variety
of foods including vegetables and grains, and in fact dogs can consume a large
proportion of these in their diet. In the wild, dogs can survive on a vegetarian
diet when animal prey is not available. Some, such as the Doberman pinscher
and the German shepherd, serve as alert and aggressive watchdogs. Others, such
as the beagle and the cocker spaniel, are playful family pets, even though they
were bred for hunting.
