Dogs are amazing creatures, which is one of the reasons they have become such wonderful pets. The animals are intelligent, loving, loyal and protective, which are all qualities that cause many households to see their dog as one of the family.

However, dogs are amazing in a number of other ways as well, and you could go your whole life without ever noticing them. Here are just a few of the incredible things our dogs can do without us knowing.

Dogs can smell disease

It seems like something out of fantasy, but it's true; dogs can detect potentially fatal diseases such as cancer, diabetes and epilepsy using nothing more than their nose. Dogs have already been trained to find traces of lung, breast, skin, bladder and prostate cancer in the same way that a sniffer dog might be used to detect illicit substances at an airport.

It is thought that the cancers have distinct scents too faint for humans to notice. Similarly, a diabetic's blood sugar levels have a sweet smell if they are too high and an acidic one if they are too low, so dogs have been used to warn their owners of issues.

Dogs have great eyes

Dogs are renowned for their excellent sense of smell, and to a lesser extent their sense of hearing, but not so much their eyesight. While it is true that dogs do not depend on their sight as much as humans, their eyes are still impressive.

Dogs' eyes contain a membrane known as tapetum lucidum, which allows them to see in the dark with few issues. A dog's eye also has three lids: the top and bottom lids that humans have, and a third lid known as the nictitating membrane that keeps the eyes moist.

Dogs are intelligent

It is obvious to anyone who has owned a dog that they are intelligent creatures, capable of recognising certain commands and learning tricks. But exactly how intelligent are our canine companions?

As it turns out, about as clever as a two-year-old human. Some dogs can understand up to 200 or even 250 words, and can count up to five. The cleverest breed of dog is the Border Collie, followed by the Poodle, German Shepherd, Golden Retriever and Dobermann.

Dogs understand jealousy

While many dogs can learn simple tasks and tricks, it is often difficult to gauge their emotional intelligence. They are obviously capable of feeling happy, sad, scared and angry, but what about more complex emotions?

As it turns out, dogs are more than capable of experiencing jealousy. This can be seen if you give a dog a treat for performing a trick such as sitting, in full view of another dog who performs the same trick for no reward. The latter dog will get agitated, and may stop performing the trick altogether.

Dogs helped create a phrase

You have almost certainly heard, during a bad rain storm, someone exclaiming that it is raining cats and dogs. But have you ever wondered where the phrase comes from? As it turns out, it is based on fact.

In 17th-century Germany, extremely heavy rain would flood city streets, as drainage was not very good back then. This would cause the many stray cats and dogs to get swept down the road, leading to the saying. The dogs probably even enjoyed the swim!

Dogs can be tiny

While many of us think of dogs as reasonably large animals, such as Labradors, it is often possible to forget that they can be tiny too. In fact, some of them can be much smaller than you would expect.

The current world record holder for smallest dog belongs to Miracle Milly, a Chihuahua measuring only 9.65 cm tall and weighing around half a kilogram. However, the smallest dog ever was a Yorkshire Terrier named Sylvia, who was just 6.3 cm tall when measured in the 1940s.

...And old!

How old would you say a dog can live for? For larger breeds, the answer is unfortunately likely to be less than ten years. Smaller breeds can get up to around 18-20 years old. However, this is by no means the limit.

The oldest dog in the world today is Pusuke, who was born on April 1st 1985. That makes him almost 29 years old, and still going strong!

Written by: Hannah