I was reading a book recently by the famous naturalist Sir David Attenborough, who was attempting to catch a Komodo dragon, the largest (and one of the most venomous) lizards on the planet, for the very first time. They built a strong cage, filled it with bait, and sat in the bushes waiting for one to appear. Well, one enormous specimen did appear – but it was behind them, and sat and stared, as our intrepid explorer and his team nervously stared back. Eventually, it moved off to take some bait hanging in a tree, which obviously beat the smell of humans as a meal. Komodo dragons (fortunately) have a very poor sense of smell, and like other reptiles, they use their forked tongues instead of their noses to smell and can detect rotting prey from 4k away.

Each species in the animal kingdom has evolved unique sensory adaptations to suit their ecological niches. When it comes to the sense of smell, some animals stand out as having exceptional ‘noses’.


Best Sniffers


Dogs are pretty well known for their sense of smell (I swear mine can detect crisps without the sound of the bag being opened) and have around 220 million smell receptors, enabling them to detect a wide range of scents. Bloodhounds, said to be the ultimate scent tracker, have up to 300 million smell receptors, and their droopy ears and wrinkly skin help to funnel smells towards their noses.

Bears have a keen sense of smell - essential for locating food and identifying potential dangers, smelling things from several miles away, and can even detect scents underwater. Grizzlies have the best smelling ability compared to any other animal, which is unsurprising since their olfactory bulb area (a structure located in the front of the brain of vertebrates that receives neural input about smells detected by cells in the nose), is five times bigger than that of an average human. Polar bears use their sense of smell to find their prey, and can smell a seal on the ice 32k away, and can smell a seal's breathing hole in the ice more than 8k away.

Elephants are strong contenders on the list of creatures with the best smell sense. According to a study, elephants have the finest and probably the sharpest sense of smell ever recorded in a particular species. They can recognise all kinds of odours in their environment, owing to their nearly 2,000 distinct genes dedicated to the sense of smell. Moreover, elephants have an excellent sense of smell over a broad range and are capable of locating underground water from up to 20k away. Another report concluded that elephants could use scent clues to tell the difference between two Kenyan tribes, the Maasai, who traditionally speared them, and the Kamba, who did not.


Previous studies have shown that African Elephants can distinguish between odour molecules with tiny structural variations - differences that humans and other species are entirely unable to detect. Their nostrils, situated at the top of their trunks, are responsible for breathing, sniffing, and collecting water.

Sharks are up there on the list of best ‘smellers’ too – Great Whites are potentially the most dangerous predatory fish alive, and all sharks rely on their sense of smell for hunting. Their smell detection is so important that the olfactory bulb occupies two-thirds of their brain. The two nares, or nostrils, are located under the snout but do not connect with the throat. As sharks swim, water flows in one side of the nostril, through a nasal sac, and out the other side, which gives them a superb sense of smell enabling them to detect a drop of blood in the water approximately 500m away.


The award for the worst sense of smell?


This goes to the Dolphins – because they have no sense of smell at all since they lack the nerves that take smell information from the nose to the brain, and thus rely on other senses to perceive their environment. But they would probably get an award for their social skills, intelligence and agility, and share many emotional similarities to us humans.

Author

Marilyn writes regularly for The Portugal News, and has lived in the Algarve for some years. A dog-lover, she has lived in Ireland, UK, Bermuda and the Isle of Man. 

Marilyn Sheridan