非洲象在动物王国中嗅觉最灵敏

If you have ever wondered how an elephant smells, scientists have the answer. Pretty good.

Researchers have discovered that African Elephants have the largest number of genes dedicated to smell of any mammal.

Given the size of their trunks, and how important it is to their survival, it is probably unsurprising that an elephant’s nose is not only the longest in the animal kingdom, but also the most effective.

In comparison, humans and other primates have a poor sense of smell.

"The functions of these genes are not well known, but they are likely important for the living environment of African elephants," said author Dr Yoshihito Niimura of the University of Tokyo.

"Apparently, an elephant's nose is not only long but also superior.

The sense of smell is critical to all mammals, and they use it for sniffing out food, avoiding predators, finding mates and locating their offspring.

In a study published in Genome Research, scientists examined the 13 mammal species and found that African Elephants have twice the number of smell genes as dogs and five times more than humans.

They have around 2,000 genes alone that are dedicated to scent. Humans in comparison have just under 400 and other primates like chimpanzees, even less.

The study found that 20,000 genes are responsible for the sense of smell in mammals, of which around half are functional, but the collections differ for each species.

Horses have around 1,000 smell genes, rabbits around 750 and rats about 1,200.

“The large repertoire of elephant (smell) genes might be attributed to elephants’ heavy reliance on scent in various contexts, including foraging, social communication, and reproduction,” added Dr Niimura

African and Asian elephants possess a specific scent gland, called the temporal gland, behind each eye, and male elephants exude an oily secretion during annual mating, which is characterized by increased aggressiveness and elevated levels of testosterone .

Research has also shown that elephants have well-developed olfactory systems that include large olfactory bulbs and large olfactory areas in the brain.

And previous studies have revealed that, African elephants can reportedly distinguish between two Kenyan ethnic groups—the Maasai, whose young men demonstrate virility by spearing elephants, and the Kamba, who are agricultural people that pose little threat to elephants through smell.

The sense of smell evolved over millions of years and our human ancestors would have used it as a tool to spot disease, avoid rotten meat and poisonous plants and sniff out food.

However our upright posture lifted our noses far from the ground where most smells originate, diluting scent molecules in the air.

And today many smells which still give us hints about rot and poor hygiene are masked behind perfumes, air fresheners and deodorants.

Yet smells are still having a greater impact than we realise, warning of danger, triggering memories and even helping us choose a partner.

Many studies have shown that pheromones emitted from the sweat glands play an important role in physical attraction.

Some experts believe that humans have a far greater sense of smell than previously thought but daily showers and fridges, which mask bad odours, have stopped us noticing.

Previously it was estimated that we could smell 10,000 odours but now researchers say it is more like one trillion.

Scientists believe our sense of smell is much closer to that of animals than appreciated, but we no longer pay attention because smells are often hidden, meaning that important information is lost.

Mammal Number of genes

Elephant 1948

Cow 1186

Dog 811

Horse 1066

Rabbit 768

Guinea Pig 796

Rat 1207

Mouse 1130

Marmoset 366

Macaque 309

Orangutan 296

Chimapanzee 380

Human 396