We humans like to smell good, and when looking for a partner, many people use perfumes and colognes to try and give us an edge. Whilst this style of scent based attraction is unique to humans, the use of smell to find and win over a partner is found throughout the animal kingdom, albeit in a slightly different fashion.

Due to a lack of opposable thumbs and some slightly tricky manufacturing processes used to create artificial scents, most animals have a pretty hard time using perfumes. Instead, animals opt for an 'au naturale' method of smelling great to the opposite sex: pheromones. Pheromones are special chemicals produced by animals to announce to potential mates "Hey! Check out me, my amazing genes and my massive abundant- resources-which-we-can-use-to-provide-for-our-offspring" or "Who wants to get it on?". At this point the metaphor reaches its limit because animal pheromones go even further than simply looking for a mate. For animals, pheromones could even be considered as a kind of language, telling others in the group a huge number of things like announcing that a female is pregnant and for suitors to back off or even more basic things like how old or what gender the animal is.

In order to communicate with others the pheromones have to be presented to the rest of the group and in most cases this is done by releasing pheromones into the air to be sensed by nearby individuals. The silk moth (Bombyx mori), however, never seemed to get the memo and instead has one of the most exceptional examples of the use of pheromones. The female silk moth releases pheromones which waft downwind to excite males, which is pretty typical of pheromone use. The stunning bit comes when males 11km downwind get the message and fly off to find her!

At the other end of spectrum, some animals have to get up close and personal to have a chemical chat. Mice have to have direct contact in order for some pheromones to interact with a special organ on the tip of their nose called the vomeronasal organ. This organ contains a large number of nerves and receptors for smells and pheromones including the TRPC2 receptor. This receptor is activated by a pheromone that has only recently been discovered, released by mice which haven't yet reached full maturity, called ESP22. This chemical, discovered by Prof Stephen Liberles and colleagues, tells male adult mice to 'back off' because the mouse is too young as the team discovered by painting adult female mice with the pheromone.  But possibly the most intimate way of checking pheromones is found in the giraffe (Giraffa camelopardalis).

Female giraffes excrete a pheromone in their urine which signals to males that she is ready for action. For most animals, this is pretty normal; when an animal releases a pheromone in its urine the pheromone evaporates and gets picked up by other individuals. Giraffes must have decided this wasn't hardcore enough for them because they took things one step further than a simple whiff of pheromone. The typical giraffe courtship ritual consists of the male giraffe pushing on the female's bottom to make her urinate. He then takes a drink and if he thinks that she's ready to mate he'll then follow her around for hours or days, mounting her and attempting to mate.

Despite being well known throughout mammals, fish, reptiles, amphibians and even some invertebrates, experts have only recently accepted the idea that birds too use pheromones. The widespread belief in the scientific community that birds don't use chemical signals in courtship came from the bird's small olfactory bulbs, the region of the brain that processes smell. This, in the past, lead experts to believe that birds' mating rituals were are based entirely on song and dance. That thinking changed with more recent experiments including one which involved using different pheromones to get ducks to swim down or avoid specific dark tunnels.

In fact, this train of thought appears to be completely opposite to what actually happens in nature. Prof Danielle Whittaker and colleagues at the Michigan State University found that there were distinct patterns of chemicals in the preen oil of male and female dark-eyed juncos and that male birds with a more 'male-like' smell and female birds with a more 'female-like' smell were more likely to reproduce successfully. The group also found that male birds with a more feminine smell often raised the young of the more masculine smelling birds, making the masculine smelling birds even better potential mates as they can have their young raised with very little cost to the parents. In fact the smell of a potential mate actually had more effect on whether the birds struck it lucky than body size or plumage, characteristics historically thought to be the main traits used to pick mates.

So take a leaf from the dark-eyed junco if you're on the lookout: forget hair, make-up and physique. It's all about the smell.