Why Does Blood Smell Like Metal?

The smell of blood often makes humans feeluncomfortable, but for meat-eating animals, it means that food is nearby. Haveyou ever considered why does blood smell like metal? Behavioral researchers atLinköping University in Sweden have identified the key molecule in mammalianblood that emits the "blood smell," a substance that alone canattract an animal's attention as if it were real blood. The research paper waspublished in the journal Public Library of Science - General (PLOS ONE).

Matthias Laska, who participated in thestudy, is a professor of zoology who focuses on olfactory research. He isconcerned with the effects of odor on animal behavior and has conducted severalresearch efforts.

According to Laska, "For predators,the odor of food is extremely attractive, and this odor is mainly associatedwith blood. And what we want to know is exactly which chemicals form the smellof blood."

Scientists also have and have studied whydoes blood smell like metal. Researchers at Sweden's Kolmården Wildlife Parkfound that a component of the blood odor was no less attractive to the animalsthan the taste of blood itself. According to Prof. Raska, "This is acompletely new discovery and raises interesting questions aboutevolution."

Professor Laska has tried searching forvolatile components in the blood of mammals, but has come up empty. Human bloodanalysis has long been used for disease identification, but little is knownabout what component gives blood its signature peculiar odor.

In search of answers, a master's studentinvolved in the study was sent to the Friedrich-Alexander-Universität inErlangen, Germany, to perform meteorological chromatography and massspectrometry on mammalian blood, techniques used to separate and identifychemical compounds in samples. The analytical instrumentation detected about 30components from the blood, some of which were breakdown products of lipids. Butthe sophisticated instruments lost out to the "odor experts" who werealso involved in the analysis, identifying odors that had been completelyoverlooked by the gas chromatography analysis.

The study eventually pinpointed a substancecalled trans-4,5-epoxy-2-decenal (trans-4,5-epoxy-(E)-2-decenal). This is analdehyde compound, it will emit a special "metallic smell", smell itwill remind people of blood.

After the researchers found this odormolecule, they then conducted a field test in animal predators to determinewhether animals are really attracted to this smell. The researchers conductedexperiments at the Kolmården Wildlife Park in Sweden, where they chose fourpredators: jackals (Cuon alpinus), African wild dogs (Lycaon pictus), SouthAmerican servals (Speothos venaticus) and Siberian tigers (Panthera tigrisaltaica), and observed these animals in The researchers prepared a number oflogs.

Related experiments are verifying why doesblood smell like metal. The researchers prepared logs and soaked them in fourdifferent liquids, including a laboratory-derived solution of the aldehydesmentioned above, horse blood, a fruit flavoring solution, and an almostodorless control solvent. The researchers placed the logs soaked in thedifferent liquids sequentially in areas frequented by these animals, one dayfor each type of log, and one day for only one type of odor. At the same time agroup of students observed the behavior of these animals carefully.

So, why does blood smell like metal? Theresults of the experiment were very clear. The logs soaked in the aldehydesmentioned above and the logs soaked in blood were highly attractive to theanimals, while the other two logs were of little interest to the predators.Common responses to the discovery of "blood-smelling" logs includedsniffing, licking, biting, scratching, and playing with them at will. Of theseanimals, tigers maintained interest in the logs the longest, while SouthAmerican servals were the first to lose interest in the inedible logs.

This is the first study to find that a keyscent compound can be as attractive as the blood of an animal with a complexcomposition.

How animals evolved to become interested inthis odor is an interesting question," said Professor Laska. Perhapsbecause it is a component common to the blood of all mammals." ProfessorLaska also plans to conduct several follow-up studies, including a study of howprey that are preyed upon - such as rats - will react when confronted with thesmell of blood.

For wildlife parks, the results of thisresearch can also be applied to daily operations. Animals surrounded by barbedwire need the right stimulus to stay alive and healthy (that's what zoos arefor). The compound treated with the attractive "blood smell" of thelog can be widely placed in the animals' living environment, to attract them tomove.