Why the Scent of Blood Lures Wolves But Repels People

When exposed to the smell of a single molecule found in blood, predator and prey had very different reactions.

A single molecule released from fresh blood, the one that gives it that metallic smell, causes humans to recoil and other animals to lick their lips in predatory anticipation, reveals a new study.

Published by researchers from the Karolinkska Institute in Sweden, the new paper in the journal Scientific Reports documents how predator and prey respond to a diluted, seemingly imperceptible molecule called trans-4,5-epoxy (E) -2-decenal, or E2D for short.

The chemical is released when lipids in blood break down after being exposed to air. Researchers were able to separate E2D from blood and diluted it to one part per trillion. That's akin to a single drop of the molecule being placed in an Olympic-sized swimming pool, said the study's lead

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