Why the metallic smell of blood attracts predators

Sniffing them, biting them and carrying them around – these were some of the behaviours that researchers observed in carnivores at a zoo when given sticks with blood or blood odour on them. (Image: 2014 Nilsson et al.)
Sniffing them, biting them and carrying them around – these were some of the behaviours that researchers observed in carnivores at a zoo when given sticks with blood or blood odour on them. (Image: 2014 Nilsson et al.)
January 7, 2015

FAU researchers discover substance that triggers hunting behaviour

We are all familiar with the expression ‘to taste blood’. In the animal kingdom just the smell of blood has an irresistible effect on carnivores. If a predator smells blood it knows that dinner is not far away. But what are the characteristic components of blood in mammals? What exactly causes the typical metallic smell of mammalian blood? Until now, very little was known about this. Aroma researchers at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have recently analysed it and made some surprising discoveries.

‘There is clearly a component which triggers typical hunting behaviour in certain mammals,’ says Prof. Dr. Andrea Büttner, food chemistry expert and professor of aroma research at FAU’s Emil Fischer Centre. Using various gas chromatographs, an aroma research group led by FAU researcher Constanze Sharapa (née Hartmann) – in conjunction with researchers at Linköping University in Sweden – carried out analyses which showed that it is an aldehyde called trans-4,5-epoxy-(E)-2-decenal which produces the characteristic, metallic blood smell that carnivores react to.

‘The results show for the first time that a single substance in blood can produce a similarly efficient effect in predators as the complex smell of blood,’ explains Prof. Dr. Andrea Büttner, a specialist in aroma research, aroma perception, aroma analytics and food chemistry.

More activity when playing with specially prepared sticks

For the study, different wooden sticks were impregnated with the aldehyde, blood from mammals and a substance with a neutral smell and thrown to three species of wild dogs and Siberian tigers living in a zoo for them to play with. While the animals showed barely any interest in the neutral-smelling substance, the sticks soaked in the aldehyde and in blood were very attractive to them. ‘All four species showed significantly more interest in the sticks which had been prepared in this way,’ says Prof. Dr. Andrea Büttner. The carnivores licked the sticks, chewed them, played with them or handled them with their paws. They did not make a distinction between the sticks soaked in the chemical substance and those soaked in blood. ‘This also shows that ‘toys’ with an aroma can provide enrichment for carnivores living in captivity,’ says Prof. Dr. Andrea Büttner.

doi:10.1371/journal.pone.0112694

  1. Nilsson, J. Sjöberg, M. Amundin, C. Hartmann, A. Buettner, M. Laska. Behavioral responses in large carnivores to mammalian blood odour and a blood odour component. PLoS ONE, 2014, 9, e112694

Further information:

Prof. Dr. Andrea Büttner
Phone: +49 9131 8522739
andrea.buettner@fau.de