Smells of death reveal a common evolution

[Tonington]

When animals die, their corpses exude a particular "stench of death" which repels their living relatives, scientists have discovered.

Corpses of animals as distantly related as insects and crustaceans all produce the same stench, caused by a blend of simple fatty acids.

The smell helps living animals avoid others that have succumbed to disease or places where predators lurk.

This 'death recognition system' likely evolved over 400 million years ago.

"We were examining the aggregation behaviour of cockroaches," says Prof Rollo.

When a cockroach finds a good place to shelter, it gives off pheromones that attract more of its kind.

In a bid to identify the exact chemicals involved, Prof Rollo's team extracted body juices from dead cockroaches to see what effect they had.

"We were astonished to find that nearly 100% of cockroaches avoid shelters treated with whole body extracts. Something in the extract was overriding any attractive chemicals," says Prof Rollo.

"We initiated extensive work to figure out what could be so important to make all these insects go away."

After eliminating a host of other possibilities, such as cockroaches producing alarm signals, they considered the idea that a specific chemical is released by the insects upon death.

"A search of the literature turned up a very old article by famous sociologist and ecologist E. O. Wilson," says Prof Rollo.

"Wilson found that ants removed the dead from their nest and dumped them in a cemetery. Moreover, he identified the active signal as oleic acid."

"The famous story goes that Wilson found that a drop of oleic acid on a perfectly healthy ant resulted in her being carried kicking and screaming to the cemetery. Ants can't scream, but you get the picture."

Read the rest here.

This research could be used in part to make very good repellents!

 

[karrie]

running grasshoppers through the blender with enough water to make a slurry, straining it, and spraying it around your yard, has always been a good way to prevent grasshoppers from staying in your yard.

I bet it works with humans too. I know it would work in keeping me away from somewhere.

 

[Tonington]

And dead crows are supposed to keep their kind away as well. It's surprising when somebody finds results like these, that given these things people know, nobody really examined the issue in detail.

 

[karrie]

And dead crows are supposed to keep their kind away as well. It's surprising when somebody finds results like these, that given these things people know, nobody really examined the issue in detail.

I guess it boils down to why overthink something so simple as 'animals don't like to be around their rotting kin'?

 

[Tonington]

Well I guess to be fair, in this case it was an accidental discovery. As I said above, you could make some very good repellents with this stuff. Not so much over-thinking as finding solutions in nature for common problems.

 

[karrie]

yeah... dropping acid on an ants' nest so they think it all smells of death, seems like a pretty handy solution... but not necessarily an environmentally friendly one to 'market', thus why there may be a lack of research on the issue. Just because something occurs in small amounts in animals or insects doesn't mean it would be safe the way we'd manufacture, etc.

 

[Tonington]

Fatty acids are found in all sorts of things, margerine, butter, fish, etc. You wouldn't need to dump pure oleic acid on the ground or anything like that.

I'm sure given the choice of natural repellent versus artifical lab product...most people would go for the natural, provided it is an effective treatment.

I just found now for instance that some research is ongoing with mosquitoes and fatty acids. Imagine a natural repellent made from easily synthesized fatty acids which could be used to keep malaria-carrying mosquitoes away. That would be quite a find.

 

[Tonington]

Oh, I should add that given that fatty acids are quite common in biology, there would also likely be small worries of persistence in the environment. There is an extensive biochemistry involving fatty acids, and I'm sure many bacteria would utilize it as an energy source.

 

[karrie]

that would be nice to see.

Personally, I'd still stick to grinding up the insects in question, instead of buying something for most garden type applications.

 

[Tonington]

that would be nice to see.

Personally, I'd still stick to grinding up the insects in question, instead of buying something for most garden type applications.

Should try it with wasps, though the collection might not be so easy...

 

[karrie]

Should try it with wasps, though the collection might not be so easy...

wasps are a different story according to common wisdom. crush a wasp and you can cause a swarming. With wasps and hornets, you're better off taking advantage of their territorial nature, and putting out a paper bag wasp's nest.

 

[Tonington]

Maybe you'd have to wait until it dies of some other means, like dessication or starved. Then crush it up.