BREATHE DEEP!

By Pam Eastlick

Welcome to The Deep science and technology column where we cover topics from the deep sea to deep space and beyond.

Greetings all! Well, I think it’s time to dip into one of my favorite files, the one labeled “Animals”. As I have mentioned many times, we humans have a hyper-inflated sense of our own importance in the overall scheme of things. We may think we’re the dominant animals on this planet, but the insects far outweigh us in importance, numbers and sheer mass.

But insects are all small and as individuals are pretty much at the mercy of the larger animals that surround them. Even the ones that don’t eat insects. Just imagine that you’re a tiny aphid, minding your own chomping business on that lovely alfalfa leaf when suddenly the goat that saw it too has made a meal of the alfalfa and gained a little extra protein by eating you!

Well, interestingly enough, some Israeli researchers have discovered that the aphid avoids being part of lunch most of the time by a very simple strategy. It smells that goat coming and drops off the leaf.

"Tiny insects like aphids are not helpless when facing large animals that rapidly consume the plants they live on,” said Moshe Inbar of the University of Haifa in Israel. “They reliably detect the danger and escape in time.”

Inbar had always wondered about the accidental predation of small plant-dwellers based on his observations of insects that don’t really move around. “As soon as we started to work on this problem, we suspected that the aphids responded to our own breath,” he said. (The researchers later used snorkels to keep their own breath from mucking up their experiments).

The researchers allowed a goat to feed on potted alfalfa plants infested with aphids and discovered that 65 percent of the aphids dropped to the ground right before they would have been eaten along with the plant. The escape maneuver could have been triggered by many cues like plant shaking, sudden shadows, or the plant-eater’s breath. While a quarter of the aphids dropped when the plants were shaken, more than half fell to the ground in response to the goat’s breath, the researchers report. Shadows had no effect at all on the dropping behavior and ladybugs, an aphid predator, didn’t inspire that synchronous response either.

So what were they responding too? In other experiments, the researchers learned that they responded to the warm and humid stream of air produced by mammalian breath. The researchers suspect that aphids aren’t the only ones that do the same thing. Want to swat a fly? Try holding your breath!

When plant-eating mammals such as goats chomp on a sprig of alfalfa, they could easily gobble up some extra protein in the form of insects that happen to get in their way. But a new report shows that plant-dwelling pea aphids have a strategy designed to help them avoid that dismal fate: The insects sense mammalian breath and simply drop to the ground. (Credit: iStockphoto)