Dr. Nadav Shashar’s research on locust flight patterns can potentially combat the devastating affect they have on crops. Swarms of locusts have, ever since Biblical times, been considered a real plague.
Hardy desert locusts are able to swarm for great distances in groups that extend for miles and in numbers measuring in the millions, destroying everything in their path. The damage they do to crops has periodically sparked food crises in poor countries that depend on agriculture.
Until now, it was thought that the directions of locust swarms were predominantly directed by prevailing winds.
Now, Hebrew University of Jerusalem scientists have shown that a physiological trait of these grasshoppers – their polarization vision – provides them with a built-in source of “surface analysis” – which is why they fly almost exclusively over land and not over water.
The research could be important in providing information that would be useful in efforts to effectively combat this periodic scourge, which has wreaked havoc in parts of Africa where crops have been decimated by locusts.
Using this knowledge ways to “deceive” the locusts can potentially be developed – placing reflective material over crops, or shining light on them in order to deter the insects from flying over agricultural lands and damaging them.
The discovery literally flew over the head of Dr. Nadav Shashar last year.
Shashar is a world-renowned expert in the field of polarized sight. A professor at Hebrew University, he works out of the Interuniversity Institute for Marine Sciences in Eilat, a facility that Israeli universities share to study the Red Sea. He works there together with four other faculty members from various universities and more than 40 researchers. The facility has existed since 1967, originally owned by Hebrew University exclusively, but becoming a cooperative venture in 1983.
During a rare locust invasion in Israel in 2004, a swarm of locusts came in an easterly direction over Sinai up to the Gulf of Eilat, and then turned northward without crossing the water. Only when the swarm reached the northern tip of the gulf did some of them turn again east in the direction of Aqaba and other areas of Jordan, as well as heading north over southern Israel.
Shashar watched it all from his office.
“They were coming just over the mountains towards our marine lab, heading for the sea and then, right in front of us, they turned, they didn’t go over water,” he told Israel 21c. “You could stand on the dock in front of the lab, go to the edge and only a few locusts would be near you. So the question came up: how do they know? Why don’t they fly over the water?”
With his specialization and background, Shashar immediately hypothesized that the cause was polarized sight. Polarization involves the vibration of light waves. Light waves can vibrate in many directions. Those that are vibrating in one direction – in a single plane such as up and down – are called polarized light. Those that are vibrating in more than one direction – in more than one plane such as both up/down and left/right – are called unpolarized light.
“We began testing. We captured some of them, and had them fly over a surface that included mirrors and plastic surfaces, and they avoided those surfaces. Then we had them fly over a black surface twice – once where there was polarized light and another time with unpolarized light – and we saw a clear difference in their behavior,” Shashar said.
“When the locusts are presented with a situation of choice between surfaces reflecting either polarized or diffused light, they exercise their preference to fly over the area of diffused light,” he explained. This, he concludes, is a survival instinct, since if they flew over a body of water, the locusts would be deprived of both nourishment and a place to land and rest.
Until he came across the locusts, Shashar’s research has focused on marine life. He fell in love with the sea while scuba diving in Sinai.
After studying marine biology in Israel, he pursued a PhD at the University of Maryland, and found his focus studying polarization of vision and marine animals. The ability to identify polarized light is a trait which is lacking in humans but exists among other species. It has been known to exist in insects since Austrian scientist Karl Von Frisch discovered it in bees – a discovery that won him a Nobel Prize.
Shashar has focused on sea creatures like cuttlefish and squid and crustaceans such as crabs in locations as exotic as the South American rain forest. “In my PhD work, I investigated the way in which animals use polarization sensitivity — some animals can use it for communication, with patterns of polarized light that they display on their body. We’ve even recruited people from military intelligence for help cracking their codes.”
He has also studied the ways in which sea animals use their polarization ability to increase their line of vision underwater for survival purposes – which is why, when he saw the locust behavior, he immediately began to suspect it as the cause.
Shashar finds the locusts to be “amazing creatures” but in some parts of the world they are indeed a plague.
“The real problem is in sub-Saharan Africa, in countries like Chad and Mali who have suffered a three-year attack of locusts,” Shashar said.
Swarms of desert locusts many miles long descended on West Africa this past summer and fall – the worst invasion of the crop-devouring pests in more than 15 years. Mauritania was been worst affected, with thousands of farmers needing food aid after the locusts devoured their year’s crops. Mali, Niger and Senegal were also been badly hit.
Attempts to exterminating locusts are extensive, with close coordination of aerial spraying and pesticides targeting the insect to decrease harm to humans. But at best, the spraying kills about 85 percent of a swarm.
Shashar says that developing a solution using polarized light could help to minimize the damage.
“Any possible solution in these places must be easy and cheap – we are talking about very poor countries, after all. The simplest thing would be to produce something that would reflect polarization and keep locusts away from the fields – or an even cheaper solution might be to shine a special light on the fields that would divert the locust elsewhere.”