By Bethany Brookshire
Now you smell it, now you don’t. Or do you? Used correctly, a little misdirection could help keep mice away from freshly planted wheat seeds.
Camouflaging wheat seeds can reduce seed loss by more than 60 percent, scientists report May 22 in Nature Sustainability. All it takes is to make the whole field smell like wheat.
Rodents, including mice, are responsible for nibbling away at 70 million metric tons of cereals every year. Some of that munching takes place in Australia, where, when the weather is right, house mice (Mus musculus) can reach plague proportions — skittering hordes of more than 1,000 mice per hectare, says Peter Banks, a behavioral ecologist at the University of Sydney. There are so many mice on the road, he says, no one can avoid them. “It’s like driving on bubble wrap.”
When farmers plant wheat, mice go down the rows, sniffing out the seeds under the soil and digging them up. Usually, farmers overrun with mice turn to poisons such as zinc phosphide, which changes to phosphine gas in a mouse’s stomach. Unfortunately, it’s hard to make any poison appealing enough to make mice ignore the wheat buffet, and farmers are having to use more and more of it, says Steve Henry, a rodent ecologist at the Commonwealth Scientific and Industrial Research Organization in Canberra, Australia, who was not involved in the study.
What if the mice couldn’t sniff out the grains at all? Banks and his colleague Finn Parker, also a behavioral ecologist at the University of Sydney, have been working on olfactory camouflage — covering scents with, well, more scents. The technique started with invasive predators who hunt for threatened bird nests by smelling them out. “We thought, well, if we put those odors everywhere, how on Earth can they then find out where the nests actually are,” Banks says.
Before or during sowing, the scientists sprayed mouse-riddled test plots with wheat germ oil, a byproduct of wheat processing that is usually used in cosmetics and animal feed. The oils are the most nutritious parts, Banks says, and the smell of the oils is “what [the mice] are using to find the seeds beneath the ground.”
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