Amid the devastation of the 2021 mouse plague, when swarms of invasive house mice destroyed $1 billion worth of crops and seeds, a photo of a wheat field riddled with a neat row of holes caught the eye of Professor Peter Banks.
The scavenging mice didn’t pick up the dirt while searching for freshly sown seeds like thugs breaking open jewelry boxes with a crowbar. They located each seed by its scent and dug precise holes – rather like gloved thieves taking diamonds from a safe and disappearing without a trace.
Banks, a conservation biologist at the University of Sydney, and PhD student Finn Parker hatched a plan. If they doused a seed patch in wheat germ oil, causing the entire plot to smell palatable, could this olfactory camouflage destroy the mice’s seed-foraging ability?
The results of their study, published in sustainability in nature, Say yes. The simple and non-toxic method of seed camouflage successfully confused the mice and significantly reduced seed loss.
“It’s like visual camouflage,” Banks said. “When an entire wall is yellow and you’re trying to find something yellow on the wall, it’s really difficult. Cloaking blends the background to the target. This is exactly the same, but with a smell.”
Banks and Parker sprayed wheat germ oil—a byproduct of wheat milling—every few days starting a week before planting. Two weeks after sowing, after seeds began to germinate and sprout, odor-camouflaged plots experienced 74 percent less mouse damage compared to a control sample. Overall, seed loss was reduced by around 60 percent.
Usually, over time after sowing, the mice are better at locating seeds. More than twice as much seed damage occurs in the second week as in the first.
The use of scent camouflage disrupted this rapid learning as the task of finding seeds was far more difficult. Animals, including mice and humans, tend to grab whatever calorie boost can be consumed with the least amount of effort. And mice are hungry creatures – each one can devour 100 seeds in one night.