Rodents such as mice are considered one of the major causes of crop damage throughout the world. They have long been a problem on fields since they find these sites plenty of food and nesting areas. They damage crops and carry 45 diseases that pose health risks to humans and livestock, as reported by the Center for Agriculture, Food, and the Environment of the University of Massachusetts Amherst.
Traditionally, mice infestation is solved by using rodenticide since it is considered the most efficacious and cost-effective method. However, these chemicals can contaminate soil, water, and turf. They can also be toxic to other organisms, such as birds, beneficial insects, and vegetation. In fact, the U.S. EPA proposed new mitigation measures for rodenticides to protect human health and the environment.
Confusing the Rodent with Scents
To solve this challenge, a group of researchers led by Finn C. G. Parker from the University of Sydney tried to find a better and more humane alternative to rodenticides. This is done by camouflaging the scent of the crops to make the newly sown seeds practically undetectable for mice.
In this research, two odor camouflage tactics were used as a misinformation strategy to prevent wild house mice (Mus musculus) from finding newly sown wheat seeds. First, wheat germ oil was dispersed as scent camouflage to separate the link between sources and seed scent cues. This makes it hard for mice to locate the buried seeds. Second, the mice were pre-exposed to unrewarding scent information before sowing the seeds, making the rodents lose their interest in using germ scent to find the buried seeds. This applies the optimal foraging theory and Bayesian updating tactics in adapting foraging strategies.
The researchers conducted their study on a 27-hectare field in southern Australia that experiences large-scale mouse plague. Mouse damage was measured by counting digging holes along the sowing lines. Cameras were also used in calculating the frequency of mouse visitation in the field.
The researchers made two predictions while the study was ongoing. First, they theorized that wheat germ scent would damage the rodent's ability to find seeds as a uniform food scent distribution was created. This will eventually lessen the amount of damage to treated wheat fields. Secondly, they concluded that if the mice learned the scent cue was unrewarding, they would visit the pre-exposed plots less often.
The result of the study supports their hypothesis that scent camouflage breaks the link between food items and their associated scent cues. It was also found that mice rapidly learned that foraging is difficult in scent-treated wheat fields. The mice could not find the seeds in areas with overwhelming scents. The wheat fields with camouflaged scent also showed 74% less damage than those untreated.
Parker and his team are confident that their scent camouflage techniques can also be applied to protect other cereal seeds that suffer from pre-germination loss due to pests. They also hope their strategy is a simple and ethical solution to manage the impacts of problems like rodents.
How Do Rodents Detect Seeds?
Foragers such as rodents usually depend on scents to find food items. In agricultural fields, newly sown seeds are dug up by mice by targeting the smell of the wheat germ.
According to the Oxford Academic Journal of Mammalogy, the odorants detected by animals are volatile molecules, either from the seed surface or from the inner substance that leaches from within. Since the seeds are buried in the soil, they are mixed with water in the environment.
However, the activity of odorants is also affected by the influences of the physical environment. The environmental conditions impact the odorants' vapor density and, thus, affect the olfaction of rodents.
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