Animals keep eating precious plants – we used ‘smell misinformation’ to keep them away

• In places where we need to protect valuable plants – whether for ecological or economic reasons – local herbivores can cause significant damage.
• But this is increasingly unacceptable due to animal welfare concerns and social pressures.
• Recently, our team discovered that herbivores – plant-eating mammals – primarily use their sense of smell to tell which plants they want to eat or avoid.

Herbivore-induced headaches

• They can devastate revegetation efforts and post-fire recovery, destroying more than half the seedlings in these areas.
• Every year, they cause billions of dollars of damage in forestry and agriculture.
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A landscape of smells

In navigating a scent landscape, herbivores use odour to recognise and select among plants and plant patches. Odour is key in guiding the foraging of marsupials in Australia, elephants in Africa and Asia, and deer in the United States. With this in mind, we explored whether the smell of a plant they don’t like could be enough to nudge animals away from highly palatable native tree seedlings.

• Studies have shown having too many swamp wallabies around can limit the number of eucalypt seedlings that survive to become trees.
• Swamp wallabies also have a fantastic sense of smell – they can find just a few eucalypt leaves buried underground among complex vegetation.
• Using odours instead of real plants is a type of olfactory misinformation – it sends a deceptive message to the animals.

Real and virtual neighbours

• We also compared if virtual neighbours were as good as the real thing in protecting eucalypt seedlings from being eaten by wallabies.
• Five virtual neighbour vials or real Boronia pinnata plants were spaced evenly around single eucalypt seedlings the wallabies would find highly palatable.
• Seedlings were 20 times less likely to be eaten when surrounded by virtual neighbours than for both controls.

A highly effective approach

• The success of our study indicates we could use this approach as a new management tool – one that works by influencing the animals’ behaviour rather than trying to get rid of them.
• We believe the concept behind developing virtual neighbours is directly transferable to any herbivore, mammal or otherwise, that uses plant odour to forage.

• Clare McArthur receives funding from the Australian Research Council, NSW Environmental Trust and NSW Department of Planning and Environment.
• Peter Banks receives funding from the Australian Research Council, NSW Environmental Trust and NSW Department of Planning and Environment, Hermon Slade Foundation and Manaaki Whenua.