Scammed by 'fake news': animals led by the nose to leave plants alone
Swamp wallaby in the experimental set at Ku-ring-gai Chase NP up sniffs unpalatable Boronia and leaves preferred Eucalyptus seedling alone. Photo: Patt Finnerty
University of Sydney researchers have shown it is possible to shield plants from the hungry maws of herbivorous mammals by fooling them with the smell of a variety they typically avoid.
Findings from the study in show tree seedlings planted next to a solution mimicking the smell of avoided plants were 20 times less likely to be eaten by animals.
鈥淭his is equivalent to the seedlings being surrounded by actual plants that are unpalatable to the herbivore; tricking the animals so they take much longer to find and feed on them,鈥� said PhD student Patrick Finnerty, the study鈥檚 lead author from the School of Life and Environmental Sciences .听
鈥淗erbivores cause significant damage to valuable plants in ecological and economically sensitive areas worldwide, but killing the animals to protect the plants can be unethical,鈥� he said.
Lead author Patt Finnerty in the field.
鈥淪o, we created artificial odours that mimicked the smell of plant species they naturally avoid, and this gently nudged problematic herbivores away from areas we didn鈥檛 want them to be.
鈥淕iven that many herbivores use plant odour as their primary sense to forage, this method provides a new approach that could be used to help protect valued plants globally, either in conservation work or protecting agricultural crops.鈥�
The experiment, conducted in Ku-ring-gai Chase National Park in Sydney, used the swamp wallaby as model herbivore. The researchers selected an unpalatable shrub in the citrus family,听Boronia pinnata, and a palatable canopy species,听Eucalyptus punctata, to test the concept.
The study compared using the听B. pinnata听odour mimic and the real plant and found both were equally successful at protecting听eucalypt听seedlings from being eaten by wallabies.
As part of his doctoral research, Mr Finnerty has also tested the method successfully with African elephants, but that fieldwork does not form part of this research paper.
Previous attempts to use repellent substances, such as chilli oil or motor oil, to control animal consumption of plants have inherent limitations, Mr Finnerty said.
鈥淎nimals tend to habituate to these unnatural cues and so deterrent effects are only temporary,鈥� he said.
鈥淏y contrast, by mimicking the smell of plants herbivore naturally encounter, and avoid in day-to-day foraging, our approach works with the natural motivators of these animals, with herbivores less likely to habituate to these smells.鈥�
Researcher Patt Finnerty with elephants in the field in South Africa.
Researchers took this idea and used solutions that produce these undesired aromas.
鈥淎s a management tool to protect palatable plants, our technique offers many advantages over using real plants as a way to nudge herbivores away from plants we are trying to protect,鈥� Mr Finnerty said. 鈥淩eal plants compete for water and resources, which can outweigh protective effects in providing browsing refuge.
鈥淥ur approach should be transferable to any mammalian, or potentially invertebrate, herbivore that relies primarily on plant odour information to forage and could protect valued plants globally, such as threatened species.鈥�
Current solutions to herbivore-related problems often involve costly and environmentally impactful measures such as lethal control or fencing.
The new research introduces an alternative low-cost, humane strategy based on understanding herbivores鈥� foraging cues, motivations and decisions.
鈥淧lant browsing damage caused by mammalian herbivore populations like deer, elephants and wallabies is a growing global concern,鈥� said senior study author听Professor Clare McArthur.
鈥淭his damage can be one of the greatest limiting factors in areas of post-fire recovery and revegetation. It also threatens many endangered plant species and causes billions of dollars of damage in forestry and agriculture globally.
鈥淐urrent methods to protect plants are expensive and increasingly limited by concerns over animal welfare, so alternate approaches are needed.鈥�
Fieldwork in South Africa
Patt Finnerty is now working to test the hypothesis with African elephants.
Research
鈥�Olfactory misinformation provides refuge to palatable plants from mammalian browsing鈥�, Finnerty, et al (). DOI: 10.1038/s41559-024-02330-x
Declaration
The authors declare no competing interests. The research was funded by the Ecological Society of Australia, Australian Academy of Science, Royal Zoological Society of Australia, Australian Wildlife Society, NSW Department of Planning and Environment, and the Australian Research Council.