Ecologists find a way to gently nudge wallabies, elephants away from eating important plants

Researchers seeking new ways to prevent animals like wallabies and elephants eating endangered or valuable plants believe companion planting – with a smelly twist – might hold the solution.

Ecologists from the University of Sydney defined and reproduced aromas from a plant herbivores naturally avoided in attempts to deter hungry herbivores away from palatable Eucalyptus seedlings.

These findings offer a novel alternative to herbivore management strategies such as lethal control efforts and fencing, and holds potential to protect threatened flora locally and across the globe – and assist everyone from the home gardener to commercial farmers.

The problem the researchers were trying to solve are being exacerbated by the growing absence of predators in Australian ecosystems, which has led to an overabundance of larger native and invasive herbivores. Browsing by over-populated herbivores like deer and wallabies, have a detrimental impact on local flora communities and threaten biodiversity. 

In a recent study, the details of which were published in Nature Ecology and Evolution, the research team surrounded high palatable eucalyptus seedings with vials containing aromas mimicking boronia, a native shrub species naturally avoided by local herbivores. 

Just as humans turn their noses up at food with bad odours, herbivores use their excellent sense of smell to differentiate and select between tasty and unpalatable plants. 

Swamp wallabies: black panther downunder?

The researchers explored if artificially replicated scents informative of an unfavourable plant alone could deter Australian swamp wallabies from consuming highly palatable eucalyptus seedlings. Findings from the study showed the seedlings placed next to the scent vials mimicking boronia were 20 times less likely to be eaten by wallabies. This level of deterrence was equivalent to Eucalyptus seedlings that were surrounded by real boronia plants.

Patrick Finnerty

A major advantage of using artificially reproduced smells over the real avoided plant species is that protection provided comes without competition costs between focal and real neighbouring plants for space and resources. By replicating leaf odour rather than floral odour, this strategy also avoids any impacts on confusing local pollinators.

“What we did was mimic the smell of leaves and stems [not flowers], so it’s a completely different set of information that pollinators and herbivores are using,” says Patrick Finnerty, a PhD student and the lead author of this study.

Above: Watch as a wallaby is gently encouraged to avoid eating the eucalypt seedling (P.Finnerty)

Recent studies conducted by Finnerty indicated this strategy could be effective on African elephants, suggesting this approach has the potential to be applied to any mammalian, and possibly invertebrate, herbivore that forage primarily using plant aroma information.

The basis of this study also means small-scale deterrence systems could be deployed in vegetable patches or garden beds in people’s backyards.  

For now, the research team is investigating the future of this strategy.

“A main step we need to take is to see whether these findings could be actually replicated at a larger scale,” Finnerty says “but also, to see how long these tools we have developed could be used to deter herbivores over time.” 

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