Tricking animals with odor could save plants from browsing damage

Scientists at the University of Sydney have made a discovery that could revolutionize the protection of plants from browsing damage by herbivorous mammals.

The researchers have found a way to deter animals from consuming desirable plant species by simulating the aroma of plants that these animals would typically avoid.

Animal control measures 

The study demonstrates that tree seedlings near the artificial odor were substantially less likely to be consumed by herbivores, mirroring the effect of being surrounded by naturally repellent plants. 

“This method effectively deceives the animals into sparing the plants, offering a promising alternative to lethal animal control measures which raise ethical concerns,” said lead author Patrick Finnerty, a PhD candidate from the School of Life and Environmental Sciences Behavioral Ecology and Conservation Lab.

Odor-based deterrence 

The research, conducted in Sydney’s Ku-ring-gai Chase National Park, focused on the swamp wallaby as the primary herbivore. By using an unpalatable shrub, Boronia pinnata, from the citrus family and a palatable canopy species, Eucalyptus punctata, researchers could test the efficacy of their odor-based deterrence method. 

Remarkably, the artificial Boronia pinnata solution proved just as effective as the actual plant in safeguarding eucalypt seedlings from wallaby predation.

Deterring larger herbivores 

Finnerty’s innovative approach also shows promise in deterring larger herbivores, such as African elephants, though these findings are part of his broader doctoral research and not included in the current publication. This strategy addresses the shortcomings of previous repellent methods, such as chili oil or motor oil, which animals can become accustomed to, diminishing their effectiveness over time. 

By leveraging the natural avoidance behaviors of herbivores, the scent-based method offers a sustainable and humane solution for plant protection.

Study implications 

The implications of this research extend beyond conservation efforts to include agricultural applications, providing a cost-effective and environmentally friendly alternative to traditional protective measures like fencing or lethal control. 

Study senior author Professor Clare McArthur emphasizes the global challenge posed by mammalian herbivores like deer, elephants, and wallabies, which can significantly hinder post-fire recovery, endanger plant species, and inflict substantial economic losses in forestry and agriculture. 

“Plant browsing damage caused by mammalian herbivore populations like deer, elephants and wallabies is a growing global concern. This damage is one of the greatest limiting factors in areas of post-fire recovery and revegetation, destroying more than half the seedlings in these areas. It also threatens endangered plants and causes billions of dollars of damage in forestry and agriculture globally,” she explained.

Therefore, this innovative approach, grounded in a deep understanding of herbivore foraging behaviors and preferences, presents a novel and much-needed solution to a pressing ecological and economic issue.

Plant browsing damage 

Plant browsing damage refers to the harm caused to plants by animals feeding on them. This type of damage can significantly affect plant health, growth, and productivity, and it’s a common concern in agriculture, horticulture, forestry, and natural habitats. Here are some key points about plant browsing damage:

Causes 

Browsing damage is primarily caused by herbivorous mammals, such as deer, rabbits, goats, and in some regions, larger animals like moose and elk. Birds can also cause browsing damage, although their impact is often less severe.

Types of damage

The damage can range from the removal of leaves and shoots to the breaking of branches and stems. In severe cases, browsing can lead to the death of young plants or significantly stunt their growth.

Effects on plants

Beyond the immediate physical damage, browsing stress can make plants more susceptible to diseases and environmental stresses. It can also lead to changes in plant morphology (shape and structure) as plants may develop physical defenses (like thorns) or chemical defenses (like increased bitterness) to deter future browsing.

Management and control

Effective management strategies are essential to minimize browsing damage, especially in areas where wildlife populations are high. These strategies may include physical barriers (like fencing), repellents, planting less palatable plant species, or controlled hunting to manage animal populations.

Ecological impact

While browsing can be detrimental in managed environments like farms and gardens, it’s a natural part of many ecosystems. Herbivory helps shape plant community structure, influences biodiversity, and can even benefit plants by pruning that encourages growth.

The research is published in the journal Nature Ecology & Evolution.

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