From macropods to megaherbivores – understanding and harnessing mammalian herbivores' use of olfactory information

Abstract

For a generalist mammalian herbivore foraging decisions are made cross a hierarchy of spatial scales from plant communities, patches within communities, individual plants within patches, and parts within plants. Thus, the consumption of any particular plant are shaped both by the quality, or ‘palatability’ of the plant itself, and by its neighbours. When neighbouring plants influence focal plant vulnerability to herbivory, it is called an associational effect.

Associational effects are well documented. But several important questions remain. Can single neighbouring plants influence vulnerability of focal plants to herbivory? Can plant odour provide the crucial information underpinning foraging decisions that lead to associational effects? Is there a component within the entire plant odour that is informative to herbivores? Can associational effects informed by odour be harnessed to protect plants from wild herbivores?

Answering these questions is fundamentally ecologically significant. By influencing plant growth and survival, mammalian herbivores around the world shape the structure of entire plant communities. Moreover, herbivore browsing can be problematic, devastating areas of habitat restoration and post fire recovery, and causing billions of dollars of damage in forestry and agriculture globally. Current solutions to problematic herbivory traditionally use lethal control, or preventing access to plants such as fencing. These approaches can have social, ecological, and economic limitations. Thus, recognising the information herbivores use to make foraging decisions is also key in developing alternative management solutions to control herbivore browsing damage.

To address these questions in this thesis, I ran a series of manipulative trials focusing on plant-herbivore interactions of free-ranging swamp wallabies, Wallabia bicolor, in open eucalypt woodland, Australia, and semi-domesticated African elephants, Loxodonta africana, in highveld savanna, South Africa.