Plant Tannins and Essential Oils Have an Additive Deterrent Effect on Diet Choice by Kangaroos

Abstract

Tannins and essential oils are well recognised as antiherbivore compounds. We investigated the relative effectiveness of the polyphenol, tannin, and the essential oils, 1,8-cineole and pine oil, as feeding deterrents against western grey kangaroos. Both groups of secondary metabolites are naturally abundant in many Australian plants. These three metabolite groups were incorporated separately or together into standard pellets for presentation to kangaroos, and their behaviour (sequence of food choice and feeding time) and amounts consumed were observed. The control (with no secondary metabolites) was much preferred. There was a sharp reduction in the ingestion of pellets containing tannins, 1,8-cineole or pine oil. Combinations of the metabolites resulted in almost no consumption. In association with tannin, pellets containing either 1,8-cineole or pine oil were as effective deterrents as both combined. There was a strong correlation between time spent feeding on the different diets and the amount of food consumed, although the rate of intake was markedly slower when secondary metabolites were present. Behavioural observations showed that the amount of food ingested is initially guided by the presence/absence of essential oils, apparently detected by smell, and later by the presence/absence of tannins, by taste. Both groups of secondary metabolites work in concert by stimulating different senses that minimise herbivory by marsupials, such as the western grey kangaroo, and help to explain their abundance in the Australian flora.

Effects of Essential Oils and Fragrant Compounds on Appetite: A Systematic Review

“…Lime (Citrus aurantifolia) essential oils suppressed food consumption and reduced body weight in both ketotifen-induced weight gain and normal mice [44] (Tables 5 and 6). Supplementation with pine essential oil and 1,8-cineole (a common aromatic compound) in the diet significantly decreased food consumption in western grey kangaroos [72]. Piglets fed diets containing caraway seed (Carvi aetheroleum) or fennel seed (Foeniculi aetheroleum) essential oils (100 mg/kg) showed a decrease in food intake [39].…”

Myrtaceae anther glands: morphology, anatomy and variation in glandular contents

“…One of the characteristics of the family Myrtaceae is the presence of oil glands in the leaves, even in the pith of stems and in various floral parts (Johnson and Briggs 1984). It is generally considered that the oils are unpleasant/poisonous to animals that might be attracted to consume plant parts, and so, they are a protection against herbivory (Rafferty and Lamont 2021;Müller et al 2022). For example, the monoterpene 1,8 cineole, which is a common component of Eucalyptus oil, was considered a deterrent to hares from eating balsam poplars in Alaska (Reichardt et al 1990).…”