The effect of Red Deer browsing pressure on the subsequent selection of bilberry plants by Red Deer and Lepidoptera Larvae

Abstract

Browsing by deer may induce defence in plants which may subsequent affect food quality for herbivores. Lepidoptera larvae are thought to be more sensitive to defence substances in plants than larger herbivores, like red deer, because of a simpler digestion system. This study focus on how previous browsing pressure by red deer, affected selection of bilberry plants by red deer and Lepidoptera larvae. Cafeteria trials were used to study bilberry preference by Lepidoptera larvae and red deer. Bilberry with four different browsing histories was presented to larvae and deer: unbrowsed, lightly browsed, moderately browsed, and highly browsed. Both larvae and deer avoided the heavily browsed bilberry which represented an artificial high level of deer densities. Larvae preferred lightly browsed plants, while the results indicated that deer preferred the moderately browsed plants. I conclude that larger herbivores do not show a strong selection against previously browsed bilberry plants. Lepidoptera larvae did avoid previously intensively browsed plants and were more selective in food choice.

Hjortbeiting kan indusere forsvar i planter, som igjen kan påvirke hvordan herbivorer selekterer planter. Lepidoptera larver antas å være mer sensitive for forsvarsstoffer i planter enn større herbivorer som hjort, på grunn av et enklere fordøyelsessystem. Denne studien undersøker hvordan tidligere hjortebeiting på blåbærplanter påvirker hjortens og Lepidoptera larvenes beitepreferanser. Kafeteriatester ble brukt for å studere blåbærpreferanse hos larver og hjort. Blåbær med fire forskjellige beitehistorikker ble presentert for larver og hjort: ubeita, lett beita, moderat beita, og hardt beita. Både larver og hjort unngikk hardt beita blåbærplanter som representerte en kunstig høy hjorttetthet. Larver foretrakk lett beita planter, mens mine resultater tyder på at hjort foretrakk moderat beita planter. Jeg konkluderer med at store herbivore ikke viste noen sterk seleksjon mot tidligere beitede blåbærplanter. Lepidoptera larver unngår tidligere hardt beita planter og var mer selektive i sine valg av planter.