Oral Presentation- Symposium 12th International Mammalogical Congress

Borrowed plant defences: Deterring browsers using a forestry by-product (#46)

Rebecca S Stutz 1 , Benjamin M Croak 1 , Olof Leimar 1 , Ulrika A Bergvall 1
  1. Department of Zoology, Stockholm University, Stockholm, SE-106 91, Sweden

Herbivorous mammals can significantly damage important tree species, particularly at the vulnerable seedling stage. Harnessing the anti-herbivore defences evolved by some tree species could reduce the appeal of more preferred trees and thus their loss to browsing. We tested whether chemicals extracted from birch bark, a forestry by-product, could protect seedlings of Scots pine from ungulate browsers in Sweden. We quantified the responses by captive moose and red deer to extract application as a function of both the distance between seedlings and whether the extract was applied to all or alternate seedlings. Both moose and red deer consumed pine seedlings less frequently when seedlings were treated with extract. At inter-seedling distances equivalent to those used in forestry, red deer browsed untreated seedlings more frequently with treated than untreated neighbours (associational susceptibility), whereas moose browsed untreated seedlings less frequently with treated than untreated neighbours (associational refuge). Red deer used a finer scale of selection for choosing between seedlings, but moose consumed more untreated relative to treated seedlings overall (4:1 compared to 2:1 by red deer). We then tested the effectiveness of the extract to protect young pine trees from browsing by wild moose, red, fallow and roe deer in a mixed forest over winter. Treated trees were significantly less likely to be browsed; proximity to and species of the nearest tree were also important. Applied with an understanding of the foraging behaviour of resident herbivores, existing plant defence chemicals have the potential to significantly reduce herbivore damage in managed forests.