DNA left on browsed twigs uncovers bite-scale resource use patterns in European ungulates
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Fine-scale resource use by large herbivores is often difficult to quantify directly. This is particularly true for browsing ungulates due to the challenges in observing shy subjects in forested environments of low visibility. As a consequence we know relatively little about resource use by diverse browsing ungulates. When browsing, ungulates leave behind saliva on the browsed twig that includes their DNA, which can be used to identify the species that was responsible for browsing the twig. We used this method, which we term “biteDNA”, to study bite-scale browsing patterns in a temperate ungulate community. This approach provides a level of detail in browsing patterns across species that was previously very hard to attain. We found that all deer species largely overlapped in terms of the tree species they used. Moose browsed larger diameters than red deer and roe deer, but these latter two species did not differ. Moose browsed at higher heights than red deer, and red deer higher than roe deer. Although the deer species differed in mean browsing height, species were comparable in terms of their minimum browsing height of ~20 cm. This means that height and diameter ranges of the smaller species were found to be completely inside the ranges of the larger species. Hence, while moose may access exclusive food resources in terms of browse height and diameter, red and roe deer cannot.
KeywordsAlces alces Capreolus capreolus Cervidae Dama dama Cervus elaphus Resource use Molecular ecology Browsing Environmental DNA
Åke Nordström assisted us during sample collection. Helena Königsson and Shiyu Yu assisted with the laboratory work. William Rice and Marco Smolla gave advice on statistical analyses. We would like to thank Marcus Clauss, Anne Loison and an anonymous reviewer for helpful comments that greatly improved this article. This work was funded by the Swedish Research Council. R. V. N. was supported by a grant to G. S. from the Swedish Research Council Formas (grant no. 217-2008-997). J. P. G. M. C. was supported by the Swedish thematic research program Wildlife and Forestry and a Marie Curie Career Integration Grant (PCIG10-GA-2011-304128).
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