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Doctoral thesis, 2013

Busted by the bite

Nichols, Ruth


Large herbivores are charismatic species known to engineer ecosystems through a variety of effects. Conflicts can sometimes arise when these effects are undesirable. However, without detailed knowledge on herbivore selectivity for landscapes, patches and plants, these positive and negative effects remain difficult to predict. Such species and sex-specific selectivity have inherent evolutionary and ecological mechanisms. In order to study such mechanisms it is important to study the partitioning of resources at multiple scales. Most studies have looked at large-scale resource partitioning (such as movement patterns) but fewer study the fine-scale levels of selectivity such as the individual bites taken by herbivores. This level of detail is, however, important because it is essentially the direct mechanism through which ecosystem effects are manifested. Specifically for the browsing herbivore guild, such fine-scale studies have largely been impractical due to forested habitats which limit direct observation of behaviors. DNA-based diagnostics are becoming more and more popular within ecology as they provide vital data to answer certain questions. In this thesis I developed two versions of a method to differentiate between five species of large herbivore browsers using trace amounts of environmental DNA left at browsed twigs. The first version uses a traditional amplification method for identifying the species of browsers and the second uses an advanced and more sensitive method for identifying the species and sex of browsers. Using environmental DNA, I determined species-specific browsing patterns across three studies. I found overall that traditional methods for attributing browsing at the species level tend to be misleading. In one study I show that although one species may be blamed for forest plantation damages, DNA evidence showed a partitioning between three herbivore species. I also document the partitioning of plant parts among different sized ungulates and show that overlap in browsing heights and bite diameters is much larger than previously assumed. In another study I experimentally verified the selectivities of free-ranging herbivores for three species of trees. This thesis thus not only develops new molecular ecological tools but also provides new insights into resource partitioning and hence the ecosystem effects of herbivores.


Browsing; Competition; Ungulates; eDNA; environmental DNA

Published in

Acta Universitatis Agriculturae Sueciae
2013, number: 2013:86
ISBN: 978-91-576-7910-9, eISBN: 978-91-576-7911-6
Publisher: Department of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural Sciences

Authors' information

Nichols, Ruth
Swedish University of Agricultural Sciences, Department of Wildlife, Fish and Environmental Studies

UKÄ Subject classification


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