Event Title

Beaver foraging activity and preferences in the Elwha river restoration basins.

Research Mentor(s)

John McLaughlin

Description

After the removal of two dams, beavers have returned to the now drained reservoirs of the Elwha River, but little is known about what motivates them inhabit certain locations. Being ecosystem engineers, beavers are a keystone species with the ability to modify their environment, which includes altering streams and channels, resulting in improved young salmon habitat, one of the goals of the dam removal. We hypothesized that beavers of the Elwha have preferential feeding behaviors that influence their habitation and range, which include plant densities, plant species, plant diameter, and the distance of food sources from water. If beavers in the Elwha River restoration sites choose where they feed based on the density of the available food sources, then signs of beaver feeding activity would have been more abundant in areas with specific plant density rather than areas with specific plant types, because the density of the food available will be the more attractive feature. If beavers chose their feeding sites based on a preference for specific food plants, then beaver cut marks would have been abundant in areas with preferred species regardless of their density, because the vegetation type was the most attractive feature. If feeding sites are based on the size (diameter) of their food types, then grazing would have been more intense in areas where food types are predominantly the preferred size, because beavers will have located areas with preferred plant size and fed in those areas. If the beavers are concerned with conserving the most energy during grazing, then cut stems and branches of food species would have been seen in areas that are closest to the actively flowing waterways and side channels, because foraging close to the waterways reduces the distance that the beaver will have to travel on land which uses more energy than traveling through water. We also hypothesized that one of these factors would have a greater influence than others, having greater weight on beaver behavior. To test our hypothesis, we located beaver grazing sites and recorded the density of stems, species fed upon, the diameter of the fed upon stems (in mm), and the distance from the active waterway (in m) of a 2m2 plots. Our results indicated that beavers are showing preferential feeding sites based on species availability with an emphasis on Willow, Alder, and Cottonwood. Knowing what is the driving factor behind the why beavers choose to inhabit an area the the preferences for their feeding sites can inform future dam restoration projects and serve as a tool for land managers seeking to have beavers reintroduced to recovering systems.

Document Type

Event

Start Date

May 2018

End Date

May 2018

Location

Environmental Sciences

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.

Language

English

Format

application/pdf

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May 17th, 12:00 PM May 17th, 3:00 PM

Beaver foraging activity and preferences in the Elwha river restoration basins.

Environmental Sciences

After the removal of two dams, beavers have returned to the now drained reservoirs of the Elwha River, but little is known about what motivates them inhabit certain locations. Being ecosystem engineers, beavers are a keystone species with the ability to modify their environment, which includes altering streams and channels, resulting in improved young salmon habitat, one of the goals of the dam removal. We hypothesized that beavers of the Elwha have preferential feeding behaviors that influence their habitation and range, which include plant densities, plant species, plant diameter, and the distance of food sources from water. If beavers in the Elwha River restoration sites choose where they feed based on the density of the available food sources, then signs of beaver feeding activity would have been more abundant in areas with specific plant density rather than areas with specific plant types, because the density of the food available will be the more attractive feature. If beavers chose their feeding sites based on a preference for specific food plants, then beaver cut marks would have been abundant in areas with preferred species regardless of their density, because the vegetation type was the most attractive feature. If feeding sites are based on the size (diameter) of their food types, then grazing would have been more intense in areas where food types are predominantly the preferred size, because beavers will have located areas with preferred plant size and fed in those areas. If the beavers are concerned with conserving the most energy during grazing, then cut stems and branches of food species would have been seen in areas that are closest to the actively flowing waterways and side channels, because foraging close to the waterways reduces the distance that the beaver will have to travel on land which uses more energy than traveling through water. We also hypothesized that one of these factors would have a greater influence than others, having greater weight on beaver behavior. To test our hypothesis, we located beaver grazing sites and recorded the density of stems, species fed upon, the diameter of the fed upon stems (in mm), and the distance from the active waterway (in m) of a 2m2 plots. Our results indicated that beavers are showing preferential feeding sites based on species availability with an emphasis on Willow, Alder, and Cottonwood. Knowing what is the driving factor behind the why beavers choose to inhabit an area the the preferences for their feeding sites can inform future dam restoration projects and serve as a tool for land managers seeking to have beavers reintroduced to recovering systems.