Land managers have invested millions of dollars annually since the 1980s to put large chunks of wood back into streams, primarily because of its importance to fish habitat. But little is known about the influence of large wood in streams on birds and terrestrial animals.
Oregon State University scientists Ezmie Trevarrow and Ivan Arismendi are beginning to change that with a just published paper in Biodiversity and Conservation that outlines what they observed from a year’s worth of footage from motion-triggered video cameras they set up near multiple major blockages in a creek just west of Corvallis.
“This study reveals a hidden role of large woods in streams,” said Trevarrow, who conducted the research as a student at Oregon State Honors College and is now a research associate at the University of Georgia. “The findings are valuable to land managers as they demonstrate the added value of restoration projects that involve placing wood in streams.”
In the paper, Trevarrow and Arismendi turned their attention to the species they saw, the most common activities observed and the seasonality of the detections. Among their findings:
- Forty species were observed during the study period. The most common species were mule deer, raccoon-belted kingfisher, Townsend’s chipmunk, western gray squirrel deer, Virginia opossum, and American robin.
- The most common animal activities around the blockages were movement (68%), rest (18%), and handling/eating food (9%), suggesting that large timbers in streams act as side corridors, or highways such as Trevarrow’s connecting terrestrial habitats for wildlife year-round.
- Strong seasonality in detections and species richness with highest values in summer and spring, and lowest values in winter. For example, most species were observed in summer (27), followed by spring (23), autumn (22) and winter (16).
Before the 1970s, land managers, recreationists and the public considered large wood in rivers to be undesirable, and removal of wood from streams was widely promoted in the United States. Think European settlers and images of clean, flat rivers, Arismendi said.
“There’s a lot of cultural legacy there, with areas of blockade seen as places of increased flood risk, hindering navigation and transportation, and accumulated debris,” said Arismendi, an associate professor in the Department of Fisheries, Wildlife, and Conservation Sciences. .
However, the scientific and managerial perception of large wood in streams has changed.
While the benefits of large woods in streams for fish, especially salmon, have been well studied, few studies have focused on the impact on land-based animals, the Oregon State researchers said.
For their study, they set up 13 cameras along Rock Creek, about 24 miles west of Corvallis, between June 2020 and June 2021. They collected 1,921 videos of at least one animal detection, including some unexpected species and activities:
- A golden eagle, a species rarely seen in the region.
- Two mule deer are swept away after attempting to climb a log during a high-current event.
- A deer mouse and raccoon separately crossed a blockade during high current, even as the water covered the entire length of the block.
Arismendi is expanding the study this summer to the Oregon State’s HJ Andrews Experimental Forest in Oregon’s Cascades Mountains with 30 motion-triggered camera locations.
“This is the beginning of going deeper into this topic,” Arismendi said. “I think there is a lot to unravel about the role of blockages in rivers.”
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Ezmie Trevarrow et al, The role of large woods in streams as ecological corridors for wildlife biodiversity, Biodiversity and Conservation (2022). DOI: 10.1007/s10531-022-02437-2
Provided by Oregon State University
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