Beavers, restoration, and wildlife - what fun!

Beavers, restoration, and wildlife - what fun!

An introduction to Julianna and her dissertation research.

You may be wondering, "who is this Julianna, and why does she want to look for frogs on my property?" If so, this booklet is for you!

Frequently Asked Questions What is Julianna's research about?............................................................2 Why are beavers considered ecosystem engineers?.....................................3 What is the connection between beavers and other wildlife?.........................4 What is a beaver dam analogue?..............................................................5 Who builds beaver dam analogues?...........................................................

6 7 How does private property fit into Julianna's study design?...........................

Where is Julianna doing surveys?............................................................ 8 What will doing an amphibian survey entail?..............................................9 How often will Julianna want to visit?........................................................9 10 What is Julianna looking for?....................................................................

11 What were Julianna's preliminary results from summer 2023?......................

Where can I find primary literature on this topic? (Sources)..........................

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A single long-toed salamander egg attched to grass underwater. This is the sort of thing I'm looking for!

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Hello! My name is Julianna Hoza, and I'm a PhD student at Washington State University. I'm interested in understanding how beavers impact other wildlife by damming rivers and creating ponds. Specifically, I'm studying the impacts of beaver habitat on amphibian breeding and trying to understand whether restoration that mimics beavers can facilitate amphibians in the same way that beavers do.

I'm also curious about the way that beaver habitat varies depending on climate, and I'm using the Cascade mountains as a natural laboratory to study beaver ponds across a gradient of high annual precipitation west of the Cascade crest to low annual precipiation east of the Cascade crest.

Read on to learn more about my research!

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Why are beavers considered ecosystem engineers? It's because their dams...

Create stillwater ponded habitat.4 Accumulate fine sediments.3 Increase flow and temperature heterogeneity.2

Decrease downstream water temperature.1

Increase lateral and hyporhiec* water flow.1

Beavers transform their environments from free-flowing (or lotic) stream habitats to still-water (or lentic) ponded habitats by building dams.

Dams made of mud, sticks, and rocks allow some water to percolate through while holding much of the water back in a pond.4 Ponded water has time to seep underground and recharge the groundwater; later, it will resurface downstream at cooler temperatures.1 The ponded water also gets pushed toward the stream banks by the dam, which connects the stream mainstem to its floodplains. Floodplain depressions fill with water, creating side-pools and off-stream channels. This increases habitat complexity for wildlife, creating a diverse landscape that multiple organisms can coexist within.4 *Hyporheic flow refers to ground water beneath the stream's surface.

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Ungulates wallow in ponds and feed on vegetation that grows in beaver habitat.8

Aerial foragers like birds and bats feed on insects above ponds.6,7

How does wildlife benefit from beaver ecosystem engineering?

Amphibians lay their eggs in still water created by beaver dams.9

Salmonids benefit from cool waters and increased habitat complexity.10

Invertebrates that depend on still water thrive in beaver ponds, and overall invertebrate abundance increases.11

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What is a beaver dam analogue?

Beaver dam analogues (BDAs) are structures that mimic beaver dams.12 They are semi-permeable barriers to water flow, and they differ from weirs or hydropower dams because BDAs are made of natural materials like sticks and tree bows rather than cement. The result is that some water still flows through the structure, and fish are able to pass without problems. Just like true beaver dams, BDAs are expected to promote healthy hydrology that supports a variety of wildlife.

Multiple structures are placed in a series to mimic a natural beaver "complex."

Water pools behind the structures, and slower moving water accumulates fine sediments.

Willows or conifer bows are woven between the posts.

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Posts are driven into the stream bottom using a hydraulic pounder.

Who builds BDAs? A variety of organizations build BDAs, often with a focus on creating salmonid habitat. The groups that build BDAs often only have capacity to rigorously monitor hydrology and can't monitor every wildlife species that might benefit from restoration sites.

Even where monitoring is possible, it is impractical for a single organziation to construct enough BDA sites for a robust scientific study of the impacts. To address this issue, I'm working with four organizations that all do similar restoration work in the Okanogan-Wenatchee region...

Do BDAs really work as well as beaver dams?

Some research indicates that BDAs have similar effects to true beaver dams hydrologically,13 but there is very little research concerning biological impacts of BDAs for wildlife (but see [14, 15]). Both true beaver dams and BDAs are temporary and eventually wash out, allowing the stream to fluxuate between a ponded and flowing state throughout time, although BDAs tend to be even more temporary than true beaver dams since there is not always a beaver to maintain the BDA. However, BDAs can have substantial impacts on degraded stream systems and help to prepare a stream for a real beaver to move in.

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Do beaver dam analogues create breeding habitat for amphibians?

STUDY DESIGN: compare the percent of beaver dam analogue sites with pond-breeding amphibians to the percent of unrestored reference and true beaver dams with amphibians.

Unrestored Reference Paired with an existing BDA site

BDAs installed in the last 4 years

5-1000 m upstream of the paired BDA

BDAs are functioning (water has not overtopped structures, floods have not blown structures out)

Matches the stream length of the paired BDA No beaver influence No restoration done

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Beaver Dam Analogue (BDA)

True Beaver Dam Dam is holding water Interspersed with BDA sites (not paired) May be actively inhabited by beavers or abandoned

Between 2 to dozens of structures

Between 100-500 m stream length

Between 30-1100 m stream length

May include multiple dams or a single dam

No beaver influence

No restoration done

Replication is key! I aim to survey for amphibian breeding at ~20 sites of each type (20 replicates x 3 site types = 60 sites total)! Where will they all come from? Sites are located on a mix of public and private property. Many sites are located in the Okanogan-Wenatchee National Forest, but lots of beaver dam analogue restoration is happening on private land, which is why I need landowner help to get the amount of replication I need for robust scientific results. To get these results, I am surveying every restoration site I can find and calculating the percent of those restoration sites with breeding amphibians. Then, I'll compare this percentage to the percent of unrestored reference and true beaver dam sites with breeding amphibians.

Unrestored reference Beaver Dam Analogue 0

5 10

20 Miles

20 mi

N

True Beaver Dam

Okanogan National Forest

Chelan Wenatchee National Forest

Leavenworth

Omak

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Working with restoration partners who create the BDA structures and landowners who allow access for surveying is the only way I can find enough sites to do a statistically robust study.

THANK YOU to everyone who has Esri, USGS helped put these sites together!!

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What does an amphibian survey look like?

At each site, our team of 2-3 people will walk the water's perimeter, searching for amphibians.

When we find amphibian egg masses, larvae, or adults, we will record the species and number of individuals.

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As we search, we'll record environmental parameters that help us assess habitat suitability and understand why amphibians lay eggs at some sites but not others.

The entire survey will take about 2 hours or less, and we may need to visit 2-3 times between April-July.

Egg masses

What are we searching for?

Larval salamanders and tadpoles

Metamorphs (frogs and salamanders that hatched this year)

Adult frogs and salamanders

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ot To ad ad e fo

r Sp

de

Beaver Beaver Beaver Beaver Beaver Beaver BDA BDA BDA BDA BDA BDA BDA BDA BDA Reference Reference Reference Reference Reference Reference Reference Reference Reference

G Sa ian la t m an

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

L Sa ong la -t m oe an d de r W e To s ad ter n

Site Type

C Fr hor og u s

Site ID

C Sp olu Fr ot mb og te ia d

Preliminary results show that amphibians breed at a lower rate at BDAs (4/9 sites) compared to true beaver ponds (6/6 sites), but that amphibians breed at higher rates in BDAs compared to unrestored streams (0/9 sites). This means that beaver dam analogues provide intermediate quality habitat for amphibians - they're not quite as good as a true beaver pond, but they're bettter than no restoration at all!

Total # Species 3 3 2 1 2 3 0 0 1 0 2 3 0 0 3 0 0 0 0 0 0 0 0 0

Why are there amphibians at some BDAs but not all of them? We're not sure, and that's why we need to gather more data in summer 2024! My hypothesis is that smaller streams are dammed more completely by BDAs, and so are more likely to have zero flow ponded habitat when BDAs are constructed. In contrast, larger streams may have their water slowed by BDAs, but the water is less likely to become completely stagnant. Since amphibians only lay their eggs in still water, I think that placing BDAs on smaller streams is more likely to create amphibian habitat than placing BDAs on larger streams.

SMALLER stream vs. LARGER stream LARGER BDA impact

SMALLER BDA impact

Still water pond

Flowing water pool

Amphibians lay eggs

No amphibians

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Sources [1] Dittbrenner, B. J., J. W. Schilling, C. E. Torgersen, and J. J. Lawler. 2022.

Relocated beaver can increase water storage and decrease stream temperature in headwater streams. Ecosphere 13:e4168.

[2] Majerova, M., B. T. Neilson, N. M. Schmadel, J. M. Wheaton, and C. J. Snow.

2015. Impacts of beaver dams on hydrologic and temperature regimes in a mountain stream. Hydrol. Earth Syst. Sci. 19:3541–3556.

[3] Meentemeyer, R. K., and D. R. Butler. 1999. Hydrogeomorphic effects of beaver dams in Glacier National Park, Montana. Physical Geography 20:436–446.

[4] Larsen, A., J. R. Larsen, and S. N. Lane. 2021. Dam builders and their works: Beaver influences on the structure and function of river corridor hydrology, geomorphology, biogeochemistry and ecosystems. Earth-Science Reviews 218:103623.

[5] Barn swallow photo credit to JJ Cadiz.

[6] Ciechanowski, M., W. Kubic, A. Rynkiewicz, and A. Zwolicki. 2011. Reintroduction of beavers Castor fiber may improve habitat quality for vespertilionid bats foraging in small river valleys. European Journal of Wildlife Research 57:737–747.

[7] Nummi, P., S. Kattainen, P. Ulander, and A. Hahtola. 2011. Bats benefit from beavers: a facilitative link between aquatic and terrestrial food webs. Biodiversity and Conservation 20:851–859.

[8] Nummi, P., W. Liao, O. Huet, E. Scarpulla, and J. Sundell. 2019. The beaver facilitates species richness and abundance of terrestrial and semi-aquatic mammals.

Global Ecology and Conservation 20:e00701.

[9] Romansic, J. M., N. L. Nelson, K. B. Moffett, and J. Piovia‐Scott. 2021. Beaver dams are associated with enhanced amphibian diversity via lengthened hydroperiods and increased representation of slow‐developing species. Freshwater Biology 66:481– 494.

[10] Kemp, P. S., T. A. Worthington, T. E. L. Langford, A. R. J. Tree, and M. J. Gaywood. 2012. Qualitative and quantitative effects of reintroduced beavers on stream fish: Impacts of beaver on freshwater fish. Fish and Fisheries 13:158–181.

[11] McCaffery, M., and L. Eby. 2016. Beaver activity increases aquatic subsidies to terrestrial consumers. Freshwater Biology 61:518–532.

[12] Wheaton, J., S. Bennett, N. Bouwes, J. Maestas, and S. Shahverdian. 2019. LowTech Process-Based Restoration of Riverscapes: Design Manual. Version 1.0.

[13] Pollock, M. M., T. J. Beechie, and C. E. Jordan. 2007. Geomorphic changes upstream of beaver dams in Bridge Creek, an incised stream channel in the interior Columbia River basin, eastern Oregon. Earth Surface Processes and Landforms 32:1174–1185.

[14] Pollock, M. M., G. R. Pess, T. J. Beechie, and D. R. Montgomery. 2004. The importance of beaver ponds to Coho Salmon production in the Stillaguamish River Basin, Washington, USA. North American Journal of Fisheries Management 24:749– 760.

[15] Wolf, J. M., and E. Hammill. 2023. Provisioning of breeding habitat by beaver and beaver dam analogue complexes within the Great Salt Lake catchment. Freshwater Biology 68:659–673.

[16] Map base layers are from ESRI and USGS. All photos are my own unless otherwise marked.