Oregon Spotted Frog Monitoring and Research Project

Adult and larval Oregon spotted frogs (photos copyright Stephen Nyman)
Adult and larval (tadpole) Oregon Spotted Frogs (photos copyright Stephen Nyman)

The current phase of WCAMP’s Oregon Spotted Frog Project (see below) involves restoring and enhancing key Oregon Spotted Frog (OSF) breeding and tadpole rearing habitats at the Whatcom Land Trust’s Samish River Preserve.  Project results indicate that the number of frogs in our study population has declined throughout the site. Of particular concern is the area we call  “Southeast Meadow”, where more than half of the frogs breed each year.  This decline is evidently related to changes in habitat, exacerbated by dry weather conditions in recent years. The culprit is reed canary-grass, an invasive, tall, densely-growing, wetland grass, which gradually degrades or eliminates sites suitable for egg laying and causes premature drying in aquatic habitats necessary for the survival of tadpoles and young-of-year frogs.

In order to reverse this population decline, we have developed and are implementing a multi-year habitat plan, beginning in Southeast Meadow. The plan combines habitat restoration and enhancement.

Habitat restoration represents long-term improvements in habitat, primarily by creating deeper pools than would otherwise exist to be used by all Oregon Spotted Frog life stages, but particularly as tadpole habitat.  We create these pools by breaking through and removing sections of a floating rooted mat of reed canary-grass that covers water more than two-feet deep. Much like a “quaking bog,” the rooted reed canary-grass is a dense layer of roots and muck that floats at or near the surface of the water, denying access to the aquatic habitat underneath.  After reed canary-grass removal exposes the water, native plant species begin to establish in the pools, providing conditions much more favorable to Oregon Spotted Frog. In the same way, we have made channels by which tadpoles can swim from the shallow water, where egg mass are deposited, to the deeper pools and thereby survive dry summer conditions.

We have just completed the fourth new pool – one each year – and expanded aquatic habitat associated with last year’s pool. This year the first three pools (Pool A, B, and C) supported large numbers of Oregon Spotted Frog tadpoles through metamorphosis in July and August, and continue to provide habitat for the young frogs.  Next year we hope to see more frogs breeding in Southeast Meadow as now mature frogs from the 2017 year class return to breed for the first time.

Habitat enhancement represents shorter-term improvements in habitat, particularly mowing the reed canary-grass in late summer and autumn. Mowing with a hand-held “trimmer” (1) reduces the tall, almost woody stems (culms) of the reed canary-grass into smaller pieces, which can be raked out to prevent thatch build-up; (2) prevents the stems from falling over, covering the water, and smothering other vegetation; and (3) creates open, shallow water areas where Oregon Spotted Frogs can lay their eggs in early spring the following year. We also make pathways for tadpole dispersal..  These habitat changes are mostly temporary – much like mowing your lawn does not have a lasting effect – but are essential. Eventually the reed canary-grass again grows tall and dense, but not before the frogs have benefited from the changes.  Studies have also shown that thatch build-up serves as a competitor-suppressing mulch for reed canary-grass dominance and a source of nutrients. Removing thatch reduces the competitive superiority of reed canary-grass and allows other species to co-exist.

Critically, our plans are guided by site-specific data from: (1) water depth monitoring performed since 2016, (2) Oregon Spotted Frog egg mass surveys that we have led since 2013, (3) studies of tadpole growth, development, and abundance at different sites used by Oregon Spotted Frog annually before (i.e., in 2014 and 2016) and after habitat restoration (since 2017), and (4) vegetation monitoring within our habitat work area at Southeast Meadow. Going forward, we will continue to collect these data, and test whether our efforts have been effective and can be sustained. We will also continue to share our methods and results with other scientists and land-managers to conserve the Oregon Spotted Frog and move the species toward recovery.

“Southeast Meadow” at the Samish River Preserve (February 27, 2016) illustrating habitats degraded by unmanaged reed canary-grass (photo copyright  Chris Brown)

Since beginning the first pool in September 2016, our volunteer effort has invested hundreds and hundreds of hours of hard, but satisfying work in this project. The habitat transformation at Southeast Meadow envisioned in our plan is slowly taking shape.  2019 was our biggest year, with an expanded project focus to include new habitat restoration techniques and work at additional sites in need of restoration. As always, the story begins and ends with the frogs, who will soon be breeding again and will tell us whether we are on the right track!  On behalf of the frogs: “Thank You!” to all the volunteers and our project partners, the Whatcom Land Trust, U.S. Fish and Wildlife Service, Washington Department of Fish and Wildlife, and Wildlife Conservation Trust, for their support.  Click on this link for more information and photos showing our progress on this habitat project:  Habitat Restoration and Management

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Help restore essential habitat for the most vulnerable life stages of Oregon Spotted Frog. (Photo copyright Stephen Nyman)
thanks for the habitat
This tiny (less than 1-inch long), young Oregon Spotted Frog, nurtured in habitat we restored, faces many perils before reaching adulthood. If all goes well, it may breed for the first time as a two-year old (male OSF) or three year-old (female OSF). (Photo Sept 5, 2018, copyright Stephen Nyman).


WCAMP coordinates with State and Federal wildlife agencies to monitor and research a population of Oregon Spotted Frog (OSF) (Rana pretiosa) at the Whatcom Land Trust’s Samish River Preserve.  The information we are collecting may help guide future site management decisions by the Land Trust, and other landowners and agencies working to conserve this rare species elsewhere.  WCAMP’s Oregon Spotted Frog monitoring and research project is authorized under a U.S. Fish and Wildlife Service (USFWS) Fish and Wildlife Species Recovery Permit issued to our Lead Scientist, Stephen Nyman.  Our projects have successfully competed for grant USFWS small grant awards. Each of these awards provide a vital portion of the costs of our projects, with the rest from donated time and expenses.  With your help, we could do much more. If you are interested in participating as a volunteer, making a financial contribution, or learning more about our studies and planned efforts, and how you can help, please contact Stephen. For much more Oregon Spotted Frog information and photographs, click on this link to the OSF Species Facts page: Oregon Spotted Frog (Rana pretiosa)


Populations of OSF were first discovered in Whatcom and Skagit Counties in 2011 as a result of survey work performed by the Washington Department of Fish and Wildlife and volunteers.  Surveys were conducted on private lands (with landholder permission) in the South Fork of the Nooksack River and the headwater region of the Samish River. Egg mass surveys in the first year resulted in the tentative detections of a number of occupied sites, which were subsequently confirmed in 2012 when adult frogs, egg masses, and larvae were all observed. A population has also been discovered in the Sumas River drainage.  The OSF population at the Samish River Preserve is the only population which has been surveyed each year since 2012.

Originally found from the Lower Fraser Valley of British Columbia to northeastern California, the OSF is believed to have disappeared from large portions of its former range. The species has been listed as State Endangered since 1997 and federally Threatened under the Endangered Species Act since August 2014.  The USFWS is currently working on the federal Species Recovery Plan for OSF.

The OSF is highly aquatic, requiring sites with permanent water, but breeding in areas of shallow water, which may dry seasonally.  Egg-laying sites tend to be open and sunny, with sparse, low vegetation when the frogs are breeding.  The ability of hatchlings to move from areas that do not hold water for a sufficient period for larval development (3-4 months) to more persistently wet areas is crucial to their survival.  The quality of egg-laying and tadpole rearing habitats is degraded in areas where the common, invasive reed canary-grass predominates.  Unfortunately for the frogs, all known OSF sites in Washington are affected by reed canary-grass, which thrives in shallow, wet areas and can reach heights of more than 6 feet, excluding other vegetation, and creating a thick layer of submerged thatch.

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Tadpoles of Northern Red-legged Frog (facing left) and Oregon Spotted Frog (facing right) (July 9, 2014). (Photo copyright Stephen Nyman)

2014: The 2014 study, approved by the Washington Department of Fish and Wildlife, monitored OSF breeding at the Preserve – recording 364 egg masses (compared to 189 in 2013) – and included a summer of non-lethal sampling (i.e., capture and release) to document OSF tadpole habitat use, growth and development, and other aspects of the population. The Preserve is an ideal site for the study because the OSF population here is relatively large and the habitats used by the species are diverse, including two large ponds and three shallow, grassy wetlands (or “meadows”) with open areas and dense stands of reed canary-grass. Based on their locations, we have named these areas North Pond, South Pond, North Meadow, Southeast Meadow, and Southwest Meadow.  In 2014, about 70 percent of the population bred at the meadow areas compared to 30 percent at the ponds.  Considerable scientific research has been devoted to OSF; however, the tadpole stage has been largely neglected and many fundamental questions have not been investigated.  Questions we asked included:

  • Do OSF eggs and larvae perform equally well in each area (i.e., comparing number and survival of egg masses to hatching; developmental rates, growth, time to metamorphosis, and relative abundance of larvae)?
  • What predators occur in each area?
  • What habitats are larvae actually using in each area and how far do they disperse from egg masses after hatching?
  • Are any of the areas “sink” habitats (i.e., habitats where few or no tadpoles survive to metamorphosis)?
  • Could any of these areas be improved with management?

Our results in 2014 provided evidence that conditions for OSF tadpoles were least favorable for growth and development at Southeast Meadow, where more than half of the population typically breeds.  Tadpoles grew and developed faster at the ponds; however, the ponds supported predators that did not occur in the meadows, including Giant Water Bug and Brown Water Scorpion.

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Oregon Spotted Frog tadpole (June 6, 2014) (Photo copyright Stephen Nyman)

2015: In 2015, the OSF population at the Samish River Preserve endured drought conditions and an unusually warm summer.  Although eggs in most of the 298 documented egg masses hatched, Southeast Meadow (where there were 159 egg masses) was completely dry by June 15, much too early for any tadpoles to have reached metamorphosis.  This early drying was probably hastened by the advanced stage of reed canary-grass invasion into deeper water areas that might have otherwise provided tadpole habitat.  A similar pattern occurred elsewhere, with North Meadow (15 egg masses) drying on June 28 and Southwest Meadow (21 egg masses) on July 29.  If any tadpoles survived to metamorphosis in these areas, the metamorphosed young-of-year would still have had to travel in dry conditions through dense reed canary-grass to reach permanent aquatic habitats after the last pools dried.

The fate of tadpoles at the ponds in 2015 is unknown.  Metamorphosed young-of-year OSF were not observed, suggesting that survival was lower than in 2014, possibly due to predation. Nevertheless, the drought illustrated the importance of the ponds in providing summer habitat for adult OSF, when other areas were dry.  However, more information is needed regarding seasonal movements within this OSF population and adequacy of aquatic connections to allow the frogs to move between sites, particularly in late summer.

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North Meadow pool on May 28 (above) and June 30, 2015 (below). This pool did not dry in 2014. (Photos copyright Stephen Nyman)
Adult Oregon Spotted Frog enjoying late summer at North Pond (September 15, 2015).  (Photo copyright Stephen Nyman)

Project News!

February 26, 2015:  WCAMP Lead Scientist, Stephen Nyman, presented two talks and one poster at the most recent meeting of the Society for Northwestern Vertebrate Biology in Portland, Oregon. These summarized the findings from our 2014 field season and were very well received. Way to go, Stephen! Here are the titles of those talks, and feel free to contact Stephen if you want more information:

  • Evaluation of characteristics to differentiate larvae of Oregon Spotted Frog and Northern Red-legged Frog.
  • Ecological aspects of Oregon Spotted Frog eggs and larvae at ponds and meadows of the Samish River Preserve, Whatcom County, WA
  • Evaluation of an aquatic funnel trap for shallow water habitats used by Oregon Spotted Frog (Rana pretiosa) – Poster

Click on this link to view a fresh clutch of Oregon Spotted Frog in Whatcom County. Listen carefully and you can here their distinctive “knock, knock, knock” call (turn up volume to max). Thank you, Stephen Nyman, for sharing this video.

Click on the link below to watch a video on the status of the Oregon Spotted Frog in the Fraser Valley, BC.

Chris Brown (WCAMP volunteer) took this video of a large congregation of Oregon Spotted Frog egg masses. This was shot in mid March 2014.

Get the latest information on the status and management recommendations for the Oregon Spotted Frog. The new Draft Washington State Oregon Spotted Frog Recovery Plan and the results of WDFW surveys for Oregon Spotted frogs in Skagit and Whatcom Counties are out.

What if you find Oregon Spotted Frogs on your property- what does it mean? What this video to learn how they can be a benefit to you:

Click on the files below to read documents.

Oregon spotted frog presence surveys in Skagit and Whatcom Counties, Washington

State of Washington Oregon Spotted Frog Recovery Plan

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