The Cascades Frog, You Heard It Here First

I started recording notes of my travels in the North Cascades in 1998. These weren’t anything as cool or romantic as memoirs. They were notes on the forests, plants, wildlife and geological features I was observing. The information included in these notes has grown in volume and scope over the years. I have tried to be diligent about getting this information in the form of copies of my field notes both to the Washington Department of Fish and Wildlife and the federal agencies that manage these lands. In recording the notes of my travels, quite by accident I seem to have stumbled across a very interesting pattern in the distribution of the Cascades frog within the North Cascades.

According to Wikipedia, the Cascades frog (Rana cascadae) occurs at elevations between about 2000 feet and 8000 feet in the Cascade Range from California to Washington and possibly Canada. It occurs in the Olympic Mountains as well. An older reference I have, Amphibians of Washington and Oregon (Seattle Audubon Society 1993) states the highest observation of this species had been about 6700 feet. There is a newer edition of this book and I don’t know if this information has changed. Another reference I have, Amphibians of Oregon, Washington and British Columbia by Charlotte C. Corkran and Christina R. Thoms (1996 Lone Pine Publishing) gives an elevation range of 2500 to 6000 feet for this species, with occasional occurrences to 1600 feet. Wikipedia states that this species sometimes occurs below 2000 feet in elevation in Washington. From my own personal observations, I haven’t seen this species much above 5500 feet in elevation in the North Cascades. This doesn’t necessarily mean they aren’t there, it’s just that I haven’t been seeing them. On the lower end of the scale I have also seen them at about 1500 feet in elevation on the White River near Enumclaw.

The distribution pattern I have come across is as follows: If you were to draw a line following the South Fork of the Cascade River and then down the main stem of the Cascade River to its confluence with the Skagit River and then down the Skagit River, south of that line Cascades frogs are common at elevations above 2000 feet. North of that line, at least in the Skagit River watershed, you would not find any Cascades frogs all the way to the Canadian border.

I don’t know as I can lay claim to being the sole discoverer of this phenomenon. Park Service biologists conducted an extensive survey in North Cascades National Park, which is all north of the South Fork Cascade River in the early to mid 1990’s that didn’t find any Cascades frogs in the park except for in the Stehekin River watershed. I know this because they told me so and I have read the report they wrote. I myself have never seen a Cascades frog in my own travels within North Cascades National Park and I have been to every mapped high lake and pond within the boundaries of the Skagit watershed in this park.

The park biologists weren’t aware of how far this phenomenon extended outside the park boundaries though. I have also been to every mapped high lake and pond in the Skagit watershed north of the line on the Cascade and Skagit Rivers that I described previously. Much of this land is on the Mount Baker-Snoqualmie National Forest which bounds North Cascades National Park on the west. There is some private timber land in this area as well. I didn’t observe any Cascades frogs in the Skagit watershed on the Forest and private lands west of the Park either.

In the Ross Lake area of the Skagit (managed by North Cascades National Park) and to the east of Ross Lake (mostly managed by the Okanogan National Forest, with a small area along the lake managed by the Park), there are no Cascades frogs to my observation or knowledge, though Columbia spotted frogs (Rana luteiventris) are fairly common here.

I don’t know where the western and eastern boundaries of the hole in Cascades frog distribution are. Obviously the Cascades frog occurs on the Stehekin River. I assume that they also occur within the Nooksack River watershed. However, I have done contract stream survey work for the U.S. Forest Service on every fork of the Nooksack at elevations where we saw Cascades frogs in other areas. We (the crew and I) didn’t observe any Cascades frogs along the three forks of the Nooksack in the areas we surveyed. However, I have been to very few high lakes and ponds in the Nooksack watershed where chances might be better for finding Cascades frogs.

I am also aware of a study in the area around Baker Lake done by contractors for Puget Sound Energy that recorded Cascades frogs. I have never observed a Cascades frog in the area of this survey and I was part of a crew that operated a smolt trap for several years in the contractor’s survey area. This smolt trap picked up a lot of amphibians (red-legged frogs (Rana aurora), roughskin newts (Taricha granulosa) and probably others) but we never, to my knowledge, observed Cascades frogs. I have also been to all the mapped lakes and ponds in the Baker River watershed without observing any Cascades frogs.

I noticed that, in the contractor survey of the Baker Lake area, all of the animals identified as Cascades frogs were all tadpoles. None were adults. From my experience tadpoles can be tricky to identify as to species. There is some reference material out there for keying tadpoles (Corkran and Thoms) but I have never been very confident in using these keys. There is a possibility that these tadpoles were misidentified red-legged frogs but I don’t this know for sure. There would really be no way to tell unless one had done genetics on the tadpoles in the study or had captured some and grown them to adults. There are a few spots in both the Baker River and Nooksack River watersheds where I have observed some intriguing looking tadpoles that might have been Cascades frogs but, frustratingly, I never saw any adults.

Of course it can be said that absence of evidence is not evidence of absence but the area we are talking about here is large and I have personally been to a lot of spots within it where I should have seen Cascades frogs and I didn't. You at least have to consider absence of evidence of a species in order to develop range maps.

In all of the areas mentioned above where Cascades frogs seem to be absent, above the normal elevation range of red-legged frogs, western toads (Bufo boreas) seem to be fairly common. I have also observed western toads in the areas where Cascades frogs are common.

So why does this apparent hole exist in Cascades frog distribution? I don’t know. Maybe it has always been this way or maybe it has been a fairly recent development. For years I nursed a pet theory that the presence of Cascades frogs was linked to the presence of large areas of sphagnum flats where ponds for breeding are often quite numerous. There are a lot of these sphagnum flats south of the north/south line I earlier described following the Cascade and Skagit Rivers and very few sphagnum flats north of the line. However, I have since made a number of observations that make me doubt the relationship between sphagnum and Cascades frogs, though, in fairness, I have also not conducted a controlled experiment to prove or disprove it.

Is this information important? I don’t know. I would think it would be. An amphibian’s skin is very permeable. They actually absorb oxygen through the skin as well as any chemicals that might be in their environment. So they are very sensitive to environmental conditions which means they are likely to be the one of the first animals to respond to problems in the environment. They are kind of like an early warning system, or canary in coal mine, if you will. Recently there has been a lot of concern about amphibians because many amphibian species have gone extinct. The Cascades frog’s range is restricted by elevation. Climate change will likely have a big impact on conditions experienced at higher elevations so the Cascades frog stands a chance of being dramatically affected by climate change if nothing else. So maybe this information is important but, then again, Cascades frogs are not charismatic megafauna that generate a lot of public attention and sympathy like polar bears are.

I have told every wildlife manager that I came across who I thought might be interested in the Cascades frog distribution pattern about it but have pretty much gotten a  “gee whiz that is kind of cool” response but little else. 

I think the distribution pattern is very interesting. Of course I would think it is interesting. All of the observations I made in order to figure this out represent 14 or more years of my life spent going to out of the way places which required a lot of physical effort and no small risk to life and limb to access, so I have a lot invested in it. You might say this has been a large part of my life's work for the last decade and a half. It would also be interesting to analyze the observations I have made on other amphibians species. I would not be surprised to see some interesting patterns pop out there too. This would be even more powerful if one combined my observations of Cascades frog and other amphibian species with amphibian observations that other people have made over the years. There are a lot of documented amphibian observations out there, though I have been told that many of mine are from areas where no information was previously available. I would be interesting to know not only the patterns by also why the patterns exist. It is possible that someone, somewhere is aware of this pattern but I doubt it. As I stated many of my observations are often the only information available for many areas so it is doubtful anyone else has put the puzzle together yet. 

To date, no one has seemed to be interested in taking on this project. It seems like there is enough here to make a nice master’s thesis for someone. A lot of the information, my observations at least, is just sitting there at Washington Department of Fish and Wildlife and at the federal agencies. I once entertained thoughts of analyzing the observations to try to pick out patterns but I couldn’t find funding for it. It would be a lot of work and one would need a stable income of some sort to pull it off, I think. My disposition doesn’t favor chasing grant money to pay for this type of thing. Ironically, if I pursued a higher degree and all of the trappings it would require to do well sponsored research, I probably wouldn’t be living here, in the North Cascades any more. There aren’t many jobs in Eastern Skagit County or in most of Skagit County for that matter for someone with an advanced degree in herpetology or wildlife biology and I would probably end up chasing work somewhere far away.

Maybe some day a graduate student will take my information along with all of the other available information and make sense of it. Until then, there it stands. But remember, you heard about the strange pattern of Cascades frog distribution here first.

Range map for the Cascades frog based on my own personal observations and other information. The base map is from USGS Map Maker. The red lines denote the boundaries of areas that I have personally been to and not observed Cascades frogs. The green lines denote the boundaries of areas that I have been to and observed Cascades frogs. The orange lines denote boundaries that I am not sure about. I have also labeled areas that I am not familiar with. I have stated that an area or boundary is unknown to me not because I am the be-all and end-all for Cascades frogs but because someone else may have the information and I am not aware of it. Every map has its trade-offs and limitations. The trade-offs for this map are the presence, no presence boundary lines. I have used the Cascade and Skagit Rivers as a boundary when the actual boundary should be at about the 2000 foot level above and away from most of the area of both of these rivers. The same holds true for all of the area below 2000 feet in elevation of the streams within the boundaries. I initially tried to make the map this way but it was too confusing. 

This is one of my favorite photos of a Cascades frog. This frog was in a small pond below Whitechuck Mountain above Rat Trap Pass 2010. 

Cascades frog at pond on Bluebell Creek in the Illabot Creek watershed 2010. 

Cascades frog at small pond/lake east of Lake Byrne on the Whitechuck River.  I was quite excited to see this frog.  It was a challenge to get to this small lake/pond and it was still mostly frozen over even though it was early September 2012, a strange year for melt-out in the high country. Anyway, I observed this frog and got to add another data point to  the overall map. There was little or no sphagnum in the immediate vicinity of this small pond/lake. 

Cascades frog at a small pond on Fern Creek, Whitechuck River 2012. This pond was also a struggle to get to. It took me three attempts over as many weekends to make it. There was a lot of sphagnum at this pond and also a lot of frogs. 

Cascades frog at same pond as in above photo.