Low-Elevation Pikas on Wind Mountain

Author: Steve Stampfli, White Salmon, WA, USA, oakridgetree@gmail.com

The twin quartz diorite domes of Shellrock Mountain on the Oregon side, and Wind Mountain on the Washington side of the Columbia River (river mile 157), have much in common.  Last summer, I noted a couple of large talus slopes on Wind’s south slope that discharged cool air from their bases.  As described in the previous article, this flow of cold air during the heat of summer is indicative of an interesting thermodynamic mechanism known as the “chimney effect”, witnessed in many talus slopes around the world.  Also proposed in the earlier article, the mechanism could be the key reason American pikas (a typically high elevation species at this latitude in the American west) occur at near sea-level in a twenty-mile segment of the western Columbia River Gorge.

Upon subsequent surveys of Wind Mountain’s south facing slope, however, no pikas were audibly detected.  This finding seemed to fit the observations of others, who recognize that low-elevation pikas exist mainly on the Oregon side of the Columbia. (That said, they have also been recorded at Cape Horn, some 20 miles WSW of Wind Mountain, and perhaps elsewhere on the Washington side).

With more thought, it occurred to me that if low elevation pikas were to exist at Wind Mountain, they would likely be found on its north or northwest flanks…  on slope aspects and angles analogous to where they appear on the Oregon-side Shellrock Mountain.  Sure enough, in early June 2018, I noted two pika calls from an individual(s) living at about 650 foot elevation on the northwest skirts of Wind Mountain, and near the base of a prominent and steep talus slope.

This observation supports the following conclusion:  the relatively high concentration of low-elevation pikas living on the Oregon side of the Columbia River Gorge is solely due to Oregon’s higher incidence of steep, north-facing, low-elevation talus slopes than occur on the Washington side.  While likely unproven at this point, it seems probable that this explanation is a given.

Why slope aspect (and probably angle) is such an important habitat consideration could be a difficult thing to quantify and understand. Certainly, north facing slopes in the northern hemisphere are simply more shaded and cooler at the surface than south facing aspects.  As referenced in the prior article, however, perhaps aspect/angle dictates the intensity of chimney effect cold air talus recharge in winter, and consequent sub-surface cool air circulation in summer (and maybe equally important, warm air circulation in winter).  Perhaps too, northern exposures are critical to the existence of suitable moss covers, which can both insulate slope surfaces from summer heat gain and maintain confined conduits for seasonal air recharge inside talus slopes.  And finally, it is certain that aspect/angle influences plant communities and their ecologies, and specifically the offering of suitable year-round forage for pikas.  All are likely factors, but there are probably others that fit into the equations that define suitable pika conditions.

If any readers of this article have noted “low elevation” pikas on the Washington side of the Gorge’s pika belt, providing this information via comments below, or email, would be appreciated.