Early Warning Signs

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Fulbright Fellow Sabuj Bhattacharyya releases an American pika sampled as part of a NWT LTER study relating stress and survival in the pika to patterns of temperature and snow cover in the pika's habitat. The pika's sensitivity to climate, and its preference for habitats containing sub-surface ice features and ample snow cover, make it a good candidate as a biological indicator of watershed health.

NWT research indicates that alpine ecosystems provide important early warning signs of global climate change. Alpine plants and animals survive on the razor's edge of environmental tolerances, making them more sensitive to changes in climate than downstream ecosystems.

Signs of stress in the American pika:

The hamster-sized American pika or "rock rabbit" is an icon of rocky landscapes that survives harsh alpine winters by living under an insulating blanket of snow. Pikas don't hibernate, so they need a store of food to last them through the winter. In alpine areas, they use the short summer months to collect and store a "haypile" of grasses and flowering plants. Building a haypile can be hot work during the summer for a round and furry pika, built to retain heat.

Pikas take refuge from the heat in the cool spaces under boulderfields, and are more common in rocky features that harbor sub-surface permafrost and seasonal ice (Millar and Westfall 2010). In a warming climate, alpine pikas are expected to have more trouble gathering the resources they need to survive a harsh winter.

In fact, pikas have disappeared in locations with warmer summers (Beever et al. 2010), especially where a lack of snowcover exposes them to extremely cold winter temperatures (Beever et al. 2011). At the NWT LTER site, researchers are studying the insulating properties of snow cover and the combined effects of summer temperatures, winter temperatures and snow cover on the survival of pikas (Figure 1).

This research is aimed not only at understanding how climate affects the pika, but how the pika might be used as biological indicator of sub-surface ice and other water features key to the productivity of western watersheds. The disappearance of pikas may indicate a reduction in snow cover and sub-surface water resources, which are difficult to measure directly.

More immediately, elevated levels of stress in pikas may provide early warning of a reduction in these water resources. NWT LTER researchers are attempting to relate stress hormones and other metrics of stress to the climate experienced by individual pikas, with the hope that this research will lead to a simple biological indicator of watershed health.

For further reading: 
Beever, E. A., C. Ray, P. W. Mote, and J. L. Wilkening. 2010. Testing alternative models of climate-mediated extirpation. Ecological Applications 20:164-178.
Beever, E. A., C. Ray, J. L. Wilkening, P. W. Mote, and P. F. Brussard. 2011. Contemporary climate change alters the pace and drivers of extinction. Global Change Biology 17(6):1-17.
Millar, C. I., and R. D. Westfall. 2010. Distribution and climatic relationships of the American pika (Ochotona princeps) in the Sierra Nevada and western Great Basin, U.S.A.; Periglacial landforms as refugia in warming climates. Arctic, Antarctic, and Alpine Research 42:76-88.
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