The American Pika (Ochotona princeps) is a diurnal(active during day and sleeps at night) species of pika. It is found in the mountains of western North America. They are usually in boulder fields at or above tree line. A recent news article suggests that species populations are declining due to various factors. They are very sensitive to high temperatures. Pikas are considered to be one of the best early warning systems for detecting global warming in the western United States.