I was spending time at a talus covered slope in Montana, observing the American pika. Virtually once a day, a short-tailed weasel would traverse the pika's talus neighborhood in search for a steaming meal. By early July, young juvenile pika were out and about and were very much vulnerable.
This short-tailed Weasel (Mustela erminea) made an appearance but did not stay long. It traversed the rocky slope - back and forth, using its strong sense of smell to locate prey but did not kill a pika.
Later that evening, a strong storm dropped buckets of rain in the high-elevation location. I did catch a glimpse of a weasel (same one?) who killed a pocket gopher; Both were drenched in rain and were soaking wet. The ermine appeared content however.
The stoat (Mustela erminea) or short-tailed weasel, is a mammal of the genus Mustela of the family Mustelidae.