The Long-tailed weasel (Mustella frenata) is one of three weasel species found in the Greater Yellowstone ecosystem. Known for their shy demeanor, small size, low stance, and nocturnal habits, these animals present a unique challenge for photographers and wildlife observers alike. Despite their elusive nature, they are relatively common throughout the parks, rewarding those with patience, persistence, and a touch of luck with memorable sightings.
Much like other members of the mustelid family, Long-tailed weasels have limited distance vision and rely heavily on detecting movement, a trait comparable to that of the prehistoric T-rex. This fine-tuned sensitivity to motion helps explain their hunting effectiveness but also their cautious behavior around humans.
On a particularly fortunate morning, just before dawn, I was guiding a group along the serene banks of the Gros Ventre River when we spotted a Short-tailed weasel (Mustella erminea) swimming steadily across the water. The group instinctively grew silent and still as the small predator climbed up the near bank, moving calmly between the legs of one of the tour guests. Such a rare close encounter with this secretive creature left a lasting impression on everyone present, especially the guest who had the privilege of a gentle, intimate wildlife moment she would surely remember forever.
Weasel ID
Long-tailed weasels have tails greater than half the length of their bodies, while short-tailed weasels have tails closer to a third of their body length. Least weasels, the smallest species, are readily identified by the lack of a white spot on the tip of their tail.
Size:
Long-tailed weasels are the size of a proportion of a large tube sock. They are typically around one foot long, not including their tail, and weigh in at just under one pound. Their long, lean body shape is an interesting adaptation and one that is fraught with trade-offs, especially when looked at through the lens of winter survival.
Diet:
Weasels, as a clade, are highly carnivorous animals; they seek out a high-protein, highly digestible diet. In part because of their body plan, they have extreme energy needs, commonly consuming 25-40% of their body weight each day. Their diet is rich in small mammals such as voles, mice, chipmunks, and all sorts of insects. They typically hunt either on the ground or in underground burrows during the summer, taking advantage of their shape to squeeze into tight spaces. In the winter much of their time is spent in the subnivean, the space under the snow but above the ground. They are known to cache food in burrows of their own.
Mating: