In the past few weeks there has been an ermine (also known as short tail weasel or stoat) visiting our trail camera. We have been able to track our ermine friend through a striking springtime change. Ermines are carnivores that hunt for small rodents such as mice, moles, and voles that may reside underneath the winter snowpack (subnivian zone). Their camouflage allows them to be stealthy and helps keep them safe from other larger predators.
This drastic change in the color of their fur happens during a 3-5 week period twice a year. Once in late October and November they change almost completely white, aside from a black tip at the end of their tail. Then another change happens in late March and April, where they go to a brown coat. As you can see from the images, the brown coat first appears as a mid-dorsal strip. The line gradually spreads down their backs and rump. The belly is the last body region to molt. In late fall, this process is reversed.
The change in pelage is primarily induced due to changes in the duration of daylight; shorter days as winter approaches and vise versa. Temperature differences may also be a significant factor. This springtime molt also coincides with the breeding season.