They also have darker shoulder patches. Their wing leather is a dark brown but not black. Long ears extend beyond the nose when pressed forward and the outside of their tail is fringed with small hairs that can be seen with a hand lens. They are difficult to tell apart from the similar looking Western Long-eared bat, Myotis evotis who is much more common and has a wider range. At first, babies are carried while hunting for insects, then as they grow, they are left behind with other babaies.
Mothers recognize their young by their voice.
Only one pup is born per year. They start to learn to fly by about 6 weeks of age. They will not mate until the next autumn. Not much is known about the Keen's bat, except from the few dead specimens that are found in BC natural history museums and one small colony found in a cave in a BC hotspring. Most of the population is thought to be within BC coastal rainforests.