Bats, the only mammals capable of true flight, are among our least understood mammals. Twelve species of bats are thought to inhabit the North Cascades. National Park Service biologists, recently conducting a parkwide bat inventory, documented eight bat species using habitats within the park. Among those species found in the Cascades, the western small-footed bat weighs as little as four grams. Nocturnal and seldom seen, all bats found in the Cascades are insectivorous and most are closely associated with mature forests.
Mule deer, including the black-tailed deer subspecies, are the most common ungulates (hoofed mammals) in the North Cascades. Occasionally elk, moose and mountain goats can be found here. In subalpine and alpine habitats, hoary marmots are common and can be seen and heard whistling at any sign of predators, such as golden eagles and coyotes. Pika (pronounced Pie-ka) are common on mid to high elevation talus slopes.