A review of molt in mammals, with an emphasis on marmots (Rodentia: Sciuridae: Marmota).

This article focuses on the biology and adaptive significance of molting in wild, terrestrial mammals, with an emphasis on marmots (genus *Marmota*), large ground squirrels adapted to cold, seasonal environments. Molting—the periodic replacement of the fur coat—is metabolically costly and typically timed to avoid overlap with other energy-demanding events such as reproduction and hibernation. Marmots exhibit diverse molting patterns, often a single annual molt constrained to a short active season, with variation in molt progression and timing influenced by environmental factors, body condition, and reproductive status. The review highlights gaps in knowledge, particularly regarding North American species and the unique molting strategy of the Olympic Marmot (*Marmota olympus*), and suggests that further study of museum specimens could clarify the relationships among molting phenology, hibernation, and fur insulation in this group.