Acclimatization or acclimatisation is the process in which an individual organism adjusts to a change in its environment, allowing it to maintain fitness across a range of environmental conditions. Acclimatization occurs in a short period of time, and within the organism's lifetime. This may be a discrete occurrence or may instead represent part of a periodic cycle, such as a mammal shedding heavy winter fur in favor of a lighter summer coat. Organisms can adjust their morphological, behavioral, physical, and/or biochemical traits in response to changes in their environment. While the capacity to acclimate to novel environments has been well documented in thousands of species, researchers still know very little about how and why organisms acclimate the way that they do.