Modern elephants are excellent swimmers, and the ancestors of "M. exilis" most likely swam the to Santa Rosae. As the population of mammoths increased, the lack of large predators such as the dire wolf, "Smilodon" and the American lion and the loss of habitat caused by the rise of sea levels at the end of the ice age as Santa Rosae split into four islands favored smaller animals. Because of this, the pygmy mammoths began evolving through generations as a survival mechanism to stay alive on the ever-shrinking Santa Rosa Island; their body size became smaller because it required less food and resources to remain energized and alive. After this evolutionary period, the mammoth had become a distinct species, the pygmy mammoth.