Lake McDonald is the largest Lake in Glacier National Park in Montana. It appears to be a pristine environment untouched by the hand of humanity. Unfortunately that appearance may only be skin deep. Scientific evidence indicates that whitefish and bull trout in the lake have levels of mercury that are higher than EPA limits for human or environmental health.
Differences in size, coloration, behavior and other characteristics between males and females of a species are termed sexual dimorphisms. There are many examples of species exhibiting sexual dimorphism, including humans, but one large species with extreme differences between the males and females is the northern elephant seal (Mirounga angustirostris).