Northern elephant seals are generally brown in color, however there are variations to this coloration. Males are usually a darker brown, while females are a light tan color. Hair is reduced on adult males and females and is completely absent for a short time after moulting. Newborns have hair that is black in color until successfully weaned, when they shed their black coat and it is replaced by a lighter one. Countershading is a feature to all adults and newly weaned youngsters, displaying a darker color dorsally and a lighter color ventrally. They possess two, lobed hind flippers. Pinnae are absent, giving the ear the appearance of being flush with the skin. The most conspicuous feature to the male body is the inflated proboscis that adorns his face. This feature is absent in females and is larger than that of their slightly larger close relatives, Mirounga leonina. Young males begin development of the proboscis at 2 years of age, but it is not fully developed until the animal reaches its 8th year of maturity. These mammals are among the largest of the group comprising aquatic carnivores in the Northern Hemisphere. Females typically weigh 600 to 900 kg and males, which outweigh females by 3 to 10 times, can top out at 2300 kg. Females reach a length of 3.1 m on average and males usually extend from 4.0 m to 5.0 m. Newborns typically weigh about 47 kg at birth. They weigh about 147 kg and measure about 1.5 m between 24 and 28 days old, when they are weaned. Teeth are dimorphic in the sexes with males having considerably enlarged canines that are used in fighting. (Bonner, 1990; Ingles, 1965; Le Boeuf et al., 2000; McConnaughey and McConnaughey, 1997; Reeves, Stewart, and Leatherwood, 1992)
- Bonner, W. 1990. The Natural History of Seals. New York, NY: Facts On File, Inc..
- Ingles, L. 1965. Mammals of the Pacific States. Stanford, California: Stanford University Press.
- Le Boeuf, B., D. Crocker, D. Costa, S. Blackwell, P. Webb. 2000. Foraging ecology of northern elephant seals. Ecological Monographs, 70 (3): 353-382.
- McConnaughey, B., E. McConnaughey. 1997. Pacific Coast. New York: Alfred A. Knopf, Inc..
- Reeves, R., B. Stewart, S. Leatherwood. 1992. The Sierra Club Handbook of Seals and Sirenians. San Francisco: Sierra Club Books.