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Despite their name, elephant seals are not closely related to elephants, and the large proboscis or trunk that males of the species possess is an example of convergent evolution. The northern elephant seal, somewhat smaller than its southern relative, ranges over the Pacific coast of the U.S., Canada and Mexico.
Southern elephant seal harem on a beach on the Kerguelen Islands. Southern elephant seal world population was estimated at 650,000 in the mid-1990s, [1] and was estimated in 2005 at between 664,000 and 740,000. [18] Studies have shown the existence of three geographic subpopulations, one in each of the three oceans.
The northern elephant seal population was estimated to be 171,000 in 2005. [1] Beginning in the 18th century, northern elephant seals were hunted extensively, almost to extinction by the end of the 19th century, being prized for oil made from their blubber, and the population may have fallen as low as only 20–40 individuals. [1]
Seals range in size from the 1 m (3 ft 3 in) and 45 kg (100 lb) Baikal seal to the 5 m (16 ft) and 3,200 kg (7,100 lb) southern elephant seal. Several species exhibit sexual dimorphism . They have streamlined bodies and four limbs that are modified into flippers .
Elephants can use their ears as threat displays in male-to-male competition. Sexual selection in mammals is a process the study of which started with Charles Darwin's observations concerning sexual selection, including sexual selection in humans, and in other mammals, [1] consisting of male–male competition and mate choice that mold the development of future phenotypes in a population for a ...
The brain of an elephant weighs 4.5–5.5 kg (10–12 lb) compared to 1.6 kg (4 lb) for a human brain. [77] It is the largest of all terrestrial mammals. [78] While the elephant brain is larger overall, it is proportionally smaller than the human brain. At birth, an elephant's brain already weighs 30–40% of its adult weight.
The effective population size (Ne), or the reproducing part of a population is often lower than the actual population size in small populations. [4] The Ne of a population is closest in size to the generation that had the smallest Ne. This is because alleles lost in generations of low populations are not regained when the population size increases.
These bachelor herds are large in size, ranging from 15,000 to more than 20,000 seals living in one area, referred to as a rookery. [ 2 ] The grounds occupied by fur seal bachelor herds are generally far away from breeding grounds , anywhere from 1 mile (1.6 km) or more.