Northern elephant seal, Southern elephant seal
Elephant seals are large marine mammals and are the largest extant carnivorans that can weigh up to 5,000 kilograms (11,000 lb). Elephant seals are classified under the order Pinnipedia, which, in Latin, means feather- or fin-footed. Both species, the Northern elephant seal (M. angustirostris) and the Southern elephant seal (M. leonina), were hunted to the brink of extinction for oil by the end of the 19th century, but their numbers have since recovered.
Elephant seals are considered true seals; they do not have external ears and reduced limbs. The reduction of their limbs helps them be more streamlined and move easily in the water. However, it makes navigating on land more difficult because they cannot turn their hind flippers forward to walk like the otariids. In addition, the hind flippers of elephant seals have a lot of surface area, which helps propel them in the water. Sexual dimorphism is extreme, with male elephant seals weighing up to 10 times more than females, and having a prominent proboscis. Elephant seals take their name from the large proboscis of the adult male (bull), reminiscent of an elephant's trunk. The bull's proboscis is used in producing extraordinarily loud roaring noises, especially during the mating season. More importantly, however, the nose acts as a sort of rebreather, filled with cavities designed to reabsorb moisture from their exhalations. This is important during the mating season when the seals do not leave the beach to feed and must conserve body moisture as there is no incoming source of water. The Northern and Southern elephant seal can be distinguished by various external features. On average, the Southern elephant seal tends to be larger than the Northern species. Adult males belonging to the Northern species tend to have a larger proboscis, and thick chest area with a red coloration compared to the southern species. Females do not have large proboscis and can be distinguished between species by looking at their nose characteristics. Southern females tend to have smaller, blunt noses compared to northern females.
The Northern elephant seal inhabits the Pacific coast of Mexico, the U.S., and Canada. Race Rocks are the most northerly breeding area on the Pacific Coast, at the southern end of Vancouver Island's Strait of Juan de Fuca. The seals inhabit gravel or sandy beaches, far away from human activity, as their preferred places for breeding. When at sea, males tend to feed over continental shelves, while females prefer deeper open water. Southern elephant seals are found on big and small islands along the coasts of South Africa, New Zealand, Argentina, and Chile. During the breeding season, these seals are generally found on rocky terrain and beaches, and sometimes on snow and ice. They live in the open ocean during the non-breeding season.
Elephant seals spend up to 80% of their lives in the ocean and usually only come to land to give birth, breed, and molt. Most of the time they are moving about, migrating while foraging for food. Both males and females spend time at sea but their feeding habits and migration routes differ: males will follow a route that is more consistent, while females will vary their route in pursuit of prey. Female elephant seals forage in the open ocean, while male elephant seals forage along the continental shelf. Males usually dive straight down to the ocean floor and stay at the bottom foraging for benthic prey. While hunting in the dark depths, elephant seals seem to locate their prey at least partly by vision; the bioluminescence of some prey animals can facilitate their capture. Elephant seals do not have a developed system of echolocation in the manner of cetaceans, but their vibrissae, which are sensitive to vibrations, are assumed to play a role in the search for food. Elephant seals when in the water are solitary in nature, but they come together on the shore during mating season. There is a social hierarchy during the mating season, but males are less aggressive with each other when they come to land for molting. This molting process takes up to a month to complete. When it comes time to molt, they will haul out on land to shed their outer layer, and will not consume any food during this time. The females and juveniles will molt first, followed by the sub-adult males, and finally the large mature males.
Elephant seals are carnivores (piscivores) and their favorite foods are skates, rays, squid, octopuses, eels, small sharks, and large fish.
Elephant seals are polygynous, and each dominant male is in control of mating access to a group of females. Dominant males arrive at potential breeding sites in spring and fast to ensure that they can mate with as many females as possible. Males use fighting, vocal noises, and different positions to determine who will be deemed the dominant male. They display their dominance by showing their noses, making loud vocalizations, and altering their postures. They fight each other by raising themselves and ramming each other with their chests and teeth. When females arrive, the dominating males have already selected their territory on the beach. Females cluster in groups called harems, which could consist of up to 50 females surrounding one alpha male. Outside of these groups, a beta bull is normally roaming around on the beach helping the alpha by preventing other males from accessing the females. Northern elephant seals haul out for birthing and breeding from December to March, while their southern relatives breed in August to late November. After a gestation period of 7-9 months for Southern elephant seals and 10-12 months for Northern elephant seals, a single pup is born. Pups are generally weaned at around 20-27 days, when the female will remain with her new pup, giving it large quantities of fatty, rich milk, relying on the thick blubber of her body for sustenance. Elephant seals gain reproductive maturity from 2 to 10 years of age.
Northern elephant seals suffer today from a significant absence of genetic diversity in their populations, the result of drastic reductions in the past. The result of this may be that the northern elephant seal is ill-equipped to cope with any changes in its environment. The main threat to these animals is large-scale fisheries, potentially competing with them for their preferred prey.
According to the IUCN Red List, the population size of Northern elephant seals in 2010 was estimated at between 210,000 and 239,000 animals. There is no recent comprehensive estimate of Southern elephant seal abundance. In the 1990s, the population of Southern elephant seals was estimated to be between 664,000 and 740,000 animals. Elephant seals are currently classified as Least Concern (LC) on the IUCN Red List of threatened species.
