''Zalophus'' is a genus of the family Otariidae (

sea lion Sea lions are pinnipeds characterized by external ear flaps, long foreflippers, the ability to walk on all fours, short and thick hair, and a big chest and belly. Together with the fur seals, they make up the family Otariidae, eared seals. ...

s and

fur seal Fur seals are any of nine species of pinnipeds belonging to the subfamily Arctocephalinae in the family Otariidae. They are much more closely related to sea lions than Earless seal, true seals, and share with them external ears (Pinna (anatomy ...

s) of the order

Carnivora Carnivora ( ) is an order of placental mammals specialized primarily in eating flesh, whose members are formally referred to as carnivorans. The order Carnivora is the sixth largest order of mammals, comprising at least 279 species. Carnivor ...

Description

The seals of the genus ''Zalophus'' present a striking

sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

, since the adult males have a pronounced

sagittal crest A sagittal crest is a ridge of bone running lengthwise along the midline of the top of the skull (at the sagittal suture) of many mammalian and reptilian skulls, among others. The presence of this ridge of bone indicates that there are excepti ...

, and weigh, in the Californian species, between 300 and 380 kg with 240 cm long, and the females 80 to 120 kg with between 180 and 200 cm. As with all ear seals, the males are significantly larger and heavier than the females. The males are dark brown in color, the females are lighter. In contrast to the other ear seals, the males do not have a clearly defined mane. In the Galapagos species the males weigh about 250 kg with a length of 250 to 270 cm, while the females weigh from 60 to 100 kg with a length of between 150 and 170 cm. They have a streamlined body, with a layer of fat under the skin, to provide warmth and buoyancy. The coat is brown. They have large eyes that help compensate for low light levels in the underwater environment, while their whiskers increase their sense of touch. The nostrils close automatically once they touch the water. Their long front fins rotate outward for better movement on land, and propel them forward in the water, where they stay as long as possible.

Systematics

For a long time, specialists debated whether the 3 taxa that make up this genus were three full, monotypic species, or instead a single species with three subspecies; in the latter case, by priority, this species would be ''Zalophus californianus''. As early as 1953, the zoologist Erling Sivertsen created a new indicative classification, after he investigated and catalogued again, in the Oslo Museum, skulls and archaeological remains, collected by the Norwegian expedition ship MK Norvegia between 1928 and 1929. Traditionally, the three populations were listed as subspecies of a common species, but this was controversial. Wilson & Reeder classified the three populations as separate species. A molecular genetic study by Wolf et al. (2007) came to the same conclusion based on mitochondrial DNA and cell nucleus DNA SNPs. Furthermore, according to a molecular clock reconstruction, the Californian and Galápagos sea lions separated around 2.3 (± 0.5) million years ago.

Species

It includes these

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

,Don E. Wilson & DeeAnn M. Reeder (editors). 2005. Mammal Species of the World. A Taxonomic and Geographic Reference (3rd ed), Johns Hopkins University Press, 2,142 pp
Online
/ref> of which one became recently

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

Ecology

These seals go to rest on the coasts. When looking for food, they dive up to 40 meters deep and prey on fish and octopus. During the breeding season, the males establish strictly guarded

territories A territory is an area of land, sea, or space, belonging or connected to a particular country, person, or animal. In international politics, a territory is usually a geographic area which has not been granted the powers of self-government, ...

on the coasts and try to gain a harem from several females. They feed on fish and mollusks. They are very sociable and are found in large groups, on cliffs, coasts, and even on human constructions, such as piers and navigation bowls.

Reproduction

Unlike fur seals (''

Arctocephalus The genus ''Arctocephalus'' consists of the southern fur seals. ''Arctocephalus'' translates to "bear head." Taxonomy The number of species within the genus has been questioned, primarily based on limited molecular data. The issue is complica ...

'') which live in well-structured social groups, the species of the genus ''Zalophus'' form variable groups lacking in organization, although the males are also territorial and usually form

harems A harem is a domestic space that is reserved for the women of the house in a Muslim family. A harem may house a man's wife or wives, their pre-pubescent male children, unmarried daughters, female domestic Domestic worker, servants, and other un ...

of about fifteen females each. Males make loud sounds to mark territory. They usually

mate Mate may refer to: Science * Mate, one of a pair of animals involved in: ** Mate choice, intersexual selection *** Mate choice in humans ** Mating * Multi-antimicrobial extrusion protein, or MATE, an efflux transporter family of proteins Pers ...

between May and January depending on the species. Females give birth to only one young, which is born on land or water after a gestation that lasts between 342 and 365 days. They are the only mammals whose milk does not contain lactose. Females wean their young after 11 to 12 months, but some nurse their one-year-old pups alongside their newborns. File:Galápagos sea lions Isabela.jpg, A pair of Galápagos sea lions (Zalophus wollebaeki) on Isabela Island, Galapagos Islands. Photographed in the early morning. File:Californian Sea Lions (16141829839).jpg, California Sea lions at Santa Cruz, California File:Zalophus californianus swimming past fish, Guadalupe Island, Mexico (14917375665).jpg, California Sea lions (''Zalophus californianus'') swimming past fish, Guadalupe Island, Mexico

References

External links

* * {{Authority control Carnivoran genera Taxa named by Theodore Gill