With their playful personalities, adorable faces, and impressive tool skills, sea otters are among the most fascinating and charismatic animals in the world's oceans. Found along the coasts of the North Pacific from Russia to California, these furry marine mammals are known for their unique adaptations to life at sea.
Sea otters are highly social animals that live in groups, called rafts, that can number up to several dozen individuals. These rafts typically consist of females and their pups, with a few males present to breed. Within the raft, sea otters communicate with each other using a variety of vocalizations, including chirps, whistles, and growls.
They play a key role in protecting coastal ecosystems by consuming excessive numbers of herbivore species, such as sea urchins, which destroy kelp forests that are vital to many marine organisms.
The species nearly disappeared from the face of the earth as the fur trade, which began to develop in the second half of the 18th century, reduced the population from several hundred thousand to just two thousand in 150 years.
Read on to find out more about these little marine mammals.
The largest subspecies is the Asian sea otter, which lives in the northwestern Pacific Ocean. The southern sea otter, which lives along the central and southern California coast, is the smallest.
The Mustelidae family includes about 70 different species such as badgers, weasels, otters, and polecats.
Females weigh about ⅓ less. The length of an adult male can vary from 1.2 to 1.5 m, while females rarely reach 1.4 m.
Sea otters grow about 150,000 hairs per 1 cm2 (about 1 million per 1 square inch). It is made up of two types of hair: underfur and guard hairs, which are waterproof and protect the underfur from soaking.
Between the coat and the skin is an air space that helps otters keep their bodies warm. This is why sea otters do not have blubber, which is common in many marine animals.
Their main food is clams and mussels, but they can also hunt squid, octopus and fish. In general, over 100 species make up their menu.
Sea otters usually do not need to dive for that long, as they live in shallow water down to 23 m (75 ft).
They are typically found up to 1 km (0.62 mi) from shore, where they can find cover among barrier reefs, rocks, and kelp forests.
In contrast to the water environment, sea otters are very clumsy on land, but this does not stop them from taking a rest on land.
They dive for stones, select the most suitable one, and use it to crush the shells of their prey (such as clams or mussels). Stones are not only used for food, but also for grooming and cleaning their fur.
Their gestation period can vary greatly. It can last from four months to a year after copulation. This is due to delayed implantation, a strategy that allows the fertilized egg not to implant in the uterus immediately after fertilization, but to enter a pause (diapause) for a while before it starts to develop further.
This strategy allows the mother to time the birth of her offspring with the most advantageous conditions for survival.
Twins are very rare, occurring in only about 2% of all births. It is even less likely that both pups will survive.
Species that (even in small numbers) have such a large positive impact on their environment are called keystone species. Sea otters consume excessive amounts of benthic herbivores (such as clams, mussels, or snails), which can damage kelp forests that are critical to coastal marine biodiversity.
Major predators of sea otters are: great white sharks, killer whales, bald eagles, gulls, crows, coyotes and wolves.
The species was saved by the enforcement of a Treaty for the Preservation and Protection of Fur Seals, signed by the United States, Russia, Japan, and Great Britain in 1911. It is estimated that when the treaty was signed, there were only about 1,000 to 2,000 otters left alive in the wild.
Of all the threats, oil spills are the most deadly to sea otters, as contact with oil makes the otters' fur soak with water, leading to hypothermia.
Their current global population is estimated at about 110,000 individuals, which is still much lower than before the 1740s, when the fur trade began on a massive scale. In addition, populations in the Aleutian Islands and California have declined in recent years and have not yet recovered.
Maximum recorded life span of sea otter is 23 years in the wild. The longest-lived specimen in captivity was 28 years old female.