Odobenus rosmarus divergens
Odobenus rosmarus laptevi
Odobenus rosmarus rosmarus
Common name: walrus
- Body length: 2.7 - 3.7 m
- Weight: 400-1700 kg
- Lifespan: 40 years in the wild
- Sexual maturity: female: 6 - 7 years; male: 8 - 10 years
HABITAT AND GEOGRAPHICAL DISTRIBUTION
The walrus, scientific name Odobenus rosmarus of the Odobenidae family is a mammal that lives in all areas surrounding the Arctic.
Three subspecies are recognized which in addition to the different geographical location differ from each other for some small anatomical differences: Odobenus rosmarus divergens lives in the Bering Sea and in the areas of the Arctic Ocean; Odobenus rosmarus laptevi (by many scholars this subspecies is not recognized but considered one with the species Odobenus rosmarus rosmarus) which occupies the Laptev Sea north of Siberia; Odobenus rosmarus rosmarus which lives in the eastern part of Arctic Canada and east of Greenland.
Characteristically, the walrus prefers to live on the ice floes along the coasts, where the waters are not too deep.
The walrus is an animal that has sexual dimorphism as the male is always larger than the female.
The most striking aspect of the walrus is undoubtedly its size and the presence of tusks. The fangs, larger in males than in females, are none other than the transformed canines which on average measure 50 cm (they can reach a length of one meter and weigh even 5 kg). These tusks are used by the walrus during fights but also have other functions: cutting the ice, hooking to the ice when they sleep to avoid slipping, like hooks to get out of the water.
Besides the fangs on the muzzle there are hard bristles called vibrissae that can grow up to 30 cm in length present in both males and females rich in nerve endings. For the rest, the body is devoid of hair because as the animal grows they are lost. They have very thick skin, on average 4 cm (thicker in the neck and shoulders) which appears wrinkled and full of folds and tends to become light in color with age. When the walrus enters the water the skin becomes even lighter in color this because the cold water decreases the vascularization because the blood vessels are compressed while when it is lying in the sun the color becomes much more vivid, tending to reddish. The fat layer is very thick and can even reach 15 cm.
The head is very small compared to the rest of the body and is devoid of auricles which are reduced to simple skin folds and with small eyes.
Another peculiarity of the walrus is to have a bone in the penis of absolutely gigantic dimensions: 63 cm in length, the largest of all mammals both in absolute sense and relative to the size in its body.
They can swim at a maximum speed of 35 km / h but the average speed is 7 km / h.
A characteristic of the walrus is that it has pharyngeal pockets on the sides of the esophagus that can hold up to 50 liters of air that function as a float and allow it to swim vertically without any effort when full. They are also useful during the mating season because they work as sound amplifiers.
Another peculiarity are the rear fins which are used as legs together with the front fins for walking on dry land.
CHARACTER, BEHAVIOR AND SOCIAL LIFE
The walrus is not a migratory animal in the strict sense of the term even if it is a mammal that follows the ice: during the summer period when the ice melts and retreats towards the north the walrus follows the ice while in winter, when it expands towards south, the walrus moves south. These movements can cover distances of up to 3000 km. In practice, during the winter the walruses are quite dispersed, having more territory on which to move, while during the summer they are concentrated, especially the males, on the coastal beaches or on the islets. On the other hand, the young and the females prefer to remain in the ice floes throughout the year.
They are very sociable animals and often live in groups made up of thousands of individuals (see video below) who live attached to each other whose noise can be heard from miles away.
They are not animals that establish real hierarchies, simply the greatest asserts his authority by frightening the other with his size, but generally there is no bloodshed.
They are peaceful animals and usually do not attack anyone unless they are teased: in this case the whole herd intervenes in defense of the harassed companion.
The walrus main diet consists of mussels, clams, echinoderms, shrimp, worms, snails, crabs, soft corals which are found mainly either above or just below the surface of the seafloor.
It was once thought that the tusks were used to dig the seabed in search of food. In reality today it has been seen, from the analysis of the type of abrasion of the fangs, that these are dragged into the seabed and therefore the food is then found thanks to the vibrissae, rich in nerve endings and therefore very sensitive and receptive.
Sometimes it has been seen that it can also feed on fish and small seals.
They usually stay up to ten minutes submerged at a depth of 10-50m looking for food. Normally they rummage in the seabed with the snout in search of food.
REPRODUCTION AND GROWTH OF THE SMALL
Not much is known about the walrus mating system in the wild. It is certain that there are no dominances or hierarchies within the group when the mating season arrives. In fact, the older males try to have an exclusive channel in a group of females by showing themselves in various ways: particularly acute vocalizations both in water and on land; fights between males even if these do not last long and are not particularly bloody. Males who attract the attention of females manage to have their favors for 1-5 days, after which they are replaced by other males.
Mating takes place between January and February and should take place underwater while blastogenesis (the first stages of embryonic development) does not occur before 4-5 months, in June - July. The pregnancy lasts about 330 days and the walrus cubs will therefore be born from mid-April to mid-June (the total duration of gestation, from fertilization of the ovum to the birth of the young therefore lasts 15-16 months). Normally only one baby is born that weighs an average of 60 kg and is about 110 cm long. At birth it is gray in color and can immediately swim.
The bond that is established between mother and child is very strong and breastfeeding lasts about 2 years even if the little one has been able to hunt and eat solid food from much earlier.
Females usually remain in the mother's group while males leave and join other groups.
Male walrus do not participate in the care of the offspring while if a cub is orphaned, it is adopted by some other female of the group.
Males are sexually mature around the age of 8-10 although before age 15 they are unable to compete with adult males for access to females. Females reach sexual maturity at 6-7 years although they become fully mature at 9-11 years.
The walrus's main enemy is the man who hunts him for his ivory tusks. Among other animals, the polar bear and the orca are the only ones capable of preying on this huge mammal.
However, the polar bear has a hard time hunting walrus and can usually only hunt cubs or sick animals if it can isolate them, as adults normally shield their bodies and prevent the bear from approaching (see video above).
STATE OF THE POPULATION
The walrus is classified in the IUNC Red list of 2009.1 among animals DATA DEFICIENT (DD) that is, of which there is no adequate information to make a direct or indirect assessment of its extinction risk based on its distribution and / or population status.
Although its population is undoubtedly large enough, climate change is thought to have disastrously negative consequences on this mammal.
SOCIAL, ECONOMIC AND ECOSYSTEM IMPORTANCE
The walrus is an animal that has been exploited by man for a very long time both for its flesh and for the skin and ivory of its teeth.
Today walruses, despite being protected animals, various populations in the north are authorized to kill them for subsistence and in any case poaching is very much alive especially to obtain ivory.
The walrus, thanks to its docility and intelligence, is one of the main attractions of the water parks for its incredible performances. Check out the video that highlights how she dances to the beat of smooth Criminal by Michael Jackson.