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At birth, Hawaiian monk seal pups are approximately 25–35 pounds and 3 feet long. Thanks to the fat-rich milk from mom, the pups increase significantly in weight during the nursing period. Upon weaning, they can weigh nearly 200 pounds! On average adult Hawaiian monk seals weigh 400–600 pounds and can be 6–7 feet long.
- Why Do Seals Have Fur?
- Molting on Land Or at Sea
- Catastrophic Molt
- Molting in Seal Pups
- Molting Moms
- Will Climate Change Affect Molting?
- The Best Time to See Huge Amounts of Seals Hauled Out
- Further Reading on Molting Seals
The development of hair structures in mammals has been of critical importance for their success on land and the colonization of a broad range of habitats. One of the main roles of the pelage is to keep the animal warm by trapping the heat between the skin and the hair. In the more marine mammals such as seals, however, the thermal function of the p...
Most seal species need to spend the majority of their time ashore while molting. This is because the blood needs to flow closer to the surface of the skin to promote hair growth. Spending too much time inside the water would incur severeheat loss as the blood loses heat much faster in water than in air. By increasing their time spent hauled out, th...
Did you know that some seals not only shed their fur but also… theirskin? This extreme molting strategy is adopted by the elephant seals and the Hawaiian monk seals. Their skin peels off and new skin emerges. This strategy requires a lot of energy, so they spend this period on land in order to increase the blood supply to the skin. During this time...
Some seal pups ‘first molt’ happens after birth…
At the beginning of the pupping season, most of the females come to land to give birth to their pups. Harp seal pups are born with “lanugo”. The lanugo is a long, fine, white fur that is present in the newborns of most species at the time of birth. Generally, the lanugo is shed after a couple of days/weeks after birth. The loss of the lanugo fur is what we can consider as a “first molt”.
Some seals molt even before they are born
Harbour seal pups (together with the hooded seals) are unique in the sense that they shed their lanugo prior to birth, while still in utero. The presence of the lanugo in these species is unnecessary, as they are born with a thicker layer of fat to keep them warm. For this reason, unlike other seal pups, they can enter the water within a few days from birth. This enables them to live on the unstable ice (for the hooded seal) or on sand bars that are frequently hit by storms or floods (for the...
The hormone’s dilemma
After the nursing period, females start to mate with the dominant male. It is the one that defended their harem from other males attacks, during the nursing period. Mating is both aggressive and loud. It leaves the females with scars from the male’s bites. A few weeks after the breeding period, seals enter the molting season. But sex hormones like estrogen (which is the female’s primary sex hormone that regulates the reproductive system) is thought to inhibit molting and hair growth. In femal...
Females pause the embryo’s development
Female seals have evolved an astounding strategy that helps them overcome this problem. It is called “embryonic diapause“: the fertilized egg remains in a state of dormancy, preventing the embryo to develop. The development will resume within 2 or 4 months depending on the species. This strategy allows females to extend the period of pregnancy so that pups are born when environmental conditions are most favorable. It also allows for the molting process to take place since the sex hormone leve...
Environmental fluctuations caused by climate change will undoubtedly affect seals populations and their molting ecology. Seals close to the poles will be the most affected since theyrely on sea iceto haul-out when molting. Sea ice cover has been declining significantly over the past few years, both in the Arctic and Antarctica. Predictions are not ...
The time over which molt takes place differs between seal species, but it always occurs right after the pupping season. In Scotland, for example, grey seals come to land to start their molt between mid-January and mid-February. Harbour seals molt in the summer between the end of July and mid-August with pups being born in June.
- Chiara Paoli
Apr 19, 2022 · They have long been considered non-migratory and typically stay within 15 to 31 miles of their natal area, but tracking data have shown they sometimes travel 62 to 486 miles from their tagging location, often to exploit seasonally available food or give birth to pups.
- Mammalia
- Chordata
- Carnivora
Feb 9, 2023 · Many species of seals are polygamous, with a single male impregnating multiple females during the season. Others, like spotted seals, are seasonally monogamous and will stay together as a couple until after the pups are weaned. Most seals have a gestation period of between eight and 12 months, while walruses are pregnant for between 15 and 16 ...
Oct 11, 2016 · The male Southern elephant seal can grow to the size of a small truck weighing over 7000 pounds and measuring over 16 feet long. Some seals can stay underwater for up to an hour without taking a breath; Seals replace their skin and their fur every year in one 30 day long molt.
Weddell Seal females are generally a little bit longer and heavier than the males. Weddell Seals have a membrane over their eyes that protect them from blowing snow and the salt in the ocean. Nothing is known about the Weddell Seal’s ability to hear. Weddell Seals can stay submerged for up to 80 minutes at a time.
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Mating season varies among the subspecies but generally occurs in late spring through fall, when females come into estrus ("heat" or "season") usually about six weeks after their pups are born. Females remain in estrus for one to nine weeks. Harbor seals usually return to the same breeding grounds every year. Prior to the pupping season, males ...
