35 Interesting Facts About Seals

1. Seals or pinnipeds are semi-aquatic marine mammals. They comprised three groups: walruses, eared seals (sea lions and fur seals), and earless (or true) seals.
2. There are 33 extant species of seals, and earless seals have the highest number of species. These include two subfamilies (Phocinae and Monachinae), present in the northern and southern hemispheres. They are named so due to the absence of external ear flaps. They hear sounds through ear holes.  
3. The estimated population of crabeater seals is 10 to 15 million, the highest among seals and large mammals.
4. The southern elephant seal is the largest semi-aquatic carnivore. It is several times bigger than the largest terrestrial carnivore (polar bear). Their bulls can weigh up to 3,500 kg, with an average length of 5 meters. (Source)
5. Baikal seals are the smallest among pinnipeds and spend their entire life in Lake Baikal, a freshwater lake. They weigh between 50 and 130 kg and attain a length of 3.6 to 4.6 feet (1.1-1.4 m).
6. Iliamna Lake seals are one of a few seals exclusive to freshwater habitats. These seals are present only in Iliamna Lake, the largest freshwater lake in Alaska. (Source)
7. A common feature in all seals is their fin-shaped feet, which are ideal for swimming. They spend most of their time in water and move to land or sea ice during mating season.
8. True seals use their bellies and fore flippers for locomotion on land. Eared seals (sea lions and fur seals) can use their four flippers to walk on land.
9. Female hooded seals produce the world’s fattiest milk having 60% fat content. This milk doubles the weight of a newborn pup in only three to five days. (Source)

   

   Hooded seal pups double their weight in days by drinking the fattiest milk

   
   
10. According to a study, the ancestor of seals was a land-based mammal present in the Arctic between 23 and 5 million years ago. This medium-sized mammal, resembling the river otter, could swim and walk on land. Researchers got this information after discovering its skeleton in Canada in 2009. (Source)
11. The captivity of seals started during the era of the Roman Empire. Almost all seal species are present in zoos and aquariums, with the largest concentration of harbor seals and California sea lions.
12. Like fish, seals have round lenses that assist in seeing better underwater. They can see well in dim light, but their eyesight is weaker in bright light on the land.
13. Seals have excellent hearing abilities in the water and on land. Their hearing threshold for airborne sounds is the best among marine mammals and parallel to land-based carnivores. Their underwater hearing is almost as good as that of marine mammals. (Source)
14. Like other marine mammals, seals have thick blubber for insulation and energy storage. The thickness of the blubber differs according to age, season, and species of seals.
15. Most seal species live in the Arctic and Antarctic oceans. However, they are present in many cold water bodies and their coasts around the globe.
16. Some seals species drink seawater occasionally, while others fulfill their fluid requirement by eating snow. The urine of seals contains two and a half times more salt than seawater. (Source)
17. Whiskers in seals have ten times more nerves than terrestrial mammals. Various species use these whiskers differently. These are useful in finding prey through sensing and by increasing vision. (Source)
18. All seals communicate vocally on land and underwater. However, the pitch and range of these sounds differ according to gender and species.
19. The blubber, meat, and fur of seals are valuable products for human usage, which are behind the large-scale hunting of these animals. However, several countries and international organizations have banned commercial hunting to prevent the extinction of remaining seal species.
20. Seals molt once a year on land. They usually replace their old fur with new fur during this process. However, the Hawaiian monk and the elephant seals shed and replace their furs and skins during molting.
21. Serum in seals contains anti-inflammatory properties that reduce inflammation and protect lungs from collapse during deep dives. Comparatively, human blood produces 50 to 500 times more inflammation during similar stress. (Source)
22. Research proves that seals consciously reduce blood flow to blubber several seconds before diving. These marine mammals also restore normal blood flow to blubber before reaching the surface. (Source)
23. Seals sleep differently on land and in water. They sleep peacefully on land, while the right side of their brain remains awake when sleeping underwater. It is due to the high concentration of a brain chemical (acetylcholine) in the conscious part of the brain during sleep. (Source)
24. Many seal species migrate to long distances for various reasons. The elephant seals’ migration is one of the longest among mammals.
25. Four seal species are the most endangered due to their limited numbers and specific locations. These include Mediterranean monk seals, Hawaiian monk seals, Saimaa ringed seals, and Lacs des Loups Marins harbor seals. (Source)
26. All seal species are carnivores. Fish is their primary food, but they also eat crustaceans, squids, etc. Leopard seals have an individual diet of penguins, other seals, and seabirds.
27. Seals have several predators in water and on land. These include killer whales, sharks, and polar bears.

    

    Killer whales are one of the top predators of seals

    
    
28. In most seal species, pups learn to swim on their own after the end of the lactation period and molting.
29. A harbor seal was the first known seal to imitate a human voice in 1978. Recent studies have proved that seals and their pups can learn and express human speech better than non-human primates. It is possibly due to the presence of the larynx, their dynamic social structure, and intelligence. (Source)
30. According to research, baby seals can change the tone of their voice according to the situation. This feature is present in humans but not in many other mammals. Most animals increase the intensity of their voice with an increase in noise. However, seal pups lower the pitch of their voice in a noisy atmosphere, which assists in carrying their voice to a long distance. (Source)
31. Seals can live for 30 years or more in the wild. However, males usually die earlier due to infighting.
32. The closest relatives of seals are skunks, weasels, raccoons, red pandas, and bears.
33. Seals mate and reproduce on land. Males fight for territories, and females who only mate with the healthiest male. Male seals may mate with multiple females. After the mating season, males retract their genitals inside their bodies.
34. Researchers have recorded several incidents of Antarctic fur seals trying to mate with king penguins. It happens due to distress or an effort to learn the process by young seals. However, sometimes baby harbor seals can also become victims of sea otters. (Source)
35. Many seal species may attack or try to bite humans if they enter their territories. However, they usually do not initiate an attack.