Explain why are seals so agile underwater?

In short (click here for detailed version)

Seals are so agile underwater because of their streamlined body, webbed limbs, and thick layer of fat that allows them to move quickly and efficiently in the water.

Explain why are seals so agile underwater?
In detail, for those interested!

Anatomy adapted of seals

The bodies of seals are shaped like a torpedo, tapered at the front and rounded at the back, which greatly reduces resistance in the water. Their front limbs, called pectoral flippers, are primarily used for steering and stabilizing their swimming, while their back limbs, known as hind flippers, provide the majority of propulsion through a very flexible undulating movement. A flexible spine allows them to change direction quickly with ease and grace underwater. The distribution of their body fat, referred to as a blubber layer, helps improve their buoyancy and balance for easy movement underwater.

Effective gestures and movements

Underwater, seals move by means of smooth undulations of their bodies and hind flippers. It's as if they glide fluidly in a natural and elegant motion. Their front flippers primarily serve to steer and stabilize their trajectory with speed and precision. The combination of a streamlined body, powerful musculature, and well-adapted movements makes them exceptional swimmers, capable of sharp and rapid changes in direction. They use their natural flexibility to turn, dive, or surface with apparent ease, as if they are dancing underwater.

Hydrodynamic fur coating

Seals have a dense fur that traps a layer of air against their skin, helping them move through the water with very little resistance. Their short, sleek, and tightly packed hairs reduce turbulence in the water, making them super fluid when they swim. It's a bit like a high-performance wetsuit: it allows for better glide and limits heat loss. This special coating combined with their thick layer of fat, called blubber, ensures top-level thermal insulation and perfect gliding, helping these animals to dart through the water with surprising ease.

Enhanced senses for underwater navigation

Seals primarily use their vibrissae, a type of hypersensitive whiskers capable of detecting the slightest movements or vibrations around them. Thanks to these true integrated tactile radars, they easily locate fish and prey, even in dark or murky waters. Their eyes, adapted to low underwater light, have a reflective layer behind the retina, the tapetum lucidum, which acts like a mirror to amplify the available light. Their hearing is also finely tuned, allowing them to hear very subtle underwater sounds, thus facilitating their orientation and hunting in depth.

High-performance respiratory system

Seals can hold their breath for a long time thanks to their large lung capacity. During dives, their heart rate drops significantly to conserve oxygen: this is known as diving bradycardia. In addition, their blood carries a large amount of oxygen due to a higher number of red blood cells and myoglobin (a protein in muscles that binds oxygen). This system allows them to dive very deep, sometimes several hundred meters, and stay down for a long time without having to come up to breathe constantly. This is useful for hunting quietly underwater!

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Frequently Asked Questions (FAQ)

1

How long can a seal stay underwater without coming up for air?

Generally, seals can stay underwater for 10 to 30 minutes, but some species can extend this duration to nearly two hours due to their enhanced oxygen storage capacity and a metabolism that can slow down significantly during prolonged dives.

2

What role do the whiskers (vibrissae) of seals play underwater?

The vibrissae, or whiskers, of seals act as ultra-sensitive sensory receptors to detect vibrations caused by the movement of potential prey, facilitating navigation and hunting even in murky or dimly lit waters.

3

Does the fur of seals really protect them from the cold underwater?

Yes, the dense fur of seals acts as an effective thermal insulator due to its thick and tight undercoat, which traps air bubbles naturally heated by body warmth, thus protecting the seal from the freezing temperatures of the deep sea.

4

What is the difference between a seal's swimming and a sea lion's swimming?

Seals primarily use their hind limbs to propel themselves underwater with powerful, undulating movements, while sea lions favor their forelimbs for swimming. This distinction gives them very different swimming styles.

5

Why do seals usually swim in a horizontal position?

Seals swim horizontally to make the most of their streamlined bodies, which significantly reduces water resistance and increases their energy efficiency, thereby facilitating their fast and smooth underwater movements.

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