Seals are a common sight on the shores of New England, Arctic icebergs, and even in California waters. These animals have many adaptations for life in and out of the water.
But can they breathe while they’re swimming under the water?
Seals do not breathe underwater because they’re mammals. However, they can spend 30 minutes or more underwater at a time. This is due to their high volume of blood and muscle tissue, which carry oxygen. In addition, they have a high amount of a protein that holds oxygen in their muscles.
Seals Store Oxygen In Their Blood And Muscles
Seals are marine mammals. While they do spend most of their lives in the water, they still need oxygen from the air.
They do not have gills, so they can’t actually breathe underwater. But seals can still dive for very long periods of time.
They can do this due to a special adaptation of their muscles and blood. Red blood cells carry oxygen, as does a protein in muscle tissue called myoglobin.
Seals have more blood and muscle mass than land mammals of similar sizes.
This means their body can naturally hold more oxygen than usual from which they draw while underwater. In addition, their muscles also have ten times as much myoglobin as human muscles.
Because they’re able to store so much oxygen in their body, seals don’t rely on their lungs as much. In fact, they don’t even hold their breath while underwater like humans have to do.
Their bodies have enough stores of oxygen to allow them to dive without needing to hold a lungful of air.
Their Heart Rate Slows Before They Dive
In addition to more blood and muscle, seals have another special adaptation that deals with their hearts.
A seal’s normal heart rate is between 75 and 120 beats per minute (bpm). Before diving, they can slow their hearts down to between four and six bpm.
They also slow their metabolic rate and drop their body temperature. This means that their body requires less oxygen to function in general.
Finally, true seals (members of the Phocidae family) exhale before diving.
This may seem counterintuitive, as humans and most other animals take deep breaths before going underwater. But experts believe that exhaling helps prevent decompression sickness, or “the bends.”
Decompression sickness is when there’s a rapid decrease in external pressure. The diving itself isn’t the problem, it’s the returning to the surface where there’s less pressure.
Rising too quickly can lead to nitrogen bubbles forming in the joints and blood. In mild cases, this causes some physical pain, but it can also lead to lung and spinal cord damage.
Seals can exhale to avoid the bends because of their blood and muscle tissue. They rely much more on the oxygen in those parts than they do on the air in their lungs.
How Long Can A Seal Stay Underwater?
So, seals don’t breathe underwater, and they don’t hold their breath, either. How long can they stay underwater by just relying on the oxygen that their blood and tissue store?
It depends on the species, but in general, seals can stay underwater for at least 30 minutes at a time.
Elephant seals can dive for up to two hours. But most dives are 3-7 minutes for most species since their prey is often closer to the surface.
Seals only feed when in the water. Their diets consist of various fish, squids, and even sharks.
Seals can also sleep underwater if they need to. Their brains remain just active enough to alert them when they need oxygen. It also helps them be aware of any dangers nearby so that they can escape.
Seals are marine mammals and spend about half of their time in the water. Their body structure is much better suited for water movement than land.
Using their tails as a propeller and their flippers as rudders, harbor seals can swim up to 12 mph. On land, they’re much more ungainly.
Their flippers don’t rotate as sea lion flippers do. Seals have to flop and bounce their round bodies along on their stomachs and tails.
Seals Need To Spend Time On Land
Even though they have special adaptations for water, seals do still spend time on land. Swimming takes energy, and even though they can sleep underwater, it’s easier for them to rest on land.
Seals also give birth on land, although they can nurse their pups both in and out of the water.
It’s important for seals to head to shore for safety as well. Seals are prey for great white sharks and sometimes killer whales. By returning to land, seals can escape these predators and also keep an eye out for danger.
Furthermore, seals need to be on land to molt. Molting is the process of shedding a seal’s fur and its top layer of skin. Harbor seals will also shed their whiskers during this time.
Seals need to be on land so that they direct their blood flow to the outer layers of skin. When they’re in the water, they have to direct the flow to their organs to keep warm.
Elephant seals go through “catastrophic molting,” which, despite the name, is natural. Their old skin and fur come off all at once, but the process still takes four to five weeks.
They stay on land that whole time, meaning they also fast.
Marine mammals may spend a lot, if not most, of their time in the water, but they are still mammals. That means that they use their lungs to pull oxygen from the air around them.
Seals are no different; they can’t breathe underwater like fish with gills can. Instead, seals rely on their blood and muscle tissue to store enough oxygen for deep dives.
They have more tissue than animals of the same size, as well as extra oxygen-storing proteins in their muscles.
Seals don’t hold their breath underwater, and actually exhale before diving to help combat the bends.