Exhale Diving

North Atlantic Grey Seals are able to dive to depths of up to 70m. These dives ranging commonly between 30-70 meters can last 5-10 minuets. After re surfacing only a short recovery time is needed before these dives can be made again. The nostrils are automatically sealed closed and this can only be done intentionally. This mean that when underwater the nostrils are closed and when the seal is breathing at the surface they can be opened to allow for large volumes of air to pass through into the lungs. This can be seen in the images below:

This image above clearly shows the Grey Seal with large open nostrils. This mean that this adult male 'Noah' is intentionally opening his nostrils to breathe.

 The above image shows the opposite. Closed nostrils at the far end of the head show that the seal is not exhaling or inhaling. This seal had just surfaced from a 4 min dive and was just about to commence breathing. This usually starts with a low pitched snort as the seal contracts a set of muscles and the nostrils are held open. 

Seals have also adapted a very interesting method of preparing for a dive.  In human freedivers, the aim of preparation breathing is to inhale as much air as possible so that a substantial amount of oxygen can be held in the blood, specifically in the haemoglobin in our red blood cells. Grey Seals are slightly different. Firstly they have a blood volume that is 1.5 - 2 times the capacity of a human. Their blood contains higher quantities of haemoglobin and therefor they are able to store higher quantities of oxygen. Also Seals are able to store oxygen with in pigments that make up the muscles, This pigment is called myoglobin. Before a seal dives they exhale the air with in their lungs. This aids them with underwater buoyancy and controls the risk of the 'bends'. In the images below, this exhalation process can be seen.

Both images above show Noah, a large adult male Grey Seal Exhaling before making a dive lasting 5-6 mins.