Thursday, 19 May 2011

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.

Tuesday, 17 May 2011

Distinguishing between Grey Seals

Telling Seals apart can be difficult but depending on the individuals can be really easy. Identification can be done by markings on the side of the neck. Finding patterns in the side of the neck can really help with distinguishing between them and also identifying new seals. One particular female grey seal that I have been following called 'Margaret' has distinctive white markings on the side of the head. This is shown in the image below:

This seal can be clearly identified at my seal site due to the white markings on the side of the neck. I have noticed that no other seals in the area have similar markings and this makes the identification of this seal very easy. The image below is of another seal in the area 'Heather', It is easy to see that this is a different seal even though they are both female, adult and found in the same location.

Monday, 16 May 2011

Identifying Male and Female

For this post I want to look at the difference between male Grey Seals and Females. This distinction can be difficult at first but after a while and with some basic information this distinction can be made with relative ease. The first real difference between the sexes is the difference in size. Adult males are larger both in length and width than Females. This can be seen with the image below:

The large adult male in the top right of the image can be seen to be larger than all the other grey seals in the photograph. Hauled out on the beach it is possible to see the size of these animals. Males are mainly dark in colour in comparison to the females which can vary in colour from brown to dark grey. So the size and general colour of the seals can help to identify males and females.

The other main difference between adult male and females are the size and shape of the head. Males are generally larger and have a more structured face and females have a smaller, shorter more rounded head.

Above is Noah, a large adult male grey seal. This can not only be seen by the dark colour of the head but also the shape of the head. A large structured face with eyes sunken into the head. A round nose bending down towards the water at the tip. This is very different to the head of a female grey seal shown below. This individual is called Margaret. Large white markings give this female a very distinctive lighter appearance and therefor, give the impression of a female seal. This is confirmed by the shape of the head. A smaller rounder head with a flat if not slightly upturned nose. The eyes are slightly more positioned on the outside of the head and less bone structure can be seen on the nose of this individual. 

When these seals are young, differentiating between the sexes is very difficult. Young pups and adolescent grey seals are hard to tell apart and greater care must be taken when doing so. 
This information is only a guide and has been gathered up by me over the last few months. I have noticed that generally males are bigger, darker and more angry looking!!

First of Many

This blog has been set up, inorder to show the natural Beauty of Grey Seals and also to investigate into the human impact upon them. My main aim from this blog is to allow me to learn more about these animals and hopefully spark an interest in them for others to get involved and help with the conservation of the species. 

I hope that through my photography I will be able to learn more about this species and identify specific behavioural patterns shown by seals in different areas. The human impact on these seals is a very sensitive subject and the welfare of these seals is always the most important factor when I am studying them. I hope that my photography will portray a very powerful message about North Atlantic Grey Seals in Cornwall. 

Image captured on a popular tourist beach on Cornwall's North Coast