Shortly before Christmas I drove to Donna Nook in Lincolnshire to see the seals. Grey seals come here each winter in their 1000s to pup and to breed.
Maternal care in seals is very short-lived. It lasts just two to three weeks. The pups are weaned after an average of 18 days. 
Seal milk is very rich though. It is made up of 52pc fat and 11pc protein - cows milk has just 3pc fat, 3pc protein and 88pc water!
The pups put on weight very quickly - an average of 1.7kg a day. By the end of the suckling period they have trebled their birth weight. The mother, in contrast, loses weight, about 3.8kg a day. 
This pup is just three days old. It's skin looks loose and wrinkly but it will soon grow into it.
This pup is roughly three weeks old, already weaned and ready to make its first journey out to sea. Pups stay on the beach for at least a week after weaning. It's fun to watch them get more alert and playful.
Because they are no longer feeding, they rely on the blubber they have accumulated while feeding from their mothers. But they do lose about 1.4kg a day for the first three days and then 1kg a day after that.
I spent quite a long time photographing this pup. It was the cleanest on the beach and was lying on a large patch of ice with gave me a clean background.
I could have been in the arctic.
In some photographs I deliberately over-exposed the pictures to soften the edges and to make the eyes and muzzles of the seal pups stand out all the more.
Females are ready to mate just three weeks after pupping. 
Males lies close to the females in order to defend her from other males. 
Males lies close to the females in order to defend her from other males.
I saw this female taking a well-earned break in a shallow pool.
The male seals are like heavyweight champions. This male bore the bloody scars of a recent battle.
A grey seal's long whiskers help them to locate food in poor visibility.
Grey seals also moult whilst they are on shore. This male was looking particularly patchy.
