Watching Grey Seal behaviour at Donna Nook

We went to see the grey seal rookery at Donna Nook today with the Hull Wildlife Watch group. While driving there it was so foggy we didn’t realise we were at the Humber Bridge until we got to the tills. We got to Donna Nook after just over an hour and a half. The car park was a quarter full, but very impressive for a foggy start of the day. Fortunately, the fog started to lift, and an hour later it was a glorious, mild still day. There were lots of seals (over 1000 pups born so far this year) and there were already some older pups with a new, grey coat.

 You are guaranteed to get a shot of a fluffy white seal pup if you come to Donna Nook at this time of year, but there is so much else going on. The atmosphere is incredible, the howling calls and snorts of the seals, their unique – intense, not unpleasant – smell wafting onto the dunes, and the ease with which you can watch a large, wild mammal behaving, completely oblivious to the attention to the hundreds of watchers and photographers a few meters away.

Grey Seal bull

cow

a watchful cow

Telling seals apart

Male seals are called bulls, female seals are called cows and the little ones are pups. Pups are easily told apart by their white coat and small size. Cows are pale brown or grey with dark blotches, while bulls are darker, chocolate brown, with paler blotches. Males are larger and have thick, creased and matted necks. Their muzzles and heads are also larger than females’. Bulls can weigh over 300 kg.

a cow (left) threatening a bull

things escalated a bit until the male -literally - rolled away

A cow and her pup

Protective females

Left to their own devices, female seals would rather be dozing all day, feeding their pups, but they need to keep a constant eye on their pup and other cows and bulls. They are very protective of their pups and aggressive towards other cows, with constant squabbles between females getting to close to each other’s pups. Females are also very aggressive towards males, fighting them vigorously with their claws and threatening them with open mouths, making them retreat and keep a safe distance from their pups, and fights can sometimes escalate.

Mating seals

Fighting bulls

Mating and fighting males

Grey seal males are in the rookery with one mission: to mate with as many cows as possible. Females become receptive around the period when they wean their pups. Bulls are not territorial, they try to find and mate with receptive females and they fight other males that get too close to their females of choice, so they do not really defend an area. Many males had reddish necks from fighting and there were some fights going on. I haven’t seen very long fights, after a few minutes, one of the bulls galumphs away, sometimes chased by the winner bull.

Pup

Nursing pup

Seals have this amazing control of their nostrils: they can close them at will, or they can breath only opening one of them as this pup shows.

Nursing and dozing pups

Pups only stay on the beach for a month or so. They are born quite high on the beach, out of reach from the high tide, covered on a white coat and looking quite thin. Grey seal milk is extremely rich (53% fat) so pups put on weight quite rapidly. They are weaned after just two or three weeks. Cows remain close to their pups, and do not feed while they are on the beach. After this short period of fasting, nursing and mating they go back to the sea, leaving the fat pups behind to their own devices. The pups will finish their moult, and spend some time on the beach before returning to sea.

Two lesser Greater Black-Backed Gulls feeding on an afterbirth

Carrion crows and gulls squabble for best positions at the carcass of a dead pup

Scavengers

Pup mortality is relatively low in Donna Nook (around 10%), and mostly happens due to desertion or accidental separation of mother and pup, and subsequent starvation. We watched how a group of Carrion Crows and Lesser Greater Black-Backed gulls fed on a dead pup. Carrion crows and gulls walked around in search of afterbirths, which they also feed on.

Conservation

The size of Grey Seal colonies in the North Sea is increasing steadily, so we are likely to enjoy the spectacle of life in a seal colony for years to come.

(figure from Harrison et al 2006) 1400 pups are predicted to be born in the 2012 season in Donna Nook.

Reference

P. J. Harrison, S.T. Buckland, L. Thomas, R. Harris, P.P. Pomeroy & J. Harwood. 2006. Incorporating movement into models of grey seal population dynamics. Journal of Animal Ecology 2006, 75, 634–645.