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men også hvilke lokaliteter, der benyttes i yngle- og par-
ringssæsonen. I fremtiden vil vi formodentlig se en fortsat
voksende gråsælbestand, der begynder at indtage flere yng-
lelokaliteter. Et nyligt eksempel er Ertholmene, hvor der i
2007 blev observeret 3 gråsæler. I 2011 var tallet steget til
250, og her observeredes i tillæg fire unger. Fremtiden vil
formodentlig bringe flere eksempler af samme skuffe.
Store dele af Vadehavet er i udgangspunktet ikke et op-
timalt ynglehabitat for gråsælen, idet de fleste banker mere
eller mindre oversvømmes ved højvande. Gråsælen fore-
trækker nemlig lokaliteter, hvor ungerne kan ligge uforstyr-
rede og i sikkerhed fra højvande, idet ungerne først går i
vandet adskillige uger efter fødslen. På trods af dette yngler
gråsælerne i Tyskland og Holland med succes på lokaliteter,
der af og til oversvømmes under storme eller ved særlig høj
vandstand. Med øje på den udvikling, som gråsælbestande-
ne i både den tyske og hollandske del af Vadehavet har un-
dergået, er det derfor ikke usandsynligt, at også den danske
del af Vadehavet med tiden tages i brug som ynglelokalitet.
Summary
The most abundant pinniped species in Denmark is the har-
bour seal Phoca vitulina, but lately another species has be-
gun to appear in increasing numbers. This is the grey seal
Halichoerus grypus. The grey seal is not only the largest
carnivore in Denmark, it is also Denmark’s biggest mam-
mal, reaching a weight of about 300 kg.
Although the grey seal and the harbour seal are closely
related, to the extent that some biologists have suggested
placing them in the same genus, the two species are quite
different in terms of their biology. While harbour seals give
birth to their pups in the summer, normally in June and July,
the pupping season for the grey seal is in autumn and winter.
The pups are born wearing a white natal coat called a lanu-
go coat, helping the pup to keep warm until an insulating
layer of blubber has built up.
Following lactation is the mating season, where males
fight aggressively for access to oestrous females. A few
dominant males gain access to the majority of the females
in this way. Unexpectedly, however, the dominant males do
not necessarily sire the majority of the pups which are born.
Alternative mating strategies also seem to have significant
reproductive success.
Archaeological findings indicate that the grey seal was
widely distributed and abundant throughout Northern Eu-
rope during the Stone Age (8000-5500 BC), where it seems
to have been the dominant pinniped species in the region,
outnumbering the harbour seal. However, increased hunting
by a growing human population, led to high mortalities and
as a result, the grey seal disappeared from the Limfjord area
around 500 BC. In the Wadden Sea, the trend was the same,
leading to extermination of the grey seal by the sixteenth
century, while the last grey seals disappeared from Danish
coastal waters by the end of the nineteenth century.
It took more than 100 years before the grey seal returned
and started to breed regularly in Denmark once again.
However, while the species breeds in low numbers at a
few locations in Danish coastal waters, the grey seal is still
not breeding in the Danish Wadden Sea. Never the less the
species is becoming increasingly abundant in this area, and
given the positive development of the grey seal populations
in Germany and the Netherlands, chances are that in the
near future, the species will once again breed in the Danish
Wadden Sea.
Den hvide fosterpels fældes typisk efter to til fire uger og erstattes
af en pels, der ligner de voksnes. Foto: Casper Tybjerg/www.ttf.dk.
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