Harbour seals 'pupping earlier' Harbour seals are giving birth
to pups earlier each year as a result of changes to the marine
ecosystem, a study has shown. It said the mammals, also known as
common seals, were being born 25 days earlier compared with 35
years ago. Scientists suggested the removal of large fish
species by fishing boats was allowing populations of smaller
species - favoured by the seals - to thrive. The findings appear
in the Royal Society journal Biology Letters. "We report on a
continual shift in the birth date of harbour seals in the Dutch
Wadden Sea," the team of researchers from the Netherlands
Institute for Marine Resources and Ecosystems Studies (IMARES)
wrote. "Given the similar results found for harbour seals (Phoca
vitulina) in other parts of the Wadden Sea, we conclude that the
factor causing this shift has acted on the entire...
population." It is understood that the mating season runs from
spring until autumn. Males may mate with more than one female,
and females give birth to one