Saturday, 19 January 2013

Strumble Diaries: Winter water babies

I remember some years ago everybody seemed to think that our Porpoises were seasonal and migrated away in the winter. It was also considered, they calved in June/July. So far as I remember this was all down to what people had found out about porpoises off the Bay of Fundy /Newfoundland where some porpoise research had been done. It  seemed to ber thet what went for Fundy Porpoises became the accepted norm.
Unfortunately for the Bay of Fundy, The Gulf Stream heads off across the Atlantic before it gets there and comes and warms up our waters, otherwise we would get their ice bergs and freezing winters. As it is, we just get wet mostly mild winters. Probably the colder water temperatures cause their porpoises to migrate south in the winter but from our observations we still have plenty here in the winter. Of course its probably best to have a synchronised breeding time if you are migratory that coincides with the most plentiful food availability.  That would also explain the June/July breeding season.
About ten years ago when I began to turn my attention from sea birds to the porpoises at Strumble, and read this stuff I was pretty sure this was not the case here. One thing became obvious,  that our porpoises do not all migrate away from here in the winter months. I think they may be less obvious and that they may be surface feeding more in the summer and deeper feeding in the winter depending upon availability of prey species.  It may be that there are much the same numbers about summer and winter, just in winter they are less easy too see.

Of course there were seemingly logical arguments that being so small they would be unable to survive here in the colder months. The fact is they are and do  but what about calves. They are tiny in comparison but we also see very small calves that must be born in the depths of winter. At the moment the water temperature is hovering just above 8 degrees celsius or centigrade whatever?  On the link is some film I made today of a mother with a very small calf. Its not that unusual; we see plenty of small calves all year round. How do they manage to stay warm in temperatures that would kill us in a matter of minutes?