Tuesday, 14 May 2013

Strumble continues to prove its extraordinary place in the world of Porpoises

Strong Westerly winds opposing a big receding tide created a maelstrom of white water and surging waves at Strumble yesterday and yet our Porpoises continued to be seen and recorded during a one hour click count. We averaged 18 surfacings  per hour but hardly any sighting was repeated. Normally a porpoise will surface three or four times in a row but in the stormy conditions each porpoise seemed to surface and dive without repeating the action.
Its interesting to speculate why this should be. One might expect that the usual repeated surfacings were neccessary to clear spent breath and oxygenate the animals blood sufficiently to allow it to dive again and go about its business eg. hunting for fish.
It seems likely that in such inshore turbulence, conditions might not be good for the porpoises to hunt effectively. The porpoises might be just biding their time until conditions became favourable again. Therefore their need for multiple surfacings to recharge their oxygen supply might not be neccessary... 
With both Hannah and myself scanning independantly but in tandem, we often  call sightings at the same time as our scans crossover which would be a natural consequence of multiple surfacings. Yesterday this hardly happened, so almost all of our sightings were of different animals.    
What is for sure is that we can probably never be sure of such a theory because as yet  its impossible to study their movements below the surface... maybe one day!