Beautiful Chance Sighting (Nov 26, 2015)
With no sperm whales seen in daylight and no sperm whales detected on the array last night, it is now perfectly clear that we had a beautiful, chance listening encounter with sperm whales the night before last.
This makes sense. The open ocean basins are deep water extending for thousands of miles, giving cetaceans plenty of room to move. We could not and should not expect, on open ocean survey voyages, to see lots of whales everyday. There just aren’t that many. We did specifically design this survey to maximise our chances of encountering cetaceans, by choosing a track line travelling along ocean ridges and between seamounts, known habitat of interest, to deep-sea dwelling cetaceans.
Click Train. Sperm whale clicks are distinctive and productive. They are finding, hunting and eating squid in the dark depths of the open ocean. It is absolutely intriguing to listen in, on their world.
As I have been discussing in the last few days, the distribution story of cetaceans can be as simple as one would like it to be, or given understandings of the multiple factors influencing habitat choice, as complex as possible. Lay a lunar cycle on sea surface temperature and add bathymetry and season with El Nino affects and you have a complex system. This is the complicated world we live in. Having stated this, spatial preservation is important, preserving habitat – for as we all know if you don’t have a home, nothing else matters.
Left-angled Blow. Characteristically heading to the left, sperm whales possess a single blowhole with the blow expelled on a low, left-angled orientation.
The sperm whales we heard the other night were most likely a nursery pod of 20-30 animals, females with calves. The continuum of hunting over the period of 7 hours indicates non-synchronicity of diving, which females do. Some dive and others remain at the surface undertaking “baby-sitting”, carefully caring for the younger members of the pod, one of the aspects of culture displayed by sperm whales.
Rounding to Dive. This whale, a male in a bachelor herd we observed near Christmas Island, rounds its’ body showing the distinctive dorsal fin, before making a deep, sounding dive.
Should we have stayed with the pod in that area (unfortunately not possible with this transit survey) we could have seen the extent of the spread, estimated the number of animals in this pod and even photo-identified some. But it’s ok, we have them marked on the chart and I will have that incredible chatter, embedded in my personal sound files forever!
Where has the impossibly blue water gone? Gone to grey clouds, everyone… when will the blue return?, When will the blue return?
The totally overcast sky with clouds of stratus and cumulus casts a gloom over the sea. Lighter grey hues fill the foreground and dark grey embodies the horizon. The easterly, east-south-east and south-south-east wind dropped and picked up variously, throughout the day. We are heading south-east still, but soon will make easting towards Fremantle.
Down For An Hour. Make a cup of coffee or two, even lunch this whale will be down for an hour!
Yes – “click, click, click, click” is booming in the wheelhouse again tonight – we are back in the biz with sperm whales clicking! This is so exciting!
Have all the layers lined up? Bathymetry, seasonality, moon phase and the whales – what a merry mix! How lucky are we?
The Deep Sea News is happening! Oh, the ups and downs of cetacean research. Don’t they know we love them?
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