The second part of the guest blog by Ursula Tscherter about feeding and surfacing Blue Whales.
Some wildlife sightings such as a gliding ivory gull, a yawning polar bear or a breaching humpback whale merely take your breath away. No more words needed. But sometimes it takes some knowledge and imagination to understand the dimension, the uniqueness and the beauty of an encounter. Like when watching a blue whale feeding at the surface in the open waters off Bellsund.
A long pointy flipper reaches vertically into the sky, sometimes showing the black, sometimes showing the white side. Getting better in catching the suddenly appearing whale, we start seeing the bluish coloured parallel lines along the throat. Nice we think, but we also wonder what exactly is this animal doing?
This blue whale, the largest animal on earth, feeds on tiny zooplankton floating in dense swarms at the water surface. When feeding the whale lunges with its mouth wide agape through this horizontal carpet-like layer of food. As the open mouth is higher than wide, the whale increases its prey intake by rolling onto the side. The incoming water expands the parallel grooves along the throat like a Chinese lantern allowing more prey to enter the mouth. Still, in forward movement, it then presses the water out through the curtain of some 800 baleen plates and swallowing thousands of tiny crustaceans at once.
The number of breaths is related to the activity state of the whale and differs when travelling, resting or feeding. When the prey patch is at depth, the whale can’t breath when feeding and can’t feed when breathing. In between lies the travel time to the patch and back to the surface. This division determines the whales surfacing pattern as it is clearly structured in long dive periods and very regular blow intervals. The pattern becomes more erratic when the prey is near the surface and even more so when the food is at the surface.
In this case, air intake and prey intake might happen simultaneously as the whale lunges into the prey patch in a horizontal plane thus exposing the blowholes during the feeding strike. When lunging sideways or even belly up the blowholes remain submerged, it will turn to breathe right away or it will interpose a sequence of blows between several feeding strikes.