At Sea Between St. Helena and Ascension Islands
Across the tropical mid-Atlantic barely a bird is found in this profoundly deep and seemingly unproductive reach of ocean. On our journey so far we have traversed a multiple of meridians and a plurality of parallels and have indeed discovered wonderful concentrations of life, but only in particular places. We have seen how topography, temperature, currents and other oceanographic features impact productivity.
Crossing watery voids may be relaxing but not particularly exciting; however, it is an important part of the puzzle how oceans work. Today, occasional flying fish share the air with the rare storm-petrel or masked booby. Otherwise, the sea is a vast empty surface rippled by light winds, nudged by subtle swells, reflecting the sun’s tropical trajectory. But we are in luck; our horizontal course intersects the more vertical one of a grouping of sperm whales, Earth’s largest toothed creatures. Seeing these boxy beings breathing obliquely on the surface reminds us of the ocean’s three-dimensionality.
These deepest diving mammals venture into the dense dark abyss below us to secure squid for sustenance. We have been cruising in water more than four kilometers deep in an area with few if any contours on the chart. These whales are truly pelagic. Sightings of sperm whales are often limited to known places with deep drop-offs near oceanic islands. More sophisticated techniques are helping scientists learn how the whales use acoustic sequences of pulsed clicks and creaks at depth to pursue prey.
Researchers have only recently discovered that sperm whale populations are structured in distinct acoustic “clans” of about 10,000 individuals associated by vocal repertoire, with particular distributions, movement patterns and feeding successes. Clans are composed of small stable family “units” of about 10 whales each. It is the females that live together for life tending young, while roving males move poleward seasonally for food resources.
The existence of fixed family groups in sperm whales (and in pilot whales, killer whales and human beings) suggests that culturally-transmitted behavior may be imperative for survival. Many of the dozen or more whales we encountered today sported dorsal fins with prominent callouses, characteristic of female sperm whales. Large bulls will return to these waters to claim rights to these tropical harems.
Seeing these live animals today after last week’s fascinating observation of a dead sperm whale being recycling by sharks and seabirds, helps lays claim of the deep ocean to this species. We enjoyed the company of the fabled beasts of ambergris, spermaceti, scrimshaw and Moby Dick fame, an intriguing and bio-massive sighting out in the big blue nothingness of the tropical mid-Atlantic.
Across the tropical mid-Atlantic barely a bird is found in this profoundly deep and seemingly unproductive reach of ocean. On our journey so far we have traversed a multiple of meridians and a plurality of parallels and have indeed discovered wonderful concentrations of life, but only in particular places. We have seen how topography, temperature, currents and other oceanographic features impact productivity.
Crossing watery voids may be relaxing but not particularly exciting; however, it is an important part of the puzzle how oceans work. Today, occasional flying fish share the air with the rare storm-petrel or masked booby. Otherwise, the sea is a vast empty surface rippled by light winds, nudged by subtle swells, reflecting the sun’s tropical trajectory. But we are in luck; our horizontal course intersects the more vertical one of a grouping of sperm whales, Earth’s largest toothed creatures. Seeing these boxy beings breathing obliquely on the surface reminds us of the ocean’s three-dimensionality.
These deepest diving mammals venture into the dense dark abyss below us to secure squid for sustenance. We have been cruising in water more than four kilometers deep in an area with few if any contours on the chart. These whales are truly pelagic. Sightings of sperm whales are often limited to known places with deep drop-offs near oceanic islands. More sophisticated techniques are helping scientists learn how the whales use acoustic sequences of pulsed clicks and creaks at depth to pursue prey.
Researchers have only recently discovered that sperm whale populations are structured in distinct acoustic “clans” of about 10,000 individuals associated by vocal repertoire, with particular distributions, movement patterns and feeding successes. Clans are composed of small stable family “units” of about 10 whales each. It is the females that live together for life tending young, while roving males move poleward seasonally for food resources.
The existence of fixed family groups in sperm whales (and in pilot whales, killer whales and human beings) suggests that culturally-transmitted behavior may be imperative for survival. Many of the dozen or more whales we encountered today sported dorsal fins with prominent callouses, characteristic of female sperm whales. Large bulls will return to these waters to claim rights to these tropical harems.
Seeing these live animals today after last week’s fascinating observation of a dead sperm whale being recycling by sharks and seabirds, helps lays claim of the deep ocean to this species. We enjoyed the company of the fabled beasts of ambergris, spermaceti, scrimshaw and Moby Dick fame, an intriguing and bio-massive sighting out in the big blue nothingness of the tropical mid-Atlantic.
