The animals tagged for this study exhibited profound diving capabilities; however, the dive depths and durations reported here far exceed the prior records for this species. The deepest dive of 2992 m.
Diel patterns in dive behaviour were strongly evident in this dataset, confirming previous observations from short overnight deployments that this whale spends significantly more time in waters above 50 m at night than they do during the day.
Researchers from the British Antarctic Survey found that although female humpback whales have crossed from one hemisphere to another at certain times in the last few thousand years, they generally stay in their ocean of birth.
This isolation means they have been evolving semi-independently for a long time, so the humpbacks in the three global ocean basins should be classified as separate subspecies. This has implications for how we think about their conservation and recovery on a regional scale.
“Further genetic sequencing and analysis should also help us to understand more about the pattern of humpback migrations in the past. Big changes in the ocean can leave signatures in the genetic code of marine species. For example, the last glacial maximum caused many to shift southwards until the ice retreated or to find ice-free areas in the north.
Humpbacks are excellent oceanographers; they go where the food is and can travel long distances to get it, so their patterns of past migration can tell us a lot about the ocean thousands of years ago.”
The Baltic Sea offers some very treacherous waters even under the best of circumstances. The price to pay for sailing the Baltic through the millenniums has been high, and traces of those costs are scattered over the bottom.
A difficulty in obtaining information about wild animal behaviour is that detailed observations of different individuals is necessary over long periods of time, and this is especially hard to achieve with sharks. But in the shallow lagoons of French Polynesia, such observation was possible without the encumbrance of scuba gear, and without the problem of the shark disappearing into the depths.
