Another new species of beaked whale?
Beaked whales are the second largest family of cetaceans with 22 species described to date. However, they are the least understood of all the cetacean groups because they favour a deep water habitat. Sightings of these elusive creatures are rare due to their long dive times and short, unobtrusive surfacing intervals.
Passive acoustic monitoring is a valuable tool in investigating their behavioural ecology. Beaked whales are the only known cetacean to use frequency modulated (FM) signals to echolocate, which are referred to as upsweep pulses. These signals appear to be species specific so analysing their unique acoustic sounds, which they use to echolocate, can be useful in indicating habitat usage, distribution, density, population trends and feeding activity.
Researchers recording whale songs in the Southern Ocean around Antarctica have discovered a unique echolocation signal called Antarctic BW29. The study, published in the journal Marine Mammal Science, states that this signal was recorded over 1,000 times throughout 14 different recordings. This signal is completely different to those produced by any known beaked whale, leading to the conclusion that it may belong to an entirely new species.
At least five species inhabit the Southern Ocean, including Cuviers beaked whales, Gray’s beaked whales, Arnoux’s beaked whales, southern bottlenose whales and strap-toothed whales. Of these five species, the Arnoux’s beaked whales, the largest of the Antarctic beaked whales, have been ruled out as producing this unique signal, as have Cuvier’s beaked whales. Researchers have confirmed the signal definitely does not match those produced by these two species. Despite not having a full description of the FM signals they produce, strap-toothed whales are generally not sighted at this latitude in the Southern Ocean, which rules out this species.
What remains is the Gray’s beaked whale and southern bottlenose whales. There is a relationship between the size of a beaked whale and the frequency of the calls it emits with smaller whales producing higher frequency signals. With this in mind the Antarctic BW29 likely did not come from Gray’s beaked whales since the call is not at the right frequency for their smaller body lengths.
Scientists are not sure even if southern bottlenose whales are the ones making these vocalisations, which is the remaining species of beaked whale that lives in the region. The closely related northern bottlenose whale produces very different calls and it is likely that their southern counterparts would vocalise in a similar way.
Additionally, a second unique, higher frequency call was recorded at six separate times called Antarctic BW37. It is possible that this pulse type was produced by the Gray’s beaked whale due to the size and call frequency theory, although scientists are still unsure who this call belongs to.
Since new species of beaked whales are still being discovered today, it is possible that the source of these signals may be from a species that is yet to be identified.
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