Whale Music Reveals Behavioural Patterns of Antarctic Minke Whales and Humpback Whales within the Weddell Sea
The AWI’s underwater recordings affirm: minke whales want the shelter of sea ice, whereas humpback whales keep away from it
Bremerhaven/GERMANY, 17 December 2020. Till not too long ago, what we knew concerning the lives of baleen whales within the Southern Ocean was mainly based mostly on analysis performed through the Antarctic summer time. The explanation: within the winter, there have been nearly no biologists on website to look at for the animals. Specialists from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Analysis (AWI) have now used completely put in underwater microphones, which have been recording for the previous 9 years, to efficiently collect and analyse whale statement knowledge from the Weddell Sea. The audio recordings supply distinctive insights into the lives of humpback whales and Antarctic minke whales. They present e.g. that there are almost definitely two humpback whale populations within the Weddell Sea, each of which keep away from the ocean ice and name or sing most continuously within the autumn. In distinction, Antarctic minke whales primarily reside in ice-covered areas and produce their attribute quacking sounds within the winter, because the researchers report in two research not too long ago printed within the on-line journal Royal Society Open Science. Their aim: for the brand new findings to assist enhance protecting measures for these baleen whales and their fundamental meals supply, the Antarctic krill.
Antarctic minke whales (Balaenoptera bonaerensis) are nonetheless a thriller to marine biologists, who do not know what number of of those whales there are, or the place precisely they reside, mate and provides start to their calves. Just a few years in the past, nonetheless, it was found that Antarctic minke whales produce sure attribute sounds. These calls, which regularly sound a bit just like the quacking of a duck, present incontrovertible proof of the presence of the small whales, which measure as much as eleven metres in size.
AWI biologist Diego Filun and his crew are actually utilizing these sounds within the first-ever complete, long-term statement of Antarctic minke whales within the Weddell Sea. “We have been monitoring our underwater microphones for 9 years. They have been deployed at 21 factors all through the Weddell Sea and alongside the prime meridian, permitting us to document the whales’ acoustic actions in areas the place analysis vessels not often enterprise. Because of the recordings, we now lastly perceive in what elements of the Weddell Sea the minke whales want to be at totally different occasions of 12 months, and know that not less than a few of them keep there for the winter and do not migrate to hotter waters,” Filun explains.
The recordings from 2008 to 2016 present that, in summer time and winter alike, Antarctic minke whales have a tendency to remain in these areas of the Weddell Sea which might be coated with sea ice. But the frequency of their calls seems to vary with the season: they are often heard much more typically within the autumn and winter months (April to October) than in the summertime months (December to March). As well as, the acoustic observations name into query sure earlier assumptions: “On aerial survey flights over the Weddell Sea in the summertime, minke whales have been primarily sighted close to the sea-ice edge and fewer continuously in areas with thick sea ice. However our audio recordings confirmed simply the alternative: the minke whales have been not often discovered within the marginal ice zone, and rather more typically below thick ice – almost definitely in an try and keep away from their archenemies, killer whales,” Filun reviews.
Humpbacks keep away from the ocean ice
In distinction, the humpback whales (Megaptera novaeangliae) of the Weddell Sea do not search shelter beneath the ice. Quite the opposite! Because the second hydroacoustic examine, led by AWI biologist Elena Schall, decided, the baleen whales keep away from ice-covered areas. As a substitute, they enterprise to the north of the ice edge on the hunt for Antarctic krill, which may be present in particularly massive swarms within the Weddell Sea and waters north of it.
“Our audio recordings from 2013 point out that not less than two humpback whale populations come to the Weddell Sea in summer time to construct up their fats reserves. Whales from South Africa appear to go searching on the japanese edge, close to the prime meridian. However humpbacks from South America have a tendency to remain within the northern coastal waters of the Antarctic Peninsula, and may be heard till later within the 12 months than their counterparts to the east,” explains first creator Elena Schall.
In each teams, a few of the animals do not start the lengthy trek to the north at summer time’s finish, and as a substitute overwinter within the ice-free areas of the Weddell Sea. On the identical time, the recordings point out that, in the summertime, the humpbacks transfer southward because the ice retreats, however solely go so far as is completely vital to seek out enough meals.
Important info for profitable marine safety within the Antarctic
“If we wish to shield the distinctive biotic communities of the Weddell Sea in the long run, we have to know as exactly as potential what number of baleen whales come to the Atlantic sector of the Southern Ocean seeking meals, what areas they hunt in, whether or not they overwinter there, and the way a lot krill is required for the whales to seek out enough meals. On this regard, long-term acoustic observations are a significant device, as a result of they provide us a much more detailed image of life beneath the water than the handful of scientific whale sightings alone,” says Dr Ilse van Opzeeland, an AWI biologist and co-author of each research.
The crew now hopes that the findings from the brand new research might be taken under consideration in future discussions on the institution of a marine protected space within the Weddell Sea, particularly by way of limiting krill fishing to make sure that there may be nonetheless sufficient meals for all marine fauna.
Within the meantime, the consultants will proceed to analyse their wealth of underwater recordings. Initially, they will search to find out the aim of Antarctic minke whales’ uncommon ‘quacking’; as well as, there are preliminary indications that the humpback whales’ recorded songs and calls could possibly be used to find why they depart the Weddell Sea a lot earlier or later than regular in sure summers, or the situations below which they often do not return to the Weddell Sea in any respect when winter ends. Understanding these behavioural patterns would imply a significant step ahead for the AWI’s marine biologists.
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