e eastern Weddell Sea was a unique event, Van Opzeeland developed a procedure for the automatic detection of humpback whale calls and analysed all PALAOA recordings from 2008 and 2009 for acoustic signs of life from these animals. "Along with variable, high-frequency calls from the whales, our recordings also contain stereotyped calls that sound a bit like a moan. We concentrated on the latter in our analysis," the marine biologist says. "Today, we know that, in 2008, the humpback whales were present near the observatory with the exception of the months May, September and October. In the following year, they were absent only in September. Therefore, it is highly likely that humpback whales spent the entire winter in the eastern Weddell Sea during both years," says the scientist.
A possible explanation for the absence of humpback whale calls during some months could be the Antarctic sea ice. "Near the observatory, open water areas in the sea-ice, also known as polynias, regularly form during winter. Such polynias form due to offshore winds which press the sea-ice off the continent out to sea. We suspect that humpback whales use these ice-free areas. When polynias close or change position, the whales may move with them and leave the recording radius of 100 kilometres, which our underwater microphones are monitoring. However, we do not yet have proof for this behaviour," Van Opzeeland explains.
Based on the underwater sounds, the AWI scientists cannot say what the whales are actually communicating and which animals are calling in the winter months: "Possibly, the calls are produced by young whale cows that are not yet pregnant and skip the more than 7,000 kilometres long, energetically-costly migration to Africa's coastal waters. A humpback whale-female loses up to 65 per cent of her body weight when giving birth to and suckling a calf. With this in mind, it appears energetically advantageous, from viewpoint of the young whale cows, to remain in AntaPage: 1 2 3 4 Related biology news :1
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