![]() "Our analysis shows that these movements are related to environmental factors such as sea surface temperature and food availability." Secondly, they are mainly on the south-eastern side from September to November, and they then migrate to the north-western side and stay until February. We found that first of all, the amount of whale songs is increasing over the study period at both sites. "And we discovered different seasonal patterns of the whales on the west and east side of the island. ![]() "We used up to 18 years of acoustic recordings of the Chagos whales from the data we got from the UN organisation, CTBTO," said lead author Lyra Huang, referring to the Comprehensive Nuclear-Test-Ban Treaty Organisation which installed the devices in 2002. In a study published recently in the journal Frontiers in Marine Science, UNSW scientists analysed up to 18 years of continuous underwater acoustic recordings from devices known as hydrophones stationed either side of Diego Garcia Island, a militarised atoll governed by the UK and part of the Chagos Archipelago. They wanted to find correlations between the presence of Chagos whales and other factors such as sea-surface temperature, food source and changing weather patterns including the El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD).īy comparing the whale song frequency recorded by the two sets of hydrophones placed at the northwest of Diego Garcia and at the southeast of the island, they pieced together a pattern of behaviour and migration that correlated with differing levels of food abundance and sea temperature of each area, some 200km apart.īut while this could be welcome news to scientists and conservationists, the researchers are concerned about the effects of climate change in rising sea-temperatures, with a potential knock-on effect on their main food source, krill. Since actual sighting of the pygmy blue whales is still extremely rare - despite their 24m length - the researchers cautiously suggest that the findings show stocks of the sub-species could be on the rebound after being hunted to near-extinction in the 20th century. And now researchers from UNSW Sydney have analysed almost two decades of recordings to conclude that the distinctive songs of these pygmy blue whales have increased in frequency over this time.
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