Kiwi scientists record rare whale sounds
The sounds of whales and dolphins rarely seen in New Zealand waters have been recorded by a Niwa scientist in a pioneering project.
Last year, Niwa marine ecologist Dr Kim Goetz led a programme to deploy seven acoustic moorings in Cook Strait that recorded the sounds of marine mammals for six months until they were retrieved in December.
“More than half the world’s whale and dolphin species are found in New Zealand waters, yet very little is known about their migration paths, their behaviour and where they go.”
However, she said, results from a preliminary investigation of the data revealed some exciting findings.
Among more common whale species, the passive acoustic devices recorded vocalisations from Antarctic blue whales, Antarctic minke whales and several different beaked whale species rarely seen because of their extensive diving behaviour.
These were likely to be the first recordings of Gray’s and straptoothed beaked whales in NZ.
Goetz said the project set out to look at what sounds could be heard in the waters of Cook Strait, in particular the man-made noise from vessels and industry, natural noise such as weather events and biological contributors such as whales and dolphins.
“One of the interesting things we found was that vessel noise could be heard over a broader region in deep waters than in more enclosed shallower waters — you hear the sound for longer and it radiates over a wider area.
“However, in Queen Charlotte Sound, the shallowest recording location where the localised contribution of vessels was substantially higher, the vessel noise at greater distances from the recorder was less due to the shallow and restricted propagation environment.”
The analysis has also matched very quiet days to huge storm systems that slashed vessel traffic. Then there are the whales. “Antarctic blues are coming into New Zealand waters,” she said. “They have a very low-frequency call so are being picked up further away but we’re really confident it’s not as far away as Antarctica.” Goetz said the data so far showed Cook Strait might be segregating different whale populations, with Antarctic blues mainly heard on the east side. But it was the beaked whale sounds Goetz was most excited about. There were 22 species of beaked whales, she said, of which 13 could be found around NZ. The hydrophones had detected several beaked whale calls, including Cuvier’s, and possibly strappedtooth and Gray’s beaked whales. “There is just nothing known about these animals — they are very elusive, deep-diving animals.” Cuvier’s beaked whales were recorded at all mooring locations, even in Queen Charlotte Sound. Goetz said the long-term aim of her research was to aid the consent process for activities in the Cook Strait. “A lot of the value of this lies in having a long-term data set and being able to determine monthly, annual and seasonal patterns. Right now we don’t know what’s in the area.”