Scientists studying Hauraki Gulf whales make startling discovery – after two-year poo hunt

Scientists studying the diet of a type of whale in the Hauraki Gulf have come up with a novel way of finding out what they eat - examining their poo.

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University of Auckland scientists spent two years collecting the whales’ scat for their study. Source: 1 NEWS

The researchers, from the University of Auckland, have spent two years scooping up the scat of the Bryde's whale, and they say the results also provide an indication of the effects of climate change on our waters.

"They're one of only three populations in the world that live around coastal waters and we have them in Auckland so we're very lucky," Auckland University researcher Rochelle Constantine says.

When Ms Constantine and the team first embarked on the study of their diet, there was a problem.

"The water in the gulf is quite murky, and often they feed underwater, so we couldn't see what they were feeding on," she says.

So she began a two-year poo-collecting mission with the help of tourism operator Auckland Whale and Dolphin Safari.

But while it's hard to see what's going in, it’s only a little easier to collect what's coming out.

"The poo actually sinks really quickly so you've got to move the boat and scoop it up quickly before it sinks," Auckland Whale and Dolphin Safari's marine research and conservation officer, Cathrine Lea, says.

"It sinks in seconds. A minute, max."

Only around 60 Bryde's whales live in the Hauraki Gulf full-time, so they can be difficult to find, let alone catch them doing their business.

The scat looks like a flocculent mass that can be pink or brown, depending on what the whale consumed.

The results from the study surprised researchers.

"What we expected in the beginning was just that they would eat fish or plankton that were available, but they actually have really clear preferences. They were eating krill and salps, which is really small zoo plankton," Ms Constantine says.

Even when the food was scarce, the whales were going out of their way to seek them rather than just eating something else such as fish.

But their favourite meals are being affected by climate change.

"We know that when it gets warm, the zoo plankton will move. It gets too warm for the prey and if the prey moves, the whales will move."

The next steps are figuring out whether warming waters will indeed push our threatened Bryde's whales out of the Hauraki Gulf.

With more than 15,000 known living species just off the shores of Tāmaki Makaurau, researchers say it's an underwater world worth protecting.