Wild weather and data crunching

An unexpected low over Raoul Island forced the Braveheart to relocate to a new location near the Meyer Islands early this morning. Nevertheless ‘Thomas the Tag Engine’ was on the water as soon as possible and off to a great start. First we sighted a mother/calf pair, and shortly after they surfaced we heard a beep on our satellite tag receiver which informed us that this whale had already been tagged. After photographing the mother’s fluke it was confirmed that we tagged this whale yesterday.

Strong winds limited where the team could work - they were forced to work close to shore where it was comparatively sheltered.

Strong winds limited where we could work this morning; after attempting to head offshore in search of untagged whales, we were forced to come back and work close to shore where it was comparatively sheltered. Luckily we came across a new mother/calf/escort pod, travelling slowly in relatively calm waters. The calf regularly surfaced right next our boat, and we were able to follow this relaxed group for a little while until our talented boat driver Remi positioned us nicely for Simon to successfully deploy our retrieved tag (Charlie’s tag) in the mother, to which she showed no reaction and continued her slow travel. Shortly after this, a second escort arrived, and the behaviour of the group changed completely. The interaction between the two escorts prevented us from getting close enough to these animals to deploy another tag; they became erratic in their surfacings, their direction of travel kept changing, and they were engaging in competitive behaviour. Meanwhile the wind and swells had continued to pick up, and although we had another sighting, it was almost impossible to collect any data on the animal.

Back on-board the Braveheart we used this wild weather as an opportunity to crunch some data. Claire made an exciting discovery – a match between a Kermadec Island whale with one from the New Caledonia breeding ground (biopsied and sighted in 2011 with a calf – so we know she is a female). This match provides another piece of evidence that some of the whales that migrate past Kermadec Islands, breed in New Caledonia. A tagging project was conducted in New Caledonia between 2007 and 2011 where 40 satellite tags were deployed in humpback whales and revealed information on migration routes (www.operationcetaces.nc). The majority of the tagged New Caledonian whales followed a south-southeast route to reach the Antarctic feeding ground, while the rest travelled west into the Coral Sea. Interestingly, two of the tagged whales travelled to the Kermadec Islands; a male in 2007 that was a regular visitor to New Caledonia; and a female in 2011.

The migration path of these whales is incredibly complex.

While the migration path of these whales is incredibly complex, finding matches between whales here in the Kermadec Islands with both the eastern breeding ground of Niue (blog #6) and the western breeding ground of New Caledonia, is exciting as it helps us to understand the movement of this endangered Oceania humpback whale population, and hopefully will provide insights into their final feeding destination in Antarctic waters.

By Becky and Claire.

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