Tuesday 23 September 2014

Migration Update #2

Another week, another 1000 km...

It's been an exciting 7 days since my last Megaptera14 humpback whale migration update! One transmitter tag has come back to life, one whale has been content cruisin' around Raro, and 4 others have made haste to new island homes. The data never cease to amaze me!

Tag #87777.14 just started transmitting locations again after a two-week hiatus. Last we heard from 87777.14, "he" was headed north away from Rarotonga. Approximately 21 hours ago, 87777.14 started sending transmissions again and it's looking like he misses Nan and the team - he's heading back towards Raro from ~700km due west of the island!

23 Sept, 2014 update of humpback whale movements.

Since transmissions stopped on Sept. 8, 2014, it's anyone's guess what 87777.14 got up to. I have sketched in an ~1735 km long circuit route on the above map in yellow dashes. At an average traveling velocity of 5 km/hr over the 347 hour-long gap in transmissions, 87777.14 would have swam 1735 kilometers - the same distance as the yellow-dash circuit route.

However, if I had to bet on where 87777.14 actually went, my money would be on Manu'a (American Samoa). It's highly unlikely that it swam any faster than 6 km/hr for any extended period of time (this based on both the 2007 and 2014 swimming speeds observed for other humpbacks in the region). That would make 87777.14's maximum total distance traveled ~2100 km for the period between Sept. 8 and Sept. 23, 2014. It could have made it all the way to Upolu, but it wouldn't have had any time hang-out once it arrived there. The only other islands it could have reached, and had time to cruise, are Palmerston and Niue. Where do you think 87777.14 went?

Most of the other whales seem content hanging/cruising around new island homes. 112726.14 has spent time around both Niue and Vava'u (but it's now heading south-southwest parallel to the Tonga Trench!). 121195.14 has been around Manu'a for a few days now, and 81126.14 has stayed true to the Cooks and has been cruising around Atiu way for several days. 112697.14 is our home-body - it's still around Raro, and 120947.14 is my favorite because it followed the same ~550 km long 'straight as' track as 2007 tag #37282.07 (highlighted by the red ellipse in the above map).

It's absolutely exhilarating logging in to the Argos system and down-loading these data every day! These tracks are revealing several new and exciting things about humpback whale movement behavior and I do hope they keep on transmitting for many days to come. Stay tuned...

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