Friday 29 August 2014

Tag Count 9

We did it! We have successfully deployed our first satellite transmitter tag in Rarotonga, 2014!!

At 11:35AM on August 28, 2014 Federico had a clean shot and he took it. The tag was deployed in one of two sub-adults (roughly 5-7 years old by best guess) that we followed for close to an hour prior to deploying the tag. The tag was deployed on a whale with a fairly recognizable dorsal fin - see below (keep your eyes peeled for this one folks in Tonga, Samoa, and New Caledonia!). The tag was duty cycled to turn on at 5:00PM local time (3AM on August 29, UTC), so we are still waiting for the Argos system to return our first locations. I'll keep you posted!

Tag placement for our first Rarotonga satellite tag deployment in seven years. Note the distinct dorsal fin shape on this 5-7 year old sub-adult. (August 28, 2014)

We followed both whales for an hour following deployment (they stayed together both before and after the tag was deployed). No noticeable changes in either whale's behavior was observed. We thought to tag the second whale, but the second tag was in the support boat to ensure that it didn't get rained on (rain damages the degradable tape we use to hold back the tag's flanges). The tagging boat pulled alongside us at 12:40 and we decided to celebrate by eating lunch while also getting a debrief from the tagging team.

Overall it was another beautiful day on the water and we saw several humpback whales - hard to ask for more than what we got today. We are fairly confident that many of the whales we saw today were some of the same ones we saw yesterday - based on coloration, fluke shape/color pattern, dorsal fin shape, and behavior - but this requires scientific analysis of the data we've been collecting out in the boats. We've been taking heaps of photos, we now have two 20 minute recordings of humpback song(s), skin samples, one tagged deployed, and nine to go!

A one to two week old humpback whale calf sun-bathing, belly-side up, just off the reef near Black Rock, Rarotonga. (August 28, 2014)

To give you an idea as to what some of the follow-up science involves, I've quickly put together the below fluke images. The image on the top is the dorsal surface of a whale's fluke and the image in the middle is a 'magnetic lasso' trace of the same fluke's edge. Although these top two images do not capture the ventral surface coloration pattern, the shape of the serrated edge of the fluke potentially be used to help confirm a re-sighting of this whale sometime in the future. The bottom image is of the ventral surface of a different whale's fluke - notice the difference in serration and the patterned colorations? These are some of the key features we use to ID whales.

Top - Dorsal (back) surface of one whale's fluke; Middle - A computer generated trace of the fluke above; Bottom - Ventral (bottom) surface of a different whale's fluke.

One of the key steps in any scientific research process is to document what you've observed. The fluke and dorsal fin photos will be compiled in a database and ultimately made available to the wider humpback whale community for possible matching between different years and/or different places.

Here's hoping we have another successful day tomorrow and my fingers are crossed for some Argos location data in the morning!

Thanks for following along, folks. We're well and truly into the journey...

- Travis Horton

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