Tuesday, 14 October 2014

Aere ra to'ora

Nan and the team have put together the below (epic!) video capturing many of the highlights of our 2014 tagging research.  Enjoy!

Migration Update #5

I don't know about you, but I sure couldn't row a boat that straight for that long in the open ocean. Check out the map!

121195.14 is our big mover of the week! 500+ km along a bearing that is straight as...
That's roughly the meridional width of Wyoming or Colorado, and I bet this whale is
swimming straighter than most folks drive on I-70.
More in depth analysis to come - as soon as I finish teaching for the year this week.

All the best and thanks for still following along!


Tuesday, 7 October 2014

Migration Update #4

Has the migration finally begun?

It seems most of our tagged whales are perfectly happy continuing to bounce between the islands of Oceania. 112716.14 continues to hang out around the small islands of northern Tonga, 112697.14 has joined the party in Samoa, and 87777.14 has shifted over to Atiu from Aitutaki in the southern Cook Islands.

121195.14 is the whale I have my eye on most at the moment. It has started swimming away from Samoa in an overall southeasterly direction. It could very well stop-over in Niue over the next few days - or it might very well keep on going all the way to the Antarctic. We'll have to wait and see if the southward migration has well and truly (finally!) begun, or if this is just another (truly remarkable!) example of island hopping...

Oct. 7, 2014 Humpback Whale Track Map 

I've updated the cumulative distance graphic as well (see below), in addition to the satellite transmission pie charts (further below). The cumulative distance plot continues to show that the open-water movements are faster than the near-shore movements - eventually I will do a piecewise linear regression breakpoint analysis on these distance versus time plots to objectively identify changes in the behavioural states of the whale movements (free from all the problems of state-space modeling and other forms of interpolation!). Meanwhile, the satellite transmission pie charts haven't changed very much (despite there being three times as many total transmissions received since my last update). This indicates to me that the current pattern of transmission quality/distribution should continue as long the whales stay in this sector of the South Pacific Ocean. As the whales start moving out of Oceania, however, the satellite transmission window gets broader and we might very well see an increase in the quality/number/distribution of the transmissions received. Maybe next week...

Cumulative Distance traveled versus time plot. Steeper slopes equate with faster open-water movements, lower slopes equate with slower near-shore movements.

An update to the Argos satellite transmission distributions and location data quality (for those techno-gearheads out there; Hi, Dad!)
And speaking of Papi (what the Grandkids call my Dad - who is also named Travis), I have changed the 'inferred' path taken by 87777.14 in the updated map at the top of this post. I agree, Papi. There's no evidence to suggest 87777.14 took such a tortuous (i.e. sinuous) course during the period that it's transmitter tag went silent. All the other data would suggest that something more like the inferred (yellow dashed) path shown in the map above is more likely (than what I had previously inferred). That said, we'll never be able to prove it one way or another...

I'm gonna getcha. Gonna getcha, getcha, getcha, getcha, next week. Or another. Gonna find ya...

Monday, 29 September 2014

Migration Update #3

We have passed the one-month mark since deployment of our first tag and what a month it has been!

One month ago we did not know how 'easily' humpback whales commute between the islands of Oceania. ['commuting' is a type of animal movement behavior distinct from migration, homing, dispersing, etc.]

One month ago we did not know that the migratory corridor between Rarotonga and American Samoa was so popular. [112697.14 and 120946.14 are swimming the route as at least a pair as I type!]

One month ago we did not know that humpback whales would swim more than 2000km across the tropics - roughly one-half the distance to the closest feeding grounds - only to come back to the same place they were at three weeks earlier! [this makes little sense considering the lack of food in tropical waters]

Rarotonga Humpback Whale Satellite Track Map - Sept. 29, 2014

Meanwhile, Nan and the team SOMEHOW have recovered tag #87625 - the one that got deflected by a wave just as it was about to deploy! Last I heard, it was sitting on 46 meters down just outside Avana Harbour, when all of a sudden - PING! - a location shows up on my Argos satellite map. Unreal.

I've been doing all I can to educate and raise awareness regarding Oceania's endangered humpback whales (when not checking Argos or teaching here at U.Canterbury). The kind folks at the U.S. Embassy in Wellington, New Zealand even invited me to give them an interview on our research. Thanks much Jamiela, Michael, Laura, Ola, Tracey, Rob, Candy and all the good people at the embassy! You can link to the interview below (it's 20 minutes long - what can I say...I'm excited!).

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...

Thursday, 18 September 2014

For Your Viewing Pleasure...

...I've prepared some YouTube clips. These are not just regular old home movies, folks. These are truly spectacular images that capture some magical moments. Enjoy!

I'll post an update on the whale movements in a few days. Thanks for following along!


Monday, 15 September 2014

Migration Update #1

One week and one-thousand kilometers later, three of our tagged whales are heading west...

Now that I am back in Christchurch, my updates to Megaptera14 are going to be about once a week. Monday nights (NZ time) work best.  But I do promise to keep updating you all so long as these tags are transmitting!

For this week's update, I've prepared some graphics. Top of the order is an update on where our whales have headed (this will be the standard lead-off position in the weeks ahead as well - Figure 1 is almost always a map when you're dealing with a ball-playing geoscientist!). There are several interesting points to make about the whale movement data presented in Figure 1 (below).

First, the migrating whales are moving west/northwest along very similar paths.  This 'route fidelity' is fascinating to me as none of these whales are ever in the same place at the same time. They might very well pass over the same chunk of ocean floor (~5000m below them!), but they're doing so at different times (n.b. - the tracks symbolized by triangles are from 2007! The larger colored circles are the 2014 data.). If there is an outbound migration corridor around Rarotonga, it is most certainly to the west-northwest. This gives us strong evidence to suggest potential 'no-long-line-fishing' zones during certain months of the year - a triangle connecting Rarotonga, Niue, and Palmerston would be a great start!

Figure 1 - Humpback Whale movements near Rarotonga (mid September, 2014)

 Second, our 2014 data is much higher temporal resolution than our 2007 data. In other words, we are receiving more transmissions per day from each tag in 2014 than we did from each tag in 2007. This is GREAT PROGRESS as the temporal resolution of the data dramatically impacts the level to which we can interpret each whale's movement behaviors! More data points means we have a greater chance of capturing turns, slow-downs, speed-ups, etc. I am very excited by the temporal quality of our data this year.  Here's hoping the tags keep transmitting for several months!!

Third, I might be seeing things, but it sure looks like 112726.14 got a call from Niue yesterday and decided to stop in for a visit. 'She' should arrive in Niue late on Sept. 15 local time if she keeps following the same trajectory. Now you might think I'm really starting to see things if you believe me when I say that it looks like one of the 2007 whales did a very similar thing just before its tag dropped (medium grey triangles approaching Niue from the east-southeast). Maybe polynesians really did 'ride whales' when they were island hopping during the past millennium?

Fourth, the Distance Traveled versus Day of Year plot shows that this year's migrators are a fast bunch.  They've been swimming ~6-7 km/hr for the past week straight without stopping - day or night. Cool.

For those of you who love data (like me), I've made a couple extra plots for your viewing pleasure and metacognitive pain. Figure 2 presents a couple pie charts. The one on the left shows the relative proportions of location data received by the 6 different Argos system satellites (MA, MB, NK, NN, NP, SR). The pie chart on the right shows the relative distribution of the location data's quality (3 is the best quality, zero is the worst quality - A and B could be good or could be bad, the Argos system couldn't tell). Clearly we're getting mostly 'B' quality data. This is not ideal, but it's not necessarily bad either...

Figure 2 - early to middle September (2014) Rarotonga humpback whale satellite transmission data - by Argos satellite (left) and data quality (right)

Figure 3 shows all of the whale locations the Argos system has received as a function of hour of the day. The vertical axis is plotting the 'error radius' of the whale location as determined by the Argos system (all those 'B' quality locations have largely 1-5 km errors - which is not so bad considering the spatial scale of the migrations). The parabolic curves are plotting when each of the Argos system satellites are able to receive radio transmissions (i.e. the vertical axis for the parabolic curves is basically how high in the sky the satellite is during its passage over the region). I can't see any clear pattern relating satellite position, or satellite count, to error radius. And it looks like our chosen transmission periods don't have many holes/gaps; we deliberately pre-programmed the transmitters to save battery and shut-down when the 'NP' satellite was passing as it was the sole satellite during its passages over Oceania this time of the year.

Figure 3 - Relationship between satellite transmission data quality (as Argos error radius), time of day, and receiving satellite position.

Perhaps the BEST thing about Figure 3 is that it shows quite clearly that we're capturing both sides of dawn and dusk nicely. Crepuscular (homework = look it up!) behaviors are common in the biosphere and I quite deliberately made sure that we set up the tags to collect data across these important times of the day. I'd estimate that half our data was collected during periods of darkness and half our data was collected during periods of daylight. The possibilities indeed are endless.

And I'm curious as to whether or not last week's class 2 solar flare wrought any havoc on the navigational systems used by these whales. Another topic for another day, perhaps?