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?

Monday 8 September 2014

Tag count 1!

Huge progress over the past few days! The team's hard work has really paid off with four more tags successfully deployed over the past 48 hours. That brings our total to 9 tags deployed - with 8 of them having transmitted humpback whale locations to us via the Argos satellite system. Great work TEAM!

Our track data are already revealing several interesting results. One of the whales (tag 87777.14) has already started migrating away from the NORTH! This is a brand new insight into Rarotonga humpback movement behavior given that all seven of the 2007 whales headed away from Raro in a west to northwest direction (see map below). In fact, 87777.14 is charting an entirely new course - and a bewildering one at that - as we'd expect these whales to start moving SOUTH in Spring, not north.

Preliminary map of 2014 and 2007 humpback whale satellite track data. One of the 2014 tagged whales has already left Rarotonga, heading north! (yellow circles, 87777.14)

Another interesting early result is the movement velocity of these whales. My preliminary analysis suggests these whales migrate at speeds around 5 km/hr, based on both the 2007 and 2014 migratory movement velocities (see below graphic). However, when they are hanging around Rarotonga, the data indicate that the whales swim at slower speeds, closer to 2 km/hr. This is an interesting result as it can help us follow whales around the island and anticipate where they will next come to the surface for a breath. These results also provide a possible means of differentiating migratory behaviors from non-migratory behaviors. Cool!

Preliminary distance versus time plot for the class of '14. Constant slopes on this plot represent constant swimming speeds (i.e. movement velocities). All of the migrating 2007 whales maintained swimming speeds of ~5 km/hr, just like 87777.14 has done over the past few days (non-stop mind you!).

But that's not all we've been discovering! Our longest track so far is for a whale that hasn't even left Raro yet (and who can blame it?). What's neat about this one's track is that we can study it to better understand the movement behaviors in the waters around the island. It seems this whale (81126.14) might be a reincarnated albatross - it seems perfectly content circumnavigating the island every few days! By studying this whale's movements in unprecedented detail we can start exploring patterns in its behavior: go clockwise if...; turn around when...; stay put in response to...etc. We've never had data of this spatial and temporal quality before so even these 'local' movements are tremendously exciting!

81126.14 circumnavigates Rarotonga! This loop took 2.5 days at a relatively constant swimming speed of 2 km/hr. It did play pinball off Fruits of Rarotonga on the 248th day of the yea - so it could make a full circuit in about 1 day of non-stop swimming at this cruising speed.

And for those of you thinking about taking a trip to Rarotonga some day, be sure to stock up on your Hawaiian shirts and dresses while on the island! It's become a tradition in our family!

Zach, Katie, and Maddy model this year's line.
More to come in the week's ahead folks!  Stay tuned....

Thursday 4 September 2014

Tag Count 5

We're down to 5 tags remaining! Our patience and persistence has paid off. After a day on-land watching for whales from shore due to extreme seas, we were back on the water again yesterday. Despite being restricted to the western side of the island due to strong easterly winds continuing to stir things up, we were able to deploy three tags. Unfortunately the first tag got deflected by a white cap just as it contacted the whale and did not deploy.  That tag is now at the bottom of the sea in 46m of water, and we followed the whale for over an hour to see if its behavior changed (it didn't).

Natalie, Alex and Federico look for whales along the west coast of Rarotonga on Tuesday Sept. 2, 2014. The lagoon (inside the reef) is calm, but the seas beyond were too choppy to tag.

The other two deployments yesterday were as close to perfect as you can ask for!  Nan did an exceptional job captaining the boat and Federico placed the tags with extreme accuracy. Alex just passed on that one of these whales has already moved off-shore and is headed towards Samoa! The second whale we tagged yesterday continues to swim around Rarotonga - and based on what we saw yesterday, this one likes to swim on its back!

Monday 1 September 2014

Still on 8

Well, the ocean has not been that cooperative the past two days. We're being extremely patient and persistent, getting on the water early, following individual whales for hours on end, putting ourselves in a position to deploy tags, but the combination of a strong southerly swell and 17 knot winds out of the east have stirred up some decent chop. The choppiness of the sea has prevented us from being able to attempt any more tag deployments the past two days - we still have 8 tags in hand.

Despite the high (and low) seas, we have been seeing whales. Not nearly the density found in other calving/breeding areas such as Abrolhos Bank, Brazil, but there are definitely multiple whales in the area.

When we have not been on the water, the team has kept extremely busy with maintaining the gear, downloading the daily datasets: photos, voice logs, whale song recordings, skin samples, waypoints of whale surface activity, among other things. A question for all the the blog followers at Ilam School (Christchurch, New Zealand) and elsewhere: What do you think we use each of these datasets for? I'm more than happy to come in to school upon my return to ChCh and learn what you come up with!

My evenings have been spent analyzing the daily whale location data and teaching the team how and why I do these analyses. I'll post a mini-lesson to the blog in the days ahead - but here's a little tidbit for y'all...

We already have one very interesting humpback track result: the first whale we tagged went on a >100 km excursion to the north of Rarotonga. The whale swam ~40km north, turned to the west at some stage, and then returned to Raro following a highly directional (i.e. straight line) path. Let's put this movement in some context. Humpbacks travel at ~5km/hour in open ocean. Thus, this 'little' excursion took at least 16 hours to complete. While we were searching for whales, washing down gear, downloading data, and sleeping, this whale was performing a remarkable feat of site fidelity. It left Rarotonga only to come straight back again. One way or another, it clearly knows where it is; my job is to try to figure how.

Last night I had the extreme pleasure of teaching. I love to teach - this is the main reason why I'm in academia. Last night's learning centered on the various theories of how animals navigate and took a closer look at Earth's magnetic field - one of the possible sources of spatial information available to migratory animals. We welcomed close friends from Muri Beach Club Hotel and Abigail's Mom, Felicity, along for the session. I hope it was an engaging learning experience!

Erica, from Muri Beach Club Hotel, passed on some awesome information last night about upcoming events down in Muri related to building and reinforcing the support for Nan's humpback whale research. It's just awesome having supporters and advocates in the community and the folks at MBCH have been leading the way!  Thank you so very much, Erica!

So we're off to the marina, hoping for flatter water! All we can do is be patient, persistent, and wise in our decision-making regarding when to attempt a tag deployment. The safety of the whales and the tagging team are our highest priorities. Although it may very well be a journey of ups and downs, its most importantly a journey that is moving forward.

- Travis Horton