“This is the worst summer ever in New Zealand.” During our four days of prep in Wellington before heading off on our vessel, almost all my friends and colleagues I spoke to said this statement (often with added emphasis). It’s been cold and windy here all summer long, and when the weather has cleared it has brought only brief respite. These comments don’t bode well for our blue whale survey dependent on calm survey conditions, but February is typically the prime month for good weather in New Zealand so I’m holding out hope. And this unpredictable weather is the common denominator of all field work. Despite months (years?) of preparation, with minute attention to all sort of details (e.g., poop net handle length, bag size limits, length of deployment lines), one of the most important factors to success is something we have absolutely no control over: the weather.
After just one day on the water, I can see that the oceanographic conditions this year are nothing like the hot-water El Niño conditions we experienced last summer. Surface water temperatures today ranged between 12.8 and 13.6 ⁰C. These temps are 10 degrees (Celsius) cooler than the 22 ⁰C water we often surveyed last summer. 10 degrees! Additionally, the current windy conditions have stirred up the upper portion of the ocean water column causing the productive mixed layer to be much deeper (therefore larger) than last year. While Kiwis may complain about the ‘terrible’ weather this summer, the resulting cold and productive oceanographic conditions are likely preferable for the whales. But where are the whales and can we find them with all this wind?
Today we had a pocket of calm conditions so our dedicated research team and crew hit it with enthusiasm, and collected a whole lot of great absence data. “Absence data?” you may ask. Absence data is all the information about where the whales are not, and is just as important as presence data (information about where the whales are) because it’s the comparison between the two sets of data (Presence vs Absence) that allows us to describe an animal’s “habitat use patterns”. Today we surveyed a small portion of the South Taranaki Bight for blue whales for about 6 hours, but the only blue animals we saw were little blue penguins and a blue shark (plus fur seals, dolphins, albatrosses, shearwaters, gannets, prions, kahawai, and saury). But during this survey effort we collected a lot of synoptic environmental data to describe these habitats, including continuous depth and temperature data along our track, nine CTD water column profiles of temperature, salinity and florescence (productivity) from the surface to the seafloor, and continuous prey (zooplankton) availability data with our transducer (echosounder).
So, now that we have absence data, we need presence data. But, the winds are howling again and are predicted to continue for the next few days. As we hunker down in a beautiful protected cove I know the blue whales continue to search this region for dense food patches, unencumbered by human-perceived obstacles of high wind and swell. So, while my Kiwi friends are right – this summer is not like previous years – I also know that it is the effects of these dynamic weather patterns that we have come so far, and worked so hard, to study. Even as my patience wears thin and my frustrations mount, I will continue to wait to pounce on the right weather window to collect our needed presence data (and more absence data too, I’m sure).
Our research team collecting absence data aboard the RV Star Keys:
Today we are flying to the other side of the world and boarding a 63-foot boat to study the largest animals ever to have inhabited this planet: blue whales (Balaenoptera musculus). Why do we study them, and how will we do it? Before I tell you, first let me say that no fieldwork is ever straightforward, and consequently no fieldwork lacks exciting learning opportunities. I have learned a lot about the logistics of an international field season in the past month, which I will share with you here!
Unmanned aerial systems (UAS, a.k.a. “drones”) are becoming more prevalent in our field as a powerful and minimally invasive tool for studying marine mammals. Last year, our team was able to capture what we believe is the first aerial footage of nursing behavior in baleen whales, in addition to feeding and traveling behaviors. And beyond behavior, these aerial images contain morphological and physiological information about the whales such as how big they are, whether they are pregnant or lactating, and if they are in good health. I’ll start making a packing list for you to follow along with. So far it contains two drones and all of their battery supplies and chargers.
Perhaps you read my first GEMM Lab blog post, about identifying individual blue whales from photographs? Using these individual IDs, I plan to generate an abundance estimate for this blue whale population, as well as look at residency and movement patterns of individuals. Needless to say, we will be collecting photo-ID images this year as well! Add two large pelican cases with cameras and long lenses to the packing list.
Now wouldn’t it be great to capture video of animal behavior in some way other than with the UAS? Maybe even from underwater? Add two GoPros and all of their associated paraphernalia to the mounting gear pile.
Now, bear with me. There is a wealth of physiological information contained in blue whale fecal matter. And when hormone analysis from fecal samples is paired with photogrammetry from UAS images, we can develop a valuable picture of individual and population-level health, stress, nutrition, and reproductive status. So, say we are able to scoop up lots of blue whale fecal samples – wouldn’t that be fantastic? Yes! Alright, add two nets, a multitude of jars, squirt bottles, and gloves to the gear list. And then we still need to bring them back to our lab here in Newport. How does that happen? Well, we need to filter out the sea water, transfer the samples to smaller tubes, and freeze them… in the field, on a moving vessel. Include beakers, funnels, spatulas, and centrifuge tubes on the list. Yes, we will be flying back with a Styrofoam cooler full of blue whale “poopsicles”. Of course, we need a cooler!
Alright, and now remember the biopsy sampling that took place last season? Collecting tissue samples allows us to assess the genetic structure of this population, their stable isotopic trophic feeding level, and hormone levels. Well, we are prepared to collect tissue samples once again! Remember to bring small tubes and scalpel blades for storing the samples, and to get ethanol when we arrive in Wellington.
An important piece in investigating the habitat of a marine predator is learning about the prey they are consuming. In the case of our blue whales, this prey is krill (Nyctiphanes australis). We study the prey layer with an echo sounder, which sends out high frequency pings that bounce off anything they come in contact with. From the strength of the signal that bounces back it is possible to tell what the composition of the prey layer is, and how dense. The Marine Mammal Institute here at OSU has an echo sounder, and with the help of colleagues and collaborators, positive attitudes, and perseverance, we successfully got the transducer to communicate with the receiver, and the receiver to communicate with the software, and the software to communicate with the GPS. Add one large pelican case for the receiver. Can we fit the transducer in there as well? Hmmm, this is going to be heavy…
Now the daunting, ever-growing to-do lists have been checked off and re-written and changed and checked off again. The mountain of research gear has been evaluated and packed and unpacked and moved and re-evaluated and packed again. The countdown to our departure date has ended, and this evening Leigh, Todd, and I fly out of Portland and make our way to Wellington, New Zealand. To think that from here all will be smooth and flawless is naïve, but not being able to contain my excitement seems reasonable. Maybe it’s the lack of sleep, but more likely it’s the dreams coming true for a marine ecologist who loves nothing more than to be at sea with the wind in her face, looking for whales and creatively tackling fieldwork challenges.
In the midst of the flurry of preparations, it can be easy to lose sight of why we are doing this—why we are worrying ourselves over poopsicle transport and customs forms and endless pelican cases of valuable equipment for the purpose of spending several weeks on a vessel we haven’t yet set foot on when we can’t even guarantee that we’ll find whales at all. This area where we will work (Figure 1) is New Zealand’s most industrially active region, where endangered whales share the space with oil rigs, shipping vessels, and seismic survey vessels that have been active since October in search of more oil and gas reserves. It is a place where we have the opportunity to study how these majestic giants fit into this ecosystem, to learn what about this habitat is driving the presence of the whales and how they’re using the space relative to industry. It is an opportunity for me as a scientist to pursue questions in ecology—the field of study that I love. It is also an opportunity for me as a conservation advocate to find my voice on issues of industry presence, resource extraction, and conflicts over ocean spaces that extend far beyond one endangered species and one region of the world.
By Dawn Barlow, MSc Student, Department of Fisheries and Wildlife, Oregon State University
The year is rapidly coming to a close, and what a busy year it has been in the Geospatial Ecology of Marine Megafauna Lab! In 2016, our members have traveled to six continents for work (all seven if we can carry Rachael’s South African conference over from the end of 2015…), led field seasons in polar, temperate, and tropical waters, presented at international conferences, processed and analyzed data, and published results. Now winter finds us holed up in our offices in Newport, and various projects are ramping up and winding down. With all of the recent turmoil 2016 has brought, it is a nice to reflect on the good work that was accomplished over the last 12 months. In writing this, I am reminded of how grateful I am to work with this talented group of people!
The year started with a flurry of field activity from our southern hemisphere projects! Erin spent her second season on the Antarctic peninsula, where she contributed to the Palmer Station Long Term Ecological Research Project.
The New Zealand blue whale project launched a comprehensive field effort in January and February, and it was a fruitful season to say the least. The team deployed hydrophones, collected tissue biopsy and fecal samples, and observed whales feeding, racing and nursing. The data collected by the blue whale team is currently being analyzed to aid in conservation efforts of these endangered animals living in the constant presence of the oil and gas industry.
Midway atoll is home to one of the largest albatross colony in the world, and Rachael visited during the winter breeding season. In addition to deploying tracking devices to study flight heights and potential conflict with wind energy development, she became acutely aware of the hazards facing these birds, including egg predation by mice and the consumption of plastic debris.
Early summertime brought red-legged kittiwakes to the remote Pribilof Islands in Alaska to nest, and Rachael met them there to study their physiology and behavior.
As the weather warmed for us in the northern hemisphere, Solene spent the austral winter with the humpback whales on their breeding grounds in New Caledonia. Her team traveled to the Chesterfield Reefs, where they collected tissue biopsy samples and photo-IDs, and recorded the whale’s songs. But Solene studies far more than just these whales! She is thoroughly examining every piece of environmental, physical, and oceanographic data she can get her hands on in an effort to build a thorough model of humpback whale distribution and habitat use.
Summertime came to Oregon, and the gray whales returned to these coastal waters. Leigh, Leila, and Todd launched into fieldwork on the gray whale stress physiology project. The poop-scooping, drone-flying team has gotten a fair bit of press recently, follow this link to listen to more!
And while Leigh, Leila, and Todd followed the grays from the water, Florence and her team watched them from shore in Port Orford, tracking their movement and behavior. In an effort to gain a better understanding of the foraging ecology of these whales, Florence and crew also sampled their mysid prey from a trusty research kayak.
With the influx of gray whales came an influx of new and visiting GEMM Lab members, as Florence’s team of interns joined for the summer season. I was lucky enough to join this group as the lab’s newest graduate student!
Our members have presented their work to audiences far and wide. This summer Leigh, Amanda, and Florence attended the International Marine Conservation Congress, and Amanda was awarded runner-up for the best student presentation award! Erin traveled to Malaysia for the Scientific Convention on Antarctic Research, and Rachael and Leigh presented at the International Albatross and Petrel Conference in Barcelona. With assistance from Florence and Amanda, Leigh led an offshore expedition on OSU’s research vessel R/V Oceanus to teach high school students and teachers about the marine environment.
Wintertime in Newport has us tucked away indoors with our computers, cranking through analyses and writing, and dreaming about boats, islands, seabirds, and whales… Solene visited from the South Pacific this fall, and graced us with her presence and her coding expertise. It is a wonderful thing to have labmates to share ideas, frustrations, and accomplishments with.
As the year comes to a close, we have two newly-minted Masters of Science! Congratulations to Amanda and Erin on successfully defending their theses, and stay tuned for their upcoming publications!
We are looking forward to what 2017 brings for this team of marine megafauna enthusiasts. Happy holidays from the GEMM Lab!
By Dawn Barlow, MSc student, Oregon State University
The season has shifted since the post I wrote this summer about diving into the world of New Zealand blue whales and the beginnings of my masters research. My fieldwork will take place during the upcoming austral summer, which will require me to miss the winter term here on campus. This quarter, I have put my research on the back burner for the time being in favor of a full load of coursework. But my project is still there, simmering subtly and persistently, and giving relevance to the coursework that I’m focusing my energy on this fall term.
As an undergraduate student, I acquired a broad scientific background and had the opportunity to dabble in the areas of biology that piqued my interest. I arrived here with a basic understanding of chemistry, physics, cell biology, anatomy, marine ecology and conservation biology. I gained experience working in the field with intertidal sea stars, snails, mussels, crabs and barnacles, with bottlenose dolphins and with humpback whales. But now my focus has narrowed as I’ve honed in on the specific questions that I will pursue over the next two years. My passion lies in marine ecology and conservation. Now, as a graduate student studying the ecology of a little-known population in a highly industrial area, this passion can come to fruition. For my masters, I hope to do the following:
A) Use photo-identification analysis to obtain a population abundance estimate for blue whales in New Zealand
B) Investigate blue whale residency and distribution patterns in New Zealand waters
C) Develop a comprehensive blue whale habitat use model for the South Taranaki Bight region of New Zealand, which incorporates physical and biological data
Down the road I hope to have implemented a capture-recapture abundance estimate model that best fits the dynamics of this population of blue whales, to have mapped where sightings have occurred and where the highest densities of blue whales are found in both space and time, and to have paired blue whale presence and absence with prey distribution, remote-sensed environmental data, and in situ oceanographic data. But how does one accomplish these things? I need a toolbox to draw from. And so this fall, I am assembling my toolbox, learning programs and analytical skills. I am taking methods courses—statistics, data management in R, analysis in GIS, methods in physiology and behavior of marine megafauna—that are no longer explorations into the world of natural science, but rather tools for exploring, identifying, and interpreting specific phenomena in ecology. While each comes with its own hiccups and headaches (see Florence’s post about this…), they are powerful tools.
Aside from coursework, the research I’m conducting has gained weight and relevance beyond being an investigation in ecology. My study area lies in the South Taranaki Bight of New Zealand, which is a contentious proposed seabed mining site for iron sands. As an undergraduate student I read case studies and wrote papers on the environmental impacts of industry, and I decided to go graduate school because I want to do research that has direct conservation applications. Last week I compiled all the data I’ve processed on blue whale sightings, seasonal residency, and photo identification for the South Taranaki Bight, which will be included as evidence submitted in environmental court in New Zealand by my advisor, Dr. Leigh Torres. “Applied conservation science” has been an abstract idea that has excited and motivated me for a long time, and now I am partaking in this process, experiencing applied conservation science firsthand.
And so my toolbox is growing, and the scope of my work is simultaneously narrowing in focus and expanding in relevance. The more tools I acquire, the more excited I am to apply them to my research. As I build my toolbox this fall, this process is something I look forward to enhancing while I’m in the field, when I dig deeper into data analysis, and as I grow as a conservation scientist.
By Dawn Barlow, MSc Student, Oregon State University
Perhaps you’ve read some posts about New Zealand blue whales on this blog from the past field season in the South Taranaki Bight (STB). I know I eagerly awaited updates from the field while the team was in New Zealand and I was in Southern California, finishing undergrad and writing funding proposals and grad school applications. Now that undergrad is done and dusted, I’ve arrived in Newport and begun to settle in to my next chapter as the newest member of the GEMM Lab, joining the blue whale research team as a MSc student in OSU’s Department of Fisheries and Wildlife. Since no blue whale news has made it onto this blog in some time, I’m excited to share what has happened since the team returned from the field!
I was welcomed into the GEMM Lab in early July, and presented with a workspace, a hard drive with thousands of photos, new software programs to learn, wonderfully accessible tea and coffee, and tasked with creating a photo-ID catalog of all the blue whales our team photographed this past field season. Here’s a great thing about blue whales: while they may be tricky to study, when someone sees a blue whale they are often excited to report it. In addition to the data collected by our team during the 2016 season and the 2014 pilot season, we are incorporating many photo-documented sightings of blue whales from all around New Zealand that we have received from collaborative researchers, whale watch organizations, and fishing vessels alike captured between 2004 and 2016. All these photos are precious data to us, as we can use them to better understand their ecology.
There are many unanswered questions about this population of blue whales in New Zealand — How many are there? Just how big are they? Do they stay in New Zealand year-round or are they migratory? Through the photo-ID analysis that I’ve done, we are just beginning to piece together some answers. We have now compiled records of sightings in New Zealand from every month of the year. I’ve identified 94 unique individual blue whales, 26 of which were sighted in the STB during the 2016 season. Five whales were seen in multiple years (Figure 1), including one whale that was seen in three different years, in three different places, and with three different calves! And what might all of this mean? At this point it’s still speculative, but these findings hint at year-round residency and seasonal movement patterns within New Zealand waters… with more data and more analysis I will be able to say these things more conclusively.
Perhaps you’ve read Leila’s post about photogrammetry, and how she is able to make measurements using aerial photographs captured using an Unmanned Aerial System (UAS, aka ‘drone’). Using the same method, I will soon be able to tell you how long these whales really are (Figure 2).
How many of them are there? Well, that’s a trickier question. Using a straightforward abundance calculation based on our rate of re-sightings, the estimate I came up with is 594 ± 438. In other words, I can say with 95% confidence that there are between 156 and 1031 blue whales in New Zealand. How helpful is this? Well, not very! The wide confidence intervals in this estimate are problematic, and it is difficult to draw any conclusions when the range of possible numbers is so large. So stay tuned as I will be learning more about modeling population abundance estimates in order to provide a more precise and descriptive answer.
But stepping back for a minute, what does it matter how many whales there are and what they’re doing? In 2014, Leigh demonstrated that the STB is an important foraging ground for these blue whales. However, the STB is also a region heavily used by industry, experiencing active oil and gas extraction (Figure 3), seismic surveying, shipping traffic, and proposed seafloor mining. If we don’t know how the blue whales are using this space, then how can we know what effect the presence of industry will have on their ecology? It is our hope that findings from this study can guide effective conservation and management of these ocean giants as well as the ecosystem they are part of.
Keeping these goals in mind, I’m eagerly awaiting the start of our 2017 field season in the STB. As I look through all these photos I feel like I’m getting to know this group of whales just a little bit and I look forward to being on the water seeing them myself, maybe even recognizing some from the 2016 photos. More time on the water and more data will bring us closer to the piecing together the story of these whales, and inevitably open doors to more questions than we started with. And in the meantime, I’m grateful for the community I’ve found here in the GEMM Lab, at Hatfield Marine Science Center, and in Newport.
By Dr. Leigh Torres, Assistant Professor, Oregon State University, Geospatial Ecology of Marine Megafauna Lab
I have been reminded of a lesson I learned long ago: Never turn your back on the sea – it’s always changing.
The blue whales weren’t where they were last time. I wrongly assumed oceanographic patterns would be similar to our last time out in 2014 and that the whales would be in the same area. But the ocean is dynamic – ever changing. I knew this. And I know it better now.
Below (Fig. 1) are two satellite images of sea surface temperature (SST) within the South Taranaki Bight and west coast region of New Zealand that we surveyed in Jan-Feb 2014 and again recently during Jan-Feb 2016. The plot on the left describes ocean surface conditions in 2014 and illustrates how SST primarily ranged between 15 and 18 ⁰C. By comparison, the panel on the right depicts the sea surface conditions we just encountered during the 2016 field season, and a huge difference is apparent: this year SST ranged between 18 and 23 ⁰C, barely overlapping with the 2014 field season conditions.
While whales can live in a wide range of water temperatures, their prey is much pickier. Krill, tiny zooplankton that blue whales seek and devour in large quantities, tend to aggregate in pockets of nutrient-rich, cool water in this region of New Zealand. During the 2014 field season, we encountered most blue whales in an area where SST was about 15 ⁰C (within the white circle in the left panel of Fig. 1). This year, there was no cool water anywhere and we mainly found the whales off the west coast of Kahurangi shoals in about 21 ⁰C water (within the white circle in the right panel of Fig. 1. NB: the cooler water in the Cook Strait in the southeast region of the right panel is a different water mass than preferred by blue whales and does not contain their prey.)
The hot water we found this year across the survey region can likely be attributed, at least in part, to the El Niño conditions that are occurring across the Pacific Ocean currently. El Niño has brought unusually settled conditions to New Zealand this summer, which means relatively few high wind events that normally churn up the ocean and mix the cool, nutrient rich deep water with the hot surface layer water. These are ideal conditions for Kiwi sun-bathers, but the ocean remains highly stratified with a stable layer of hot water on top. However, this stratification does not necessarily mean the ocean is un-productive – it only means that the SST satellite images are virtually useless for helping us to find whales this year.
Although SST data can be informative about ocean conditions, it only reflects what is happening in the thin, top slice of the ocean. Sub-surface conditions can be very different. Ocean conditions during our two survey periods in 2014 and 2016 could be more similar when compared underwater than when viewed from above. This is why sub-surface sensors and data collection is critical to marine studies. Ocean conditions in 2014 and 2016 could both potentially provide good habitat for the whales. In fact, where and when we encountered whales during both 2014 and 2016 we also detected high densities of krill through hydro-acoustics (Fig. 2). However, in 2014 we observed many surface swarms of krill that we rarely saw this recent field season, which could be due to elevated SST. But, we did capture cool drone footage this year of a brief sub-surface foraging event:
An overhead look of a blue whale foraging event as the animal approaches the surface. Note how the distended ventral (throat) grooves of the buccal cavity (mouth) are visible. This is a big gulp of prey (krill) and water. The video was captured using a DJI Phantom 3 drone in the South Taranaki Bight of New Zealand in on February 2, 2016 under a research permit from the New Zealand Department of Conservation (DOC) permit # 45780-MAR issued to Oregon State University.
Below are SST anomaly plots of January 2014 and January 2016 (Fig. 3). These anomaly plots show how different the SST was compared to the long-term average SST across the New Zealand region. As you can see, in 2014 (left panel) SST conditions in our study area were ~1 ⁰C below average, while in 2016 (right panel) SST conditions were ~1 ⁰C above average. So, what are normal conditions? What can we expect next year when we come back to survey again for blue whales across this region? These are challenging questions and illustrate why marine ecology studies like this one must be conducted over many years. One year is just a snap shot in the lifetime of the oceans.
Like all marine megafauna, blue whales move far and fast to adjust their distribution patterns according to ocean conditions. So, I can’t tell you what the ocean will be like in January 2017 or where the whales will be, but as we continue to study this marine ecosystem and its inhabitants our understanding of ocean patterns and whale ecology will improve. With every year of new data we will be able to better predict ocean and blue whale distribution patterns, providing managers with the tools they need to protect our marine environment. For now, we are just beginning to scratch the (sea) surface.
Senior Ranger, Marine – Department of Conservation, Taranaki, New Zealand
During the end of January, I had the privilege to be part of the research team studying blue whales in the South Taranaki Bight, New Zealand. My role, along with assisting with visual survey, was to obtain biopsy samples from whales using a Paxarm modified veterinary rifle. This device fires a plastic dart fitted with a sterilized metal tip that takes a small skin and blubber sample for genetic and stable isotope analysis. This process is very carefully managed following procedures to ensure that the whales are not put under any undue stress. Biopsy sampling provides a gold mine of genetic and dietary information to help us understand the dynamics of this whale population.
Although firing a dart at a creature that is considerably larger than a city bus sounds reasonably easy, it is rarely the case. The first challenge is to find whales within a large expanse of ocean. The team then needs to photograph the side of each animal and take note of any distinctive features so that each individual is only sampled once. Sometimes other work will be undertaken (such as collecting fecal samples, or deploying a drifting hydrophone or unmanned aerial system/drone). Finally the team will attempt to get close enough to the whales, while taking care not to unduly disturb them, to get a biopsy sample. Wind, vessel movement, glare, the length of time whales spend underwater and the small target they sometimes present above the water are further challenges.
The video below shows a successful biopsy attempt. It is a well-coordinated team effort that relies on great communication. You can hear observer Todd Chandler direct the skipper of the vessel Ikatere into position while keeping me (the biopsy sampler) informed as to which whale is surfacing and where. From the vantage point of the flying bridge, Todd can see the whales’ position and movement (my view is limited from the lower deck). Todd points out where the whale is surfacing and it momentarily presents a target. This was the second sample from the two racing whales previously discussed by Dr. Torres, so it will be interesting to see their relationship to one-another.
The ideal angle to approach a whale to take a biopsy sample is from behind at a 45 degree angle, as this causes the least disturbance. The following video was taken from an unmanned aerial system. It shows the vessel Ikatere approaching from the whale’s left flank. Department of Conservation (DOC) biodiversity ranger Mike Ogle is on the bow of the vessel and fires a biopsy dart at the whale. After the biopsy is taken the vessel maneuvers to collect the dart/sample from the water while the whale continues to travel.
In addition to blue whale samples, the DOC permit issued to Oregon State University also allowed for opportunistic sampling of other whales. The following video was taken during an encounter with a large pod of pilot whales. The video shows how the lightweight dart bounces off the animal and floats in the water. Care is taken to communicate its location to the skipper who positions the vessel so it can be retrieved with a net.
Once samples have been retrieved they are handled very carefully to prevent contamination. The sample is split, with some preserved for genetic analysis and the rest for stable isotope analysis. Analysis of genetic samples provides information on sex, abundance (through genetic capture-recapture, which is calculated by analyzing the proportion of individuals repeatedly sampled over subsequent seasons), and relationships to other blue whale populations. Stable isotope analysis provides information on diet. Also, a portion of all samples will be stored for potential future opportunities such as hormone and fatty acid analysis. It blows me away how much information can be gleaned from these tiny samples!
Over the past few weeks, we have surveyed the South Taranaki Bight, New Zealand, collecting biological and oceanographic data to learn more about the population of blue whales in this region. Our efforts have been successful: we have encountered multiple blue whales, and recorded information about their identification, behavior, and habitat. While our visual survey efforts have provided us with an invaluable dataset, our field season is shortly coming to an end. So how can we continue to learn more about the blue whale population, if we cannot collect visual survey data?
Solution: we will study the sounds they make.
Bioacoustics is a non-invasive method to study acoustically-active animal populations in terrestrial and marine habitats. Scientists can eavesdrop on animals by recording and analyzing their sounds, and in turn gain insights about their occurrence, behavior, and movement patterns. This is especially useful for studying elusive or rare species, such as the blue whale, that can be difficult to find in the field. Since blue whales produce high intensity, infrasonic calls and songs that can travel for many miles across ocean basins, we can capture information regarding their spatial and temporal occurrence, even if we cannot see them. (To listen to a blue whale call recorded off of Chile click here.)
We are using Marine Autonomous Recording Units (MARUs), developed by the Cornell Bioacoustics Research Program, to record blue whales (Fig. 1). The MARU is a digital audio recording system contained in a buoyant sphere, which is deployed on the bottom of the ocean using an anchor. Each MARU has a hydrophone that collects acoustic data, and these sounds are recorded and stored on electronic storage media inside the MARU. The MARUs are programmed to record continuous, low-frequency sounds for approximately six months, after which they pop up to the surface of the ocean, ready to be retrieved for data analysis and redeployed with fresh batteries and storage media.
Over the course of this field season, we strategically deployed five MARUs across the South Taranaki Bight (Fig. 2), and we will record acoustic data in these five sites over the next couple of years. This will allow us to understand patterns of occurrence at larger spatial and temporal scales than we can accomplish with visual survey alone. Our acoustic dataset will complement the biological and oceanographic data we collected on survey, providing a more complete picture of the blue whale population in the bight.
To see us deploy a MARU in New Zealand, check out this video:
Although blue whales are big, the South Taranaki Bight is bigger. So finding them is not straight forward. In fact, with little prior research in this area, the main focus of our project is to gain a better understanding of blue whale distribution patterns in the region. So, while bouncing around on the sea, we are collecting habitat data that we relate to whale occurrence data to learn what makes preferred whale habitat.
We conduct CTD casts. CTD stands for Conductivity, Temperature and Depth. This is an instrument we lower down to the bottom of the ocean on a line and along the w ay it records temperature and salinity (conductivity) data at all depths. This data describes the water structure at that location, such as the depth of the thermocline. The ocean is often layered with warm, low-salt water on top, and cooler and salty water at the bottom. This thermocline can act as a boundary above which prey aggregate.
We also have a transducer on board that we use to record the presence of biological material in the ocean, like krill (blue whale prey). This transducer emits pings of sound through the water column and the echoes bounce back, either off the seafloor, krill or fish. This glorified echosounder records where blue whale prey is, and is not.
Additionally, the research vessel is always recording surface temperature (SST). I monitor this SST readout somewhat obsessively while at-sea as well as study the latest SST satellite images. Using these two bits of data as my “blues clues”, we search for blue whales.
After a bumpy ride across the Cook Strait we had a good spell of weather last week. We covered a lot of ground, deploying our 5 hydrophones across the Bight and keeping our eyes peeled for blows. Our first day out we found three whales. Fantastic sightings. But, as we continued to survey through warm, low productivity water we found no signs of blue whales. The third day out was a beauty – the type of day I wish for: low swell and low winds – perfect for whale finding. We covered 220 nautical miles this day (deploying 2 hydrophones) and we searched and searched. But no whales. I could see from the SST satellite image that the whole Bight was really warm: about 20 ⁰C. I could also see a strip of cold water down south, toward Farewell Spit. I said “Let’s go there”.
After twelve and a half hours of survey effort through clear, blue, warm water, we finally saw the water temperature drop (to about 18 ⁰C) and the water color turn green. We started to see gannets, petrels, shearwaters, and common dolphins feeding. Then I heard the magic words come from Todd’s mouth: “Blow!” So began our sunset sighting. From 7:30 to 10 pm we worked with four blue whales capturing photographs and biopsy samples, and echosounder prey data.
This is an example of a species-habitat relationship that marine ecologists like me seek to document. We observe and record patterns like this so that we can better understand and predict the distribution of blue whales. Such information is critical for environmental managers to have in order to effectively regulate where and when human activities that may impact blue whales can occur. Over the next two weeks we will continue to document blue whale habitat in the South Taranaki Bight region of New Zealand.