Photo ID on the Dolphin Explorer

I finally went on my first hike in NZ in early March. A small group of us went to the coastline west of Auckland, in the Waitakere Ranges, to hike the Pararahas Gorge. The trip was originally slated for early February, with the only potential postponing factor being heavy rain the day before—the gorge floods. Of course, the night before the trip, Auckland saw the more rain than it had the whole month previous. But we did eventually go, and it was certainly worth the trip: a great downhill walk through forest dominated by silver ferns, Kauri trees, and native palms, emerging along the marshy coastline, and regained our elevation via the steep and narrow Pararahas gorge.

There were some fun stretches where we could traverse the rock wall along the stream if we wanted to. I did. (photo credit: E. Hooper)

There were some fun stretches where we could traverse the rock wall along the stream if we wanted to. I did. (photo credit: E. Hooper)

The weather also seemed to affect my field days rather disproportionately: for my first 2 months working on the project, I was only out on Auckland’s dolphin watching boat for perhaps 5 or 6 days. This is not due to rain, but to wind: this year’s summer season on the North Island was an unsettled one, with frequent trip cancellations due to average wind speeds greater than 30 knots (the limit for the boat). The de facto wind limit was even less than that, around 15 knots; any higher, and the rougher water surface made taking clear pictures of fins very difficult. All in all, we needed very good weather to make a boat trip productive, and there weren’t that many good days this season.

Still, after 3 months of working on the project, I probably managed around 12 or 13 days total on the Dolphin Explorer (DE). Massey University has an agreement with the Explorer company allowing research volunteers for the Hauraki Gulf Common Dolphin Catalogue Project (H.G.C.D.C.P.) on for free, so we didn’t have to pay the $NZ160 (about $140 US) ticket every trip. We did need to pay our own bus fare, which at about $NZ12 round trip downtown does accumulate over time. Still, 4 hours on a catamaran was worth the trip every time.

The memorable Auckland skyline, dominated by the Sky Tower in the middle.

The memorable Auckland skyline, dominated by the Sky Tower in the middle.

One day we rode past a sailing regatta, which was fun to watch. Several yachts seen here with Motukorea, one of Auckland's 40+ volcanoes, in the background.

One day we rode past a sailing regatta, which was fun to watch. Several yachts seen here with Motukorea, one of Auckland’s 40+ volcanoes, in the background.

There were several captains on the DE, Andy and Rob, whom I got to know pretty well, along with the few rotating crew members. And, after several days spent familiarizing myself with Beaufort Sea States and general cetacean behavior, I felt welcome on the bridge like an old salt. As researchers aboard, we were expected to help the crew locate the animals during the trip; I am no stranger to long days spent looking through binoculars, but it can get difficult to stay concentrated when battling a swell and lots of seasick Chinese passengers (sorry for the stereotype, Allison, but I’d now have a hard time disproving it). Days which passed without seeing any marine mammals were the most difficult to stay concentrated, but there was always something interesting to look at out on the water.

The researchers were also asked to distribute a questionnaire for the Auckland University of Technology on the trip back to the harbor. I didn’t like handing these out, and was pleased when I had a good excuse not to, e.g. the boat didn’t find any whales or dolphins, the sea was too rough, everyone aboard was Chinese and didn’t speak English (sorry again Allison). But I recognize that the surveys contribute to the Department of Conservation’s growing knowledge of the Gulf’s marine mammal population, tourist’s perception of them, and therefore a body of information useful for making informed conservation decisions.

As the skippers always joked, we rarely looked for whales or dolphins on the DE. For some animals found in the Hauraki Gulf, such as hammerhead sharks, killer whales, and bottlenose dolphins, looking for the animal itself is indeed the most effective; this is the case when there are fewer other associated species which may indicate an animal’s presence. But in the case of the Common Dolphins, the target species for our research, spotting a dorsal fin twenty centimeters tall while it’s above water for a fifth of a second in a 1.2 million hectare search area is much too difficult. Instead, we were constantly scanning the horizon for seabirds. The About one third of the world’s 300+ seabirds are found in the Hauraki Gulf, including our favorites, the Australasian Gannet. Gannets and Common Dolphins feed on the same kind of baitfish, and dolphins are extraordinary hunters when it comes to efficiently and effectivdly gathering fish together. Every day gannets go looking for dolphins, and every day we went looking for gannets.

Australasian gannets are also one of the world’s fastest animals—they feed by diving into the water after fish, capable of reaching speeds just shy of 100mph. So how did the gannets help us find dolphins? The best case scenario was when lots of gannets gathered together in a “work-up”: from a distance, we’d see tens or even hundreds of gannets tightly circling a small patch of water. Many of them would be diving in, and this is very visible to us. Often, tight diving from gannets signified that dolphins were gathering up lots of fish underneath the surface, making it easier for the gannets to fish for them. Once the boat got close to the work up, we could tell soon enough if dolphins were there because a few would usually come racing over. They would recognize our boat via ultra-sensitive physiological acoustic capabilities and were often excited to ride our bow wave; the bow of the boat slicing through the water creates a pressure wave which literally pushes the dolphins along. Bow-riding dolphins were the easiest to photograph for fin identification: being a catamaran, the DE had two hulls, so it was easy to stand on the bow of one hull while photographing the dolphins bow-riding in front of the other one.

A small work up with gannets diving into the water after fish.

A small work up with gannets diving into the water after fish.

Common Dolphins are one of only several 3-toned species worldwide.

Common Dolphins are one of only several 3-toned species worldwide.

A common dolphin exhales as it comes to the surface.

A common dolphin exhales as it comes to the surface.

January through March, the summer season in the Hauraki Gulf, is the slowest time of year for spotting marine mammals. This makes sense: dolphins have the same body temperature as humans, and require a thick blubber layer to insulate them against the colder water temperature. In the winter, the water temperature goes down, and the dolphins need to eat a lot more to maintain their insulating blubber. Eating more requires hunting more, which means attracting more birds, which means they are much easier to find. Nevertheless, I was treated to some exciting and memorable encounters. One trip, we had a Bryde’s Whale—a resident species in the gulf, but one of only two I saw on the DE—just 30 feet or so off the bow and swim right under the boat. And my final trip on DE, we saw a group of bottlenose dolphins (the “Flipper” variety), a coastal species famous for their aerobatics and violence. Contrary to popular playful perception, bottlenose dolphins are one of the most violent creatures in the ocean.

A bottlenose dolphin riding in the wake of the boat.

A bottlenose dolphin riding in the wake of the boat.

A bottlenose dolphin shows heavy scarring from rake marks, or the teeth of other dolphins. These were seen on most of the bottlenose we saw, and although present on common dolphins as well, not nearly as densely.

A bottlenose dolphin shows heavy scarring from rake marks, or the teeth of other dolphins. These were seen on most of the bottlenose we saw, and although present on common dolphins as well, not nearly as densely.

A day’s work of pictures added up to anywhere between zero and 6 or 7 thousand, depending on the success of the day’s encounters. The majority of my time in NZ was spent on the next tedious task: isolating, organizing, and cataloging all of the fin photographs. Beginning with the raw photographs, we sort different categories of pictures into different folders and identify each individual seen each day. Fortunately, I was able to draw on my experience using Adobe Lightroom software to make the sorting progress relatively rapidly. The best picture of each individual on each day was then added to a smaller matching “pool,” where it would be compared to a picture of each distinct individual the project has identified. Some individuals are quite distinguishable, due to scars and notches on their fins. Others have distinct pigmentation that do not seem to change over time. Others, however, have very few telling markers, so we have a large “unmarked” folder for all of the fins we haven’t been able to match yet. To date there are around 1300 cataloged individuals, although that number is growing every day.Dolphin_Explorer_NZ_20140130_237 Dolphin_Explorer_NZ_20140130_71 Dolphin_Explorer_20140227_187

Scars, notches, lesions, and deformities are some of the identifying markers that allow us to distinguish between individual dolphins' dorsal fins.

Scars, notches, lesions, and deformities are some of the identifying markers that allow us to distinguish between individual dolphins’ dorsal fins.

 

 

 

 

 

 

 

 

 

 

 

 

As may be evident, I’ve now left NZ and returned home to New Jersey. I was able to travel around the North Island for a week before leaving the country, seeing many majestic places peppered with a few high-octane thrills…this will be the subject of my next post.

 

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