Written by Gussie Hollers
Members of the MMRP spent the last ten days working with the Pacific Whale Foundation off the coast of Lānaʻi. The primary goal of this fieldwork was to deploy Customized Animal Tracking Solutions (CATS) suction-cup tags on false killer whales (Pseudorca crassidens) as part of the dissertation project for new MMRP graduate student Jens Currie. With this data, Jens will be able to gather new insights into the foraging ecology of the endangered Main Hawaiian Islands insular population of false killer whales and contribute to their ongoing recovery efforts. Through the integration of multiple sensors and data streams, CATS tags can give a unique window into cetaceans’ behaviors. This suite of sensors includes: a triaxial accelerometer to measure orientation of the whale’s body, a triaxial magnetometer to measure the direction the whale is pointing, a gyroscope to measure its rotational velocity, a pressure sensor to measure depth, a GPS, a video camera, and a hydrophone. By combining these data-streams, we can make important inferences about an animal’s social behavior, energy budget, or foraging strategy.
Our team in Lānaʻi included: Jens Currie, Stephanie Stack, Liah McPherson, Brijonnay Madrigal, Will Gough, Gussie Hollers, Aude Pacini, and Shannon Barber-Meyer
We spent seven days on the water and saw five species of cetaceans! We observed large groups of melon-headed whales (Peponocephala electra) and spotted dolphins (Stenella attenuata), and smaller groups of short-finned pilot whales (Globicephala macrorhynchus), bottlenose dolphins (Tursiops truncatus), and false killer whales. We collected photo-ID and UAV drone data to help estimate population size, age composition, and individual body condition. Encountering the group of melon-headed whales on Monday was especially exciting because they travel in large groups with hundreds of animals. Parts of the group were often bow riding, which gave us the opportunity to get underwater footage. We use this data to assess scars over the entire body and observe behaviors not visible from the surface. The groups spent most of the time socializing, which allowed MMRP graduate student Brijonnay Madrigal to collect high quality recordings of their vocalizations with a hydrophone to be used towards her Ph.D. dissertation.
Melon headed whale recordings and spectrogram
Short-finned pilot whales were our most frequently encountered species and their slow movements at the surface allowed us to deploy a CATS tag on a large male. Jens timed our approaches to line up with the animal’s surfacing intervals, and MMRP postdoc Will Gough successfully attached the CATS tag. We used a VHF radio to listen for pings emitted by the tag when it was at the surface, and conducted a focal follow for the afternoon in hopes of retrieving the tag if it came off. The tag ended up staying on far longer than we expected (over 50 hours) and recorded 11 hours of video footage and 41 hours of data! It was one of the first times that a CATS tag had been deployed on a short-finned pilot whale, and the first ever use of a new series of depth-rated CATS tags developed specifically for MMRP and PWF.
CATS suction-cup tag deployed on the left side of a male short-finned pilot whale. Research activities conducted under NMFS/MMPA Research Permits # 21476/21321
Audio recordings taken by the CA TS tag hydrophone on the short-finned pilot whale. The whistles can be seen on the spectrogram at the 2 second and 11.5 second marks.
While we were waiting for the tag to come off the short-finned pilot whale, we received notice from Robin Baird with Cascadia Research Collective that the two false killer whales they satellite tagged on Friday off of Kona were moving past Lānaʻi. False killer whales were the priority species for the trip, and we were able to locate them early in the morning in hopes of getting an opportunity to deploy a CATS tag. However, finding them was the easier task, as you need to wait for the animals to begin milling or bow riding so you can approach and reach them with a 20-foot pole to attach a tag. Unfortunately, the false killer whales spent most of their time traveling quickly past Lānaʻi and the calm waters favorable for tagging. In total, we had three good approaches where the animals came over to bow ride and Will was able to attempt tag deployment. After we had been with the group for a while, we saw them jumping out of the water and milling frantically, chasing a mahi-mahi. We tried a final time to tag them, but the wind and swell picked up significantly and made it even more difficult. Although we could not get a tag to stick this time, we gathered important insights to help guide future tagging attempts.
Second attempt to deploy a CATS tag on a false killer whale. Research activities conducted under NMFS/MMPA Research Permits # 21476/21321
On Friday evening, the tag finally fell off the pilot whale, and the ARGOS satellite positions showed that the tag was 20 miles offshore. We went out as early as possible on Saturday morning to recover the tag, but when we got out to the 20-mile mark, a new ARGOS hit showed that the tag was another 16 miles offshore. The wind and swell were picking up, and it wasn’t safe for us to keep pursuing the tag in our small 26-foot boat. Luckily, we were able to regroup that afternoon and climb aboard the 65-foot Ocean Odyssey PacWhale Eco-Adventures boat that could take us safely out to the tag. Using the ARGOS satellite locations and the VHF radio, Will and MMRP graduate student Gussie Hollers were able to direct Captain Bobby to the tag location. After four hours on the water and more than 50 miles offshore, we homed in on the tag’s signal and MMRP graduate student Liah McPherson spotted it floating in the six-foot swell. Battling the waves crashing against the stern platform, Liah and crew member Agostina reeled the tag in! We were all so relieved and excited to finally have the tag back. We turned back towards Lānaʻi, and began the five hour journey home. The ocean swell made the boat pitch and roll relentlessly, but the sunset and the stars were incredibly beautiful. We made it back to Manele harbor after 10 pm, exhausted but glad to have the tag with all its data back safely.
Video 2 (Tag deployment to recovery montage): The entire process of deploying a CATS tag, from attachment to recovery. Research activities conducted under NMFS/MMPA Research Permits # 21476/21321
During the final two days of our trip, we experienced gale force winds, which made it unsafe for us to be out on the boat. This time was instead spent processing the data we had collected that week. We were especially excited about watching the video from the CATS tag on the pilot whale which included probable nighttime foraging dives. A new feature on the depth-rated tags is a spotlight that triggers in low light conditions in hope of capturing foraging events occurring at night at 800 meters depth. A sneak peak of the videos showed the group of pilot whales socializing at the surface, with one animal appearing to investigate the tag. In total, we surveyed over 500 nautical miles and gathered data over 18 different encounters supporting long-term catalogs, grad students, and the research community. This year’s Lānaʻi field season was very productive, and would not have been possible without funds from the National Marine Fisheries Service, Marine Mammal Research Program, and Pacific Whale Foundation. We are looking forward to analyzing more of the data in the coming weeks and planning the next field effort!