Cetacean Field Work Update, Summer 2023

This summer 2023, Costa Lab graduate students Haley Robb, Theresa Tatom-Naecker, and Florencia Vilches received UC Santa Cruz EEB Department summer funds to support their field research efforts. Read more about their adventures below!

Sampling humpback whale blubber and hormones in Juneau, Alaska – Haley Robb

This summer, I traveled to Juneau, Alaska, to collect data for my dissertation. My fieldwork primarily takes place in Maui, where I study the reproductive physiology and behavior of humpback whales during their breeding season. I use steroid hormones as biomarkers for reproductive state and health, which are stored in the whale’s blubber layer. I can access these hormones by taking a remote biopsy sample of the blubber using a dart with a modified hollow tip. My research goals are to understand how reproductive and stress hormones cycle through male and female humpbacks over the course of the breeding season. But first, I need to know what their baseline levels are before they arrive in Hawaii, which brought me to their feeding grounds in Alaska!

A significant number of Juneau’s whales use Hawaii as their breeding ground, making Juneau an excellent comparison site to my field site in Maui. Not to mention the humpbacks in Juneau are well-known by local researchers and whale watchers, and there is extensive sighting history for the individuals that feed there, including calving history. I spent three incredible days on the water and collected 12 blubber samples. We had unusually sunny, calm weather for the first couple of days and there was no shortage of wildlife to be found.  Although I was in search of humpbacks, I came across pods of orcas, sea otters, sea lions, Dall’s porpoises, and eagles, and even saw a few bears along the shoreline. But the highlight of my trip by far was watching the humpbacks bubble net feed. Needless to say, I am sold on Alaska, and I have tentative plans to return next summer. In the meantime, I have returned to Maui, where I will welcome the whales back from their feeding season. At the end of my Hawaii field season in March, I will return to Santa Cruz with my samples from Alaska and Hawaii to analyze in our lab.

Bottlenose dolphin health assessments in Sarasota, Florida – Theresa Tatom-Naecker

This past May, I traveled to Sarasota, Florida to take part in the Sarasota Dolphin Research Program’s regular field work effort, referred to as the “health assessments”. During health assessments, the SDRP, which is directed by my co-advisor Randy Wells, collaborates with 100+ scientists and veterinarians from around the world to temporarily catch free-ranging dolphins (Tursiops truncatus) and collect health information, including blood, urine, and blubber samples. This was my third year working on the sample processing boat, where I was in charge of blood-based analyses, including spinning, subsampling, separation of plasma, and labeling and organization, for approximately 30 research projects.

Despite difficult weather and water conditions and large numbers of manatees and sharks, we caught and sampled six dolphins, three females and three males. The minimally invasive blubber biopsies collected from these dolphins are the last samples for my third dissertation chapter, which will use quantitative fatty acid signature analysis (QFASA) to understand how dolphin diet is impacted by harmful algal bloom (HAB) disturbances that decrease prey fish abundance. QFASA estimates diet by minimizing the statistical divergence between the fatty acid signature (FAS) of a predator’s blubber and model diets created from prey FASs, using the fact that prey FAs are deposited directly in predator blubber. Sarasota has experienced several severe HABs over the last 6 months, and prey fish monitoring shows continued low abundances. Thus, dolphins sampled during the assessment are considered HAB-impacted. The samples collected will supplement samples collected during HAB and non-HAB periods in 2019-2022 (n = 54 non-HAB and n = 33 HAB) which have already been analyzed. I am currently completing the lab analyses of these new samples, which includes subsampling the tissues, extracting lipids using a Soxtec apparatus, derivatizing fatty acid methyl esters, and determining the quantities of fatty acids in the samples using gas chromatography with flame ionization detection. I conduct the first steps – subsampling and lipid extraction – in the Costa lab at UCSC, and then send the samples to collaborators at Dalhousie University in Halifax, Nova Scotia for the final steps. Understanding how bottlenose dolphins respond to HABs has implications for understanding dolphin vulnerability and response to disturbances worldwide, as HABs serve as proxies for other disturbances, such as commercial and recreational fisheries and changing climate conditions, that are increasingly impacting dolphin populations.

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