Humpback whale #441 (Festus): Life, death, necropsy, and research findings

Christine M. Gabriele; Louise F. Taylor; Kathy Burek Huntington; C. Loren Buck; Kathleen E. Hunt; Kathi A. Lefebvre; Christina Lockyer; Carley Lowe; John R. Moran; Amanda Murphy; Matthew C. Rogers; Stephen J. Trumble; Stephen Raverty

doi:10.36967/nrr-2285345

In late June 2016, a mature male humpback whale was found dead in Glacier Bay National Park waters just outside the mouth of Glacier Bay, Alaska, coincident with an elevated rate of whale deaths attributed to the “Blob” marine heatwave that dominated the Northeast Pacific Ocean from late 2013–2016. This whale, Southeast Alaska catalog #441 (nicknamed Festus) had been documented over a period of 45 years in Alaska and Hawaii. Sightings of the whale over many years documented a large swelling on the whale’s left flank, likely as a result of having been satellite-tagged in 1999. At the necropsy, the whale had no visible external injuries but was emaciated and his skin was in poor condition and heavily infested with cyamids (whale lice). The whale’s internal organs were moderately decomposed; thus, only limited sampling was possible. Histological analysis of tissue samples revealed a variety of health conditions that we describe in this report and its Appendices. Counts of annual growth layers in the ear plug collected at the necropsy indicate that the whale was about 66–68 years old, indicating that he was born around 1950. Poor body condition and low oil content in the blubber suggest nutritional stress as the primary proximate cause of death. Multiple infections were detected in tissue samples: Toxoplasma gondii and Sarcocystis spp. in the heart, and bacteria, yeast and diatom infections in the lymph nodes. The detection of both domoic acid and saxitoxin in the feces confirms that harmful algal bloom toxins (HABs) were present in the environment, but without clinical signs of neurotoxicity, toxin values alone are not sufficient to determine if toxin exposures would cause health impacts. A five-year stable-isotope (SI) profile in the baleen showing a continued rise of 15N in the final year of life suggests extreme nutritional stress that is consistent with results from the baleen of other humpback whales that died during the marine heatwave (Rogers et al. in review). A five-year endocrine profile from the whale’s baleen shows a long period of elevated levels of the adrenal stress hormones cortisol and corticosterone, and low levels of testosterone until a large spike prior to death, all of which are consistent with poor health. Analysis of the whale’s ear plug provided lifetime profiles including bulk C and N stable isotopes as well as testosterone and cortisol. The lifetime SI profile revealed relatively stable periods prior to 1970 and from 1980 until death. Variability in bulk C and N signatures could indicate migratory movements and/or trophic shifts whereas the decline in bulk signatures between 1970 and 1980 may represent behavioral (movements), trophic (prey), or anthropogenic inputs (fossil fuel carbon in the ocean). The ear plug lifetime hormone reconstruction revealed typical male mammalian peaks early in life with maximum values at approximately 12 years (i.e. probable puberty). An increase in stress response (cortisol concentrations) in 1999 may be associated with possible negative response to satellite tag attachment, validated with sighting data. Months after the necropsy, thorough examination of the whale’s bones on the beach revealed two unusual bone pathologies; 1) severe infective spondylo-osteomyelitis and ruptured facets in nine caudal vertebrae and 2) severe ankylosing spondylitis in three thoracic vertebrae. Given the osteological response near the tag site, there is a high probability that microbes introduced during or after the tagging event resulted in the localized bone infection. Moreover, these bone pathologies likely limited the whale’s mobility in ways that contributed to the whale’s degenerating health. This collaborative work represents a remarkably thorough workup of a well-documented individual whale. Validating physiological profiles with life history and pathology results provided powerful insights on the life and death of this individual whale and suggests two significant recommendations.

Humpback whale #441 (Festus): Life, death, necropsy, and research findings

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