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Fernández Ajó A, Teixeira C, M D de Mello D, Dillon D, Rice JM, Buck CL, Hunt KE, Rogers MC, Torres LG. A longitudinal study of endocrinology and foraging ecology of subadult gray whales prior to death based on baleen analysis. Gen Comp Endocrinol 2024; 352:114492. [PMID: 38479678 DOI: 10.1016/j.ygcen.2024.114492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Revised: 03/04/2024] [Accepted: 03/06/2024] [Indexed: 03/18/2024]
Abstract
Individual-level assessments of wild animal health, vital rates, and foraging ecology are critical for understanding population-wide impacts of exposure to stressors. Large whales face multiple stressors, including, but not limited to, ocean noise, pollution, and ship strikes. Because baleen is a continuously growing keratinized structure, serial extraction, and quantification of hormones and stable isotopes along the length of baleen provide a historical record of whale physiology and foraging ecology. Furthermore, baleen analysis enables the investigation of dead specimens, even decades later, allowing comparisons between historic and modern populations. Here, we examined baleen of five sub-adult gray whales and observed distinct patterns of oscillations in δ15N values along the length of their baleen plates which enabled estimation of baleen growth rates and differentiation of isotopic niche widths of the whales during wintering and summer foraging. In contrast, no regular patterns were apparent in δ13C values. Prolonged elevation of cortisol in four individuals before death indicates that chronic stress may have impacted their health and survival. Triiodothyronine (T3) increased over months in the whales with unknown causes of death, simultaneous with elevations in cortisol, but both hormones remained stable in the one case of acute death attributed to killer whale predation. This parallel elevation of cortisol and T3 challenges the classic understanding of their interaction and might relate to increased energetic demands during exposure to stressors. Reproductive hormone profiles in subadults did not show cyclical trends, suggesting they had not yet reached sexual maturity. This study highlights the potential of baleen analysis to retrospectively assess gray whales' physiological status, exposure to stressors, reproductive status, and foraging ecology in the months or years leading up to their death, which can be a useful tool for conservation diagnostics to mitigate unusual mortality events.
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Affiliation(s)
- Alejandro Fernández Ajó
- Geospatial Ecology of Marine Megafauna Lab, Marine Mammal Institute, Department of Fisheries, Wildlife and Conservation Sciences, Oregon State University, Newport 97365, OR, USA.
| | - Clarissa Teixeira
- Marine Mammal Institute, Department of Fisheries, Wildlife and Conservation Sciences, Oregon State University, Newport 97365, OR, USA
| | - Daniela M D de Mello
- Department of Physiology, Institute of Bioscience, University of São Paulo, São Paulo 05508090, SP, Brazil
| | - Danielle Dillon
- Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011, USA
| | - James M Rice
- Oregon Marine Mammal Stranding Network, Marine Mammal Institute, Oregon State University, Newport 97365, OR, USA
| | - C Loren Buck
- Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011, USA
| | - Kathleen E Hunt
- George Mason University & Smithsonian-Mason School of Conservation, 1500 Remount Rd, Front Royal, VA 22630, USA
| | - Matthew C Rogers
- NOAA, National Marine Fisheries Service, Alaska Fisheries Science Center Auke Bay Laboratories, Juneau, AK 99801, USA
| | - Leigh G Torres
- Geospatial Ecology of Marine Megafauna Lab, Marine Mammal Institute, Department of Fisheries, Wildlife and Conservation Sciences, Oregon State University, Newport 97365, OR, USA
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Fernandez Ajó A, Pirotta E, Bierlich KC, Hildebrand L, Bird CN, Hunt KE, Buck CL, New L, Dillon D, Torres LG. Assessment of a non-invasive approach to pregnancy diagnosis in gray whales through drone-based photogrammetry and faecal hormone analysis. ROYAL SOCIETY OPEN SCIENCE 2023; 10:230452. [PMID: 37476509 PMCID: PMC10354484 DOI: 10.1098/rsos.230452] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Accepted: 06/26/2023] [Indexed: 07/22/2023]
Abstract
Knowledge of baleen whales' reproductive physiology is limited and requires long-term individual-based studies and innovative tools. We used 6 years of individual-level data on the Pacific Coast Feeding Group gray whales to evaluate the utility of faecal progesterone immunoassays and drone-based photogrammetry for pregnancy diagnosis. We explored the variability in faecal progesterone metabolites and body morphology relative to observed reproductive status and estimated the pregnancy probability for mature females of unknown reproductive status using normal mixture models. Individual females had higher faecal progesterone concentrations when pregnant than when presumed non-pregnant. Yet, at the population level, high overlap and variability in progesterone metabolite concentrations occurred between pregnant and non-pregnant groups, limiting this metric for accurate pregnancy diagnosis in gray whales. Alternatively, body width at 50% of the total body length (W50) correctly discriminated pregnant from non-pregnant females at individual and population levels, with high accuracy. Application of the model using W50 metric to mature females of unknown pregnancy status identified eight additional pregnancies with high confidence. Our findings highlight the utility of drone-based photogrammetry to non-invasively diagnose pregnancy in this group of gray whales, and the potential for improved data on reproductive rates for population management of baleen whales generally.
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Affiliation(s)
- A. Fernandez Ajó
- Geospatial Ecology of Marine Megafauna Lab, Marine Mammal Institute, Department of Fisheries, Wildlife and Conservation Sciences, Oregon State University, Newport 97365, OR, USA
| | - E. Pirotta
- Centre for Research into Ecological and Environmental Modelling, University of St Andrews, St Andrews, UK
| | - K. C. Bierlich
- Geospatial Ecology of Marine Megafauna Lab, Marine Mammal Institute, Department of Fisheries, Wildlife and Conservation Sciences, Oregon State University, Newport 97365, OR, USA
| | - L. Hildebrand
- Geospatial Ecology of Marine Megafauna Lab, Marine Mammal Institute, Department of Fisheries, Wildlife and Conservation Sciences, Oregon State University, Newport 97365, OR, USA
| | - C. N. Bird
- Geospatial Ecology of Marine Megafauna Lab, Marine Mammal Institute, Department of Fisheries, Wildlife and Conservation Sciences, Oregon State University, Newport 97365, OR, USA
| | - K. E. Hunt
- Smithsonian-Mason School of Conservation, Department of Biology, George Mason University, 1500 Remount Road, Front Royal, VA 22630, USA
| | - C. L. Buck
- Department of Biological Sciences, Northern Arizona University, 617 South Beaver Street, Flagstaff, AZ 86011, USA
| | - L. New
- Ursinus College, 601 East Main Street, Collegeville, PA 19426, USA
| | - D. Dillon
- Department of Biological Sciences, Northern Arizona University, 617 South Beaver Street, Flagstaff, AZ 86011, USA
| | - L. G. Torres
- Geospatial Ecology of Marine Megafauna Lab, Marine Mammal Institute, Department of Fisheries, Wildlife and Conservation Sciences, Oregon State University, Newport 97365, OR, USA
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Hunt KE, Buck CL, Ferguson SH, Fernández Ajo A, Heide-Jørgensen MP, Matthews CJD. Male Bowhead Whale Reproductive Histories Inferred from Baleen Testosterone and Stable Isotopes. Integr Org Biol 2022; 4:obac014. [PMID: 35617113 PMCID: PMC9125798 DOI: 10.1093/iob/obac014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Synopsis
Male mammals of seasonally reproducing species typically have annual testosterone (T) cycles, with T usually peaking during the breeding season, but occurrence of such cycles in male mysticete whales has been difficult to confirm. Baleen, a keratinized filter-feeding apparatus of mysticetes, incorporates hormones as it grows, such that a single baleen plate can record years of endocrine history with sufficient temporal resolution to discern seasonal patterns. We analyzed patterns of T every 2 cm across the full length of baleen plates from nine male bowhead whales (Balaena mysticetus) to investigate occurrence and regularity of T cycles and potential inferences about timing of breeding season, sexual maturation, and reproductive senescence. Baleen specimens ranged from 181–330 cm in length, representing an estimated 11 years (smallest whale) to 22 years (largest whale) of continuous baleen growth, as indicated by annual cycles in stable isotopes. All baleen specimens contained regularly spaced areas of high T content (T peaks) confirmed by time series analysis to be cyclic, with periods matching annual stable isotope cycles of the same individuals. In 8 of the 9 whales, T peaks preceded putative summer isotope peaks by a mean of 2.8 months, suggesting a mating season in late winter / early spring. The only exception to this pattern was the smallest and youngest male, which had T peaks synchronous with isotope peaks. This smallest, youngest whale also did not have T peaks in the first half of the plate, suggesting initiation of T cycling during the period of baleen growth. Linear mixed effect models suggest that whale age influences T concentrations, with the two largest and oldest males exhibiting a dramatic decline in T peak concentration across the period of baleen growth. Overall, these patterns are consistent with onset of sexual maturity in younger males and possible reproductive senescence in older males. We conclude that adult male bowheads undergo annual T cycles, and that analyses of T in baleen may enable investigation of reproductive seasonality, timing of the breeding season, and life history of male whales.
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Affiliation(s)
- Kathleen E Hunt
- Smithsonian-Mason School of Conservation & Department of Biology, George Mason University, 1500 Remount Rd, Front Royal, VA 22630, USA
| | - C Loren Buck
- Department of Biological Sciences, Northern Arizona University, 617 S. Beaver St., Flagstaff, AZ 86011, USA
| | - Steven H Ferguson
- Fisheries and Oceans Canada, Arctic Aquatic Research Division, 501 University Crescent, Winnipeg, MB R3T 2N6, Canada
| | - Alejandro Fernández Ajo
- Marine Mammal Institute, Fisheries and Wildlife Department, Oregon State University, Newport, OR 97365, USA
| | | | - Cory J D Matthews
- Fisheries and Oceans Canada, Arctic Aquatic Research Division, 501 University Crescent, Winnipeg, MB R3T 2N6, Canada
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