Abstract

Reconstructing lifetime profiles that may reveal possible ecological patterns and drivers are of considerable interest to biologists and managers who seek to understand past and possible future trends with aims of reducing the loss of biodiversity.¹ Unfortunately, reconstructing complete lifetime patterns is elusive for most, if not all, long-lived terrestrial or aquatic vertebrate species. Because of costs and logistics, biologists typically incorporate sampling strategies that rely on relatively few temporal and spatial “snap-shots” covering a pre-determined life history phase. Baleen whales (Mysticeti) are large, lipophilic, long-lived mammals, with estimates approximating 200 years, which are suitable ecosystem models because of their ecological diversity and ubiquitous distribution and as such are proxies in studies focusing on natural or anthropogenic stressors.² Reconstructing lifetime chemical profiles in these large aquatic species was unsolved until recently when whale earplugs were determined to sequester chemicals in discrete lamina throughout the life of the animal.³ Historically used as a proxy for aging in Balaenopterids, earplugs consist typically of semiannual bands of alternating dark and light laminae (growth layer; GL) that remain mostly undisturbed during the lifetime of the animal.⁴ First described by Lillie,⁵ an earplug is a two-part keratin and lipid structure isolated within the auditory meatus of these 15 whale species⁶. Recent lifetime cortisol profiles in 20 individual animals (N=20; 11 females, 9 males) reveal an interaction between sex and age, indicating there are significant timing (age) differences in the levels of cortisol between the sexes. Progesterone analysis on the same earplugs reveals species-specific pregnancy intervals and 6-month increase in overall inter-pregnancy intervals when comparing pre- with post-1972 (Marine Mammal Protection Act). Stable isotope values indicate demographic, as well as sex differences, in trophic feeding. These data may also be indicative of changes in ocean productivity. Assessing lifetime chemical profiles reconstructed from earplugs of baleen whales will allow tracking of long-term trends in health, reproduction, stress, and feeding ecology, as well as comparison to historical populations within and between ocean basins. We consider this analysis a novel method to assess the potential impact of climate change and anthropogenic activity on marine ecosystems.

Acknowledgements

The authors acknowledge the dedicated work and contributions of F. Gulland, C. Gabriele, R. Andrews, K. Burek-Huntington, C. Potter, R. Sabin, D. Crain, F. Mansouri, Z. Winfield, as well as many others involved in the extraction and analysis of earplugs.

* Presenting author

Literature Cited

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