No abstract

We compared known calving events to longitudinal baleen progesterone profiles from baleen plates of two stranded adult female North Atlantic right whales. Reproductive history of the previous ten years was recorded accurately in baleen, with pronounced elevations in progesterone in regions of baleen grown during known pregnancies.

Progesterone, testosterone, 17β-estradiol, cortisol, corticosterone, aldosterone, thyroxine and tri-iodothyronine are detectable in baleen of eight whale species. The presence of a broad array of hormones in baleen of multiple species indicates that baleen hormone analysis may be widely applicable for studies of reproduction, stress and metabolism of the large whales.

Research into stress physiology of mysticete whales has been hampered by difficulty in obtaining repeated physiological samples from individuals over time. We investigated whether multi-year longitudinal records of glucocorticoids can be reconstructed from serial sampling along full-length baleen plates (representing ~10 years of baleen growth), using baleen recovered from two female North Atlantic right whales (Eubalaena glacialis) of known reproductive history. Cortisol and corticosterone were quantified with immunoassay of subsamples taken every 4 cm (representing ~60 d time intervals) along a full-length baleen plate from each female.In both whales, corticosterone was significantly elevated during known pregnancies (inferred from calf sightings and necropsy data) as compared to intercalving intervals; cortisol was significantly elevated during pregnancies in one female but not the other. Within intercalving intervals, corticosterone was significantly elevated during the first year (lactation year) and/or the second year (post-lactation year) as compared to later years of the intercalving interval, while cortisol showed more variable patterns. Cortisol occasionally showed brief high elevations ("spikes") not paralleled by corticosterone, suggesting that the two glucocorticoids might be differentially responsive to certain stressors. Generally, immunoreactive corticosterone was present in higher concentration in baleen than immunoreactive cortisol; corticosterone:cortisol ratio was usually >4 and was highly variable in both individuals. Further investigation of baleen cortisol and corticosterone profiles could prove fruitful for elucidating long-term, multi-year patterns in stress physiology of large whales, determined retrospectively from stranded or archived specimens. Hunt et al. -Baleen Hormones 3 HIGHLIGHTS• Immunoreactive cortisol and corticosterone are detectable in whale baleen• Single baleen plates contain multi-year longitudinal time series of glucocorticoids• Glucocorticoids tend to be elevated in baleen growth coincident with pregnancy• Corticosterone was present in baleen at much greater concentration than cortisol

North Atlantic right whales (Eubalaena glacialis) are highly endangered and frequently exposed to a myriad of human activities and stressors in their industrialized habitat. Entanglements in fixed fishing gear represent a particularly pervasive and often drawn-out source of anthropogenic morbidity and mortality to the species. To better understand both the physiological response to entanglement, and to determine fundamental parameters such as acquisition, duration, and severity of entanglement, we measured a suite of biogeochemical markers in the baleen of an adult female that died from a well-documented chronic entanglement in 2005 (whale Eg2301). Steroid hormones (cortisol, corticosterone, estradiol, and progesterone), thyroid hormones (triiodothyronine (T 3) and thyroxine (T 4)), and stable isotopes (δ 13 C and δ 15 N) were all measured in a longitudinally sampled baleen plate. This yielded an 8-year profile of foraging and migration behavior, stress response, and reproduction. Stable isotopes cycled in annual patterns that reflect the animal's north-south migration behavior and seasonally abundant zooplankton diet. A progesterone peak, lasting approximately 23 months, was associated with the single known calving event (in 2002) for this female. Estradiol, cortisol, corticosterone, T 3 , and T 4 were also elevated, although variably so, during the progesterone peak. This whale was initially sighted with a fishing gear entanglement in September 2004, but the hormone panel suggests that the animal first interacted with the gear as early as June 2004. Elevated δ 15 N, T 3 , and T 4 indicate that Eg2301 potentially experienced increased energy expenditure, significant lipid catabolism, and thermal stress approximately 3 months before the initial sighting with fishing gear. All hormones in the panel (except cortisol) were elevated above baseline by September 2004. This novel study illustrates the value of using baleen to reconstruct recent temporal profiles and as a comparative matrix in which key physiological indicators of individual whales can be used to understand the impacts of anthropogenic activity on threatened whale populations.

Baleen from three adult male whales (North Atlantic right, bowhead and blue) contains regularly spaced areas of high testosterone content suggestive of annual testosterone cycles. Patterns in glucocorticoids (cortisol and corticosterone) show potential relationships with breeding-related stress as well as with entanglement in fishing gear and possible disease episodes.

Diel vertical migration (DVM) by herbivorous copepods likely has a profound effect on the behavior and ecology of copepod predators. We characterized the DVM behavior of late-stage Calanus finmarchicus in the southwestern Gulf of Maine during the spring seasons of 2005 to 2007, and investigated the influence of this behavior on the occurrence of zooplanktivorous baleen whales. On 5 occasions, we occupied an oceanographic station for 1 to 2 d and conducted (1) a half-hourly census of whales and (2) a half-hourly cast with an instrument package measuring temperature, salinity, chlorophyll fluorescence, and copepod abundance. We observed significant variability in DVM behavior both within and among years that was unrelated to stratification or chlorophyll concentration. Instead, DVM appeared to be influenced by the vertical distribution of phytoplankton, the presence of visual predators (sand lance Ammodytes spp.), copepod developmental stage, and the feeding history of individual copepods. Migrating copepods had oil sacs that were 44% larger than non-migrating copepods at the surface after accounting for developmental stage, which suggests that well-fed copepods are more likely to vertically migrate. While the occurrence of North Atlantic right whales Eubalaena glacialis was unrelated to variability in the migration behavior of C. finmarchicus, sei whales Balaenoptera borealis were significantly less abundant during times of strong DVM behavior. We speculate that right whales do not compete directly with sand lance and herring for C. finmarchicus, but by inducing DVM behavior, these fish are likely influencing the distribution and abundance of sei whales in the southwestern Gulf of Maine.

Endangered North Atlantic right whales Eubalaena glacialis suffer from unacceptably high rates of ship strikes and fishing gear entanglements, but little is known of the role that diving and foraging behavior plays in mediating human-caused mortality. We conducted a study of right whale foraging ecology by attaching tags to whales for short periods of time (hours), tracking their movements during daytime, and repeatedly sampling oceanographic conditions and prey distribution along the whales' tracks. Right whales were tagged from late winter to late fall in 6 regions of the Gulf of Maine and southwestern Scotian Shelf from 2000 to 2010. The diving behavior of the tagged whales was governed by the vertical distribution of their primary prey, the copepod Calanus finmarchicus. On average, right whales tagged during spring spent 72% of their time in the upper 10 m (within the draft of most large commercial vessels), indicating the need for expanded ship speed restrictions in western Gulf of Maine springtime habitats. One out of every 4 whales dove to within 5 m of the sea floor during the short time they were tagged, spending as much as 45% of their total tagged time in this depth stratum. Right whales dove to the sea floor in each habitat studied except for one (where only 1 whale was tagged). This relatively high incidence of near-bottom diving raises serious concerns about the continued use of floating ground lines in pot and trap gear in coastal Maine and Canadian waters.