A total of 48 eye globes were collected and analyzed to estimate ages of bowhead whales using the aspartic acid racemization technique. In this technique, age is estimated based on intrinsic changes in the D and L enantiomeric isomeric forms of aspartic acid in the eye lens nucleus. Age estimates were successful for 42 animals. Racemization rate (kAsp) for aspartic acid was based on data from earlier studies of humans and fin whales; the estimate used was 1.18 10-3/year. The D/L ratio at birth ((D/L)0) was estimated using animals less than or equal to 2 years of age (n = 8), since variability in the D/L measurements is large enough that differences among ages in this range are unmeasurable. The (D/L)0 estimate was 0.0285. Variance of the age estimates was obtained using the delta method. Based on these data, growth appears faster for females than males, and age at sexual maturity (age at length 12-13 m for males and 13-13.5 m for females) occurs at around 25 years of age. Growth slows markedly for both sexes at roughly 40-50 years of age. Four individuals (all males) exceed 100 years of age. Standard error increased with estimated age, but the age estimates had lower coefficients of variation for older animals. Recoveries of traditional whale-hunting tools from five recently harvested whales also suggest life-spans in excess of 100 years of age in some cases.

SummaryThe bowhead whale (Balaena mysticetus) is estimated to live over 200 years and is possibly the longest-living mammal. These animals should possess protective molecular adaptations relevant to age-related diseases, particularly cancer. Here, we report the sequencing and comparative analysis of the bowhead whale genome and two transcriptomes from different populations. Our analysis identifies genes under positive selection and bowhead-specific mutations in genes linked to cancer and aging. In addition, we identify gene gain and loss involving genes associated with DNA repair, cell-cycle regulation, cancer, and aging. Our results expand our understanding of the evolution of mammalian longevity and suggest possible players involved in adaptive genetic changes conferring cancer resistance. We also found potentially relevant changes in genes related to additional processes, including thermoregulation, sensory perception, dietary adaptations, and immune response. Our data are made available online (http://www.bowhead-whale.org) to facilitate research in this long-lived species.

The recent evolutionary history, population structure and movement patterns of beluga whales in the western Nearctic were inferred from an analysis of mitochondrial DNA control region sequence variation of 324 whales from 32 locations representing five summer concentration areas in Alaska and north‐west Canada. Phylogenetic relationships among haplotypes were inferred from parsimonious networks, and genetic subdivision was examined using haplotypic frequency‐based indices and an analysis of variance method modified for use with interhaplotypic distance data. MtDNA relationships were characterized by a series of star‐like phylogenies which, when viewed in conjunction with information on haplotype frequency and distribution, suggested a rapid radiation of beluga whales into the western Nearctic following the Pleistocene, and an early divergence of the Beaufort Sea from the Chukchi and Bering Seas subpopulations. Overall nucleotide diversity was low (0.51%) yet all major summering concentrations were significantly differentiated (ΦST= 0.33) from one another. Stratification of samples by gender and age from the three northernmost subpopulations suggested that female cohorts from neighbouring subpopulations were more differentiated than males. Further stratification of adult animals by age revealed that older adults were substantially less subdivided among locations than younger adults, particularly for males, suggesting that dispersal, although limited, is biased toward older adult males. Overall, the patterns of mtDNA variation in beluga whales indicated that the summering concentrations are demographically, if not phyletically distinct. Population structure appears to be maintained primarily by natal homing behaviour, while asymmetries in dispersal may be associated with the type of mating system.

No abstract

No abstract

Beluga whales (Delphinapterus leucas) congregate in nearshore waters of the eastern Chukchi Sea, especially in Kotzebue Sound and Kasegaluk Lagoon, in June and July. Where they travel after they leave this area was unknown before this study. We live-captured five belugas in Kasegaluk Lagoon and attached satellite-linked depth recorders to them. The belugas, caught between 26 June and 1 July 1998, were all males, ranging in length from 398 to 440 cm. A 310 cm gray beluga accompanied the smallest male. Two tags transmitted for only about two weeks, during which time one animal remained in the vicinity of Icy Cape, 80 km north of the capture site, and the other traveled to Point Barrow, about 300 km north. The other three tags operated for 60-104 days, and those belugas traveled more than 2000 km, reaching 80˚ N and 133˚ W, almost 1100 km north of the Alaska coast. This journey required them to move through 700 km of more than 90% ice cover. Two of the whales then moved southward into the Beaufort Sea north and east of Point Barrow. Two whales later moved to an area north of the Mackenzie River delta, where they spent 2-3 weeks before once again heading southwest towards Barrow.

The 2001 survey of western Arctic (Bering, Chukchi, and Beaufort seas) bowhead whales was conducted from 5 April to 7 June near Barrow, Alaska. Visual observers recorded a total of 3,295 “new” (not seen before) and 532 “conditional” (possibly seen before) whales in 1,130 h of watch effort, including 121 new calves (3.7% of the new whales). Concurrent with the visual survey, passive acoustic surveillance was conducted almost continuously from 16 April to 31 May, resulting in 27,023 locations of vocalizing bowhead whales. The estimated number of whales within 4 km of the perch (N4) was 7,025 (SE = 1,068). The estimated proportion of the whales within 4 km of the perch (P4) was 0.862 (SE = 0.044, computed by a moving blocks bootstrap). Combining these, the abundance estimate (N4/P4) for 2001 is 10,470 (SE = 1, 351) with a 95% confidence interval of 8, 100–13, 500. The estimated annual rate of increase (ROI) of the population from 1978 to 2001 is 3.4% (95% CI 1.7%‐5%). Reports from hunters and results of an aerial survey in June 2001 indicate whales continued to pass Barrow after the survey had ended. In 2001 51% (572 h) of the watch was scored as occurring during “fair‐excellent” visibility conditions, somewhat lower than the average for all surveys since 1978. Sea ice in the leads and fog were the principle environmental factors affecting visibility for all years. The estimated rate of increase and the fact that the number of calves counted in 2001 is the highest ever recorded suggest a steady recovery of this population. Other populations of large balaenids, notably the North Atlantic right whale, have failed to recover despite 70 yr of protection. The recovery of the howhead whale is likely attributable to low anthropogenic mortality, a relatively pristine habitat, and a well‐managed subsistence hunt. Nonetheless, offshore oil development, increasing shipping traffic, changes in the Bering Sea ecosystem, sea ice retreat, and possibly killer whale predation within its range could impact this bowhead population and should be carefully monitored.

Baleen samples from sixteen bowhead whales contained measurable cortisol and progesterone, and both hormones demonstrated significant correlations with sex, age class and reproductive state. Analysis of hormones in baleen shows promise as a novel tool for retrospective analysis of stress and reproductive physiology of large mysticete whales.