Characterization of 25 microsatellite loci in bowhead whales (Balaena mysticetus)

Bowhead whales (Balaena mysticetus) experienced a severe demographic population bottleneck caused by commercial whaling that ceased in 1914. Aboriginal subsistence whale harvests have continued and are managed by the International Whaling Commission. In an effort to provide management advice for bowhead whales, 25 microsatellite loci were isolated from genomic DNA libraries. This panel of markers will be utilized to analyse stock structure hypotheses of current bowhead whale populations.     

Behaviour and kinematics of continuous ram filtration in bowhead whales (Balaena mysticetus)

Balaenid whales perform long breath-hold foraging dives despite a high drag from their ram filtration of zooplankton. To maximize the volume of prey acquired in a dive with limited oxygen supplies, balaenids must either filter feed only occasionally when prey density is particularly high, or they must swim at slow speeds while filtering to reduce drag and oxygen consumption. Using digital tags with three-axis accelerometers, we studied bowhead whales feeding off West Greenland and present here, to our knowledge, the first detailed data on the kinematics and swimming behaviour of a balaenid whale filter feeding at depth. Bowhead whales employ a continuous fluking gait throughout the bottom phase of foraging dives, moving at very slow speeds (less than 1 m s⁻¹), allowing them to filter feed continuously at depth. Despite the slow speeds, the large mouth aperture provides a water filtration rate of approximately 3 m³ s⁻¹, amounting to some 2000 tonnes of water and prey filtered per dive. We conclude that a food niche of dense, slow-moving zooplankton prey has led balaenids to evolve locomotor and filtering systems adapted to work against a high drag at swimming speeds of less than 0.07 body length s⁻¹ using a continuous fluking gait very different from that of nekton-feeding, aquatic predators.     

Microflora associated with the skin of the bowhead whale (Balaena mysticetus)

A study of the microbiological flora isolated from cultures of normal and lesional skin tissue samples collected from 19 bowhead whales (Balaena mysticetus) over a 4 yr period is presented. These cultures were obtained from 30 tissue samples (17 normal, 13 lesion) and 248 swab samples (157 normal, 91 lesion). Seven hundred-thirty bacterial and yeast isolations were made (285 normal, 445 lesion). Distribution revealed that 56% of the gram positive bacterial isolates, 75% of the gram negative bacterial isolates and 64% of the yeast isolates recovered were associated with lesional skin. It was found that 80% of one group of Corynebacterium sp. isolates, 90% of the Acinetobacter sp. isolates and 94% of the Moraxella sp. isolates were associated with lesional skin. Although the primary yeasts recovered were Candida spp., they were found on both normal and lesional skin. Enzymatic assays of isolates from normal and lesional skin demonstrated production of enzymes capable of causing necrosis. The majority of the microorganisms recovered were facultative anaerobes and many of them could be considered potential pathogens of mammalian hosts.     

Stomach contents of bowhead whales (Balaena mysticetus) from four locations in the Canadian Arctic

The stomach contents of four bowhead whales (Balaena mysticetus) harvested between 1994 and 2008 from the Canadian Arctic were examined to assess diet composition. Three samples were collected from bowhead whales of the Eastern Canada–West Greenland (EC–WG) population and represent, according to our knowledge, the first diet analysis from this bowhead whale stock. We also examined the stomach content of one bowhead whale from the Bering-Chukchi-Beaufort (BCB) population hunted in 1996. All four whales had food in their stomachs and their diet varied from exclusively pelagic (BCB whale), with Limnocalanus macrurus being the main prey, to epibenthic and benthic (EC–WG) with Mysis oculata playing an important role. These results indicate broad foraging spectrum of the bowhead whales and add to a basic knowledge of their diet.     

Presence and behavior of bowhead whales (Balaena mysticetus) in the Alaskan Beaufort Sea in July 2011

The Western Arctic bowhead whale (Balaena mysticetus) is highly adapted to sea ice and annually migrates through the Bering, Chukchi, and Beaufort seas. While the overall distribution and seasonal movements of bowhead whales are mostly understood, information about their distribution in the Alaskan Beaufort Sea in early to mid-summer has not been well documented. In July 2011, we conducted an exploratory flight in the Alaskan Beaufort Sea, north of Camden Bay (71°N 144°W), near the location of a single satellite-tagged bowhead whale. Eighteen bowhead whales were observed, and behavior consistent with feeding was documented. To our knowledge, this is the first documentation of behavior consistent with feeding north of Camden Bay in mid-July. Few studies have focused on bowhead whale distribution in the Alaskan Beaufort Sea in early to mid-summer, and no long-term, region-wide surveys have been conducted during summer. Bowhead whales are already exposed to anthropogenic disturbance in the Canadian Beaufort Sea in summer, the Alaskan Beaufort Sea in fall, and the Chukchi and Bering seas from fall through spring. The presence of bowhead whale aggregations in the Alaskan Beaufort Sea in summer should be considered when assessing the cumulative effects of human-related activities.     

Fractured mandible and associated oral lesions in a subsistence-harvested bowhead whale (Balaena mysticetus)

A fractured right mandible with midlength nonunion and oral lesions were noted in a subsistence-harvested female bowhead whale (Balaena mysticetus) near Wainwright, Alaska (USA). The cause of the fracture was not apparent. The fracture resulted in misalignment of the mandible. The abnormal mobility at the fracture site probably caused irregular baleen stowage within the oral cavity, leading to breakage of many baleen plates and extensive ulceration of the tongue and lips. Good body condition suggested the fracture was not debilitating.     

Survival of bowhead whales,Balaena mysticetus,estimated from 1981-1998 photoidentification data

Annual survival probability of bowhead whales, Balaena mysticetus, was estimated using both Bayesian and maximum likelihood implementations of Cormack and Jolly-Seber (JS) models for capture-recapture estimation in open populations and reduced-parameter generalizations of these models. Aerial photographs of naturally marked bowheads collected between 1981 and 1998 provided the data. The marked whales first photographed in a particular year provided the initial 'capture' and 'release' of those marked whales and photographs in subsequent years the 'recaptures'. The Cormack model, often called the Cormack-Jolly-Seber (CJS) model, and the program MARK were used to identify the model with a single survival and time-varying capture probabilities as the most appropriate for these data. When survival was constrained to be one or less, the maximum likelihood estimate computed by MARK was one, invalidating confidence interval computations based on the asymptotic standard error or profile likelihood. A Bayesian Markov chain Monte Carlo (MCMC) implementation of the model was used to produce a posterior distribution for annual survival. The corresponding reduced-parameter JS model was also fit via MCMC because it is the more appropriate of the two models for these photoidentification data. Because the CJS model ignores much of the information on capture probabilities provided by the data, its results are less precise and more sensitive to the prior distributions used than results from the JS model. With priors for annual survival and capture probabilities uniform from 0 to 1, the posterior mean for bowhead survival rate from the JS model is 0.984, and 95% of the posterior probability lies between 0.948 and 1. This high estimated survival rate is consistent with other bowhead life history data.     

Olfaction and brain size in the bowhead whale (Balaena mysticetus)

Although there are several isolated references to the olfactory anatomy of mysticetes, it is usually thought that olfaction is rudimentary in this group. We investigated the olfactory anatomy of bowhead whales and found that these whales have a cribriform plate and small, but histologically complex olfactory bulb. The olfactory bulb makes up approximately 0.13% of brain weight, unlike odontocetes where this structure is absent. We also determined that 51% of olfactory receptor genes were intact, unlike odontocetes, where this number is less than 25%. This suggests that bowheads have a sense of smell, and we speculate that they may use this to find aggregations of krill on which they feed.     

Occurrence of killer whale Orcinus orca rake marks on Eastern Canada-West Greenland bowhead whales Balaena mysticetus

Killer whales (Orcinus orca) are increasing in occurrence and residence time in the eastern Canadian Arctic (ECA) in part due to a decrease in sea ice associated with global climate change. Killer whales prey on bowhead whales (Balaena mysticetus) of the Eastern Canada-West Greenland (EC-WG) population, but their patterns of predation pressure and effect on the EC-WG population’s ability to recover from historical whaling remain unknown. We analyzed photographs of individual bowhead whale flukes from five regions within the EC-WG population’s geographic range (Cumberland Sound, Foxe Basin, Isabella Bay, Repulse Bay and Disko Bay), taken during 1986 and from 2007 to 2012, to estimate the occurrence of rake marks (parallel scars caused by killer whale teeth). Of 598 identified whales, 10.2 % bore rake marks from killer whales. A higher occurrence of rake marks was found in Repulse and Disko Bays, where primarily adult bowhead whales occur seasonally, than in Foxe Basin, where juveniles and females with calves occur. Older bowheads, which have had greater exposure time to killer whales due to their age, had higher occurrences of rake marks than juveniles and calves, which may indicate that younger whales do not survive killer whale attacks. A high proportion of adult females also had rake marks, perhaps due to protecting their calves from killer whale predation. In order to quantify the effect of killer whales on EC-WG population recovery, further research is needed on the relationship between the occurrence of rake marks and bowhead adult, calf, and juvenile mortality in the ECA, as well as more information about Arctic killer whale ecology.     

Serology and virology of the bowhead whale (Balaena mysticetus L.)

Sera from four bowhead whales (Balaena mysticetus L.) were examined for the presence of specific antibodies, and tissue and swab samples from six and four animals respectively were processed for isolation of viruses and for initiation of bowhead whale cell cultures. All sera were negative for antibodies to nine serovars of Leptospira interrogans and to 21 orthomyxovirus subtypes and a paramyxovirus (Newcastle disease virus). All sera were positive, however, for neutralizing antibodies to one or more calicivirus serotypes. Two untyped adenoviruses were isolated from colon samples of two different whales, but neutralizing antibodies to the agents could not be demonstrated in any sera. Three primary bowhead whale cell cultures were derived from kidney (two cultures) and testis (one culture), from three individual whales.     

Molecular genetic analysis of the Shantar summer group of bowhead whales (Balaena mysticetus L.) in the Okhotsk Sea

The results of molecular genetic analysis (full-length sequences of the mtDNA cytochrome b gene and control region and the allelic composition of 14 microsatellite loci) of 65 tissue samples from the endangered bowhead whale (Balaena mysticetus) population of the Sea of Okhotsk are presented. The data obtained enable the suggestion that at present, the state of the Sea of Okhotsk bowhead whale population is relatively stable.     

Examination of ten thousand years of mitochondrial DNA diversity and population demographics in bowhead whales (Balaena mysticetus) of the Central Canadian Arctic

Mitochondrial DNA (mtDNA) sequences were analyzed from 106 bowhead whale (Balaena mysticetus) specimens dating 471 ± 44 ¹⁴C b.p. –10,290 ± 150 ¹⁴C b.p. to evaluate whether historical changes in distribution and connectivity were detectable in levels of diversity and population structuring in the Central Canadian Arctic. The species has maintained levels of mtDNA diversity over 10,000 yr comparable to other nonbottlenecked large whale species. When compared to data from the Holocene East Greenland/Spitsbergen and contemporary Bering‐Chuckchi‐Beaufort populations, differentiation was low (F_ST≤ 0.005, Φ_ST≤ 0.003) and no temporal or geographical genetic structuring was evident. A combination of analyses suggests that the population has expanded over the past 30,000 ¹⁴C yr. This genetic signature of expansion could result from population growth, admixture of multiple gene pools, or a combination of both scenarios. Despite known climatic change that altered bowhead distribution and led to isolation of populations, there is no detectable population structuring or change in genetic diversity during the Holocene. This may be due to long generation time, occasional population connectivity and a historically large global population. These characteristics warrant caution when interpreting contemporary bowhead whale DNA data, as it is unlikely that any population will be in mutation‐drift equilibrium.     

Recent sightings of the bowhead whale (Balaena mysticetus) in Northeast Greenland and the Greenland Sea

By the end of the 19th century, European whalers had brought the bowhead whale (Balaena mysticetus) in the “Spitsbergen stock” ranging the waters between eastern Greenland and the western Russian Arctic to the verge of extinction. This paper presents observations of this species in Northeast Greenland and in the Greenland Sea between 1940 and 2004. The number of observations has increased in Northeast Greenland since the mid-1980s. Only three observations are known for the period 1940–1979 but during the 1980s, the 1990s and between 2000 and 2004, six, six and eight observations of bowhead whales were made, involving an absolute minimum of three, five and eight to ten different individuals, respectively. It remains uncertain whether this represents an increase in survey effort, an immigration from other areas, a recent recovery of an eastern Greenland relict “tribe” belonging to the Spitsbergen stock, or a combination of these factors.     

Song sharing and diversity in the Bering‐Chukchi‐Beaufort population of bowhead whales (Balaena mysticetus), spring 2011

Bowhead whales (Balaena mysticetus) of the Bering‐Chukchi‐Beaufort population migrate in nearshore leads through the Chukchi Sea each spring to summering grounds in the Beaufort Sea. As part of a population abundance study, hydrophones were deployed in the Chukchi Sea off Point Barrow, (12 April to 27 May 2011) and in the Beaufort Sea (12 April to 30 June 2011). Data from these sites were analyzed for the presence of bowhead whale song. We identified 12 unique song types sung by at least 32 individuals during ~95 h of recordings off Point Barrow. Six of these songs were detected at the Beaufort MARU site as well as six additional song types that were not analyzed. These results suggest a shared song repertoire among some individuals. This report represents the greatest number of songs to date during the spring migration for this population. We attribute this greater variety to population growth over the 30 yr since acoustic monitoring began in the early 1980s. Singing during early to mid‐spring is consistent with the hypothesis that song is a reproductive display, but further research is necessary to understand the exact function of this complex vocal behavior.     

Gene flow on ice: the role of sea ice and whaling in shaping Holarctic genetic diversity and population differentiation in bowhead whales (Balaena mysticetus)

Sea ice is believed to be a major factor shaping gene flow for polar marine organisms, but it remains unclear to what extent it represents a true barrier to dispersal for arctic cetaceans. Bowhead whales are highly adapted to polar sea ice and were targeted by commercial whalers throughout Arctic and subarctic seas for at least four centuries, resulting in severe reductions in most areas. Both changing ice conditions and reductions due to whaling may have affected geographic distribution and genetic diversity throughout their range, but little is known about range‐wide genetic structure or whether it differed in the past. This study represents the first examination of genetic diversity and differentiation across all five putative stocks, including Baffin Bay‐Davis Strait, Hudson Bay‐Foxe Basin, Bering‐Beaufort‐Chukchi, Okhotsk, and Spitsbergen. We also utilized ancient specimens from Prince Regent Inlet (PRI) in the Canadian Arctic and compared them with modern stocks. Results from analysis of molecular variance and demographic simulations are consistent with recent and high gene flow between Atlantic and Pacific stocks in the recent past. Significant genetic differences between ancient and modern populations suggest PRI harbored unique maternal lineages in the past that have been recently lost, possibly due to loss of habitat during the Little Ice Age and/or whaling. Unexpectedly, samples from this location show a closer genetic relationship with modern Pacific stocks than Atlantic, supporting high gene flow between the central Canadian Arctic and Beaufort Sea over the past millennium despite extremely heavy ice cover over much of this period.     

Age estimates based on aspartic acid racemization for bowhead whales (Balaena mysticetus) harvested in 1998–2000 and the relationship between racemization rate and body temperature

Fifty‐two eyes were collected and analyzed to estimate ages of 42 bowhead whales using the aspartic acid racemization aging technique. Between‐eye and within‐eye variance components for the ratio of the D and L optical isomers (D/L ratio) were estimated via analysis of variance using multiple measurements from nine whales with both eyes sampled and analyzed. For whales with more than one (D/L)_act value, an inverse variance weighted average of the values was used as (D/L)_act for the whale. Racemization rate (k_Asp) and D/L ratio at birth (D/L)₀ were estimated using (D/L)_act from 27 bowhead whales with age estimates based on baleen or ovarian corpora data and two term fetuses. The estimates were k_Asp = 0.977 × 10^?3/yr and (D/L)₀ = 0.0250. The nonlinear least squares analysis that produced these estimates also estimated female age at sexual maturity as ASM = 25.86 yr. SE(age) was estimated via a bootstrap that took into account the SE of (D/L)_act and the variances and covariance of k_Asp and (D/L)₀. One male exceeded 100 yr of age; the oldest female was 88. A strong linear relationship between k_Asp and body temperature was estimated by combining bowhead data with independent data from studies of humans and fin whales. Using this relationship, we estimated k_Asp and ASM for North Atlantic minke whales.