Pierre R. Richard

Population-specific home ranges and migration timing of Pacific Arctic beluga whales (Delphinapterus leucas)

Two populations of beluga whales (Delphinapterus leucas), the Eastern Beaufort Sea (BS) and Eastern Chukchi Sea (ECS), make extensive seasonal migrations into the Pacific Arctic. However, the extent to which these populations overlap in time and space is not known. We quantified distribution and migration patterns for BS and ECS belugas using daily locations from whales tracked with satellite-linked transmitters. Home ranges and core areas in summer (July and August) and in each month (July–November), daily displacement, dispersal from core areas, and autumn migration timing were estimated. Distinct summer and fall distribution patterns and staggered autumn migration timing were identified for BS and ECS whales. Summer home ranges for each population had less than 10xa0% overlap. Monthly home ranges were also relatively distinct between populations except in September (up to 88xa0% home range overlap). A distinct east–west shift in focal area use occurred in September that persisted into October, with the two populations essentially switching longitudinal positions. Highest daily displacements occurred during the migratory period in September for BS whales and October for ECS whales, further indicating westward fall migration was offset between populations. Sexual segregation of males and females within a population also varied monthly. Autumn migration timing as well as differences in spatial and temporal segregation between BS and ECS beluga populations may be a result of maternally driven philopatry and population-specific adaptations to dynamically available resources. Our results contribute to the management of these populations by identifying seasonal area use and differences in migration patterns.

Upside-down swimming behaviour of free-ranging narwhals

BackgroundFree-ranging narwhals (Monodon monoceros) were instrumented in Admiralty Inlet, Canada with both satellite tags to study migration and stock separation and short-term, high-resolution digital archival tags to explore diving and feeding behaviour. Three narwhals were equipped with an underwater camera pod (Crittercam), another individual was equipped with a digital archival tag (DTAG), and a fifth with both units during August 2003 and 2004.ResultsCrittercam footage indicated that of the combined 286 minutes of recordings, 12% of the time was spent along the bottom. When the bottom was visible in the camera footage, the narwhals were oriented upside-down 80% of the time (range: 61100%). The DTAG data (14.6 hours of recordings) revealed that during time spent below the surface, the two tagged narwhals were supine an average of 13% (range: 9–18%) of the time. Roughly 70% of this time spent in a supine posture occurred during the descent.ConclusionPossible reasons for this upside-down swimming behaviour are discussed. No preference for a clockwise or counter-clockwise direction of roll was observed, discounting the possibility that rolling movements contribute to the asymmetric left-handed helical turns of the tusk.

Beluga (Delphinapterus leucas) habitat selection in the eastern Beaufort Sea in spring, 1975–1979

An understanding of the adaptability of belugas (Delphinapterus leucas) to changing ice conditions is required to interpret and predict possible changes in habitat selection in response to projected loss of sea ice throughout the circumpolar Arctic. We analyzed beluga observations made during spring aerial surveys for ringed seals conducted from 1975 to 1979 in the eastern Beaufort Sea. Despite inter-annual variability in the extent and distribution of sea ice, belugas consistently selected areas with water depths of 200–500xa0m and heavy ice concentrations (8/10 to 10/10) while areas of open water to light ice concentrations (0/10 to 1/10) were not selected. Belugas were also found in proximity to regions with ≥0.5 degrees seafloor slope which include the continental slope and other areas with the potential for oceanographic upwellings. In most years (4 of 5), fast-ice edges and coastal areas were not selected. In the lightest ice year analyzed, belugas showed less specificity in habitat selection as their distribution expanded and shifted shoreward to fast-ice edges. The observed distribution is discussed in terms of predator–prey relationships particularly with reference to beluga feeding on polar cod (Boreogadus saida). More research is required to examine and compare possible changes in distribution since the late 1970s and to investigate the factors driving the patterns described.

Vestigial Tooth Anatomy and Tusk Nomenclature for Monodon Monoceros

Narwhal tusks, although well described and characterized within publications, are clouded by contradictory references, which refer to them as both incisors and canines. Vestigial teeth are briefly mentioned in the scientific literature with limited descriptions and no image renderings. This study first examines narwhal maxillary osteoanatomy to determine whether the erupted tusks are best described as incisiform or caniniform teeth. The study also offers evidence to support the evolutionary obsolescence of the vestigial teeth through anatomic, morphologic, and histologic descriptions. Examination of 131 skull samples, including 110 museum skull specimens and 21 harvested skulls, revealed the erupted tusks surrounded by maxillary bone over the entire length of their bone socket insertion, and are thus more accurately termed caniniform or canine teeth. The anatomy, morphology, and development of vestigial teeth in five skull samples are more fully described and documented. Vestigial tooth samples included 14 embedded pairs or individual teeth that were partially exposed or removed from the maxillary bone. Their location was posterior, ventral, and lateral to the tusks, although male vestigial teeth often exfoliate in the mouth lodging between the palatal tissue and underlying maxillary bone. Their myriad morphologies, sizes, and eruption patterns suggest that these teeth are no longer guided by function but rather by random germ cell differentiation and may eventually cease expression entirely. The conclusions reached are that the narwhal tusks are the expression of canine teeth and that vestigial teeth have no apparent functional characteristics and are following a pattern consistent with evolutionary obsolescence. Anat Rec, 2012.

Migration Route and Seasonal Home Range of the Northern Hudson Bay Narwhal (Monodon monoceros)

The northern Hudson Bay narwhal (Monodon monoceros) population gathers in the area of Repulse Bay, Nunavut in the summer season. This population is hunted by local Inuit and co-managed by the Nunavut Wildlife Management Board and the Department of Fisheries and Oceans. There is some uncertainty as to the size of the population, the migration route this population takes to its wintering areas, if its winter range overlaps with that of other narwhal populations, and whether it is hunted by other communities during migrations. In the face of a changing climate, this ecological information is essential to understanding the success of the population in the future.

Decadal shifts in autumn migration timing by Pacific Arctic beluga whales are related to delayed annual sea ice formation.

Migrations are often influenced by seasonal environmental gradients that are increasingly being altered by climate change. The consequences of rapid changes in Arctic sea ice have the potential to affect migrations of a number of marine species whose timing is temporally matched to seasonal sea ice cover. This topic has not been investigated for Pacific Arctic beluga whales (Delphinapterus leucas) that follow matrilineally maintained autumn migrations in the waters around Alaska and Russia. For the sympatric Eastern Chukchi Sea (Chukchi) and Eastern Beaufort Sea (Beaufort) beluga populations, we examined changes in autumn migration timing as related to delayed regional sea ice freeze-up since the 1990s, using two independent data sources (satellite telemetry data and passive acoustics) for both populations. We compared dates of migration between early (1993-2002) and late (2004-2012) tagging periods. During the late tagging period, Chukchi belugas had significantly delayed migrations (by 2 to >4xa0weeks, depending on location) from the Beaufort and Chukchi seas. Spatial analyses also revealed that departure from Beaufort Sea foraging regions by Chukchi whales was postponed in the late period. Chukchi beluga autumn migration timing occurred significantly later as regional sea ice freeze-up timing became later in the Beaufort, Chukchi, and Bering seas. In contrast, Beaufort belugas did not shift migration timing between periods, nor was migration timing related to freeze-up timing, other than for southward migration at the Bering Strait. Passive acoustic data from 2008 to 2014 provided independent and supplementary support for delayed migration from the Beaufort Sea (4xa0dayxa0yr-1 ) by Chukchi belugas. Here, we report the first phenological study examining beluga whale migrations within the context of their rapidly transforming Pacific Arctic ecosystem, suggesting flexible responses that may enable their persistence yetxa0also complicate predictions of how belugas may fare in the future.

Habitat selection by two beluga whale populations in the Chukchi and Beaufort seas

There has been extensive sea ice loss in the Chukchi and Beaufort seas where two beluga whale (Delphinapterus leucas) populations occur between July-November. Our goal was to develop population-specific beluga habitat selection models that quantify relative use of sea ice and bathymetric features related to oceanographic processes, which can provide context to the importance of changing sea ice conditions. We established habitat selection models that incorporated daily sea ice measures (sea ice concentration, proximity to ice edge and dense ice) and bathymetric features (slope, depth, proximity to the continental slope, Barrow Canyon, and shore) to establish quantitative estimates of habitat use for the Eastern Chukchi Sea (‘Chukchi’) and Eastern Beaufort Sea (‘Beaufort’) populations. We applied ‘used v. available’ resource selection functions to locations of 65 whales tagged from 1993–2012, revealing large variations in seasonal habitat selection that were distinct between sex and population groups. Chukchi whales of both sexes were predicted to use areas in close proximity to Barrow Canyon (typically <200 km) as well as the continental slope in summer, although deeper water and denser ice were stronger predictors for males than females. Habitat selection differed more between sexes for Beaufort belugas. Beaufort males selected higher ice concentrations (≥40%) than females (0–40%) in July-August. Proximity to shore (<200 km) strongly predicted summer habitat of Beaufort females, while distance to the ice edge was important for male habitat selection, especially during westward migration in September. Overall, our results indicate that sea ice variables were rarely the primary drivers of beluga summer-fall habitat selection. While diminished sea ice may indirectly affect belugas through changes in the ecosystem, associations with bathymetric features that affect prey availability seemed key to habitat selection during summer and fall. These results provide a benchmark by which to assess future changes in beluga habitat use of the Pacific Arctic.

Availability bias in population survey of Northern Hudson Bay narwhal (Monodon monoceros)

Population estimates are important for the development of management plans of harvested species and thereby ultimately important for species sustainability. Aerial surveys are one of the methods used in preparing population estimates. For marine mammals, aerial population surveys require that animal biology is understood in order to account for availability bias. Availability bias in this case derives from animals that are invisible to the survey due to diving behavior. In order to understand diving behavior of the Northern Hudson Bay narwhal (Monodon monoceros), nine whales were tagged with satellite tracking devices in the Repulse Bay, Nunavut area in August 2006 (nxa0=xa05) and 2007 (nxa0=xa04). Of specific interest was time at depth of 0–2xa0m of water, the depth at which studies have shown that whales could be distinguished at the species level during an aerial survey. The proportion of time spent in 0–2xa0m of water can then be used to correct the population estimate from aerial survey. This research found that narwhals spent approximately 32xa0% of their time at the surface where they would be available to be seen by an aerial survey. This paper provides raw data that can be used to correct population survey estimates.