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.

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 >4 weeks, 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 (4 day yr-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 yet also complicate predictions of how belugas may fare in the future.

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.

Safety of short-term discontinuation of antiplatelet therapy in patients with drug-eluting stents.

BACKGROUND: Antiplatelet therapy is often discontinued in patients with drug-eluting stents who are undergoing surgical procedures. However, discontinuation of antiplatelet therapy is an important risk factor for late stent thrombosis. Our objective was to examine the safety of short-term discontinuation of antiplatelet therapy. METHODS AND RESULTS: We systematically searched Medline for reported cases of late stent thrombosis and very late stent thrombosis published between January 2001 and July 2008. We restricted our search to Academic Research Consortium-defined definite cases. We identified 161 cases of late stent thrombosis or very late stent thrombosis from 84 articles (79 from case reports, 61 from registries, and 21 from randomized clinical trials). Patients had a mean age of 58.4+/-13.4 years, and 88% were male. A total of 19 cases occurred in patients who were receiving dual antiplatelet therapy at the time of the event. If patients stopped both antiplatelet agents simultaneously, the median time to event was 7 days. If patients had previously stopped a thienopyridine with no ill effect and subsequently stopped acetylsalicylic acid, the median time to event was also 7 days from the time of acetylsalicylic acid cessation. If the thienopyridine was stopped but acetylsalicylic acid was maintained, the median time to event was 122 days. Among the 48 patients who stopped both agents, 36 cases (75%) occurred within 10 days. Among the 94 patients who discontinued a thienopyridine but continued acetylsalicylic acid, only 6 cases (6%) occurred within 10 days. CONCLUSIONS: If acetylsalicylic acid therapy is maintained, short-term discontinuation of a thienopyridine may be relatively safe in patients with drug-eluting stents.