Morphology of nares associated with stereo-olfaction in baleen whales.

The sensory mechanisms used by baleen whales (Mysticeti) for locating ephemeral, dense prey patches in vast marine habitats are poorly understood. Baleen whales have a functional olfactory system with paired rather than single blowholes (nares), potentially enabling stereo-olfaction. Dimethyl sulfide (DMS) is an odorous gas emitted by phytoplankton in response to grazing by zooplankton. Some seabirds use DMS to locate prey, but this ability has not been demonstrated in whales. For 14 extant species of baleen whale, nares morphometrics (imagery from unoccupied aerial systems, UAS) was related to published trophic level indices using Bayesian phylogenetic mixed modelling. A significant negative relationship was found between nares width and whale trophic level (ß = -0.08, lower 95% CI = -0.13, upper 95% CI = -0.03), corresponding with a 39% increase in nares width from highest to lowest trophic level. Thus, species with nasal morphology best suited to stereo-olfaction are more zooplanktivorous. These findings provide evidence that some baleen whale species may be able to localize odorants e.g. DMS. Our results help direct future behavioural trials of olfaction in baleen whales, by highlighting the most appropriate species to study. This is a research priority, given the potential for DMS-mediated plastic ingestion by whales.

DNA methylation-based biomarkers for ageing long-lived cetaceans.

Epigenetic approaches for estimating the age of living organisms are revolutionizing studies of long-lived species. Molecular biomarkers that allow age estimates from small tissue biopsies promise to enhance studies of long-lived whales, addressing a fundamental and challenging parameter in wildlife management. DNA methylation (DNAm) can affect gene expression, and strong correlations between DNAm patterns and age have been documented in humans and nonhuman vertebrates and used to construct "epigenetic clocks". We present several epigenetic clocks for skin samples from two of the longest-lived cetaceans, killer whales and bowhead whales. Applying the mammalian methylation array to genomic DNA from skin samples we validate four different clocks with median errors of 2.3-3.7 years. These epigenetic clocks demonstrate the validity of using cytosine methylation data to estimate the age of long-lived cetaceans and have broad applications supporting the conservation and management of long-lived cetaceans using genomic DNA from remote tissue biopsies.

Correction: Evidence of molting and the function of "rock-nosing" behavior in bowhead whales in the eastern Canadian Arctic.

[This corrects the article DOI: 10.1371/journal.pone.0186156.].

Evidence of molting and the function of "rock-nosing" behavior in bowhead whales in the eastern Canadian Arctic.

Bowhead whales (Balaena mysticetus) have a nearly circumpolar distribution, and occasionally occupy warmer shallow coastal areas during summertime that may facilitate molting. However, relatively little is known about the occurrence of molting and associated behaviors in bowhead whales. We opportunistically observed whales in Cumberland Sound, Nunavut, Canada with skin irregularities consistent with molting during August 2014, and collected a skin sample from a biopsied whale that revealed loose epidermis and sloughing. During August 2016, we flew a small unmanned aerial system (sUAS) over whales to take video and still images to: 1) determine unique individuals; 2) estimate the proportion of the body of unique individuals that exhibited sloughing skin; 3) determine the presence or absence of superficial lines representative of rock-rubbing behavior; and 4) measure body lengths to infer age-class. The still images revealed that all individuals (n = 81 whales) were sloughing skin, and that nearly 40% of them had mottled skin over more than two-thirds of their bodies. The video images captured bowhead whales rubbing on large rocks in shallow, coastal areas-likely to facilitate molting. Molting and rock rubbing appears to be pervasive during late summer for whales in the eastern Canadian Arctic.

Cetacean sightings and acoustic detections during a seismic survey off Nicaragua and Costa Rica, November-December 2004 / Avistamientos y detecciones acústicas de cetáceos durante un sondeo sísmico en aguas fuera de las costas de Nicaragua y Costa Rica, en Noviembre y Diciem bre 2004

AbstractAlthough the wider Eastern Tropical Pacific has been systematically surveyed during summer/fall, relatively little effort has focused on shelf and slope waters of Nicaragua and Costa Rica. Such data are useful for establishing baseline information and assessing potential changes in cetacean occurrence and distribution relative to natural (e.g., El Niño-Southern Oscillation, climate change) and anthropogenic factors. A visualacoustic survey for cetaceans occurred as part of a monitoring and mitigation program during an academic geophysical seismic study off Nicaragua and Costa Rica, during November-December 2004. Approximately 2 067 cetaceans representing at least seven species were seen in 75 groups during 373 h (3 416 km) of daytime observations from the seismic research vessel (R/V) Maurice Ewing. The humpback whale (Megaptera novaeangliae) and the pantropical spotted dolphin (Stenella attenuata) were the most frequently sighted species (30 % of all groups sighted); both were seen in shelf waters < 100 m deep and in slope waters. The bottlenose dolphin (Tursiops truncatus; 10 % of sightings) was the third most frequently sighted species and was only seen in water > 100 m deep. In addition, sightings were made of spinner dolphins (S. longirostris), short-beaked common dolphins (Delphinus delphis), Risso's dolphins (Grampus griseus), short-finned pilot whales (Globicephala macrorhynchus), and unidentified dolphins and whales. Unconfirmed sightings of a minke whale (Balaenoptera acutorostrata) and a pod of false killer whales (Pseudorca crassidens) were also recorded. An additional six groups of dolphins (50 % confirmed to species, all pantropical spotted dolphins) were made during 187 h (1 549 km) of observation effort during darkness, two of which were detected within 30 m of the vessel bow using a night vision device. A total of 217 cetacean detections occurred during 633 h of passive acoustic monitoring. A small concentration of 12 humpback whales was seen in eight groups, and two humpbacks were recorded singing in the Gulf of Fonseca on 9 December 2004. To our knowledge, such concentrations of humpback whales, particularly singing humpbacks, have not been previously reported in this specific area. In addition, a humpback mother-calf pair, likely from the Northern Hemisphere population, was seen off Northern Costa Rica on 25 November 2004. Although cetacean sighting rates were significantly different during seismic and non-seismic periods even when corrected for differential detection probability related to sea conditions, our survey results do provide information to address previous data gaps on cetacean occurrence in shelf and slope waters off the Pacific coast of Central America during late fall.

ResumenAunque el ancho Pacífico Tropical Oriental ha sido sistemáticamente sondeado durante el verano/otoño, relativamente poco esfuerzo se ha aplicado tanto en aguas de la plataforma continental como el talud de Nicaragua y Costa Rica. Tales datos son útiles para establecer una información base y evaluar los cambios potenciales en la presencia y distribución relacionada tanto a factores naturales (ej., fenómeno de El Niño, cambio climático) como a factores antropogénicos. Un sondeo visual y acústico de cetáceos fue realizado como parte de un programa de monitoreo y mitigación durante un estudio académico de geofísica (sísmica) en las afueras de las costas de Nicaragua y Costa Rica durante Noviembre y Diciembre 2004. Aproximadamente 2 067 cetáceos representantes de al menos siete especies fueron avistados en 75 grupos durante 373 h (3 416 km) de observación diurna desde el buque de prospección sísmica (R/V) Maurice Ewing. La ballena jorobada (Megaptera novaeangliae) y el delfín manchado pantropical (Stenella attenuata) fueron las especies más frecuentemente avistadas (30 % de todos los grupos avistados); ambas fueron avistadas tanto en aguas de la plataforma continental < 100 m de profundidad como en aguas del talud. El delfín nariz de botella (Tursiops truncatus; con un 10 % de los avistamientos) fue la tercera especie más avistada, solamente visto en aguas > 100 m de profundidad. Adicionalmente, se registraron avistamientos de delfines acróbatas (S. longirostris), delfines comunes de hocico corto (Delphinus delphis), calderones grises (Grampus griseus), ballenas piloto de aleta corta (Globicephala macrorhynchus) además de ballenas y delfines no identificados. También se registró un avistamiento no confirmado de una ballena de minke (Balaenoptera acutorostrata) y uno de un grupo de falsas orcas (Pseudorca crassidens). Un adicional de seis avistamientos de delfines (confirmándose en un 50 % de ellos para la especie de delfín manchado pantropical) se observaron durante 187 h (1 549 km) de esfuerzo durante lapsos de oscuridad, dos de los cuales se detectaron a 30 m de la proa de la embarcación utilizando dispositivos de visión nocturna. Un total de 217 detecciones de cetáceos ocurrieron durante 633 h de monitoreo acústico pasivo. Una pequeña concentración de 12 ballenas jorobadas fue avistada en ocho grupos, y dos jorobadas fueron registradas cantando en el Golfo de Fonseca el 9 de Diciembre 2004. Para nuestro conocimiento, tal concentración de ballenas jorobadas, particularmente jorobadas cantando, no han sido reportadas previamente en esta área específica. Adicionalmente, una pareja de jorobadas madre-cría, probablemente de la población del Hemisferio Norte, fue avistada en las afueras de la costa de Costa Rica el 25 de Noviembre 2004. A pesar de que las tasas de avistamiento fueron significativamente distintas durante los periodos sísmicos y no sísmicos, incluso siendo corregidos según la probabilidad de detecciones relacionadas a las condiciones del mar, nuestro sondeo provee información que cubre vacíos previos de datos en la presencia de cetáceos en las aguas tanto de la plataforma como del talud continental fuera de las costas del Pacífico de América Central durante el otoño tardío.