Bowhead Research Articles

Effects of industrial tones on bowhead whale calling rates

In summer 2012, exploratory drilling was performed by Shell at Sivulliq, a lease holding in the Beaufort Sea, located within the autumn migration corridor of bowhead whales. The drilling operation involved a number of vessels performing various activities, such as towing the drill rig, anchor handling, and drilling. We aimed to assess the effect of sounds from these activities on bowhead whale calling rates. Acoustic data were collected with six arrays of directional recorders (DASARs) deployed on the seafloor over ~7 weeks in Aug-Oct. Industrial sound was quantified with the use of indices, that measured the presence and amplitude of tones from machinery, or the presence of airgun pulses. For each 10-min period of data collected at each of the 40 recorders, the number of whale calls detected was matched with the “dose” of industrial sound received, and the relationship between calling rates and industrial sound was modeled using negative binomial regression. The analysis showed that with increasing tone ...

A preliminary acoustic survey of echolocating marine mammals in the Bering Sea

As the Arctic seas rapidly change with increased ocean temperatures and decreased sea ice extent, traditional Arctic marine mammal distributions will be altered, and non-traditionally Arctic species may shift poleward. Arctic species typically include sperm, bowhead, humpback, right, gray, fin, and blue whales; odontocetes, specifically killer and beluga whales; and several pinnipeds species. Their acoustic presence has been documented because they produce relatively low-frequency sounds that are detectable by many common, remotely-deployed recording platforms. Until recently, however, recording constraints of power and storage limited higher sampling rates and prevented the detection of many high-frequency-producing species in the Arctic seas. Such species likely include Baird’s, Cuvier’s, and Stejneger’s beaked whales, as well as Northern right whale and Pacific white-sided dolphins. Using one of the first long-term data sets to record relatively high frequencies in the Bering Sea, signal types similar ...

Inter-pulse sound field from a marine seismic survey in the Arctic and its potential effects on marine mammal acoustic masking

It has been documented that reverberant fields from marine seismic surveys elevate sound levels, and thus has the potential to mask acoustic signals that are important to marine mammals. In this study, we investigated one-third-octave (OTO) bands of airgun inter-pulse sound fields from a shallow water (<15 m) seismic survey in the Beaufort Sea. The results show that at close distances less than 3 km, peak energy of the OTO band levels were concentrated around 80-110 Hz and the median sound levels were 40-50 dB above ambient. The higher frequency components (>3 kHz) of inter-pulse sound field at these close distances ranged 5-20 dB above ambient. At distances beyond 3 km, the received acoustic energy becomes more uniform up to 1000 Hz. The median OTO band levels at these distances were approximately 10-20 dB above ambient. For higher frequencies, sound levels at these distances were approximately the same as ambient. These results imply that low-frequency bowhead whales could be affected by acoustic masking from seismic airgun inter-pulse sound fields, especially at relatively close distances. However, potential acoustic masking effects to mid-frequency beluga whale echolocation signals are expected to be less profound.

Is it 'boom times' for baleen whales in the Pacific Arctic region?

The marine ecosystem in the Pacific Arctic region has experienced dramatic transformation, most obvious by the loss of sea ice volume (75%), late-summer areal extent (50%) and change in phenology (four to six weeks longer open-water period). This alteration has resulted in an opening of habitat for subarctic species of baleen whales, many of which are recovering in number from severe depletions from commercial whaling in the nineteenth and twentieth centuries. Specifically, humpback, fin and minke whales (Megaptera novaeangliae, Balaenoptera physalus and Balaenoptera acutorostrata) are now regularly reported during summer and autumn in the southern Chukchi Sea. These predators of zooplankton and forage fishes join the seasonally resident grey whale (Eschrichtius robustus) and the arctic-endemic bowhead whale (Balaena mysticetus) in the expanding open-ocean habitat of the Pacific Arctic. Questions arising include: (i) what changes in whale-prey production and delivery mechanisms have accompanied the loss of sea ice, and (ii) how are these five baleen whale species partitioning the expanding ice-free habitat? While there has been no programme of research specifically focused on these questions, an examination of seasonal occurrence, foraging plasticity and (for bowhead whales) body condition suggests that the current state of Pacific Arctic marine ecosystem may be 'boom times' for baleen whales. These favourable conditions may be moderated, however, by future shifts in ecosystem structure and/or negative impacts to cetaceans related to increased commercial activities in the region.

Beyond thermoregulation: metabolic function of cetacean blubber in migrating bowhead and beluga whales.

The processes of lipid deposition and utilization, via the gene leptin (Lep), are poorly understood in taxa with varying degrees of adipose storage. This study examines how these systems may have adapted in marine aquatic environments inhabited by cetaceans. Bowhead (Balaena mysticetus) and beluga whales (Delphinapterus leucas) are ideal study animals-they possess large subcutaneous adipose stores (blubber) and undergo bi-annual migrations concurrent with variations in food availability. To answer long-standing questions regarding how (or if) energy and lipid utilization adapted to aquatic stressors, we quantified variations in gene transcripts critical to lipid metabolism related to season, age, and blubber depth. We predicted leptin tertiary structure conservation and assessed inter-specific variations in Lep transcript numbers between bowheads and other mammals. Our study is the first to identify seasonal and age-related variations in Lep and lipolysis in these cetaceans. While Lep transcripts and protein oscillate with season in adult bowheads reminiscent of hibernating mammals, transcript levels reach up to 10 times higher in bowheads than any other mammal. Data from immature bowheads are consistent with the hypothesis that short baleen inhibits efficient feeding. Lipolysis transcripts also indicate young Fall bowheads and those sampled during Spring months limit energy utilization. These novel data from rarely examined species expand the existing knowledge and offer unique insight into how the regulation of Lep and lipolysis has adapted to permit seasonal deposition and maintain vital blubber stores.

Dietary habits of polar bears in Foxe Basin, Canada: possible evidence of a trophic regime shift mediated by a new top predator.

Polar bear (Ursus maritimus) subpopulations in several areas with seasonal sea ice regimes have shown declines in body condition, reproductive rates, or abundance as a result of declining sea ice habitat. In the Foxe Basin region of Nunavut, Canada, the size of the polar bear subpopulation has remained largely stable over the past 20 years, despite concurrent declines in sea ice habitat. We used fatty acid analysis to examine polar bear feeding habits in Foxe Basin and thus potentially identify ecological factors contributing to population stability. Adipose tissue samples were collected from 103 polar bears harvested during 2010–2012. Polar bear diet composition varied spatially within the region with ringed seal (Pusa hispida) comprising the primary prey in northern and southern Foxe Basin, whereas polar bears in Hudson Strait consumed equal proportions of ringed seal and harp seal (Pagophilus groenlandicus). Walrus (Odobenus rosmarus) consumption was highest in northern Foxe Basin, a trend driven by the ability of adult male bears to capture large‐bodied prey. Importantly, bowhead whale (Balaena mysticetus) contributed to polar bear diets in all areas and all age and sex classes. Bowhead carcasses resulting from killer whale (Orcinus orca) predation and subsistence harvest potentially provide an important supplementary food source for polar bears during the ice‐free period. Our results suggest that the increasing abundance of killer whales and bowhead whales in the region could be indirectly contributing to improved polar bear foraging success despite declining sea ice habitat. However, this indirect interaction between top predators may be temporary if continued sea ice declines eventually severely limit on‐ice feeding opportunities for polar bears.

Summer refugia of polar bears (Ursus maritimus) in the southern Beaufort Sea

Climate change is altering habitats and causing changes to species behaviors and distributions. Rapid changes in Arctic sea ice ecosystems have increased the need to identify critical habitats for conservation and management of species such as polar bears (Ursus maritimus). We examined the distribution of adult female and subadult male and female polar bears tracked by satellite telemetry (n = 64 collars) in the southern Beaufort Sea, Canada, to identify summer refugia in 2007–2010. Using utilization distributions, we identified terrestrial and sea ice areas used as summer refugia when nearshore sea ice melted. Habitat use areas varied between months, but interannual variation was not significant. Overall, bears made high use of ice over shallow waters, and bears that remained near terrestrial areas used sea ice (presumably to hunt from) when it was available. The majority of the bears remained on sea ice during summer and used the edge of the pack ice most notably west of Banks Island, Canada. A mean of 27 % (range 22–33 %) of bears used terrestrial areas in Alaska and use was concentrated near the remains of subsistence harvested bowhead whales (Balaena mysticetus). Energetic expenditure is anticipated to increase as bears are required to travel further on a seasonal basis.

Bowhead whale localization using asynchronous hydrophones in the Chukchi Sea.

This paper estimates bowhead whale locations and uncertainties using non-linear Bayesian inversion of their modally-dispersed calls recorded on asynchronous recorders in the Chukchi Sea, Alaska. Bowhead calls were recorded on a cluster of 7 asynchronous ocean-bottom hydrophones that were separated by 0.5-9.2 km. A warping time-frequency analysis is used to extract relative mode arrival times as a function of frequency for nine frequency-modulated whale calls that dispersed in the shallow water environment. Each call was recorded on multiple hydrophones and the mode arrival times are inverted for: the whale location in the horizontal plane, source instantaneous frequency (IF), water sound-speed profile, seabed geoacoustic parameters, relative recorder clock drifts, and residual error standard deviations, all with estimated uncertainties. A simulation study shows that accurate prior environmental knowledge is not required for accurate localization as long as the inversion treats the environment as unknown. Joint inversion of multiple recorded calls is shown to substantially reduce uncertainties in location, source IF, and relative clock drift. Whale location uncertainties are estimated to be 30-160 m and relative clock drift uncertainties are 3-26 ms.

Severe Bone Loss as Part of the Life History Strategy of Bowhead Whales.

The evolution of baleen constituted a major evolutionary change that made it possible for baleen whales to reach enormous body sizes while filter feeding on tiny organisms and migrating over tremendous distances. Bowhead whales (Balaena mysticetus) live in the Arctic where the annual cycle of increasing and decreasing ice cover affects their habitat, prey, and migration. During the nursing period, bowheads grow rapidly; but between weaning and approximately year 5, bowhead whales display sustained baleen and head growth while limiting growth in the rest of their bodies. During this period, they withdraw resources from the skeleton, in particular the ribs, which may lose 40% of bone mass. Such dramatic changes in bones of immature mammals are rare, although fossil cetaceans between 40 and 50 million years ago show an array of rib specializations that include bone loss and are usually interpreted as related to buoyancy control.

Inactivation of Cone-Specific Phototransduction Genes in Rod Monochromatic Cetaceans

Vertebrate vision is mediated by two types of photoreceptors, rod and cone cells. Rods are more sensitive than cones in dim light, but are incapable of color discrimination because they possess only one type of photosensitive opsin protein (rod opsin = RH1). By contrast, cones are more important for vision in bright light. Cones also facilitate dichromatic color vision in most mammals because there are two cone pigment genes (SWS1, LWS) that facilitate color discrimination. Cone monochromacy occurs when one of the cone opsins (usually SWS1) is inactivated and is present in assorted subterranean, nocturnal, and aquatic mammals. Rod monochromacy occurs when both cone photoreceptors are inactivated, resulting in a pure rod retina. The latter condition is extremely rare in mammals and has only been confirmed with genetic evidence in five cetacean lineages, golden moles, armadillos, and sloths. The first genetic evidence for rod monochromacy in these taxa consisted of inactivated copies of both of their cone pigment genes (SWS1, LWS). However, other components of the cone phototransduction cascade are also predicted to accumulate inactivating mutations in rod monochromats. Here, we employ genome sequences and exon capture data from four baleen whales (bowhead, two minke whales, fin whale) and five toothed whales (sperm whale, Yangtze River dolphin, beluga, killer whale, bottlenose dolphin) to test the hypothesis that rod monochromacy is associated with the inactivation of seven genes (GNAT2, GNB3, GNGT2, PDE6C, PDE6H, CNGA3, CNGB3) in the cone phototransduction cascade. Cone-monochromatic toothed whales that retain a functional copy of LWS (beluga, Yangtze River dolphin, killer whale, bottlenose dolphin) also retain intact copies of other cone-specific phototransduction genes, whereas rod monochromats (Antarctic minke whale, common minke whale, fin whale, bowhead whale, sperm whale) have inactivating mutations in five or more genes in the cone phototransduction cascade. The only shared inactivating mutations that were discovered occur in the three Balaenoptera species (two minke whales, fin whale), further suggesting that rod monochromacy evolved independently in two clades of baleen whales, Balaenopteroidea and Balaenidae. We estimate that rod monochromacy evolved first in Balaenopteroidea (~28.8 Ma) followed by P. macrocephalus (~19.5 Ma) and Balaenidae (~13.0 Ma).

Rapid Environmental Change Drives Increased Land Use by an Arctic Marine Predator.

In the Arctic Ocean’s southern Beaufort Sea (SB), the length of the sea ice melt season (i.e., period between the onset of sea ice break-up in summer and freeze-up in fall) has increased substantially since the late 1990s. Historically, polar bears (Ursus maritimus) of the SB have mostly remained on the sea ice year-round (except for those that came ashore to den), but recent changes in the extent and phenology of sea ice habitat have coincided with evidence that use of terrestrial habitat is increasing. We characterized the spatial behavior of polar bears spending summer and fall on land along Alaska’s north coast to better understand the nexus between rapid environmental change and increased use of terrestrial habitat. We found that the percentage of radiocollared adult females from the SB subpopulation coming ashore has tripled over 15 years. Moreover, we detected trends of earlier arrival on shore, increased length of stay, and later departure back to sea ice, all of which were related to declines in the availability of sea ice habitat over the continental shelf and changes to sea ice phenology. Since the late 1990s, the mean duration of the open-water season in the SB increased by 36 days, and the mean length of stay on shore increased by 31 days. While on shore, the distribution of polar bears was influenced by the availability of scavenge subsidies in the form of subsistence-harvested bowhead whale (Balaena mysticetus) remains aggregated at sites along the coast. The declining spatio-temporal availability of sea ice habitat and increased availability of human-provisioned resources are likely to result in increased use of land. Increased residency on land is cause for concern given that, while there, bears may be exposed to a greater array of risk factors including those associated with increased human activities.

Behavioral responses affect distribution analyses of bowhead whales in the vicinity of seismic operations

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 549:243-262 (2016) - DOI: https://doi.org/10.3354/meps11665 Behavioral responses affect distribution analyses of bowhead whales in the vicinity of seismic operations Frances C. Robertson1,2,*, William R. Koski2, Andrew W. Trites1 1Department of Zoology and Marine Mammal Research Unit, Institute for the Oceans and Fisheries, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada 2LGL Ltd, Environmental Research Associates, 22 Fisher Street, King City, ON, L7B 1A6, Canada *Corresponding author: f.robertson@fisheries.ubc.ca ABSTRACT: Aerial surveys are sometimes used to assess the densities of wide-ranging whales, as well as changes in their distributions in response to human activity. Such surveys also provide data used to estimate numbers of animals exposed to different received levels of seismic sound, as required by regulators. However, estimates of abundance are often biased because they fail to account for the effects of seismic operations on the surfacing and diving behavior of whales. Our objective was to determine the extent to which analyses of the distribution of bowhead whales Balaena mysticetus are affected by changes in visual ‘availability’ caused by seismic operations. We used aerial survey data collected during seismic operations in the Alaskan Beaufort Sea from late August to early October 2008 and fit spatial density surface models to bowhead sighting data to predict whale density in an ensonified area. We also incorporated availability correction factors to determine the sensitivity of density estimates to changes in surfacing and diving behavior caused by seismic operations. The influence of altered whale behavior was then evaluated by comparing a series of realistic simulated scenarios in which models incorporated undisturbed or seismic disturbance-related correction factors. Results suggest that the numbers of bowhead whales present in the vicinity of seismic operations during the bowhead autumn migration are underestimated if the behavioral effects of seismic operations on whales are ignored. Our study highlights the importance of accounting for changes in whale behavior that can affect sightability when estimating numbers and distribution of whales in the vicinity of industrial activity. KEY WORDS: Bowhead whale · Seismic survey · Distance sampling · Beaufort Sea · Availability · g(0) · Alaska · Spatial models · Behavior · Generalized additive model Full text in pdf format Supplementary material PreviousNextCite this article as: Robertson FC, Koski WR, Trites AW (2016) Behavioral responses affect distribution analyses of bowhead whales in the vicinity of seismic operations. Mar Ecol Prog Ser 549:243-262. https://doi.org/10.3354/meps11665 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 549. Online publication date: May 10, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

Modeling the aggregated exposure and responses of bowhead whales Balaena mysticetus to multiple sources of anthropogenic underwater sound

This work was supported in part by a contract between BP Exploration (Alaska) Inc. and the University of California, Santa Barbara (E.F.), and by the North Slope Borough.

The distribution of zooplankton and bowhead whales, Balaena mysticetus Linnaeus, 1758, in Akademiya Bay, Sea of Okhotsk

The modern pattern of distribution and feeding habits of the bowhead whale, Balaena mysticetus, in the Sea of Okhotsk are studied. The existence of a feeding aggregation of this whale species in the southwesternmost portion (apex) of Ulban Bay has been confirmed. There, the animals feed in shallow waters with depths of 3–5 m, which are only slightly larger than their body height. The quantitative composition and species structure of zooplankton at the stations that were set near feeding whales have been analyzed. In the samples taken in the immediate proximity to the feeding whales, the abundance of zooplankton reached 31409 ind./m3, with the average value of 17565 ind./m3. The lowest abundance, from 56 to 1879 ind./m3 (mean 927 ind./m3), was in the samples from western Konstantin Bay, where bowhead whales were not observed. In 16 samples collected in the immediate proximity to the feeding whales in the shallow waters of Ulban Bay, the average zooplankton biomass was 547.9 mg/m3, which is 3.9 times higher than that in the samples from waters where the whales were absent. Copepods dominated quantitatively at all the stations in Akademiya Bay. The proportion of euphausiids in the zooplankton biomass was lower than 1%, both near the feeding whales and in the absence of whales.

Morphometric Correlates of the Ovary and Ovulatory Corpora in the Bowhead Whale, Balaena mysticetus.

Gross morphology and morphometry of the bowhead whale ovary, including ovulatory corpora, were investigated in 50 whales from the Chukchi and Beaufort seas off the coast of Alaska. Using the presence of ovarian corpora to define sexual maturity, 23 sexually immature whales (7.6-14.2 m total body length) and 27 sexually mature whales (14.2-17.7 m total body length) were identified. Ovary pair weights ranged from 0.38 to 2.45 kg and 2.92 to 12.02 kg for sexually immature and sexually mature whales, respectively. In sexually mature whales, corpora lutea (CLs) and/or large corpora albicantia (CAs) projected beyond ovary surfaces. CAs became increasingly less interruptive of the surface contour as they regressed, while remaining identifiable within transverse sections of the ovarian cortex. CLs formed large globular bodies, often with a central lumen, featuring golden parenchymas enfolded within radiating fibrous cords. CAs, sometimes vesicular, featured a dense fibrous core with outward fibrous projections through the former luteal tissue. CLs (never more than one per ovary pair) ranged from 6.7 to 15.0 cm in diameter in 13 whales. Fetuses were confirmed in nine of the 13 whales, with the associated CLs ranging from 8.3 to 15.0 cm in diameter. CLs from four whales where a fetus was not detected ranged from 6.7 to 10.6 cm in diameter. CA totals ranged from 0 to 22 for any single ovary, and from 1 to 41 for an ovary pair. CAs measured from 0.3 to 6.3 cm in diameter, and smaller corpora were more numerous, suggesting an accumulating record of ovulation. Neither the left nor the right ovary dominated in the production of corpora. Anat Rec, 299:769-797, 2016. © 2016 Wiley Periodicals, Inc.

Bowhead whale localization and environmental inversion using asynchronous hydrophones

This paper estimates bowhead whale locations and environmental properties using Bayesian inversion of the modal dispersion of whale calls recorded on asynchronous recorders in the shallow waters of the northeastern Chukchi Sea, Alaska. Bowhead calls were recorded on a Y-shaped cluster of seven autonomous ocean-bottom hydrophones, separated by up to 9.2 km. We use a warping time-frequency analysis to obtain frequency-dependent relative mode arrival times for nine frequency-modulated whale calls. Trans-dimensional inversion is applied to invert mode arrival times for the whale location, water sound-speed profile, subbottom layering and geoacoustic parameters, source instantaneous frequency (IF), relative recorder clock drifts, and residual error standard deviation, all with estimated uncertainties. Joint inversion of multiple calls is found to substantially reduce uncertainties on whale location, source IF, and clock drifts. Estimated whale location uncertainties are 30–160 m and clock drift uncertainties a...

Time-difference-of-arrival localization of bowhead whales using asynchronous recorders

This paper estimates bowhead whale locations and uncertainties using linearized Bayesian inversion of the time-difference-of-arrival (TDOA) of whale calls recorded on omni-directional asynchronous recorders in the Chukchi Sea, Alaska. A Y-shaped cluster of seven autonomous ocean-bottom hydrophones, separated by 0.5–9.2 km, was deployed for several months over which time their clocks drifted out of synchronization. Hundreds of recorded whale calls are manually annotated with time-frequency bounds and associated between recorders. The TDOA between all hydrophone pairs are calculated from filtered waveform cross-correlations and depend on the whale locations, hydrophone locations, relative recorder clock drifts, and an effective waveguide sound speed. The inversion estimates all of these parameters and their uncertainties as well as data error statistics using prior information to constrain the otherwise underdetermined problem. Whale location uncertainties are estimated to be approximately 100 m which allow...

Acoustic vector sensor beamforming reduces masking from underwater industrial noise during passive monitoring.

Masking from industrial noise can hamper the ability to detect marine mammal sounds near industrial operations, whenever conventional (pressure sensor) hydrophones are used for passive acoustic monitoring. Using data collected from an autonomous recorder with directional capabilities (Directional Autonomous Seafloor Acoustic Recorder), deployed 4.1 km from an arctic drilling site in 2012, the authors demonstrate how conventional beamforming on an acoustic vector sensor can be used to suppress noise arriving from a narrow sector of geographic azimuths. Improvements in signal-to-noise ratio of up to 15 dB are demonstrated on bowhead whale calls, which were otherwise undetectable using conventional hydrophones.

Estimating source levels and depth distributions of calling bowhead whales using geoacoustic inversion

Every year during open-water season in 2008–2014, up to 40 passive acoustic recorders (DASARs) were deployed in the Beaufort Sea. Over the eight-year period, more than 3.1 million bowhead calls were localized. A vertical array was also deployed near DASARs in some years, enabling the matched-field geoacoustic inversion of bowhead whale calls to estimate the local acoustic propagation environment. In turn, these environments were used to estimate the source level and calling depth distributions of nearly 50,000 calls between 2008 and 2014. The resulting source level distributions exhibited a stable mode near 160 dB re 1 uPa @ 1 m (rms), which proved robust to the year investigated, the whale call analysis method (manual or automated), and the type of acoustic propagation model (a simple empirically-derived “power-law” transmission loss model or a detailed waveguide propagation model). Depth distributions of calling whales were more sensitive to the environmental model used but always showed a mode at ~25 m...

Evolutionary loss of cone photoreception in balaenid whales reveals circuit stability in the mammalian retina.

The classical understanding of mammalian vision is that it occurs through "duplex" retinae containing both rod and cone photoreceptors, the signals from which are processed through rod- and/or cone-specific signaling pathways. The recent discovery of rod monochromacy in some cetacean lineages provides a novel opportunity to investigate the effects of an evolutionary loss of cone photoreception on retinal organization. Sequence analysis of right whale (Eubalaena glacialis; family Balaenidae) cDNA derived from long-wavelength sensitive (LWS) cone opsin mRNA identified several mutations in the opsin coding sequence, suggesting the loss of cone cell function, but maintenance of non-photosensitive, cone opsin mRNA-expressing cells in the retina. Subsequently, we investigated the retina of the closely related bowhead whale (Balaena mysticetus; family Balaenidae) to determine how the loss of cone-mediated photoreception affects light signaling pathways in the retina. Anti-opsin immunofluorescence demonstrated the total loss of cone opsin expression in B. mysticetus, whereas light microscopy, transmission electron microscopy, and bipolar cell (protein kinase C-α [PKC-α] and recoverin) immunofluorescence revealed the maintenance of cone soma, putative cone pedicles, and both rod and cone bipolar cell types. These findings represent the first immunological and anatomical evidence of a naturally occurring rod-monochromatic mammalian retina, and suggest that despite the loss of cone-mediated photoreception, the associated cone signaling structures (i.e., cone synapses and cone bipolar cells) may be maintained for multichannel rod-based signaling in balaenid whales. J. Comp. Neurol. 524:2873-2885, 2016. © 2016 Wiley Periodicals, Inc.