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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.
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Evidence of molting and the function of “rock-
nosing” behavior in bowhead whales in the
eastern Canadian Arctic
Sarah M. E. Fortune
*, William R. Koski
, Jeff W. Higdon
, Andrew W. Trites
, Mark
F. Baumgartner
, Steven H. Ferguson
1Department of Zoology and Marine Mammal Research Unit, Institute for the Oceans and Fisheries,
University of British Columbia, Vancouver, British Columbia, Canada, 2Biology Department, Woods Hole
Oceanographic Institution, Woods Hole, Massachusetts, United States of America, 3LGL Limited, King City,
Ontario, Canada, 4Higdon Wildlife Consulting, Winnipeg, Manitoba, Canada, 5Fisheries and Oceans
Canada, Freshwater Institute, Winnipeg, Manitoba, Canada
Bowhead whales (Balaena mysticetus) have a nearly circumpolar distribution, and occa-
sionally occupy warmer shallow coastal areas during summertime that may facilitate molt-
ing. 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.
The skin (epidermis) and hair (keratinized epidermal cells) of marine mammals are specially
adapted for life in an aquatic environment. The periodic shedding of part or all of their outer
layer of epidermal covering, which is then replaced by new growth [1] has been well studied
for seals and sea lions—which molt annually to repair and renew their skin and pelt [28]. In
contrast, whales, dolphins and porpoises are generally thought to continuously shed and
replace their epidermis [9,10]. However, this may not be the case for Arctic species that experi-
ence pronounced changes in environmental conditions by seasonally occupying uncharacter-
istically warmer areas such as estuaries and fiords [11].
PLOS ONE | November 22, 2017 1 / 15
Citation: Fortune SME, Koski WR, Higdon JW,
Trites AW, Baumgartner MF, Ferguson SH (2017)
Evidence of molting and the function of “rock-
nosing” behavior in bowhead whales in the eastern
Canadian Arctic. PLoS ONE 12(11): e0186156.
Editor: Songhai Li, Institute of Deep-sea Science
and Engineering, Chinese Academy of Sciences,
Received: July 6, 2017
Accepted: September 26, 2017
Published: November 22, 2017
Copyright: ©2017 Fortune et al. This is an open
access article distributed under the terms of the
Creative Commons Attribution License, which
permits unrestricted use, distribution, and
reproduction in any medium, provided the original
author and source are credited.
Data Availability Statement: All relevant data are
within the paper and its Supporting Information
Funding: Fieldwork was funded by: Fisheries and
Oceans Canada (Emerging Fisheries 41436-810-
120-4D875), Nunavut Wildlife Research Trust Fund
(project 3-13-29 Bowhead Whale Movement’s and
Ecology), Molson Foundation (318366), Ocean
Tracking Network (NSERC NETGP 375118-08),
and ArcticNet Centre of Excellence (317588)
Beluga whales (Delphinapterus leucas) and most likely narwhal (Monodon monoceros) (e.g.,
Inuit hunter observation [12]) undergo a seasonal epidermal molt during summer. The beluga
whale molt appears to be facilitated in part by the warm and low salinity environmental condi-
tions found in seasonally occupied estuaries [11,13]. The elevated water temperatures are pos-
tulated to influence the growth and turnover of epidermis by increasing metabolic activities
[11] or provide an evolved physiological cue (e.g., daylight [14]). Furthermore, physical fea-
tures of estuaries such as gravel bottoms provide an abrasive surface to rub against and expe-
dite exfoliation [15].
In contrast to what is known about molting for beluga whales, little is known about this
phenomenon in bowhead whales (Balaena mysticetus). It is known, for example, that the struc-
ture of epidermal, dermal and hypodermal layers of balaenid whales (bowhead and right
whale, Eubalaena sp.), closely resembles that of odontocete species that are known to slough
skin (e.g., beluga whales) and differs from the more closely related balaenopterids (e.g., fin,
blue, and sei whale) [1]. Furthermore, southern right whale (Eubalaena australis) calves are
known to shed multiple layers of their epidermis [16], which is similar to beluga calves that
conduct a multilayered molt to remove fetal epidermis [17]. Histological analysis has revealed
that bowhead whales belonging to the Okhotsk Sea population molt during summer months
while occupying a warm, shallow bay in the Shantar Achipelago [18]. However, it is not
known whether other populations of bowhead whales, such as the Eastern Canada-West
Greenland (EC-WG) population, undergo a seasonal molt or whether they molt continuously
and whether the molting process is similar for all age classes of whales.
Materials and methods
We opportunistically made boat-based sightings of EC-WG bowhead whales in Cumberland
Sound, Nunavut, Canada—specifically in Kingnait Fiord (located on the northeast side of
Cumberland Sound Fig 1)—on five days from 13–21 August, 2014. As a result of these prelimi-
nary observations, a directed study to test the hypothesis that bowhead whales use Cumberland
Sound in part for molting during summer months was carried out in August 2016.
Zooplankton samples were opportunistically collected during August 2014 from surface
waters (0.5 m) near bowhead whales, and also following an unusual observation of bowhead
whales in shallow, coastal waters in Kingnait Fiord. All samples were collected using 333-
micrometer (μm) conical mesh net (30 cm in diameter) fitted with a General Oceanics helical
flow meter. The zooplankton net was sprayed down with a hose using seawater to collect the
sampled organisms in an attached cod-end bucket once it was brought onboard the boat.
Once organisms were no longer visible in the zooplankton net, the cod-end bucket samples
were filtered through a 333 μm mesh sieve and transferred to a 250 mL sample jar and pre-
served in 5% buffered formalin solution for identification.
Boat-based and aerial sightings of bowhead whales were made in Pangnirtung Fiord,
Brown Harbour (located between Pangnirtung Fiord and Kingnait Fiord, Fig 1) and Kingnait
Fiord from 7–31 August 2016. High-resolution aerial images (n = 1143) and video were
obtained of encountered whales using a small unmanned aerial system (sUAS), the DJI Phan-
tom 3 Professional. The sUAS was equipped with a global positioning system (GPS) and altim-
eter that allowed for the whale’s position and the sUAS altitude to be automatically recorded
when each image was captured. The sUAS was flown at an average altitude of 12.9 m (±5.4 SD)
with a maximum distance of 1000 m from the survey vessel, and was hand-deployed and
hand-retrieved from the ~8 m aluminum vessel. Flight times lasted ~8–12 min. The sUAS data
were collected under Special Flight Operation Certificate File Number 5812-11-682, ATS 16-
17-00014027, RDIMS 12044419 and approved by the University of British Columbia Animal
Bowhead whale molting and rock-nosing
PLOS ONE | November 22, 2017 2 / 15
awarded to S.H. Ferguson and World Wildlife Fund
Canada (Arctic Species Conservation Fund)
awarded to W.R. Koski and S.M.E. Fortune.
Additional field work support was provided by: U.S.
Department of the Interior, Minerals Management
Service (MMS; now Bureau of Ocean Energy
Management), through Inter-agency Agreement
No. M08PG20021 with the U.S. Department of
Commerce, National Oceanic and Atmospheric
Administration, as part of the MMS Alaska
Environmental Studies Program awarded to M.F.
Baumgartner. Personnel support was provided by:
Natural Sciences and Engineering Research
Council Canadian Graduate Scholarship, the W.
Garfield Weston Award for Northern Research,
University of British Columbia Affiliated Fellowship
and Northern Scientific Training Program
(Canadian Polar Commission) awarded to S.M.E.
Competing interests: Two co-authors (WRK &
JWH) have commercial affiliations (LGL Limited &
Higdon Wildlife Consulting). The commercial
affiliations of our co-authors has not altered our
adherence to all PLOS ONE policies on data sharing
and materials.
Care Committee (Animal Care Amendment A14-0064-A002). Bowhead whale behavioral data
were collected under permit Department of Fisheries and Oceans License to Fish for Scientific
Purposes S-16/17 1005-NU and Animal Use Protocol FWI-ACC-2016-09.
Still sUAS images of bowhead whales were used to determine unique animals during
August 2016 as well as their body lengths and skin conditions. Individual animals were identi-
fied using well-established permanent black and white dorsal patterns [19]. The markings used
to identify unique individuals included: 1) white scars on their body attributed to breaking sea
ice, encounters with fishing gear or from interactions with killer whales (Orcinus orca) (i.e.,
killer whale rake marks [20]; and 2) white pigmentation found on the dorsal flukes, caudal
peduncle and lower jaw. Body length measurements (distance between snout and fluke notch)
were made for animals that were photographed with the vessel (an object of known size used
for calibration) in the same frame or another animal of known size (i.e., previously photo-
graphed with the vessel). The measuring tool in Adobe Photoshop CS6 extended was used to
measure body length. Skin condition was also assessed from still images to determine: 1) pro-
portion of the body that contained sloughing skin (0 = none, 1 = <33%, 2 = 33–66%, 3 =
>66% and <100% and 4 = 100%; Fig 2); and 2) the type of sloughing (0 = none, 1 = light gray
lines across the body likely caused by rock rubbing, 2 = irregular patches of gray sloughed
skin, 3 = smooth gray body attributed to complete or near complete sloughing; Fig 3). The
Fig 1. Locations of fieldwork conducted in the eastern Canadian Arctic showing Baffin Island, Canada (left panel), and Iqaluit, the capitol of
Nunavut (designated with a black ) and Pangnirtung, a community located in Cumberland sound (red ). The inset map of Cumberland Sound
shows where bowhead whale (Balaena mysticetus) observations were made in a small bay in Kingnait Fiord (blue ) in 2014 from a vessel and from sUAS
in Brown Harbour (blue ), Pangnirtung Fiord and Kingnait Fiord in 2016. The polygon shapefiles and polyline shapefile used to generate this map were
accessed through Esri Canada and were licensed through Natural Resources Canada for free distribution.
Bowhead whale molting and rock-nosing
PLOS ONE | November 22, 2017 3 / 15
presence of gray tissue is indicative of new skin growth—based on our observations and those
of bowheads molting in the Okhotsk Sea [18]. Three people independently scored each animal,
and agreement between at least two people was required to obtain a final score.
We opportunistically collected oceanographic data during August 2016 to evaluate the
physical properties of Kingnait Fiord. Vertical profiles of the water column were made using a
seabird SBE19Plus conductivity, temperature, and depth (CTD) profiler. CTD data were cor-
rected using Seabird software and temperature and salinity plots were generated using the
downcast data for each cast (n = 86).
Results and discussion
2014 Observations
Unusual behaviors of bowhead whales in shallow coastal-waters were first noted on 21 August
2014 in Kingnait Fiord when 8–10 bowhead whales were observed frequently rolling onto
Fig 2. Example of an animal with nearly no sloughing skin (i.e., proportion of body with sloughing skin = <33%) (A)
and another bowhead whale with a high degree of sloughing (>66% of body) and a blotchy skin type (B).
Bowhead whale molting and rock-nosing
PLOS ONE | November 22, 2017 4 / 15
their sides and backs and lifting their pectoral flippers out of the water (Fig 4). The small, shal-
low bay was marked with large boulders (65˚ 55’15.2”N and 65˚ 17’50.8” W, Figs 4&5) and
the whales were in ~8 m of water. The animals did not appear to be associated with one
another as they were widely distributed throughout the bay and exhibited individually specific
behaviors. Several audible vocalizations were heard without a hydrophone from the vessel
over the course of the sighting. Net sampling revealed very low zooplankton biomass, particu-
larly for species that are known bowhead whale prey (e.g., calanoid copepods, euphausiids,
Fig 3. Example of (A) a bowhead whale with thin and sharp light gray lines and (B) of a whale with shorter and
wider gray lines, that both likely reflect prior rock-rubbing behavior.
Bowhead whale molting and rock-nosing
PLOS ONE | November 22, 2017 5 / 15
amphipods), indicating that the whales were not feeding in the bay. There was little likelihood
that the whales were feeding because subsequent zooplankton sampling failed to capture bow-
head whale prey.
Irregularities in bowhead whale skin condition were observed from animals visiting the
bay. Photographs taken of two whales before they reached the bay revealed large pieces of
loose epidermis. The sloughing epidermis was predominately located posterior to the whale’s
blowholes (Fig 6). Animals also presented mottled skin consisting of light gray irregular
patches on their heads near the blowholes and on their backs (Fig 6). Furthermore, histological
analysis of a sample of loose epidermis from one whale obtained using a crossbow and biopsy
dart was consistent with molting. These documented skin irregularities were similar to the his-
tology of biopsy and opportunistic skin collected from bowhead whales in the Okhotsk Sea
[18], and provide support that molting occurs during summer based on the timing of collec-
tion and histological properties of our bowhead samples [21].
2016 Observations
Rock rubbing. Following our initial observations in 2014, we used the sUAS to document
four bowhead whales rubbing on large boulders in shallow coastal waters on 7 August 2016
in Brown Harbour (65˚ 58’31.0” N and 65˚ 57’19.0” W, Fig 1). While simultaneously filming
this rubbing behavior, we made boat-based observations of whales rolling onto their sides
with pectoral flippers extended out of the water similar to our prior observations (during
summer 2014). The aerial video and high-resolution still images of the animals displaying
surface behaviors confirmed that they were rubbing their bodies against rocks (Fig 7 &S1
Movie). The whales were seen rubbing their chins, head, back and sides on a cluster of boul-
ders and had mottled skin with what appeared to be long superficial scratches that ran length-
wise and widthwise along their bodies (e.g., Fig 7 animal C). This rubbing behavior was
consistent with previous observations and supported our hypothesis that bowhead whales
Fig 4. Example of observed behavior and relative distribution of three individual bowhead whales (A-C)
inside the bay in Kingnait Fiord (2014). Whale (A) is resting close to shore with its head out of the water, (B) is
on its back with pectoral flippers extended, and (C) is breaking the surface of the water in the distance.
Bowhead whale molting and rock-nosing
PLOS ONE | November 22, 2017 6 / 15
engage in exfoliation activities during the summer in Cumberland Sound. We presume that
rubbing activities caused the linear markings. One animal was observed rock rubbing for a
minimum of 8 minutes based on aerial imagery (S1 Movie).
Previous observations of bowhead rock-rubbing behavior have been documented during
late summer and early fall in Isabella Bay (Baffin Bay), whereby bowhead whales engaged in
“grooming” activities by rubbing on the bottom [22,23]. Similarly, whaling records [24] pro-
vide historical support for bowhead rubbing behavior dating back to ~1845, whereby whales
found in the bays and inlets of Davis Strait (such as Cape Searl) were referred to as “rock-nose”
whales because they would place their head or “nose” close to the shore on a rock [25]. More
recently, similar “rock-nose” behavior was observed during an aerial survey of Isabella Bay on
13 September 1979 [26].
Recent Inuit observations of bowhead whales with molting skin during summer were made
near Clyde River (nearest community to Isabella Bay) [27]. Whales were also observed circling
around a large rock off the coast of Clyde River [27], and were hypothesized to use the rocks
for resting purposes [24]. However, the association between EC-WG bowhead whales with
molting skin and their physical environment suggests otherwise. The whaling data provide fur-
ther evidence that they have engaged in rock-rubbing behavior off the coast of Baffin Island
for at least hundreds of years.
Aerial image analysis. Our analysis of high-resolution images from the sUAS indicates
pervasive molting for individuals occupying Cumberland Sound during summer. Overall,
Fig 5. Large boulders located in the shallow bay where the bowhead whales (Balaena mysticetus) aggregated in
Kingnait Fiord, NU, during 2014 and where prey samples were subsequently collected.
Bowhead whale molting and rock-nosing
PLOS ONE | November 22, 2017 7 / 15
image quality was sufficient to assess molting extent and type for 97.6% (n = 81) of the
uniquely identified individuals (n = 83), and revealed that 100% of the individuals had skin
irregularities consistent with molting (Fig 8A &S1 Data). We found that molting was extensive
for 37.4% of the identified whales, whereby sloughing skin represented >66% of their body.
We also found that 37.04% of animals had sloughing skin over 33 to 66% of their body and
25.93% had molting skin on <33% of their body. Over half (58.02%) of the photographed ani-
mals had the mottled skin pattern without evidence of rubbing, while 40.74% showed signs of
rock-rubbing behavior (Fig 8B).
Our estimated occurrence of rock rubbing from our photographs is likely underestimated
due to: 1) limited image quality, particularly when whales were photographed below ~10 m
depth; and 2) limited perspective of individual’s body whereby evidence of rock rubbing (i.e.,
light gray lines) may be on the ventral side of the animal and thus excluded from our analysis.
As a consequence, our estimate of the proportion (40.74%) of unique individuals bearing
marks from probable rock-rubbing behavior is a minimum estimate.
Overall, we measured body lengths for 16 unique whales ranging from 6.3–14.2 m, with a
mean length of 10.60 m (±2.01 SD) (Fig 9). Age-class was broadly inferred based on previous
studies [23,28,29] that found calves (i.e., young-of-the year) are ~4–7.5 m in August and Sep-
tember, young juveniles (1 to 8–10 y) are 5.8–10 m [26], sexually immature sub-adults (8–10
to ~25 y) are 10–13 m, and sexually mature adult (25+ y) males exceed 12.5 m [30] and females
exceed 13 m [31]. We used the threshold of 13 m for assigning individuals adult status. Of the
Fig 6. Example of sloughing epidermis (A) located behind the blowholes of a bowhead whale (Balaena mysticetus) and
mottled skin (B) found near the blowholes.
Bowhead whale molting and rock-nosing
PLOS ONE | November 22, 2017 8 / 15
animals measured, none were calves based on the morphological differences between calves
and yearlings [26]. However, we did observe one small yearling measuring 6.26 m. Conse-
quently, we concluded that 38% (n = 6) of the measured animals were young juveniles (8.59 m,
±1.33 SD), 56% (n = 9) were sub-adults (11.54 m, ±0.91 SD), and only one animal was an
adult (6%) with a body length of 14.22 m. Overall, our measurements of total body length dem-
onstrated that both juvenile and adult animals occupied Cumberland Sound, and that all ani-
mals had sloughing skin.
Energetic implications of molting. Although we were unable to quantify the proportion
of time allocated to molting activities, whales were routinely observed, during daylight hours,
resting in addition to actively rubbing against the rocks suggesting that individuals allocate
considerable time to these two activities. On numerous occasions, our sUAS deployments doc-
umented molting individuals resting in nearshore waters where rock rubbing was previously
Molting is energetically costly for pinniped species that elevate their resting metabolism
while increasing blood flow to the epidermis and generating new hair [3235]. Seals and sea
lions have behavioral adaptations to partially offset the metabolic costs associated with molt-
ing, such as increasing the time spent on land (i.e., reduced energy expenditure due to thermo-
regulation and activity costs associated with swimming). Similarly, bowhead whales may
adjust their daily activity costs by increasing the proportion of time spent resting. This may be
simultaneously beneficial as warmer water may expedite the molting process [4] and taking
refuge in shallow, protected bays may mitigate predation from killer whales.
Unlike seals and sea lions that reportedly experience thermoregulatory benefits by hauling
out while molting, bowhead whales may overheat while molting in warmer water because they
are too well-insulated (bowheads have the thickest blubber of any marine mammal, ranging
from 20–35 cm) [3640] and have small surface area to volume ratios that favor retention of
Fig 7. Example of four bowhead whales (Balaena mysticetus) with mottled skin rubbing their bodies
against boulders in Brown Harbour on 7 August 2016. Animal (A) pictured rubbing the right side of its
head on a boulder (S1 Movie) and animal (D) is using the rocks to exfoliate its chin. Evidence of prior rock-
rubbing is apparent for animal (C) with long, thin lines running length and width-wise across the body.
Bowhead whale molting and rock-nosing
PLOS ONE | November 22, 2017 9 / 15
metabolic heat. Maximum daily surface water temperatures ranged from ~4 to 9.5˚ C in King-
nait Fiord based on the CTD data collected during August 2016, and appeared to be highest
near the rock-rubbing habitat with surface temperatures ranging from ~8 to 9.5˚ C. However,
maximum water temperatures encountered by bowhead whales may be even warmer in shal-
lower (~8 m) areas compared with our measurements, which were made in comparatively
deep (~100 m) areas of the bay just outside of where rock rubbing occurred. Consequently,
Fig 8. Percentage of photographically identified bowhead whales with sufficient image quality to quantify the
amount of the body containing sloughing skin (n = 81) (A). Overall, all animals showed signs of molting in late
August, and no animals had bodies with 100% new skin cover. Also shown is type of sloughing skin (B)
whereby ‘none’ represents animals with no skin irregularities, ‘rock rubbing’ is indicated by animals with both
sharp, thin light gray lines and/or wider, less pronounced light gray lines which are likely a result of prior rock
rubbing, ‘blotchy’ comprises animals with irregular patches of new epidermis and ‘covered’ includes animals
with extensive new skin growth.
Bowhead whale molting and rock-nosing
PLOS ONE | November 22, 2017 10 / 15
bowheads may have to use vascular adaptations to dissipate excess heat while rock rubbing in
the warmer, coastal waters.
One way for bowhead whales to dump excess heat may be to use their intraoral thermoreg-
ulatory organ located in the root of the tongue (i.e., counter current retial vessels) [41] and at
the center of the hard palate stretching to the tip of the rostral palate (i.e., palate rete or corpus
cavernosum maxillaris) [36]. They could effectively use this organ by slightly opening their
mouths to permit cooling seawater to enter their mouth and flow over the retial vessels in the
tongue and the palate rete. We observed several bowhead whales in the aerial images with their
mouths slightly agape (S1 Image) near rock rubbing areas (i.e., Brown Harbour). While it is
possible that they were feeding, prior prey sampling in similar shallow habitats in Kingnait
Fiord found very few zooplankton and their baleen was not visibly extended. It therefore
seems more plausible that the whales opened their mouths to cool themselves because they
were thermally stressed in the warmer, shallow rock-rubbing habitat while actively swimming
during exfoliation activities. They may have thus regulated their body temperature by exchang-
ing heat from enlarged blood vessels in their tongues and palates with the comparatively cooler
seawater [3641].
Biological significance of molting. There are biological factors affecting skin condition
that may explain why bowhead whales molt. One is that they may slough their skin to shed
ectoparasites such as cyamids (i.e., whale lice) [42,43] and accumulated diatoms (i.e., phyto-
plankton) [44] that may damage their epidermis and potentially impede thermoregulation.
Another possibility is that bowhead whales are shedding solar damaged skin [45]. Annual
replacement of skin may reduce the risk of extended exposure to ultraviolet radiation during
summer in high-latitude habitats [46], and may be particularly important for long-lived species
such as bowhead whales because skin damage accumulates with age [47]. Regularly sloughing
Fig 9. The measured body lengths of 16 unique bowhead whales separated into 8 bins where ~6 m
was the minimum size and ~14 m was the maximum. The total body length represents the straight-line
distance calculated between the tip of the snout to the fluke notch.
Bowhead whale molting and rock-nosing
PLOS ONE | November 22, 2017 11 / 15
skin damaged by the accumulation of parasites, diatoms and solar radiation may thus allow
bowhead whales to maintain epidermal function and integrity over time.
Overall, our observation of skin irregularities (e.g., mottled skin pattern, sharp light gray lines,
loose epidermis) of various age-classes (juveniles, sub-adults and adults) provides strong evi-
dence that molting is pervasive for bowhead whales during summer in Cumberland Sound. In
Cumberland Sound, molting occurred in shallow, warm coastal areas that had low-salinity sur-
face waters (characteristic of sub-Arctic fiords), and appeared to be facilitated by rubbing on
large rocks. The elevated water temperature in rock-rubbing habitat may stimulate epidermal
growth [11,48], whereby increased water temperature elevates skin temperature and enhances
the rate of cutaneous metabolic processes [11]. Furthermore, increased ambient temperatures
promotes cutaneous blood flow, bringing nutrients and hormones (e.g., thyroid hormone)
known to stimulate epidermal proliferation [11]. Such habitat is comparable to areas where
beluga whales rub on rocky substrate in estuaries [24,25], and where bowheads belonging to
the Okhotsk Sea population were observed molting [11,15,48].
Our findings lend support to previous hypotheses that molting is facilitated by pronounced
changes in oceanographic conditions such as water temperature [18], and suggest that rock-
rubbing behavior is used to facilitate the molting process through exfoliation. Additional
research needs to address questions regarding the seasonality of the molt (i.e., is molting more
pronounced during summer months or does it occur uniformly and continuously throughout
the year?) by collecting year-round aerial imagery (excluding winter months with 24 hour
darkness), and monitoring the skin condition of bowhead whales over time. Finally, our obser-
vations provide evidence that the function of “rock-nosing” observed by whalers, scientists,
and northern community members is related to exfoliation to facilitate molting.
Supporting information
S1 Movie. sUAS video of one bowhead whale rubbing on a large rock in Brown Harbour on
7 August 2016. This individual (A) was observed with three other individuals that subse-
quently engaged in rubbing behavior (Fig 6).
S1 Data. sUAS data for 83 unique bowhead whales used to determine body length (m),
sloughing amount (0 = none, 1 = <33%, 2 = 33–66%, 3 = >66% and <100% and 4 = 100%),
sloughing type (0 = none, 1 = light gray lines from probable rock-rubbing behavior, 3 = cov-
ered) and whether the mouth was closed (e.g., 0), slightly open (1), wide open (2), or inde-
terminable (9).
S1 Image. Example of a bowhead whale with mouth slightly agape near Brown Harbour
during August 2016.
We are appreciative of the aerial imagery and video collected and generously provided by
Thomas Seitz (VDOS Global LLC) and the boat-based images collected by Maha Ghazal. We
are grateful for the logistical support provided by our community partners, Ricky and Peter
Kilabuk, who were responsible for vessel operations. Histological analysis of sloughing
Bowhead whale molting and rock-nosing
PLOS ONE | November 22, 2017 12 / 15
bowhead whale epidermis was graciously conducted by Stephen Raverty. This manuscript was
improved by the helpful comments and edits provided by Julie Mocklin and an anonymous
Author Contributions
Conceptualization: Sarah M. E. Fortune, Steven H. Ferguson.
Data curation: Sarah M. E. Fortune, William R. Koski.
Formal analysis: Sarah M. E. Fortune, William R. Koski, Jeff W. Higdon.
Funding acquisition: Sarah M. E. Fortune, William R. Koski, Mark F. Baumgartner, Steven H.
Investigation: Sarah M. E. Fortune, William R. Koski, Steven H. Ferguson.
Methodology: Sarah M. E. Fortune, William R. Koski, Jeff W. Higdon.
Project administration: Sarah M. E. Fortune.
Resources: Andrew W. Trites, Mark F. Baumgartner, Steven H. Ferguson.
Software: Sarah M. E. Fortune.
Supervision: Sarah M. E. Fortune, Andrew W. Trites, Steven H. Ferguson.
Validation: Sarah M. E. Fortune, William R. Koski, Jeff W. Higdon.
Visualization: Sarah M. E. Fortune, Jeff W. Higdon.
Writing – original draft: Sarah M. E. Fortune, Steven H. Ferguson.
Writing – review & editing: Sarah M. E. Fortune, William R. Koski, Jeff W. Higdon, Andrew
W. Trites, Mark F. Baumgartner, Steven H. Ferguson.
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... Baleen whales were also observed exhibiting behaviours, such as bottom contact, that are not associated with feeding. Aerial footage from drones showed that bowhead whales (Balaena mysticetus) were using rocks to assist with removal of skin during summer with the whales selecting their habitats based on geological and oceanographic features [12,18]. A similar activity was described for belugas (Delphinapterus leucas) undertaking active abrasion of the skin to enhance moulting by rubbing on pebble, mud, and limestone on the bottom of shallow waters [19]. ...
... This type of behaviour is also known from other cetaceans such as bowhead whales. These baleen whales were seen rubbing on rocks regularly, which likely facilitates their moulting [18]. Throughout the class, Mammalia skin care is an essential component of well-being and health. ...
... Singing male humpback whales, for example, have a preference for shallow water (between 15-55 m depth), sandy substrates, and flat seafloors [65,66]. It is reasonable to speculate that humpback whales seek sandy substrate specifically to roll, similar to bowhead whales selecting habitat with suitable rocks for rubbing [18]. Undisturbed access to such habitats is likely important for the whale's well-being and should be considered in whale conservation. ...
Full-text available
Cetaceans are known for their intelligence and display of complex behaviours including object use. For example, bowhead whales (Balaena mysticetus) are known to rub on rocks and some humpback whale (Megaptera novaeangliae) populations undertake lateral bottom feeding. Such underwater behaviour is difficult to observe but can play a critical role in the whales’ survival and well-being. Distinguishing social behaviours from those which serve a specific function remains challenging due to a lack of direct observations and detailed descriptions of such behaviours. A CATS (Customized Animal Tracking Solutions) suction cup tag with on board video and a 3D inertial measurement unit was deployed on three different humpback whales to assess their behaviour in the Gold Coast bay, Australia. Here, we present evidence of humpback whales (tagged and untagged individuals) performing bottom contact with prolonged rolling on sandy substrate. In addition, we showed that fish were actively feeding from the whales’ skin during this behaviour. We detail the behaviour and discuss possible drivers, with a focus on cetacean innovation, possible ectoparasite removal, and habitat preferences.
... Low swimming speeds and high turning angles reflected 'resident' behaviour, whereas faster and more linear movements reflected 'transit' behaviour. Resident behaviour is expected to be associated with foraging (e.g., Haskell 1997;Hill et al., 2000;Fauchald and Tveraa 2003;Thums et al., 2011;Byrne and Chamberlain, 2012) and other spatially limited behaviours such as reproduction (Würsig et al., 1993;Kraus and Hatch, 2001) and rock-rubbing (Fortune et al., 2017). During winter when sea ice thickness and cover are maximized, resident behaviour may also reflect a degree of spatial restriction such that horizontal movement is limited. ...
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The ecological impact of environmental changes at high latitudes (e.g., increasing temperature, and decreased sea ice cover) on low-trophic species, such as bowhead whales, are poorly understood. Key to understanding the vulnerability of zooplanktivorous predators to climatic shifts in prey is knowing whether they can make behavioural or distributional adjustments to maintain sufficient prey acquisition rates. However, little is known about how foraging behaviour and associated environmental conditions fluctuate over space and time. We collected long-term movement (average satellite transmission days were 397 (± 204 SD) in 2012 and 484 (± 245 SD) in 2013) and dive behaviour data for 25 bowhead whales (Balaena mysticetus) equipped with time-depth telemetry tags, and used hierarchical switching-state-space models to quantify their movements and behaviours (resident and transit). We examined trends in inferred two-dimensional foraging behaviours based on dive shape of Eastern Canada-West Greenland bowhead whales in relation to season and sea ice, as well as animal sex and age via size. We found no differences with regards to whale sex and size, but we did find evidence that subsurface foraging occurs year-round, with peak foraging occurring in fall (7.3 hrs d-1 ± 5.70 SD; October) and reduced feeding during spring (2.7 hrs d-1 ± 2.55 SD; May). Although sea ice cover is lowest during summer foraging, whales selected areas with 65% (± 36.1 SD) sea ice cover. During winter, bowheads occurred in areas with 90% (± 15.5 SD) ice cover, providing some open water for breathing. The depth of probable foraging varied across seasons with animals conducting epipelagic foraging dives (< 200 m) during spring and summer, and deeper mesopelagic dives (> 400 m) during fall and winter that approached the sea bottom, following the seasonal vertical migration of lipid-rich zooplankton. Our findings suggest that, compared to related species (e.g., right whales), bowheads forage at relatively low rates and over a large geographic area throughout the year. This suggests that bowhead whales have the potential to adjust their behaviours (e.g., increased time allocated to feeding) and shift their distributions (e.g., occupy higher latitude foraging grounds) to adapt to climate-change induced environmental conditions. However, the extent to which energetic consumption may vary seasonally is yet to be determined.
... (2017) even though they are shorter than blue whales. As bowhead whales also undergo a molt during summer (Fortune et al. 2017), we assume skin samples represent the isotopic niche integrated over a maximum period of one year, but likely reflects the isotopic niche of the previous summer/fall when skin is re-grown and the most intense foraging occurs (Fortune et al. 2020b). ...
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Shifts in zooplankton quantity and quality caused by climate change could challenge the ability of bowhead whales to meet their energetic requirements. When facing such selection pressure, intra-population variation dampens the negative effects and provides population-level resilience. Previous studies observed inter-individual diet variation in bowhead whales, but the mechanism responsible for the variation was undetermined. We investigated foraging variability in Eastern Canada-West Greenland bowhead whales using dietary biomarkers (stable isotopes, fatty acids) and movement data (satellite telemetry with time-depth recorders) from the same individuals. We found that bowhead whale individuals using distinct summer and fall foraging habitats displayed differences in horizontal movements, foraging dive depth, and diet. For individuals using the Canadian Arctic Archipelago habitat (Foxe Basin, Gulf of Boothia, Prince Regent Inlet, Lancaster Sound and Admiralty Inlet, Nunavut), they performed long distance movements across regions, and their foraging dive depth was generally shallow, but increased from July to November. These whales displayed higher δ ¹³ C and δ ¹⁵ N values and ratios of C16:1n7/C16:0. Individuals using the West Baffin Bay habitat (Cumberland Sound, Baffin Bay, Davis Strait) were more localized in their horizontal movements and consistent over time in their foraging dive depth, which was generally deeper. These whales displayed lower δ ¹³ C and δ ¹⁵ N values and ratios of C16:1n7/C16:0. Overall, this inter-individual variation in diet and foraging behaviour could indicate some niche variation which would be beneficial for the population under changing habitats and prey availability.
... Histological analysis has revealed that bowhead whales belonging to the Okhotsk Sea population moult during summer months while occupying a warm, shallow bay. Shedding of epidermal sheets of varying sizes and thickness, enhanced by tail slapping and breaching was classified as proper moulting in bowhead whales (Chernova et al., 2017;Fortune et al., 2017;Shpak & Paramonov, 2018). The detailed histological study by Chernova et al. (2017), comparing moulting to non-moulting skin, showed differences in features of the typical adult skin moult from the temporal moult in bowhead whales. ...
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Cetacean skin continues to be the investigative focus of researchers from several different scientific disciplines. Yet, most research on the basic functions of lipo‐keratinocytes, which constitute most of the cetacean epidermis, providing the first layer of protection against various environmental aggressors (including an ever‐increasing level of pollutants), is restricted to specialized literature on the permeability barrier only. In this review, we have attempted to bring together much of the recent research on the functional biology of cetacean skin, including special adaptations at the cellular, genetic and molecular level. We have correlated these data with the cetacean permeability barrier’s unique structural and metabolic adaptations to fully aquatic life, including the development of secondary barriers to ward off challenges such as biofouling as well as exposure to extreme cold for the epidermis, which is outside of the insulation provided by blubber. An apparent contradiction exists between some of the reported gene loss for lipogenic enzymes in cetacean skin and the high degree of cetacean epidermal lipogenesis, as well as loss of desmocollin 1 and desmoplakin genes [while immunolocalization of these proteins is reported (Journal of Anatomy, 234, 201)] warrants a re‐evaluation of the gene loss data.
... Cetaceans spend the vast majority of their lives at various depths below the ocean surface, consequently vertical movement must be considered equally if not more so than horizontal movement to fully understand the ecological significance of animal behavior. Dive behavior of marine mammals may serve a number of functions depending on the structure of the dive and depths targeted, including foraging (Viviant et al., 2014), transiting (McGovern et al., 2019), resting (Wright et al., 2017), aiding digestion (Crocker et al., 1997), reproductive behaviors (Baechler et al., 2002), predator avoidance (Aguilar de Soto et al., 2020), molting (Fortune et al., 2017), and possibly navigation (Matsumura et al., 2011). ...
Full-text available
Dive behavior represents multiple ecological functions for marine mammals, but our understanding of dive characteristics is typically limited by the resolution or longevity of tagging studies. Knowledge on the time-depth structures of dives can provide insight into the behaviors represented by vertical movements; furthering our understanding of the ecological importance of habitats occupied, seasonal shifts in activity, and the energetic consequences of targeting prey at a given depth. Given our incomplete understanding of Eastern Beaufort Sea (EBS) beluga whale behavior over an annual cycle, we aimed to characterize dives made by belugas, with a focus on analyzing shifts in foraging strategies. Objectives were to (i) characterize and classify the range of beluga-specific dive types over an annual cycle, (ii) propose dive functions based on optimal foraging theory, physiology, and association with environmental variables, and (iii) identify whether belugas undergo seasonal shifts in the frequency of dives associated with variable foraging strategies. Satellite-linked time-depth-recorders (TDRs) were attached to 13 male belugas from the EBS population in 2018 and 2019, and depth data were collected in time series at a 75 s sampling interval. Tags collected data for between 13 and 357 days, including three tags which collected data across all months. A total of 90,211 dives were identified and characterized by twelve time and depth metrics and classified into eight dive types using a Gaussian mixed modeling and hierarchical clustering analysis approach. Dive structures identify various seasonal behaviors and indicate year-round foraging. Shallower and more frequent diving during winter in the Bering Sea indicate foraging may be energetically cheaper, but less rewarding than deeper diving during summer in the Beaufort Sea and Arctic Archipelago, which frequently exceeded the aerobic dive limit previously calculated for this population. Structure, frequency and association with environmental variables supports the use of other dives in recovery, transiting, and navigating through sea ice. The current study provides the first comprehensive description of the year-round dive structures of any beluga population, providing baseline information to allow improved characterization and to monitor how this population may respond to environmental change and increasing anthropogenic stressors.
... It appears that cetaceans migrate to warmer waters at lower latitudes to reduce heat loss during moult, a period during which they enlarge blood flow through the skin. Similarly, the pagophilic species that remain in the Arctic year-round, make seasonal migrations towards warmer waters in estuaries and shallows to moult [68][69][70]. ...
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Climate warming in the Arctic has led to warmer and earlier springs, and as a result, many food resources for migratory animals become available earlier in the season, as well as become distributed further northwards. To optimally profit from these resources, migratory animals are expected to arrive earlier in the Arctic, as well as shift their own spatial distributions northwards. Here, we review literature to assess whether Arctic migratory birds and mammals already show shifts in migration timing or distribution in response to the warming climate. Distribution shifts were most prominent in marine mammals, as expected from observed northward shifts of their resources. At least for many bird species, the ability to shift distributions is likely constrained by available habitat further north. Shifts in timing have been shown in many species of terrestrial birds and ungulates, as well as for polar bears. Within species, we found strong variation in shifts in timing and distributions between populations. Ou r review thus shows that many migratory animals display shifts in migration timing and spatial distribution in reaction to a warming Arctic. Importantly, we identify large knowledge gaps especially concerning distribution shifts and timing of autumn migration, especially for marine mammals. Our understanding of how migratory animals respond to climate change appears to be mostly limited by the lack of long-term monitoring studies.
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Nest predation is a primary cause of reproductive failure in birds; thus, predators apply strong selective pressure on nesting behaviour, especially risk assessment behaviours during predator encounters at nests. Prey's risk assessments are not static; rather, dynamic risk assessment theory predicts that prey assess risk in real-time and update it according to changes in cues posed by the predator(s). We used drone videography to film nest-flushing behaviours of common eiders, Somateria mollissima, in response to foraging polar bears, Ursus maritimus, on East Bay Island (Nunavut, Canada). We assessed how cue use influenced flushing behaviour and nest fate in a path analysis using 200 observations of 193 eiders in 2017. Our most supported model found that more direct angles of visual gaze and travel angle by polar bears resulted in conspicuous nest flushes by eiders (β = −0.236 ± 0.059), whereas the presence of herring gulls, Larus argentatus, resulted in more discrete flushes of hens walking from their nests (β = −0.181 ± 0.059). Shorter flush initiation distances between eiders and approaching bears resulted in greater nest predation by polar bears (β = −0.203 ± 0.076). We found no support that an eider's visibility from the nest influenced any component of flushing behaviour. We suggest that during encounters with bears, eiders are capable of assessing risk and making appropriate behavioural decisions to reduce the chances of nest loss. However, as the colony experienced heavy predation by bears in 2017, behavioural responses alone appear to be insufficient to mitigate polar bear predation at the population level.
With the booming development of information technology and the growing demand for remote sensing data, unmanned aerial vehicle (UAV) remote sensing technology has emerged. In recent years, UAV remote sensing technology has developed rapidly and has been widely used in the fields of military defense, agricultural monitoring, surveying and mapping management, and disaster and emergency response and management. Currently, increasingly serious marine biological and environmental problems are raising the need for effective and timely monitoring. Compared with traditional marine monitoring technologies, UAV remote sensing is becoming an important means for marine monitoring thanks to its flexibility, efficiency and low cost, while still producing systematic data with high spatial and temporal resolutions. This study visualizes the knowledge domain of the application and research advances of UAV remote sensing in marine monitoring by analyzing 1130 articles (from 1993 to early 2022) using a bibliometric approach and provides a review of the application of UAVs in marine management mapping, marine disaster and environmental monitoring, and marine wildlife monitoring. It aims to promote the extensive application of UAV remote sensing in the field of marine research.
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In conducting Arctic field research, hiring local field guides has long been a necessity for providing field teams with local knowledge and fundamental needs of boat operation and navigation, general field logistics/safety, and traditional ecological knowledge (TEK) of local animal distribution and natural history. As new threats to Arctic wildlife emerge and as field research methods evolve, including local Inuit as long-standing members of research teams has provided additional collaborative benefits through expanded local knowledge, greater efficiency of data collection, and longer temporal sampling which provides the opportunity to study uncommon events. We describe the collaboration between southern-based scientists and local Inuit from the community of Pangnirtung, Nunavut, to conduct field research on marine mammals in Cumberland Sound from 1997 to 2021. Through a keen interest in marine mammal field research, Inuit partners in Pangnirtung have become highly proficient in all aspects of sample and data collection and have received advanced technical training to allow for an expanded role in achieving research objectives. This expanded role includes running field research operations independently, as well as the extensive use of drones to capture photographs of whales for the purposes of photographic-identification and to record behavior. Collaboration with local Inuit also provides benefits through employment opportunities, development of technical skills, and opportunities to actively participate in research that aims to conserve culturally important local wildlife populations.
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In bowhead whales summering in Ulbanskiy Bay of the Okhotsk Sea, molting of epidermis has been found and histologically confirmed. The outer layer of the molting whale epidermis is longitudinally stratified and rejected in the form of relatively large plates up to several millimeters thick, each representing a lamellar formation consisting of longitudinal rows of parakeratocytes with degenerated nuclei, numerous pigment granules, and lipid inclusions. Molting intensity is correlated with the level of proliferation and regeneration of all epidermal layers, which helps to maintain the optimal skin thickness.
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We present findings on the prevalence and abundance of cyamid ectoparasites (Cyamus ceti) or “whale lice” on bowhead whales (Balaena mysticetus) harvested for subsistence in the Bering, Chukchi, and Beaufort Seas from 1973 to 2015. Cyamids were present on 20% of the 673 whales that were examined for cyamid ectoparasites. Logistic regression was used to determine factors associated with cyamid prevalence. The probability of cyamid presence increased with age, length, and improving body condition, but decreased over the past 35 years. Cyamid presence was also more probable on whales harvested in the spring than on those harvested in the fall. When present, cyamid abundance was typically low(< 10 per whale). Case histories provide ancillary information about the relationships between abundance of cyamids and their bowhead hosts. Environmental change and increasing anthropogenic disturbances are expected to occur in the Arctic regions inhabited by bowheads. We recommend continued monitoring of subsistence harvested whales for cyamids, as well as further investigations into the roles of environmental and anthropogenic variables in cyamid prevalence and abundance, as part of a comprehensive program of Arctic ecosystem assessment.
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Since the mid-1970s, study has focused on reproductive biology of female bowhead whales, while little has been described for males. This study evaluates testicular morphology (mass and length) and histology in relation to body length to determine the onset of male sexual maturity. Mean testis mass and mean testis length were highly correlated. Body length and mean testis mass were significantly correlated and an inflection of increased testicular mass occurred at approximately 12.5-13.0m suggesting the onset of puberty, and also indicated by histologic findings. Biological variability and the fact that few male animals have been examined within this critical length cohort do not allow determination of the onset of maturity with higher precision. Too few mature males have been landed in spring to make statistical comparisons of testes mass with autumn-landed animals within specific size cohorts. Two large (15.7m and 17.7m) males landed in spring had relatively small inactive testes and were diagnosed as pseudohermaphrodites; body length and mean testis length and seminiferous tubule diameter (STD) were not correlated with the other 'normal' whales. The smallest male confirmed as mature based on the presence of spermatocytes was 12.7m. The largest testes measured (combined mass 203kg) were from a whale landed in autumn. Mean STD for individual whales ranged from 33.3-170.9m and increased with mean testis weight and whale length. The STD is similar within a testis regardless of region evaluated, with minor variability. Some variation was noted for transverse sections within a cross section for some whales but no pattern was evident.
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A current threat to the marine ecosystem is the high level of solar ultraviolet radiation (UV). Large whales have recently been shown to suffer sun-induced skin damage from continuous UV exposure. Genotoxic consequences of such exposure remain unknown for these long-lived marine species, as does their capacity to counteract UV-induced insults. We show that UV exposure induces mitochondrial DNA damage in the skin of seasonally sympatric fin, sperm, and blue whales and that this damage accumulates with age. However, counteractive molecular mechanisms are markedly different between species. For example, sperm whales, a species that remains for long periods at the sea surface, activate genotoxic stress pathways in response to UV exposure whereas the paler blue whale relies on increased pigmentation as the season progresses. Our study also shows that whales can modulate their responses to fluctuating levels of UV, and that different evolutionary constraints may have shaped their response strategies.
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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 analysed 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 were 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 attacks. 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.
Large catches of bowhead whales, Balaena mysticetus, were made in the Eastern Arctic of North America, principally in Davis Strait, Baffin Bay, the Lancaster Sound region, Hudson Bay, and southern Foxe Basin, between 1719 and 1915. Initial stock sizes have been estimated as 11 000 in 1825 for the "Davis Strait stock" and 680 in 1859 for the "Hudson Bay stock." The separate identity of these two putative stocks needs confirmation through direct evidence. Three sets of data were used to evaluate historic and present-day trends in the distribution of bowheads in the Eastern Arctic and to test hypotheses concerning the nature, timing, and routes of their migration. Published records from commercial whale fisheries prior to 1915, unpublished and some published records from the post-commercial whaling period 1915-1974, and reported sightings made mainly by environmental assessment personnel between 1975 and 1979, were tabulated and plotted on charts. Comments made by whalers and nineteenth-century naturalists concerning bowhead distribution and movements were summarized and critically evaluated. The major whaling grounds were: (1) the west coast of Greenland between ca. 60°N and 73°N, the spring and early summer "east side " grounds of the British whalers; (2) the spring "south-west fishing" grounds, including the northeast coast of Labrador, the mouth of Hudson Strait, southeast Baffin Island, and the pack ice edge extending east from Resolution Island; (3) the summer "west water" grounds, including Pond Inlet, the Lancaster Sound region, and Prince Regent Inlet; (4) the autumn "rock-nosing" grounds along the entire east coast of Baffin Island; (5) Cumberland Sound, a spring and fall ground; and (6) northwest Hudson Bay/southwest Foxe Basin. The belief of whalers that some segregation occurs within the "Davis Strait stock" cannot be refuted or confirmed on the above evidence. However, the evident predominance of young whales and females with calves in early season catches at the Pond Inlet floe edge and in summer catches well inside Lancaster Sound and Prince Regent Inlet suggests that the route and timing of their migration differs from that of adult males. Apparently most of the whales taken on the autumn "rock-nosing" grounds were large males. The possibility that females and calves circumnavigate Baffin Island, returning south by way of Fury and Hecla Strait, is neither proven nor unproven. Evaluation of harpoon recoveries did not yield irrefutable evidence of interchange between any presently recognized bowhead stocks; however, this evidence along with recognition of distinctive morphological features does indicate that bowheads exhibit site fidelity to some degree. The conclusion is that the bowhead population in the Eastern Arctic, severely reduced by whaling activities, continues to occupy much of its former range and follows the same migratory schedule. There is no reliable and consistent evidence of appreciable recovery in absolute abundance of any Eastern Arctic stock. Key words: bowhead whale, Balaena mysticetus, distribution, migration, population identity, whaling history, Davis Strait, Baffin Bay, Lancaster Sound, West Greenland, Hudson Bay, Foxe Basin
In Svalbard, Norway, bearded seals give birth on small, first-year, ice flows in the free-floating packice or on similarly sized white, glacial-ice areas frozen into gray, land-fast ice. Sites of the latter type usually were located near the edge of the ice. Access to the sea was always readily available; all birth sites were <1 m from water. Well-formed, dark, gray, lanugo hair disks, similar to those of hooded seals (Cystophora cristata), were found at all parturition sites of bearded seals. All young weighing <40 kg had a mixture of 30-mm long, wavy, gray hairs and 20-mm, straight, coarser hair of a somewhat darker gray. Older, larger young had increasingly less lanugo and more stiff hair.
The annual moult in harbour seals (Phoca vitulina L.) follows a few weeks after the end of lactation and is characterised by a progressive loss and regrowth of hair which is apparent over a 4–6 week period. It is thought that during the moult harbour seals increase the time spent ashore as an adaptation to avoid additional energy costs associated with blood flow to the skin surface. The aim of this study was to determine the extent to which harbour seals regulated their surface temperature in order to maximise hair regrowth during the moult. The surface temperatures of two female harbour seals were recorded in captivity from late pregnancy to completion of the moult using infrared thermography. In this study, animals hauled out (exited the water onto land) more frequently during lactation and throughout the moult. Compared to the premoult period the temperature difference between body surface and air temperature (dT¯) showed a ∼10 °C elevation at the peak of the moult. Also, during the moult dT¯ reached a higher maximum at a faster rate over a two hour haul-out period. Heat loss was estimated to increase during the moult and was equivalent to an approximate doubling of resting metabolic rate. It was therefore evident that harbour seals minimise the energetic cost of the moult by hauling out so that they can maintain optimal high skin surface temperature for hair growth. Human disturbance at haul-out sites that causes animals to enter the water during the moult may have consequences for harbour seals for two reasons. Firstly, reduced time spent ashore in optimal conditions for hair regeneration may prolong the duration of the moult and secondly, repeatedly forcing animals into the water when their skin temperature is high will incur an energetic cost.
This paper presents evidence of the presence and subsequent loss of postnatal skin in an ecdysis-like process in southern right whales, Eubalaena australis. Individuals whose skin was noticeably uneven, spongy, broken, and often light gray in color formed ≥20% of right whale neonates seen on the South African coast on any day up to and including the 1st week of September. Thereafter ≥85% of calves were of the normal, smooth-skinned appearance. The 50% transition point between the 2 forms occurred on 31 August (95% CI 1.1 days), or about a week after birth. Histological analysis of skin from stranded neonates showed a definite cleavage plane in the midepidermis, the mechanical integrity of which was further compromised by low concentrations of desmosomes and intracellular filaments. We propose that focal edema develops between the cells and forms the cleavage plane, which eventually leads to separation of the outer epidermal cell layer (cf. spongiosis in humans). The movement from the intrauterine to the oceanic milieu, and the osmoregulatory consequences thereof, may be a catalytic factor for this process to occur. This ecdysis may have important consequences for the cyamid fauna of neonatal right whales.