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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. https://doi.org/10.1371/journal.pone.0186156.g003
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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, Nuna...
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... 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 presence of gray tissue is indicative of new skin growth-based on our observations and those of bowheads molting in the Okhotsk Sea [18]. ...
Citations
... and rocks (Fortune et al., 2017;Meynecke et al., 2023). However, this is the first account of whales expanding the pleated ventral oral pouch to remove dead skin or organisms in otherwise difficult-to-reach folds or creases of skin, a location where barnacles and cyamids ("whale lice") are known to congregate (Rowntree, 1996). ...
... Cetaceans have been observed rubbing their bodies to shed skin in many regions of the world, often but not exclusively in warmer waters (Pitman et al., 2020;Whitehead et al., 1990). Skin rubbing has been described in odontocetes such as belugas, Delphinapterus leucas (Finley, 1982;Smith et al., 1992), and killer whales, Orcinus orca (Condy et al., 1978;Pitman et al., 2020;Williams et al., 2009), and in mysticetes, including bowhead, Balaena mysticetus (Fortune et al., 2017), gray, Eschrichtius robustus (Woodward & Winn, 2006), and humpback whales (Pinheiro et al., 2016). Using video, accelerometry, and bathymetric data from biologging tags temporarily suction-mounted to humpback whales in Australia's Gold Coast Bay, Meynecke et al. (2023) studied rubbing behaviors of whales along the sandy bottom. ...
... Additionally, no fish or other organisms were seen picking at or feeding on exfoliated skin or shed epibionts around the Bermuda humpbacks, as reported by Meynecke et al. (2023) for humpbacks exfoliating in Australian waters. However, striated skin markings appear similar to those of bowhead whales observed rubbing on rocks (Fortune et al., 2017). Scarring along jaw lines may come from foraging along the bottom and from fighting or sparring among males, but other skin marks likely relate to rubbing on sand and coral. ...
... This behavior included nudging or pushing the log with their head or body, lifting the log onto their back or tail stock, and while supine and keeping it between their pectoral flippers (Würsig et al. 1989). However, this activity also may be used to facilitate skin sloughing (Fortune et al. 2017). 156 V. M. F. da Silva and L. G. Spinelli The Amazon river dolphin or boto (Inia geoffrensis) is an inquisitive animal that approaches boats, the landing stages of riverside houses, and people swimming or fishing. ...
Cetaceans use objects and interact with conspecifics for play and socializing, often exhibiting complex behaviors that we do not understand. A few seconds of activity on the water’s surface rarely indicates intraspecific behaviors and interactions. What has already been described chiefly for common bottlenose dolphins ( Tursiops truncatus ) has been extrapolated to other species, with little information on river dolphins despite their accessibility. In this chapter, we review what is known about sexually related behaviors in different contexts, such as learning, play, sexual display, aggression, and boredom (weariness and restlessness through a lack of interest) among cetacean species, especially the Amazon river dolphin ( Inia geoffrensis ).
... Bowhead whale behaviors associated with mating have been seen throughout the year, but a recent study (Fortune et al. 2017) found that some of this behavior is associated with stimulation of the epidermis during the molt, and therefore is not a reproductive activity (Würsig and Koski 2021). In particular, close physical presence and rubbing with pectoral appendages seem to assist with removal of dead skin and stimulation of new skin. ...
... Drones have become a valuable tool for observing the behavior of animals while minimizing disturbance (Fortune et al. 2017;Ramos et al. 2023, this book). Recent studies of bowhead whales in eastern Canada have provided more detailed information on behavior than earlier studies from fixed wing aircraft because camera resolution has improved, and whales do not appear to be disturbed by batterypowered drones flying at low altitudes above them (W Koski, pers obs). ...
Bowhead whales ( Balaena mysticetus ) have adopted growth and reproductive strategies to survive in a challenging environment where no other mysticete whales reside. They grow slowly, become sexually mature at around 25 years (later than other mammals), and do not give birth until they have sufficient energy reserves for the best possible chance of survival of the calf to weaning and long-term survival of the mother. To compensate for late maturity and long inter-birth intervals, some seem to have the capability to live to 200+ years of age, making them the longest-lived mammal known to date. Bowhead whale males have large testes per body size, and it is hypothesized that the basic polygynandrous system of females and males mating with multiple partners per estrous cycle allows for males to not compete violently against each other. Instead, they use sperm competition by volume of sperm for enhanced capability to father as many offspring as possible. Also, as in right whales ( Eubalaena spp.), the length of the penis is proportionally longer than those of balaenopterids. Details of sperm volume, potential variabilities of sperm viabilities, and actual paternities are unknown, but some patterns can be inferred from the closely related right whales with similar morphologies.
... Skin care is also evident in other marine mammals. Sea lions rub against rocks [50], and some baleen whales, such as bowhead whales (Balaena mysticetus), use rocks for the possible facilitation of their moulting [51]. Sand rolling of humpback whales on sandy substrate has been described as possible assistance in excess skin removal [52], and there are reports emerging of gray whales seeking humans for possible ectoparasite removal (https://www.theguardian.com/environment/2023/jul/06/grey-whales-seenseeking-human-help-to-remove-parasites ...
The use of objects by cetaceans is well known, and their ability to interact with their environment in complex behaviours has been demonstrated previously. However, baleen whales, including humpback whales (Megaptera novaeangliae), are less often observed to perform object use, but this behaviour might be more common than previously thought. Only a few isolated observations of interactions with seaweed have been reported in the scientific literature to date. The recovery of humpback whale populations, as well as the rise of technology such as unmanned aerial vehicles (UAVs) and the use of social media, allow for a new assessment of this object interaction. Here, we describe in detail three instances of “kelping” on the east coast of Australia derived from aerial observations. A summary of over 100 separate and unrelated events drawn from social media, documented by photographs and videos, suggests that this form of interaction with seaweed is observed across different populations. The form of interaction with seaweed is similar between regions, predominantly displayed between the rostrum and dorsal fin. This behaviour may be playful but could also serve additional benefits in the context of learning and socializing, as well as ectoparasite removal and skin treatment by utilizing brown algae’s antibacterial properties. Establishing this type of behaviour as distributed across different populations is important to better understand the species’ habitat preferences.
... 14 sperm whales were sighted with extensive pale skin patches. These lesions were attributed to shedding and not listed as disorder (Brownell Jr. et al., 2007;Fortune et al., 2017). Extensive skin lesions were detected in two bottlenose dolphins. ...
Cetacean populations in the Strait of Gibraltar are heavily impacted by human activities. Photographs are a valuable tool to monitor the external health of cetaceans. We visually screened 27,866 pictures taken during whale watching operations in the years 2016–2020 for abnormal conditions, such as emaciation, dermal diseases and epizoic infestations. Prevalence levels could not be calculated as data were obtained opportunistically. Dermal diseases were detected in 566 sightings and occurred in all species. Bottlenose dolphins were most strongly affected (n = 192). Hypopigmented skin lesions were most common in all species (n = 291). Tattoo skin disease‐like lesions affected 16 animals (T. truncatus: n = 12; G. melas: n = 3; D. delphis: n = 1). Other observed conditions include expansive annular lesions in three juvenile pilot whales. Furthermore, we report the presence of open wounds in 28 animals (G. melas: n = 23; T. truncatus: n = 2; P. macrocephalus: n = 3). In three pilot whales, these wounds did not heal over a period of several years. Epizoic and ectoparasitic infestations include the observation of Xenobalanus spp. and Pennella balaenopterae. Multiple fin whales were sighted with very high numbers of Pennella balaenopterae, ranging up to 84 parasites per host. Emaciation was mainly detected in bottlenose dolphins (n = 36) and seemed to affect these animals more severely during specific years, potentially indicating fluctuations in prey availability. KEYWORDS: CETACEANS; DERMAL DISEASES; EMACIATION; ECTOPARASITES; STRAIT OF GIBRALTAR
... It has been reported in southern right whales from South Africa and in young belugas [77], who hypothesized that the thick stratum corneum might provide insulation for the newborn and may not be needed once the animal begins to develop a subcutaneous blubber layer. This thermoregulatory hypothesis is further supported by examples of molt in multiple age classes of bowhead whales (Balaena mysticetus) when they seasonally enter warmer water [100]. In captivity, killer whales can undergo multiple episodes of neonatal ecdysis (HN, unpublished data). ...
Photographic identification catalogs of individual killer whales (Orcinus orca) over time provide a tool for remote health assessment. We retrospectively examined digital photographs of Southern Resident killer whales in the Salish Sea to characterize skin changes and to determine if they could be an indicator of individual, pod, or population health. Using photographs collected from 2004 through 2016 from 18,697 individual whale sightings, we identified six lesions (cephalopod, erosions, gray patches, gray targets, orange on gray, and pinpoint black discoloration). Of 141 whales that were alive at some point during the study, 99% had photographic evidence of skin lesions. Using a multivariate model including age, sex, pod, and matriline across time, the point prevalence of the two most prevalent lesions, gray patches and gray targets, varied between pods and between years and showed small differences between stage classes. Despite minor differences, we document a strong increase in point prevalence of both lesion types in all three pods from 2004 through 2016. The health significance of this is not clear, but the possible relationship between these lesions and decreasing body condition and immunocompetence in an endangered, non-recovering population is a concern. Understanding the etiology and pathogenesis of these lesions is important to better understand the health significance of these skin changes that are increasing in prevalence.
... 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. ...
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.
... (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). ...
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.
... 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. ...
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.
... 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. ...
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.
