North Atlantic Humpback Whales Research Articles

Development of a machine learning detector for North Atlantic humpback whale song.

The study of humpback whale song using passive acoustic monitoring devices requires bioacousticians to manually review hours of audio recordings to annotate the signals. To vastly reduce the time of manual annotation through automation, a machine learning model was developed. Convolutional neural networks have made major advances in the previous decade, leading to a wide range of applications, including the detection of frequency modulated vocalizations by cetaceans. A large dataset of over 60 000 audio segments of 4 s length is collected from the North Atlantic and used to fine-tune an existing model for humpback whale song detection in the North Pacific (see Allen, Harvey, Harrell, Jansen, Merkens, Wall, Cattiau, and Oleson (2021). Front. Mar. Sci. 8, 607321). Furthermore, different data augmentation techniques (time-shift, noise augmentation, and masking) are used to artificially increase the variability within the training set. Retraining and augmentation yield F-score values of 0.88 on context window basis and 0.89 on hourly basis with false positive rates of 0.05 on context window basis and 0.01 on hourly basis. If necessary, usage and retraining of the existing model is made convenient by a framework (AcoDet, acoustic detector) built during this project. Combining the tools provided by this framework could save researchers hours of manual annotation time and, thus, accelerate their research.

Abundance estimates of humpback whales (Megaptera novaeangliae) in Irish coastal waters using mark-recapture and citizen science

Abundance estimates are crucial for implementing effective conservation measures for large marine megafauna – particularly cetaceans. When combined with robust research methodologies, citizen science can provide a very useful tool to monitor large baleen whale populations, especially given their migratory nature, with individuals covering large areas typically exceeding the capacity of single research teams. The Irish Whale and Dolphin Group has been collecting humpback whale photo‐ID data in the inshore waters of Ireland since 1999. The Group curates a catalogue that contained 120 individual humpback whales up to 2022. Most of these data were obtained through citizen science and the catalogue was built following robust methodologies and strict data‐quality protocols. We used this photo‐ID catalogue to derive the first comprehensive abundance estimates for the species in Irish waters using mark‐recapture modelling techniques. We applied two approaches: (1) open population maximum likelihood mark‐recapture models based on the POPAN formulation; (2) a multi‐site mark‐recapture model selection framework based on Bayesian inference. The first method yielded a humpback whale superpopulation size of 154 ± 9 (95% CI = 138–172, CV = 0.06) between 1999–2022, with annual abundance ranging between 2 ± 1 and 77 ± 8 individuals. The second approach provided annual abundance estimates from 3 ± 2 to 76 ± 11 for the same period. This study supports the idea of an increased presence of humpback whales in inshore Irish waters, especially during the last decade. Despite this increase, results also highlight the apparently very small size of the North Atlantic humpback whale subgroup occurring in the inshore waters of Ireland.

Stock identity of a humpback whale taken in a southeastern Caribbean hunt

North Atlantic humpback whales migrate annually between discrete high latitude feeding areas and shared low latitude breeding areas. St. Vincent and the Grenadines is a low density breeding area in the Lesser Antilles and the site of the only ongoing aboriginal humpback whale hunt in the North Atlantic. The Scientific Committee of the International Whaling Commission recently concluded that catches were likely drawn from a large, panmictic breeding population, but encouraged the collection of additional data. On 6 March 1999, two humpback whales were landed at St. Vincent and the Grenadines and we obtained images from an opportunistic source. Photographic matching identified one individual as ‘Haar’ (NAHWC #0694), a catalogued whale from the Gulf of Maine. This is the first stock assignment from this fishery and the most southeasterly sighting of a Gulf of Maine whale. Based on its reported length, the second animal was probably a calf and, if so, a member of the same population. This match provides further support for the hypothesis that catches at St. Vincent and the Grenadines involve a variety of high-latitude populations. Furthermore, it reinforces the scientific and management value of collecting and sharing individual identification data when hunts are performed.

Reconciling data on the trends and abundance of North Atlantic humpback whales within a population modelling framework

Populations of humpback whales (Megaptera novaeangliae) in the North Atlantic appear to have been increasing at least during the last few decades, following the cessation of substantial hunting almost 100 years ago. Several sources of data are available for these populations (survey and mark-recapture estimates of absolute and relative abundance, estimated catches, and estimates of the proportion of the animals on two feeding grounds that are from the West Indies breeding ground). These data were analysed using an age- and sex-structured population dynamics model that is spatially-explicit to the extent that abundance is tracked on five feeding and two breeding grounds. Several alternative hypotheses, including depensation and changes over time in carrying capacity, were captured within the model framework. Two scenarios form the focus of the analyses, based on alternative interpretations of the size of the breeding population off the Cape Verde Islands. The results of these analyses confirm the increase in the number of humpback whales in the North Atlantic, although it is not possible to determine the extent of such increases. Whether both the West Indies and Cape Verde Islands breeding stocks have increased depends on whether the estimate of abundance for the Cape Verde Islands population of approximately 100 animals is valid. Although many of the data sources can be reconciled given the model applied, some conflicts remain; resolution of these conflicts will require collection of additional data.

A note on the spatial and temporal distribution of humpback whales (Megaptera novaeangliae) off Venezuela, Southeastern Caribbean

This paper presents information on the spatial and temporal distribution of humpback whales in Venezuelan waters. Using a relational database containing information from the museums of Venezuela, published and unpublished records were incorporated into a Geographical Information System (MapInfo Professional 7.0). A total of 53 records were gathered, of which sightings made up 72%, followed by acoustic sampling (9%) intentional capture (6%), stranding (6%) and unknown records (8%). Humpback whales were mainly sighted over the continental shelf of the northeastern region in shallow waters of 0-100m in depth. The date on which each record was made supports the seasonal occurrence of North Atlantic humpback whales off the Venezuelan coast. Opportunistic sightings and stranding records from the austral winter months do not give conclusive proof that Southern Hemisphere humpback whales are present during this time, but lead to the hypothesis that whales migrate from Brazil. Systematic research effort (especially photo-identification) is recommended in order to better understand humpback whale movements, distribution and identity.

A decade of humpback whale abundance estimates at Bermuda, an oceanic migratory stopover site

We constructed annual abundance of a migratory baleen whale at an oceanic stopover site to elucidate temporal changes in Bermuda, an area with increasing anthropogenic activity. The annual abundance of North Atlantic humpback whales visiting Bermuda between 2011 and 2020 was estimated using photo-identification capture-recapture data for 1,204 whales, collected between December 2009 and May 2020. Owing to a sparse data set, we combined a Cormack-Jolly-Seber (CJS) model, fit through maximum likelihood estimation, with a Horvitz-Thompson estimator to calculate abundance and used stratified bootstrap resampling to derive 95% confidence intervals (CI). We accounted for temporal heterogeneity in detection and sighting ratesviaa catch-effort model and, guided by goodness-of-fit testing, considered models that accounted for transience. A model incorporating modified sighting effort and time-varying transience was selected using (corrected) Akaike’s Information Criterion (AICc). The survival probability of non-transient animals was 0.97 (95% CI 0.91-0.98), which is comparable with other studies. The rate of transience increased gradually from 2011 to 2018, before a large drop in 2019. Abundance varied from 786 individuals (95% CI 593-964) in 2016 to 1,434 (95% CI 924-1,908) in 2020, with a non-significant linear increase across the period and interannual fluctuations. These abundance estimates confirm the importance of Bermuda for migrating North Atlantic humpback whales and should encourage a review of cetacean conservation measures in Bermudian waters, including area-based management tools. Moreover, in line with the time series presented here, regional abundance estimates should be updated across the North Atlantic to facilitate population monitoring over the entire migratory range.

Seasonal song ontogeny in western North Atlantic humpback whales: drawing parallels with songbirds

ABSTRACT The use of song as a reproductive display is common in the animal kingdom; however, for many taxa, little is known of song ontogeny. Male humpback whales produce elaborate songs on low latitude breeding grounds in winter and begin to sing on high latitude feeding grounds in late summer, yet songs from the two locations are rarely compared. Seasonal song ontogeny in western North Atlantic humpback whales was explored by comparing songs recorded in high latitude feeding grounds (Canada in spring 2016 and fall 2016 to winter 2017) with songs recorded in a low latitude breeding ground (Dominican Republic in winter and spring 2017). High-quality song samples were selected, and every phrase annotated. Song theme order, song duration, and number of phrase repetitions were compared across samples. The most variability in theme order was found between November and December in the Canadian recordings, a phase in song ontogeny that may be important for learning. Song duration gradually increased, via an increase in phrase repetitions, through the breeding season, before peaking in the Dominican Republic between January and March. A comparison to oscine bird seasonal song ontogeny revealed many similarities, highlighting potentially similar physiological processes between humpback whales and songbirds.

Where, when, and why do western North Atlantic humpback whales begin to sing?

ABSTRACT At the onset of the winter breeding season, male humpback whales begin a prominent breeding behaviour, singing. Early songs are produced on summer feeding grounds prior to migration, but little is known about the proximate cues for the initiation of this behaviour, nor where or when it begins. We document the phenology of humpback whale singing along the western North Atlantic coast ranging from Newfoundland and Labrador, Canada to Massachusetts, USA through the fall-winter of 2015–16 (seven stations) and 2016–17 (three stations). Acoustic data from static recorders were categorised as containing humpback whale non-song calls, song fragments, or full songs. First heard in September, singing occurred throughout the fall-winter, but was not regular until October. Latitude, temperature, photoperiod, sea surface pressure, and wind speed were considered as potential explanatory variables for four definitions of song onset using forward stepwise regression. Final models included the environmental variables with photoperiod negatively correlated to singing (coefficient = −657; p-value = 0.04). Reliable environmental cues, such as photoperiod, may produce a heritable physiological response, resulting in whales acquiring the capacity and motivation to sing, with the subsequent timing and nature of song production influenced by other factors.

Humpback Whale (Megaptera novaeangliae) Song on a Subarctic Feeding Ground

Male humpback whales (Megaptera novaeangliae) are known to produce long complex sequences of structured vocalizations called song. Singing behavior has traditionally been associated with low latitude breeding grounds but is increasingly reported outside these areas. This study provides the first report of humpback whale songs in the subarctic waters of Northern Norway using a long-term bottom-moored hydrophone. Data processed included the months January–June 2018 and December 2018–January 2019. Out of 189 days with recordings, humpback whale singing was heard on 79 days. Singing was first detected beginning of January 2018 with a peak in February and was heard until mid-April. No singing activity was found during the summer months and was heard again in December 2018, continuing over January 2019. A total of 131 song sessions, including 35 full sessions, were identified throughout the study period. The longest and shortest complete sessions lasted 815 and 13 min, respectively. The results confirm that singing can be heard over several months in winter and spring on a high latitude feeding ground. This provides additional evidence to the growing literature that singing is not an explicit behavior confined to low latitude breeding grounds. The peak of song occurrence in February appears to coincide with the reproductive cycle of humpback whales. Finally, this study indicates that song occurrence on a subarctic feeding ground likely aids the cultural transmission for the North Atlantic humpback whale population.

Return to the Sea, Get Huge, Beat Cancer: An Analysis of Cetacean Genomes Including an Assembly for the Humpback Whale (Megaptera novaeangliae).

Cetaceans are a clade of highly specialized aquatic mammals that include the largest animals that have ever lived. The largest whales can have ∼1,000× more cells than a human, with long lifespans, leaving them theoretically susceptible to cancer. However, large-bodied and long-lived animals do not suffer higher risks of cancer mortality than humans—an observation known as Peto’s Paradox. To investigate the genomic bases of gigantism and other cetacean adaptations, we generated a de novo genome assembly for the humpback whale (Megaptera novaeangliae) and incorporated the genomes of ten cetacean species in a comparative analysis. We found further evidence that rorquals (family Balaenopteridae) radiated during the Miocene or earlier, and inferred that perturbations in abundance and/or the interocean connectivity of North Atlantic humpback whale populations likely occurred throughout the Pleistocene. Our comparative genomic results suggest that the evolution of cetacean gigantism was accompanied by strong selection on pathways that are directly linked to cancer. Large segmental duplications in whale genomes contained genes controlling the apoptotic pathway, and genes inferred to be under accelerated evolution and positive selection in cetaceans were enriched for biological processes such as cell cycle checkpoint, cell signaling, and proliferation. We also inferred positive selection on genes controlling the mammalian appendicular and cranial skeletal elements in the cetacean lineage, which are relevant to extensive anatomical changes during cetacean evolution. Genomic analyses shed light on the molecular mechanisms underlying cetacean traits, including gigantism, and will contribute to the development of future targets for human cancer therapies.

Western North Atlantic humpback whale fall and spring acoustic repertoire: Insight into onset and cessation of singing behavior.

Humpback whale songs have been described worldwide and studies exploring non-song vocal behavior continue to expand; however, studies on the transition periods when whales shift to and from the seasonal behavioral state of singing are lacking and may be potentially informative regarding the proximal factors controlling the onset and offset of humpback whale male singing. Acoustic recorders collected data off eastern Canada continuously from the Bay of Fundy in the fall of 2015 and near-continuously off northeast Nova Scotia in the spring of 2016. Humpback whale acoustic occurrence and behavior were identified by systematically reviewing a subset of acoustic recordings for presence before analyzing the highest quality recordings for behavior. The onset of singing in the fall was gradual over a period of about three weeks with an intermediate form, termed "song fragment," occurring prior to full songs. In comparison, singing in the spring seemed to end abruptly with few song fragments. Song fragments could be produced by juveniles learning to sing for the first time or mature males preparing for breeding activities prior to migrating to southern breeding grounds. The authors propose an alternative hypothesis that the timing and manner of transitions could be driven by physiological processes similar to those documented in songbirds.

From Whaling to Tagging: The Evolution of North Atlantic Humpback Whale Research in the West Indies

From Whaling to Tagging: The Evolution of North Atlantic Humpback Whale Research in the West Indies

Singing through winter nights: Seasonal and diel occurrence of humpback whale (Megaptera novaeangliae) calls in and around the Gully MPA, offshore eastern Canada

AbstractHumpback whale use of areas off eastern Canada is poorly understood, a knowledge gap that could impact future conservation efforts. We describe the acoustic occurrence of humpback whales in and around the Gully Marine Protected Area (MPA), an eastern Scotian Shelf submarine canyon. Near‐continuous acoustic recordings sampling at 16 kHz were collected from the MPA and nearby slope areas from October 2012 to September 2014 using near‐bottom recorders. In an offshore region where humpbacks were thought to be rare, we observed calls from October to June with a peak in song and nonsong calls in December and January. This suggests that some individuals occur in Canadian waters in winter and the Gully region may be a North Atlantic humpback whale migratory corridor. Calls were predominantly songs indicating potential mating activities. Song and nonsong calls occurred more at sunset and during hours of darkness than during daylight. This study improves our understanding of the seasonal occurrence of humpback whales on the Scotian Slope and, more specifically, their use of an offshore protected area.

Vessel collision injuries on live humpback whales, Megaptera novaeangliae, in the southern Gulf of Maine

AbstractNorth Atlantic humpback whales (Megaptera novaeangliae) in the Gulf of Maine overlap with both recreational and commercial vessel activity. Vessel strikes are one source of anthropogenic impact that has the potential to inhibit the recovery of this protected species. There are currently no regulations or guidelines specifically devised to reduce the likelihood of collisions for vessels transiting in the vicinity of humpback whales, except for vessels actively engaged in whale watching. To understand interactions between vessels and humpback whales better, we analyzed injuries on 624 individuals photographed in the southern Gulf of Maine from 2004 to 2013. Multiple reviewers evaluated 210,733 photos for five categories of injury consistent with a vessel strike. In total, 14.7% (n = 92) of individuals photographed showed injuries consistent with one or more vessel strikes. These results likely underestimate vessel collision rates and impacts because multiple events, events resulting in mortality, and those that involved only blunt force trauma could not be detected. Nevertheless, our results indicate that vessel strikes are underreported and that healing is dependent on the severity and location of the injury. We recommend that a management strategy be developed for all classes of vessels transiting in the vicinity of whales.

North Atlantic humpback whale (Megaptera novaeangliae) hotspots defined by bathymetric features off western Puerto Rico

North Atlantic humpback whales (Megaptera novaeangliae (Borowski, 1781)) are increasing in number, necessitating current data from winter areas for assessing potential interactions with humans. Occurrence patterns of humpback whales wintering off Puerto Rico were investigated to predict where whales aggregate in nearshore areas. Here we describe the relationship between group associations of humpback whales and bathymetric features off western Puerto Rico. Data were collected from 2011 to 2014. Effort consisted of 240.9 vessel h, 13.0 aerial h, and 303.6 h of land observations conducted over 165 days. A total of 197 humpback whale groups were observed with n = 331 individuals: 91 (46.2%) singletons, 67 (34%) dyads, 17 (8.6%) mother–calf pairs, 8 (4.1%) competitive groups, 8 (4.1%) mother–calf–escort groups, and 6 (3.1%) mixed-species associations. A linear regression model supported that group composition correlated with hotspots associated with four bathymetric features. Dyads and competitive groups were dispersed among features in deeper water. Singletons were observed farther from a shelf edge, whereas singing males were closely associated with a shelf edge. Mother–calf pairs occurred nearshore in shallow water; however, when mother–calf pairs were sighted with an escort, they were offshore. This study is especially important ahead of possible removal from the Endangered Species list.

Distribution, abundance, and feeding ecology of baleen whales in Icelandic waters: have recent environmental changes had an effect?

The location of Iceland at the junction of submarine ridges in the North-East Atlantic where warm and cold water masses meet south of the Arctic Circle contributes to high productivity of the waters around the island. During the last two decades, substantial increases in sea temperature and salinity have been reported. Concurrently, pronounced changes have occurred in the distribution of several fish species and euphausiids. The distribution and abundance of cetaceans in the Central and Eastern North Atlantic have been monitored regularly since 1987. Significant changes in the distribution and abundance of several cetacean species have occurred in this time period. The abundance of Central North Atlantic humpback and fin whales has increased from 1,800 to 11,600 and 15,200 to 20,600, respectively, in the period 1987-2007. In contrast, the abundance of minke whales on the Icelandic continental shelf decreased from around 44,000 in 2001 to 20,000 in 2007 and 10,000 in 2009. The increase in fin whale abundance was accompanied by expansion of distribution into the deep waters of the Irminger Sea. The distribution of the endangered blue whale has shifted northwards in this period. The habitat selection of fin whales was analyzed with respect to physical variables (temperature, depth, salinity) using a generalized additive model, and the results suggest that abundance was influenced by an interaction between the physical variables depth and distance to the 2000m isobaths, but also by sea surface temperature and sea surface height, However, environmental data generally act as proxies of other variables, to which the whales respond directly. Overall, these changes in cetacean distribution and abundance may be a functional feeding response of the cetacean species to physical and biological changes in the marine environment, including decreased abundance of euphausiids, a northward shift in summer distribution of capelin and a crash in the abundance of sand eel.

Utility of telomere length measurements for age determination of humpback whales

This study examines the applicability of telomere length measurements by quantitative PCR as a tool for minimally invasive age determination of free-ranging cetaceans. We analysed telomere length in skin samples from 28 North Atlantic humpback whales (Megaptera novaeangliae), ranging from 0 to 26 years of age. The results suggested a significant correlation between telomere length and age in humpback whales. However, telomere length was highly variable among individuals of similar age, suggesting that telomere length measured by quantitative PCR is an imprecise determinant of age in humpback whales. The observed variation in individual telomere length was found to be a function of both experimental and biological variability, with the latter perhaps reflecting patterns of inheritance, resource allocation trade-offs, and stochasticity of the marine environment.

Local and migratory movements of humpback whales (Megaptera novaeangliae) satellite-tracked in the North Atlantic Ocean

North Atlantic humpback whales (Megaptera novaeangliae (Borowski, 1781)) migrate from high-latitude summer feeding grounds to low-latitude winter breeding grounds along the Antillean Island chain. In the winters and springs of 2008 through 2012, satellite tags were deployed on humpback whales on Silver Bank (Dominican Republic) and in Guadeloupe (French West Indies) breeding areas. Whales were monitored, on average, for 26 days (range = 4–90 days). Some animals remained near their tagging location for multiple days before beginning their northerly migration, yet some visited habitats along the northwestern coast of the Dominican Republic, northern Haiti, the Turks and Caicos islands, and off Anguilla. Individuals monitored during migration headed towards feeding grounds in the Gulf of Maine (USA), Canada, and the eastern North Atlantic (Iceland or Norway). One individual traveled near Bermuda during the migration. This study provides the first detailed description of routes used by North Atlantic humpback whales towards multiple feeding destinations. Additionally, it corroborates previous research showing that individuals from multiple feeding grounds migrate to the Antilles for the breeding season. This study indicates that North Atlantic humpbacks use an area broader than the existing boundaries of marine mammal sanctuaries, which should provide justification for their expansion.

Levels of persistent organic pollutants in eastern North Atlantic humpback whales

Blubber lipid concentrations of 14 organochlorine compounds and 10 polychlorinated biphenyls (PCB) were measured by gas chromatography with electron-capture detection in eastern North Atlantic humpback whales Megaptera novaeangliae from Cape Verde (n = 20) and Ireland (n = 4). Concentrations were statistically compared to those from 20 samples collected from the Gulf of Maine in the western North Atlantic. Pollutant burdens were compared using males only, in order to circum- vent biases associated with reproductive offloading. Lipid-normalised PCB concentrations were below the estimated threshold toxicity value of 17 000 ng g �1 for blubber in marine mammals. Dichlorodiphenyltrichloroethane (DDT), PCB and chlordane concentrations were an order of mag - nitude lower than those previously reported for Gulf of Maine humpback whales and higher than those reported from the North Pacific Ocean. Higher concentrations of lower-chlorinated PCB con- geners (28, 31 and 52), hexachlorocyclohexanes and hexachlorobenzene in males in eastern North At- lantic sites is consistent with higher latitude feeding grounds. Lower p,p'-DDE (dich loro di phe nyl - dichloroethane):ΣDDT ratios suggest that whales from the eastern North Atlantic harbour more recent inputs of DDT. The ΣDDTs:ΣPCBs ratio was higher for males from Cape Verde (1.69) and Ireland (1.44), indicating proportionately greater sources of agricultural rather than industrial sources of pol- lutants than for the Gulf of Maine whales (0.75). We demonstrate potential for persistent organochlo- rine pollutants (POPs) as tracers to determine foraging ground provenance for samples collected on breeding grounds in the North Atlantic. Low concentrations suggest that POPs are unlikely to be a factor in the poor recovery rate of humpback whales in Cape Verde.

Differential rates of killer whale attacks on humpback whales in the North Atlantic as determined by scarification

As in other populations of killer whales, Orcinus orca, prey selectivity in the North Atlantic population may indicate behaviourally or ecologically distinct types of killer whales. Some killer whale ecotypes are known to prey on large whales, but the ecological impact of such predation events is unknown. Since killer whale attacks on humpback whales, Megaptera novaeangliae, are rarely witnessed, resultant scars may be used to determine the frequency of non-fatal predatory interactions. Using images from the North Atlantic Humpback Whale Catalogue (NAHWC), we examined humpback whale flukes for the presence of rake marks from killer whales (N = 5040). Scarring frequencies range from 2.7 to 17.4% and differ significantly among five regions of the North Atlantic (Gulf of Maine, Canada, West Greenland, Iceland and Norway). The scarring rate in the Canada region is significantly higher than all other regions, and Norway has a significantly lower scarring rate than all other regions, despite more frequently reported killer whale sightings in that region. Within the western North Atlantic, Canada has a scarring rate nearly twice that of either the Gulf of Maine or West Greenland. These data may reflect differential prey choice among killer whale ecotypes and/or the distribution of specific ecotypes across the North Atlantic basin.