Coherence betwwen 19th century sperm whale distributions and satellite-derived pigments in the tropical Pacific

It has often been suggested that, given their large food requirements, sperm whale Physeter macrocephalus distributions should reflect the distribution of productive ocean environments, and it seems therefore that chlorophyll concentration might be a good indicator of sperm whale distribution. To examine the existence of such a relationship, and to determine over which sclaes it occurs, sperm whale density was correlated with phytoplankton pigment concentration over a range of spatial and temporal scales. Sperm whale distribution was detrmined using records of kills from 19th century Yankee whaling, and the distribution of pigment concentration from satellite colour observations averaged over 8yr interval. These measures were compared over scales of 220km square to 1780km square. The distribution of sperm whales in the temperature and tropical Pacific Ocean was associated with distributions of phytoplankton pigment over every spatial scale considered, and the coefficient of correlation increased with increasing spatial scale. However, a few exceptions to this scheme were found, implying that other factors would be of importance in some regions. This study confirmed the existence of space lag and a time lag between a peak in chlorophyll concentration and a peak in sperm whale density. It also demonstrated that over large spatial scales, and when the data are averaged over large temporal scales, chlorophyll concentration is a good indicator of sperm whale distribution and that over these scales ocean colour recorded from space could help predict areas of high or low sperm whale density

Computer-Assisted Photo-Identification of Narwhals

Although the narwhal (Monodon monoceros) is economically and culturally important to northern residents, sound management of this species is impaired by large gaps in knowledge. Research on this species has been limited partly by the cost of the methods used, and partly because some of these methods are invasive and therefore condemned by Inuit communities. Photo-identification, a non-invasive, inexpensive, and easy-to-use method recently developed for narwhals, uses photographs of natural marks to identify individuals. Its main drawback is the extended time required to process photographs. We developed a computer program to accelerate the identification process and thus mitigate the main drawback of photo-identification. This program uses the locations of notches on the dorsal ridge to compare a new image to each individual in a catalogue and lists those individuals in decreasing order of similarity. We tested consistency in user assignment of dorsal ridge features and the accuracy of the program by comparing sets of known individuals. While assignment errors were common, the program ranked the true match within the first 10% of the catalogue 78% of the time. The program accelerates the matching process by 1.2 to 4.1 times for catalogues ranging in size from 40 to 500 individuals, and the degree of acceleration increases with the size of the catalogue. This program could also be applied to the beluga whale (Delphinapterus leucas), another important northern species.Bien que le narval (Monodon monoceros) soit une espèce exploitée d’importance économique et culturelle pour les résidents du Nord, la gestion efficace de cette espèce est affaiblie par des lacunes importantes en matière de connaissance de l’espèce. La quantité de recherche sur le narval est limitée par le coût des méthodes utilisées et par le fait que certaines de ces méthodes sont invasives, ce qui est désapprouvé par les communautés inuites. La photo-identification, soit une méthode non-invasive, peu coûteuse et facile d’utilisation, a été récemment mise au point pour le narval. Cette méthode utilise des photographies de marques naturelles pour identifier les individus. Toutefois, le plus grand défaut de cette méthode est qu’elle requiert beaucoup de temps pour comparer les photographies. Nous avons mis au point un programme informatique dans le but d’accélérer le processus d’identification et donc remédier au principal inconvénient de la photo-identification. Ce programme utilise l’emplacement des entailles dans la crête dorsale des narvals pour comparer une nouvelle image à celles d’un catalogue et les ordonne en ordre décroissant selon leur similarité. Nous avons testé la constance de l’utilisateur lorsqu’il attribue les caractéristiques de la crête dorsale et l’exactitude du programme en comparant des photographies d’individus précédemment identifiés. Bien que les erreurs de l’utilisateur soient fréquentes, le programme classe le bon individu parmi le premier 10 % des individus du catalogue, et ce 78 % du temps. Ce nouveau programme permet alors un meilleur rendement du processus d’identification de 1,2 à 4,1 fois plus rapide que sans l’assistance d’un programme pour un catalogue comprenant de 40 à 500 individus. Par ailleurs, plus le catalogue est grand, plus le degré d’accélération augmente. Ce programme informatique pourrait aussi être appliqué au béluga (Delphinapterus leucas), une autre espèce d’importance pour les résidents du Nord

Abundance estimate of Eastern Caribbean sperm whales using large scale regional surveys

This research was funded by the National Geographic Society (NGS-62320R-19-2), the Agoa Sanctuary, the Natural Sciences and Engineering Research Council of Canada, and the Animal Behavior Society and approved by the Dalhousie University Committee on Laboratory Animals.Peer reviewe

Cultural turnover among Galápagos sperm whales

Funding: Marine Alliance for Science and Technology for Scotland pooling initiative, which is funded by the Scottish Funding Council (#HR09011) and contributing institutions.While populations may wax and wane, it is rare for an entire population to be replaced by a completely different set of individuals. We document the large-scale relocation of cultural groups of sperm whale off the Galápagos Islands, in which two sympatric vocal clans were entirely replaced by two different ones. Between 1985 and 1999, whales from two clans (called Regular and Plus-One) defined by cultural dialects in coda vocalizations were repeatedly photo-identified off Galápagos. Their occurrence in the area declined through the 1990s; by 2000, none remained. We reassessed Galápagos sperm whales in 2013–2014, identifying 463 new females. However, re-sighting rates were low, with no matches with the Galápagos 1985–1999 population, suggesting an eastward shift to coastal areas. Their vocal repertoires matched those of two other clans (called Short and Four-Plus) found across the Pacific but previously rare or absent around Galápagos. The mechanisms behind this cultural turnover may include large-scale environmental regime shifts favouring clan-specific foraging strategies, and a response to heavy whaling in the region involving redistribution of surviving whales into high-quality habitats. The fall and rise of sperm whale cultures off Galápagos reflect the structuring of the Pacific population into large, enduring clans with dynamic ranges. Long-lasting clan membership illustrates how culture can be bound up in the structure and dynamics of animal populations and so how tracking cultural traits can reveal large-scale population shifts.Publisher PDFPeer reviewe

Using identity calls to detect structure in acoustic datasets

1.  Acoustic analyses can be powerful tools for illuminating structure within and between populations, especially for cryptic or difficult to access taxa. Acoustic repertoires are often compared using aggregate similarity measures across all calls of a particular type, but specific group identity calls may more clearly delineate structure in some taxa. 2.  We present a new method-the identity call method-that estimates the number of acoustically distinct subdivisions in a set of repertoires and identifies call types that characterize those subdivisions. The method uses contaminated mixture models to identify call types, assigning each call a probability of belonging to each type. Repertoires are hierarchically clustered based on similarities in call type usage, producing a dendrogram with 'identity clades' of repertoires and the (identity calls) that best characterize each clade. We validated this approach using acoustic data from sperm whales, grey-breasted wood-wrens, and Australian field crickets, and ran a suite of tests to assess parameter sensitivity. 3.  For all taxa, the method detected diagnostic signals (identity calls) and structure (identity clades; sperm whale subpopulations, wren subspecies, and cricket species) that were consistent with past research. Some datasets were more sensitive to parameter variation than others, which may reflect real uncertainty or biological variability in the taxa examined. We recommend that users perform comparative analyses of different parameter combinations to determine which portions of the dendrogram warrant careful versus confident interpretation. 4.  The presence of group-characteristic identity calls does not necessarily mean animals perceive them as such. Fine scale experiments like playbacks are a key next step to understand call perception and function. This method can help inform such studies by identifying calls that may be salient to animals and are good candidates for investigation or playback stimuli. For cryptic or difficult to access taxa with group-specific calls, the identity call method can aid managers in quantifying behavioural diversity and/or identifying putative structure within and between populations, given that acoustic data can be inexpensive and minimally invasive to collect.Publisher PDFPeer reviewe

Distinctive, fine‐scale distribution of Eastern Caribbean sperm whale vocal clans reflects island fidelity rather than environmental variables

This research would not have been possible without support from our partners: CARIMAM and the University of the West Indies, and funders: the National Geographic Society (NGS-62320R-19-2), the AGOA Sanctuary, the Natural Sciences and Engineering Research Council of Canada (NSERC), and the Animal Behavior Society.Environmental variables are often the primary drivers of species' distributions as they define their niche. However, individuals, or groups of individuals, may sometimes adopt a limited range within this larger suitable habitat as a result of social and cultural processes. This is the case for Eastern Caribbean sperm whales. While environmental variables are reasonably successful in describing the general distribution of sperm whales in the region, individuals from different cultural groups have distinct distributions around the Lesser Antilles islands. Using data collected over 2 years of dedicated surveys in the Eastern Caribbean, we conducted habitat modeling and habitat suitability analyses to investigate the mechanisms responsible for such fine‐scale distribution patterns. Vocal clan‐specific models were dramatically more successful at predicting distribution than general species models, showing how a failure to incorporate social factors can impede accurate predictions. Habitat variation between islands did not explain vocal clan distributions, suggesting that cultural group segregation in the Eastern Caribbean sperm whale is driven by traditions of site/island fidelity (most likely maintained through conformism and homophily) rather than habitat type specialization. Our results provide evidence for the key role of cultural knowledge in shaping habitat use of sperm whales within suitable environmental conditions and highlight the importance of cultural factors in shaping sperm whale ecology. We recommend that social and cultural information be incorporated into conservation and management as culture can segregate populations on fine spatial scales in the absence of environmental variability.Publisher PDFPeer reviewe

Ocean nomads or island specialists? Culturally driven habitat partitioning contrasts in scale between geographically isolated sperm whale populations

This research was funded by the National Geographic Society (grant no. NGS-62320R-19-2), the Agoa Sanctuary, the Natural Sciences and Engineering Research Council of Canada and the Animal Behavior Society.The sperm whale (Physeter macrocephalus) is a deep-diving cetacean with a global distribution and a multi-leveled, culturally segregated, social structure. While sperm whales have previously been described as ‘ocean nomads’, this might not be universal. We conducted surveys of sperm whales along the Lesser Antilles to document the acoustic repertoires, movements and distributions of Eastern Caribbean (EC) sperm whale cultural groups (called vocal clans). In addition to documenting a potential third vocal clan in the EC, we found strong evidence of fine-scale habitat partitioning between vocal clans with scales of horizontal movements an order of magnitude smaller than from comparable studies on Eastern Tropical Pacific sperm whales. These results suggest that sperm whales can display cultural ecological specialization and habitat partitioning on flexible spatial scales according to local conditions and broadens our perception of the ecological flexibility of the species. This study highlights the importance of incorporating multiple temporal and spatial scales to understand the impact of culture on ecological adaptability, as well as the dangers of extrapolating results across geographical areas and cultural groups.Publisher PDFPeer reviewe