Spatial ecology of humpback whales in breeding areas : habitats, distribution and movements in the South Pacific

Comprendre les facteurs sociaux et environnementaux de la distribution et des mouvements de la mégafaune marine est essentiel à sa conservation. Les cétacés sont des espèces rares et mobiles, dont la gestion nécessite une meilleure compréhension des habitats qu’ils occupent. Cette thèse a eu pour but d’étudier l’écologie spatiale d’une population en danger de baleines à bosse (Megaptera novaeangliae) dans l’océan Pacifique Sud. En utilisant un ensemble de données multidisciplinaires collecté entre 1995 et 2018 en Nouvelle-Calédonie et en Océanie, cette thèse a poursuivi trois objectifs : 1) étudier les meilleures pratiques de modélisation de la distribution des cétacés, 2) acquérir une meilleure compréhension de la distribution, des habitats et des mouvements des baleines à bosse dans leur zone de reproduction d’Océanie, 3) prédire les zones de conservation prioritaires et les menaces potentielles pour les baleines à bosse dans cette région. La modélisation de la distribution d’une grande baleine migratrice à partir de données de recherche non systématique et issues de la science participative a fourni des prédictions de bonne qualité, tant que l’hétérogénéité spatiale de l’échantillonnage et la tendance statistique au surapprentissage étaient correctement prises en compte. Les modèles additifs généralisés ont été privilégiés pour leur équilibre en termes de complexité des relations modélisées, leur rendu écologiquement explicite et leur capacité de transferabilité. Les modèles d’utilisation de l’habitat à différentes échelles spatiales ont révélé une préférence pour une diversité d’habitats peu profonds répartis dans une large gamme de température des eaux en Océanie. Les monts sous-marins et bancs peu profonds ont été identifiés comme d’importants habitats de reproduction et de développement pour les baleineaux. Ces reliefs sous-marins jouent également un rôle clé dans la connectivité au sein et entre les populations. Cette utilisation unique et inattendue de l’habitat pélagique a des conséquences importantes sur la gestion spatiale des baleines à bosse. La prédiction des habitats de reproduction présents et futurs à des échelles multiples fournit une base scientifique pour la désignation de zones de conservation prioritaires et la protection contre les menaces générées par les activités humaines et le changement climatique dans le Pacifique Sud.Understanding the social and environmental drivers of the distribution and movements of marine megafauna is essential to their conservation. Cetaceans are elusive and mobile species, whose management requires an improved understanding of habitat use patterns. This thesis is aimed at investigating the spatial ecology of an endangered population of humpback whales (Megaptera novaeangliae) in the South Pacific Ocean. Using a multidisciplinary dataset collected between 1995 and 2018 in New Caledonia and Oceania, this thesis addressed three objectives, 1) investigate best practices to cetacean species distribution modeling, 2) acquire fundamental knowledge on the distribution, habitats and movements of humpback whales in Oceania breeding grounds, and 3) predict priority conservation areas and potential threats to humpback whales. Modeling the distribution of a migratory large whale from non-systematic visual survey and citizen science data provided valuable space-use predictions when uneven survey effort and statistical overfitting were specifically addressed. Generalized Additive Models were favored for their complexity trade-off, ecological interpretability and transferability. Models of habitat use revealed a preference for a diversity of shallow habitats (low island and atoll lagoons, barrier reef and high island slopes, banks and seamounts) spread over a relatively large thermal range over Oceania. Shallow seamounts and banks were identified as major breeding and nursing habitats and play a key role in the connectivity within and between populations. This unique and unexpected use of pelagic waters has important consequences for the spatial management of humpback whales. The predictions of present and future suitable humpback whale breeding habitats at multiples scales provide science-based evidence for priority conservation areas, and enable mitigation of threats from anthropogenic activities and climate change in the South Pacific

Écologie spatiale des baleines à bosse en zone de reproduction : habitats, distribution et mouvements dans le Pacifique Sud

Understanding the social and environmental drivers of the distribution and movements of marine megafauna is essential to their conservation. Cetaceans are elusive and mobile species, whose management requires an improved understanding of habitat use patterns. This thesis is aimed at investigating the spatial ecology of an endangered population of humpback whales (Megaptera novaeangliae) in the South Pacific Ocean. Using a multidisciplinary dataset collected between 1995 and 2018 in New Caledonia and Oceania, this thesis addressed three objectives, 1) investigate best practices to cetacean species distribution modeling, 2) acquire fundamental knowledge on the distribution, habitats and movements of humpback whales in Oceania breeding grounds, and 3) predict priority conservation areas and potential threats to humpback whales. Modeling the distribution of a migratory large whale from non-systematic visual survey and citizen science data provided valuable space-use predictions when uneven survey effort and statistical overfitting were specifically addressed. Generalized Additive Models were favored for their complexity trade-off, ecological interpretability and transferability. Models of habitat use revealed a preference for a diversity of shallow habitats (low island and atoll lagoons, barrier reef and high island slopes, banks and seamounts) spread over a relatively large thermal range over Oceania. Shallow seamounts and banks were identified as major breeding and nursing habitats and play a key role in the connectivity within and between populations. This unique and unexpected use of pelagic waters has important consequences for the spatial management of humpback whales. The predictions of present and future suitable humpback whale breeding habitats at multiples scales provide science-based evidence for priority conservation areas, and enable mitigation of threats from anthropogenic activities and climate change in the South Pacific.Comprendre les facteurs sociaux et environnementaux de la distribution et des mouvements de la mégafaune marine est essentiel à sa conservation. Les cétacés sont des espèces rares et mobiles, dont la gestion nécessite une meilleure compréhension des habitats qu’ils occupent. Cette thèse a eu pour but d’étudier l’écologie spatiale d’une population en danger de baleines à bosse (Megaptera novaeangliae) dans l’océan Pacifique Sud. En utilisant un ensemble de données multidisciplinaires collecté entre 1995 et 2018 en Nouvelle-Calédonie et en Océanie, cette thèse a poursuivi trois objectifs : 1) étudier les meilleures pratiques de modélisation de la distribution des cétacés, 2) acquérir une meilleure compréhension de la distribution, des habitats et des mouvements des baleines à bosse dans leur zone de reproduction d’Océanie, 3) prédire les zones de conservation prioritaires et les menaces potentielles pour les baleines à bosse dans cette région. La modélisation de la distribution d’une grande baleine migratrice à partir de données de recherche non systématique et issues de la science participative a fourni des prédictions de bonne qualité, tant que l’hétérogénéité spatiale de l’échantillonnage et la tendance statistique au surapprentissage étaient correctement prises en compte. Les modèles additifs généralisés ont été privilégiés pour leur équilibre en termes de complexité des relations modélisées, leur rendu écologiquement explicite et leur capacité de transferabilité. Les modèles d’utilisation de l’habitat à différentes échelles spatiales ont révélé une préférence pour une diversité d’habitats peu profonds répartis dans une large gamme de température des eaux en Océanie. Les monts sous-marins et bancs peu profonds ont été identifiés comme d’importants habitats de reproduction et de développement pour les baleineaux. Ces reliefs sous-marins jouent également un rôle clé dans la connectivité au sein et entre les populations. Cette utilisation unique et inattendue de l’habitat pélagique a des conséquences importantes sur la gestion spatiale des baleines à bosse. La prédiction des habitats de reproduction présents et futurs à des échelles multiples fournit une base scientifique pour la désignation de zones de conservation prioritaires et la protection contre les menaces générées par les activités humaines et le changement climatique dans le Pacifique Sud

Mno_observations_2003-2016_Derville.et.al_Fidding the right fit

This table contains geographic positions of humpback whale (Megaptera novaeangliae) group encounters recorded between 2003 and 2016 in New Caledonia. Observations were obtained through crowdsourcing or research surveys conducted by Opération Cétacés and Institut de Recherche pour le Développement. This data was used in the study: "Finding the right fit: Comparative cetacean distribution models using multiple data sources" by Derville S, Torres L G, Iovan C, and Garrigue C

Social segregation of humpback whales in contrasted coastal and oceanic breeding habitats

International audienceMaternal habitat preferences of humpback whales (Megaptera novaeangliae) are well documented from decades of coastal research but oceanic areas have received less attention. Whales breeding in New Caledonia occupy both ecosystems: a coastal reef complex (South Lagoon) and oceanic seamounts (Southern Seamounts). Generalized additive models were applied to 20 years of boat-based whale observations (n = 1,526) to describe habitat preferences and permissive home range estimations were used to explicitly model spatial segregation in relation to social context. Groups with calves (n = 206) preferred shallow coastal waters throughout the season in the South Lagoon, whereas no habitat segregation was observed between groups with (n = 74) and without calves (n = 140) in the Southern Seamounts. As a result, spatial overlap between groups with and without calves was more common in the Southern Seamounts than the South Lagoon. Despite a lack of social segregation around seamounts, mother-calf pairs were proportionally more frequent in the Southern Seamounts (27%) than in the South Lagoon (16%). Photographs of the calves’ dorsal flanks were analyzed to compare age and ecological markers across sites. Calves appeared older in the Southern Seamounts than in the South Lagoon but no difference in scarring or shark bites was found across sites, suggesting that calves experienced similar lifestyles and may move between offshore and coastal waters during the breeding season. This study highlights the flexible habitat-use patterns of breeding humpback whales and raises new questions about the environmental and social drivers of their presence in offshore breeding grounds

Social segregation of humpback whales in contrasted coastal and oceanic breeding habitats

Article available for download at publisher's website: https://doi.org/10.1093/jmammal/gyx185Maternal habitat preferences of humpback whales (Megaptera novaeangliae) are well documented from decades of coastal research but oceanic areas have received less attention. Whales breeding in New Caledonia occupy both ecosystems: a coastal reef complex (South Lagoon) and oceanic seamounts (Southern Seamounts). Generalized additive models were applied to 20 years of boat-based whale observations (n = 1,526) to describe habitat preferences and permissive home range estimations were used to explicitly model spatial segregation in relation to social context. Groups with calves (n = 206) preferred shallow coastal waters throughout the season in the South Lagoon, whereas no habitat segregation was observed between groups with (n = 74) and without calves (n = 140) in the Southern Seamounts. As a result, spatial overlap between groups with and without calves was more common in the Southern Seamounts than the South Lagoon. Despite a lack of social segregation around seamounts, mother-calf pairs were proportionally more frequent in the Southern Seamounts (27%) than in the South Lagoon (16%). Photographs of the calves’ dorsal flanks were analyzed to compare age and ecological markers across sites. Calves appeared older in the Southern Seamounts than in the South Lagoon but no difference in scarring or shark bites was found across sites, suggesting that calves experienced similar lifestyles and may move between offshore and coastal waters during the breeding season. This study highlights the flexible habitat use patterns of breeding humpback whales and raises new questions about the environmental and social drivers of their presence in offshore breeding grounds.Key words: breeding ground, habitat use, humpback whales, Pacific Ocean, seamounts, social interaction

Fiches d'identification des phanérogames marines de Nouvelle-Calédonie

Outil pédagogique, projet Science en Herbe, IRD et association Opération Cétacés, Nouméa, Nouvelle-Calédoni

Les phanérogames marines de Nouvelle-Calédonie, clé de détermination simplifiée

Outil pédagogique, projet Science en Herbe, IRD et association Opération Cétacés, Nouméa, Nouvelle-Calédoni

Social Structure, Habitat Use and Injuries of Indo-Pacific Bottlenose Dolphins (Tursiops aduncus) Reveal Isolated, Coastal, and Threatened Communities in the South Pacific

Understanding population structure and habitat use of poorly known cetacean species is a first step toward scientifically informed management decisions. In the southern range of New Caledonia (South Pacific), a long-term dataset of Indo-Pacific bottlenose dolphins (Tursiops aduncus) encounters primarily during winter seasons 1997 to 2019 (473 group observations) was used to assess social structure, habitat use and potential threats. A total of 338 individuals were photographically identified, forming three distinct communities in the south-west lagoon, the south lagoon and the Isle of Pines. Mark-recapture histories revealed that the three communities were weakly connected and might be considered as independent management units. Suitable habitats were estimated with presence-only distribution models relative to topographic and seabed substrate predictors. Habitat suitability increased with proximity to coasts or reefs, at shallow depth, and over muddy bottom. These habitats had various levels of protection and were used by humans, mostly in the south-west lagoon. External injuries were interpreted to determine natural interactions and potential anthropogenic threats. The prevalence in injuries did not vary among the three areas. A substantial proportion of injuries related to propeller hits was reported, representing a total of 16.7% (34 of 204) of all injuries observed on dolphins. The three communities of Indo-Pacific bottlenose dolphins revealed in the southern part of New Caledonia are particularly vulnerable due to their insularity, their coastal habitat use and the low levels of connectivity found among them. In a context of increasing maritime traffic, fishing and recreational activities, this study provides a useful baseline to the urgent assessment of the conservation status of dolphins in New Caledonia

Horizontal and vertical movements of humpback whales inform the use of critical pelagic habitats in the western South Pacific

International audienceAbstract Humpback whales ( Megaptera novaeangliae ) are known for their nearshore distribution during the breeding season, but their pelagic habitat use patterns remain mostly unexplored. From 2016 to 2018, 18 humpback whales were equipped with depth-recording satellite tags (SPLASH10) to shed light on environmental and social drivers of seamount association around New Caledonia in the western South Pacific. Movement paths were spatially structured around shallow seamounts (80 m, max 616 m) were also recorded (11.5%), including by maternal females. Deep dives often occurred in series and were characterized by U-shapes suggesting high energy expenditure. This study provides new insights into the formerly overlooked use of pelagic habitats by humpback whales during the breeding season. Given increasing anthropogenic threats on deep sea habitats worldwide, this work has implications for the conservation of vulnerable marine ecosystems

Reproductive capacity of an endangered and recovering population of humpback whales in the Southern Hemisphere

International audienceEstimating demographic parameters is essential to assessing the recovery potential of severely depleted populations of marine mammal species such as the baleen whales, which were decimated by commercial whaling of the past century. The Oceania humpback whale Megaptera novaeangliae population is classified as endangered by the IUCN because of low numbers and a slow recovery rate. Nevertheless, an anomalously strong increase has recently been detected in the New Caledonia breeding population. To determine the drivers of population growth, reproductive parameters were estimated for the first time for a humpback whale population of Oceania. Based on an extensive monitoring program (1995-2018), recapture histories were reconstructed for 607 females and incorporated in multi-event capture-recapture models. As the females’ ages were generally unknown (87%), 2 models with contrasting age scenarios were investigated. For females of unknown age, the mature scenario assumed maturity at the first encounter, while the immature scenario assumed immaturity within 7 yr after the first encounter, unless the female was encountered breeding. These models respectively resulted in a calving interval of 1.49 yr (95% CI: 1.21-2.08) or 2.83 yr (95% CI: 2.28-3.56) and a calving rate of 0.67 or 0.35. The relatively high calving rate modelled by the mature model is consistent with high pregnancy rates recently observed in the migratory corridors of the Kermadec Islands and on the feeding grounds of the Antarctic Peninsula. Therefore, our results suggest that the recovery of the New Caledonia humpback whale population from past exploitation may be partially driven by an increased reproductive capacity