Archived project

Whales of the deep: analyzing movement and diving of humpback whales to understand oceanic breeding congregations in New Caledonia

Goal: Humpback whale’s (Megaptera novaeangliae) habitat use in low-latitude breeding grounds is well documented from decades of coastal research. Yet, the use of pelagic habitats during the breeding period and migration has only recently been given attention. In New Caledonia, an archipelago located in the Pacific South West, several seamounts and banks are now considered as breeding ‘arenas’ playing an important role in the hypothesized floating lek breeding system of the local humpback whale
population. Yet, the reason why whales would aggregate and move between these offshore waters remains unknown. The relative abundance of maternal females in these unsheltered waters is also puzzling, in comparison to the shallow coastal waters usually occupied by these groups. Using the newest satellite tracking technology, this project aims at understanding the environmental and social drivers
of humpback whale oceanic habitat use during the breeding season. Dive depth will be related to environmental context in order to shed light on the role played by offshore seamounts for humpback whales of the Pacific South West. Patterns of connectivity and behavioural modes will be derived from the movements and dives of individuals from different social class and sex (males and females with or without calf). This study case will provide a unique opportunity to understand the spatio-temporal scale of the humpback whale floating lek systems and explore the drivers of habitat selection during the breeding season.

Date: 1 September 2015 - 1 September 2019

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Project log

Solène Derville
added a research item
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 (<200 m). Indeed, two males stopped over the Lord Howe seamount chain during the first-ever recorded longitudinal transit between New Caledonia and the east coast of Australia. Residence time significantly increased with proximity to shallow seamounts, while dive depth increased in the vicinity of seafloor ridges. Most of the 7,986 recorded dives occurred above 80 m (88.5%), but deep dives (>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.
Solène Derville
added a research item
Humpback whales (Megaptera novaeangliae) are known for their nearshore distribution during the breeding season, but their pelagic habitat use patterns remain mostly unexplored. In New Caledonia, an archipelago located in the western South Pacific, several offshore seamounts and banks are visited by humpback whales. Yet, the reasons why whales would aggregate and move between these offshore waters remain poorly known. From 2016 to 2018, 18 humpback whales were equipped with depth-recording satellite tags to shed light on environmental and social drivers of seamount association around New Caledonia. Shallow seamounts (< 500 m deep) spatially structured movement paths at small and large scale. Indeed, two males stopped over the Lord Howe seamount chain (3 to 7 days) during the first-ever recorded longitudinal transit between New Caledonia and the Australian East coast. Movement paths were modeled with Correlated Random Walks to estimate the position of dive events. Residence time was found to significantly increase with proximity to shallow seamounts, while dive depth increased within 100 km of these seabed features. Most of the 7,986 recorded dives occurred above 80 m (88.5%), but deep dives (> 80 m, max 616 m) were also regularly recorded (11.5%), including by maternal females. Deep dives often occurred in series and were characterized by U-shapes suggesting high-energy expenditure. Based on observed patterns of vertical and horizontal movements, we hypothesize that seamounts could 1) constitute navigational landmarks, 2) provide favorable conditions for opportunistic feeding, and 3) have acoustic properties facilitating male song propagation. At a broader scale, humpback whale use of seamounts is predicted from habitat models based on boat-based surveys conducted over the entire Oceania breeding range. Given increasing anthropogenic threats to deep sea habitats worldwide, these new insights into the use of seamounts by humpback whales during the breeding season have both ecological and conservation implications.
Solène Derville
added an update
We are at the peak of the breeding season here in New Caledonia, and it’s time for a sum up. Two MARACAS-7 surveys have already been conducted this winter, one is about to finish, and the fourth will take place at the end of September. The goal of the MARACAS-7 surveys is to characterize pelagic ecosystems around seamounts, and understand the social and environmental drivers of humpback whale aggregations around these seabed structures. More info: https://operationcetaces.wordpress.com/whales-of-the-deep-analyzing-movement-and-diving-of-humpback-whales-to-understand-oceanic-breeding-congregations-in-new-caledonia/
 
Solène Derville
added an update
Four cruises will be conducted aboard the Alis oceanographic vessel from June to September 2019. The goal? Survey a group of three shallow seamounts located south of the New Caledonia mainland. By doing so, we aim to understand why humpback whales appear to favor certain seamounts over others, and ultimately know what are the adaptive advantages to using these offshore unsheltered habitats during the breeding season.
 
Solène Derville
added a project goal
Humpback whale’s (Megaptera novaeangliae) habitat use in low-latitude breeding grounds is well documented from decades of coastal research. Yet, the use of pelagic habitats during the breeding period and migration has only recently been given attention. In New Caledonia, an archipelago located in the Pacific South West, several seamounts and banks are now considered as breeding ‘arenas’ playing an important role in the hypothesized floating lek breeding system of the local humpback whale
population. Yet, the reason why whales would aggregate and move between these offshore waters remains unknown. The relative abundance of maternal females in these unsheltered waters is also puzzling, in comparison to the shallow coastal waters usually occupied by these groups. Using the newest satellite tracking technology, this project aims at understanding the environmental and social drivers
of humpback whale oceanic habitat use during the breeding season. Dive depth will be related to environmental context in order to shed light on the role played by offshore seamounts for humpback whales of the Pacific South West. Patterns of connectivity and behavioural modes will be derived from the movements and dives of individuals from different social class and sex (males and females with or without calf). This study case will provide a unique opportunity to understand the spatio-temporal scale of the humpback whale floating lek systems and explore the drivers of habitat selection during the breeding season.