ABSTRACT: Humpback whales breeding in the southwest Indian Ocean are thought to exhibit population substructure between Madagascar and east Africa. To investigate regional movements, breeding behavior and habitat utilization, 23 whales were satellite-tagged off Madagascar during peak breeding season off the northeast and southwest coasts. Mean tag duration was 24.2 d (3 to 58 d), during which time no individual remained near the immediate tagging sites and several displayed extensive long-range movements. We applied a switching state-space model to estimate behavioral modes of ‘transiting’ (b-mode approaching 1.0) vs. ‘localized’ (b-mode approaching 2.0) movement. A general linear mixed-effects model indicated females were more likely to display transiting behavior than males (mean b-mode females = 1.27, males = 1.65; p = 0.031). Whales tagged in the northeast displayed localized movements off the central east coast, whereas whales tagged in the southwest did so on the southern coasts, with little overlap. Long-distance movements included north-westerly trajectories to eastern Africa and southerly transits to Walters Shoals and the Crozet Islands. Despite these long-range movements in short periods, no whale travelled to the northwest coast of Madagascar, nor to Mozambique or the Mascarene Islands. These results suggest there may be more interchange between Madagascar and central-east Africa than previously thought, and whales off east and west Madagascar may not use the same habitat within breeding seasons; important findings for defining sub-population structure and conservation management strategy. Furthermore, male mating strategy may involve more localized searching or displaying, whereas females travel more extensively during the breeding season, observations that are consistent with a large-scale lek mating system.Trudelle et al, 2016. Influence of environmental parameters on movements and habitat utilization of humpback whales (Megaptera novaeangliae) in the Madagascar breeding ground. R. Soc.open sci. 3: 160616. http://dx.doi.org/10.1098/rsos.160616

ABSTRACT: Assessing the movement patterns and key habitat features of breeding humpback whales is a prerequisite for the conservation management of this philopatric species. To investigate the interactions between humpback whale movements and environmental conditions off Madagascar, we deployed 25 satellite tags in the northeast and southwest coast of Madagascar. For each recorded position, we collated estimates of environmental variables and computed two behavioural metrics: behavioural state of ‘transiting’ (consistent/directional) versus ‘localized’ (variable/nondirectional), and active swimming speed (i.e. speed relative to the current). On coastal habitats (i.e. bathymetry<200m and in adjacent areas), females showed localized behaviour in deep waters (191±20 m) and at large distances (14±0.6 km) from shore, suggesting that their breeding habitat extends beyond the shallowest waters available close to the coastline. Males’ active swimming speed decreased in shallow waters, but environmental parameters did not influence their likelihood to exhibit localized movements, which was probably dominated by social factors instead. In oceanic habitats, both males and females showed localized behaviours in shallow waters and favoured high chlorophyll-a concentrations. Active swimming speed accounts for a large proportion of observed movement speed; however, breeding humpback whales probably exploit prevailing ocean currents to maximize displacement. This study provides evidence that coastal areas, generally subject to strong human pressure, remain the core habitat of humpback whales off Madagascar. Our results expand the knowledge of humpback whale habitat use in oceanic habitat and response to variability of environmental factors such as oceanic current and chlorophyll level.--