Influence of environmental parameters on movements and habitat utilization of humpback whales (Megaptera novaeangliae) in the Madagascar breeding ground

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/non-directional), and active swimming speed (i.e. speed relative to the current). On coastal habitats (i.e. bathymetry < 200 m 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.

Continuous movement behavior of humpback whales during the breeding season in the southwest Indian Ocean: on the road again!

“…This result is consistent with a hypothesis that deep-water transit could be comparable to trans-oceanic migration, while transit in shallow water could rather reflect roving movement, at lower speed, between suitable breeding sites (i.e., searching for localized patches of breeding whales). Mean travel speed during deep-water transit was within the range of speed reported during off-shore migration between feeding and breeding areas [11, 22, 23, 25, 28, 31]. In wintering areas generally, it was previously shown that whales usually travelled at slower speed [11, 22, 25, 31], although changes in movement behavior within and between breeding sites (localized vs. transit behavior) were not accounted for (excepted in [31]).…”

Whales in warming water: Assessing breeding habitat diversity and adaptability in Oceania's changing climate

“…The reasons for such extensive migrations are still debated but could be linked to increased calf fitness in warmer waters of the tropical and subtropical breeding grounds (Clapham, ). Although this hypothesis suggests a direct link between humpback whale life history and water temperature, it remains unclear how sea surface temperature (SST) drives distributions within breeding latitudes, as studies have shown both strong relationships (Bortolotto, Danilewicz, Hammond, Thomas, & Zerbini, ; Guidino, Llapapasca, Silva, Alcorta, & Pacheco, ; Rasmussen et al, ; Smith et al, ) and weak or no effects of this variable (Dulau et al, ; Trudelle et al, ). SST is dynamic, with complex changes through time as it fluctuates on multiple temporal scales (monthly, seasonally, annually) and follows patterns that may be stochastic, cyclic (e.g., El Niño Southern Oscillation [ENSO], Pacific Decadal Oscillation, Antarctic Oscillation [AAO]) or continuous (climate change).…”

“…The reasons for such extensive migrations are still debated but could be linked to increased calf fitness in warmer waters of the tropical and subtropical breeding grounds (Clapham, 2000). Although this hypothesis suggests a direct link between humpback whale life history and water temperature, it remains unclear how sea surface temperature (SST) drives distributions within breeding latitudes, as studies have shown both strong relationships (Bortolotto, Danilewicz, Hammond, Thomas, & Zerbini, 2017;Guidino, Llapapasca, Silva, Alcorta, & Pacheco, 2014;Rasmussen et al, 2007;Smith et al, 2012) and weak or no effects of this variable (Dulau et al, 2017;Trudelle et al, 2016).…”

“…Compared to other breeding regions of the world, Oceania encompasses a remarkably large extent of potential breeding habitat (Valsecchi, Corkeron, Galli, Sherwin, & Bertorelle, 2010). It covers thousands of islands and reefs that offer the conditions usually regarded as preferred for humpback whale breeding and nursing behavior: sheltered, shallow, and warm waters (Bortolotto et al, 2017;Cartwright et al, 2012;Derville, Torres, Iovan, & Garrigue, 2018;Lindsay et al, 2016;Rasmussen et al, 2007;Smith et al, 2012;Trudelle et al, 2016).…”

Baleen whale distribution and seasonal occurrence revealed by an ocean bottom seismometer network in the Western Indian Ocean

“…Recent knowledge on baleen whales in the IO relies on coastal areas visual sighting or telemetry. For instance, humpback whale (Megaptera novaengliae) population in the western IO have been studied in their breeding areas throughout the austral winter (Kiszka et al, 2010;Trudelle et al, 2016) and Pygmy Blue Whale (PBW) (Balaenoptera musculus brevicauda) population have been observed in the eastern IO in their feeding areas throughout the austral summer (Gill et al, 2011;Double et al, 2014). However, these methods are expensive, require dedicated manpower and are often poorly efficient, especially in deep waters (Mellinger et al, 2007).…”