Habitats and movement patterns of white whales Delphinapterus leucas in Svalbard, Norway in a changing climate

Abstract

BackgroundThe Arctic is experiencing rapid reductions in sea ice and in some areas tidal glaciers are melting and retracting onto land. These changes are occurring at extremely rapid rates in the Northeast Atlantic Arctic. The aim of this study was to investigate the impacts of these environmental changes on space use by white whales (Delphinapterus leucas) in Svalbard, Norway. Using a unique biotelemetry data set involving 34 animals, spanning two decades, habitat use and movement patterns were compared before (1995–2001) and after (2013–2016) a dramatic change in the regional sea ice regime that began in 2006.ResultsWhite whales were extremely coastal in both study periods, remaining near the islands within the Svalbard Archipelago, even when winter sea ice formation pushed them offshore somewhat (later in the year in the recent period), into areas with drifting sea ice (concentrations up to 90%). In both periods, the whales followed the same basic patterns seasonally; they occupied the west coast in summer and shifted to the east coast as winter approached. However, space use did change between the two periods, with the whales spending less time close to tidal glacier fronts in the second period compared to the first (2nd-36% vs 1st-51%), a habitat characterized by low swimming speeds and high turning angles, and more time out in the fjords (2nd-26% vs1st-10%). Use of coastal transit corridors remained the same in both periods; the whales appear to minimize time spent moving between fjords.ConclusionsGlacier fronts have previously been shown to be important foraging areas for white whales in Svalbard and the movement metrics documented in this study confirms that this is still the case. However, use of the Fjords habitat in summer and fall (frequency of occupancy and movement metrics) seen in the recent period suggests that the white whales might now also be feeding on Atlantic prey that is increasingly common in the fjords, concomitant with influxes of Atlantic Water along the west coast of Svalbard. Such behavioural flexibility, if confirmed by further diet studies, would likely be important for white whales in adapting to new conditions in Svalbard.Electronic supplementary materialThe online version of this article (10.1186/s40462-018-0139-z) contains supplementary material, which is available to authorized users.

First abundance estimate for white whales Delphinapterus leucas in Svalbard, Norway

“…Most glaciers in the area are in a state of negative mass balance , Nuth et al 2010, Lydersen et al 2014, Torsvik et al 2019. The white whale stock in this region is genetically differentiated from the West Greenland stock to the west (O'Corry-Crowe et al 2010); its genetic relationship with white whales in Frans Josef Land to the east is currently unknown (Lønø & Øynes 1961, O'Corry-Crowe et al 2010, although tracking data from Svalbard do not suggest routine movements between these archipelagos in recent decades (Lydersen et al 2001, Vacquié-Garcia et al 2018.…”

“…Despite the large number of animals caught in the past, white whales are one of the most commonly observed cetaceans in this area (Storrie et al 2018). In recent years, the habitat use of white whales in Svalbard waters has been investigated using satellite tracking, which has revealed that they are year-round residents and occupy areas close to the coast (Lydersen et al 2001, Vacquié-Garcia et al 2018. A seasonal movement pattern occurs, with animals generally spending more time on the west coast of Spitsbergen in summer and then moving southward and eastward to the east coast as winter approaches (Lydersen et al 2001, Vacquié-Garcia et al 2018.…”

“…In recent years, the habitat use of white whales in Svalbard waters has been investigated using satellite tracking, which has revealed that they are year-round residents and occupy areas close to the coast (Lydersen et al 2001, Vacquié-Garcia et al 2018. A seasonal movement pattern occurs, with animals generally spending more time on the west coast of Spitsbergen in summer and then moving southward and eastward to the east coast as winter approaches (Lydersen et al 2001, Vacquié-Garcia et al 2018. During ice-free periods of the year, the white whales in Svalbard spend most of their time close to the fronts of tidewater glaciers (Lydersen et al 2001, Vacquié-Garcia et al 2018, similar to many other Arctic species (Lydersen et al 2014), likely foraging on polar cod Boreogadus saida (Dahl et al 2000) which congregate in the cold water areas in front of glaciers.…”

Contrasting changes in space use induced by climate change in two Arctic marine mammal species

“…In contrast with RS, WW are not retracting into Arctic glacial refugia. They had larger home ranges and spent less time near glacier fronts and more time in the centre of fjords (figure 2; electronic supplementary material, figure S2) in 2013-2016 compared with 1995-2001 [16]. It is likely that they have shifted to foraging on Atlantic prey such as capelin (Mallotus villosus) and herring (Clupea harengus), similar to the situation in the Canadian Arctic [23].…”

“…15: 20180834 use of them was not explained by their characteristics for RS, though for WW frontal length remained important (electronic supplementary material, tables S5 and S6). Differences in tagging locations in the two study years (electronic supplementary material, figure S1 and tables S1 and S2) are unlikely to have impacted our results because WW move across much of the archipelago constantly [16] and RS results were not dependent on tagging location in the analyses herein. Concomitant with the physical changes (increased Atlantic water intrusion and decreased sea ice) that have occurred over the last decade in Svalbard waters, large ecosystem changes have taken place, including a general 'borealization' of the fish community.…”