Movements and behaviour of blue whales satellite tagged in an Australian upwelling system

Abstract

Knowledge about the movement ecology of endangered species is needed to identify biologically important areas and the spatio-temporal scale of potential human impacts on species. Blue whales (Balaenoptera musculus) are endangered due to twentieth century whaling and currently threatened by human activities. In Australia, they feed in the Great Southern Australian Coastal Upwelling System (GSACUS) during the austral summer. We investigate their movements, occupancy, behaviour, and environmental drivers to inform conservation management. Thirteen whales were satellite tagged, biopsy sampled and photo-identified in 2015. All were genetically confirmed to be of the pygmy subspecies (B. m. brevicauda). In the GSACUS, whales spent most of their time over the continental shelf and likely foraging in association with several seascape variables (sea surface temperature variability, depth, wind speed, sea surface height anomaly, and chlorophyll a). When whales left the region, they migrated west and then north along the Australian coast until they reached West Timor and Indonesia, where their movements indicated breeding or foraging behaviour. These results highlight the importance of the GSACUS as a foraging ground for pygmy blue whales inhabiting the eastern Indian Ocean and indicate the whales’ migratory route to proposed breeding grounds off Indonesia. Information about the spatio-temporal scale of potential human impacts can now be used to protect this little-known subspecies of blue whale.

The first three records of killer whales (Orcinus orca) killing and eating blue whales (Balaenoptera musculus)

“…The blue whales that were not attacked were all moving westward, along the south coast of Australia during the months of February-April. The timing, location, and direction of these movements are consistent with the known migratory patterns of a genetically identified population of pygmy blue whales (B. m. brevicauda), which feeds in the Bonney Upwelling off southern Victoria and South Australia and subsequently migrates westward off southern Australia and then north to Indonesia, possibly to breeding grounds (Double et al, 2014;Möller et al, 2020). We infer that our observations pertain to this subspecies although it appears that at least some of these migrating whales had calves with them already.…”

“…BSB killer whales forage mainly in deep water, beyond the continental shelf edge (Salgado Kent et al, 2020; Figure 1). Off southern Australia, some of the westward migrating pygmy blue whales from the Bonney Upwelling region travel far offshore, but at least some travel in shallower waters, close in along the coast (Möller et al, 2020; Figure 1). As mentioned above, the three blue whales that were attacked were the ones nearest to the shelf edge, adjacent to where the BSB killer whales normally occur (Figure 1).…”

On the rise: Climate change in New Zealand will cause sperm and blue whales to seek higher latitudes

“…However, dynamic process-based models require environmental predictor variables with a high spatio-temporal resolution, as well as temporally and spatially unbiased sightings, which are often unavailable (see discussion in El-Gabbas et al, 2021). Finally, we suggest that including species migration in our model would be at this stage irrelevant because of (i) the lack of conclusive understanding regarding the migratory behaviour (Goetz et al, 2021;Mӧller et al, 2020;Szesciorka et al, 2020;Warren et al, 2021), and movement (Whitehead, 2003) of our species for the New Zealand region, and (ii) the mobility of our species, which would be high enough to allow them to track the changes in their habitat suitability (Goetz et al, 2021). Despite some regional differences between their projected future distributions, both species are expected to shift their range southward which opens a whole range of socioeconomic implications for New Zealand.…”

Biologically Important Areas II for cetaceans within U.S. and adjacent waters – Hawaiʻi Region

“…Residence time was calculated by aggregating each whale's 10-minute crawl locations into the hexagonal grid cells and summing the total number of locations contained within each cell (represented as time in cell, in days). To account for varying track durations and mitigate bias associated with short tracks near deployment sites, we weighted residence time in each cell by the whale's track duration (within MHI breeding area perimeter) divided by the longest whale track duration in the dataset (within the MHI breeding area perimeter), following Möller et al (2020). A full description of the weighted occupancy pattern modeling is available in the humpback whale section of Supplementary File A.…”