abstract |
Killer
whales (KWs) are apex marine predators. In Antarctica,
they have diverse trophic interactions and belong
to five ecotypes that have differences in morphology,
ecology, and acoustic repertoire. Around the Antarctic
Peninsula (AP), two sympatric forms of Type B KWs
are the most common. They have similar pigmentation
patterns, but a larger form has been observed to
feed mainly on seals (B1), and a smaller form feed
on Pygoscelis penguins (B2). The waters of the West
AP are experiencing ecosystem transformations caused
by climate change at one of the fastest rates on
Earth. Little is known about the austral winter
distribution and ecology of KWs in this changing
environment. The purpose of the study was to reveal
the winter distribution and ecology patterns of
KWs in the waters of the Wilhelm Archipelago. Boat-based
visual observations and photo-identification were
performed. The boat cruises were conducted within
14 nm of the Ukrainian Akademik Vernadsky Research
Station, Galindez Island. In 2019, 10 surveys of
a total of 194 nm were conducted, and in 2021 –
37 surveys of 605 nm. During both winters, three
groups of KWs were recorded. A group of 7 KWs was
encountered on 27 June 2019 near Hovgaard and Pleneau
islands. It consisted of adults of both sexes and
juveniles. In the same area, on 13 July 2021, another
group of KWs was observed, consisting of at least
5 individuals (up to 7): 1 adult male, 2 adult females,
a calf, and a juvenile of unknown sex. According
to the external morphology patterns, it was determined
that both groups belong to Type B, most likely of
a smaller form (B1). Large gatherings of Pygoscelis
penguins were observed in this area during both
winters. On 22 July 2021, a group of KWs consisting
of 2 adult males was observed in the Penola Strait.
Observations of their joint feeding on a crabeater
seal were performed. According to morphology and
behaviour, they belong to the ecotype B2. As Antarctic
krill move inshore during winter, penguins and crabeater
seals likely took advantage of ice-free areas to
feed on it, and their gatherings could attract KWs
of both Type B ecotypes. Future work should include
collecting photogrammetry data, skin biopsy samples,
behaviour observations, and acoustic recordings
to clearly differentiate between KW ecotypes and
better understand their winter distribution and
ecological patterns. |
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