Gerlache Killer Whales

A mature female Gerlache killer whale surfacing next to a calf. Photo provided by Lex.

### Common Features

* Yellow "cast" due to diatoms
* Large oval eyepatches (narrower than Pack Ice individuals)
* Dorsal cape; sometimes shows narrow white border
* Closed or slightly open saddle patch
* Medium-sized

### Distribution

Antarctic Peninsula

Antarctic Type B2 killer whales, also known as Small Type B killer whales or Gerlache killer whales are a medium-sized killer whale ecotype that inhabits the offshore waters of the Western Antarctic Peninsula, being found primarily in the Gerlache Strait. They are known to be morphologically similar to Pack Ice killer whales, however, they specialize primarily on hunting pygoscelid penguins, may take also on fish and/or squid.

### Social Structure

Gerlache killer whales are more gregarious than Pack Ice killer whales, traveling in large pods that consist of thrity-six individuals in average, ranging from eight to seventy-five individuals.

### Comon Physical Features

Gerlache killer whales have a two-tone gray pigmentation, with the rostrum, pectoral fins, part of the dorsal fin, and flukes being darker than the rest of the body. They have a dorsal cape that extends from the saddle to the post-ocular patch (eyepatch), it may have a narrow 'white border' on its sides; saddle patch can be slighly open. The eyepatch is large and wide, but slimmer than Antarctic Type B1 (Pack Ice) killer whales. They often show a yellow-brownish cast due to the presence of Diatoms on its skin. Flanks are narrow, a trait also observed in Pack Ice (type B1) and Ross Sea (type C) killer whales. Body is slightly slimmer than Pack Ice killer whales, and their dorsal fins are shorter.

Males reach on average 6.4m, and females reach 5.8m on average; maximum size is unknown.

### Diet

The diet consists mainly of pygocelid penguins, primarily Gentoo Penguins *(Pygocelis papua)*, which may feed on fish and/or squid; it also has been documented taking on Weddell Seals *(Leptonychotes weddellii)*.

## Habitat, Migration and Dive Depth

Gerlache killer whales are found year-round in Antarctica, often observed in the Gerlache Strait, Western Antarctic Peninsula; Though they make short travels to lower latitudes, in order to shed their diatom-covered skin, they were tracked passing through the Scotia Sea, east of the Falkland Islands, and northward off the eastern coast of South America. The average mean dive depthwas 121.7 m (range of individual means 80.9–168.5, mean of individual maximums 608m, range of individual maximums 552–696m.

## References

1. ↑ 1.0 1.1 #Fearnbach, Holly & Durban, John & Ellifrit, David & Paredes, Alyssa & Hickmott, Leigh & Pitman, Robert. (2021). A decade of photo‐identification reveals contrasting abundance and trends of Type B killer whales in the coastal waters of the Antarctic Peninsula. Marine Mammal Science. 38. 10.1111/mms.12846.
2. ↑ 2.0 2.1 Durban, J. & Fearnbach, Holly & Burrows, Douglas & Ylitalo, Gina & Pitman, R.. (2016). Morphological and ecological evidence for two sympatric forms of Type B killer whale around the Antarctic Peninsula. Polar Biology. 40. 10.1007/s00300-016-1942-x.
3. ↑ Durban, JW & Fearnbach, Holly & Paredes, A & Hickmott, Leigh & LeRoi, DJ. (2021). Size and body condition of sympatric killer whale ecotypes around the Antarctic Peninsula. Marine Ecology Progress Series. 677. 10.3354/meps13866.
4. ↑ Pitman RL, Durban JW, Joyce T, Fearnbach H, Panigada S, Lauriano G. Skin in the game: Epidermal molt as a driver of long-distance migration in whales. *Mar Mam Sci*. 2020; 36: 565–594. https://doi.org/10.1111/mms.12661