An encounter with rare ecotype-D orcas

dsc_7535

On May 13, 1955, 17 killer whales washed up on Paraparaumu Beach on New Zealand’s North Island. The stranding attracted extra attention because of the whales’ strange appearances. Instead of the sleek, streamlined bodies of typical killer whales, these ones had large bulbous foreheads, almost like a pilot whale, pointy, scimitar-shaped dorsal fins and where killer whales generally display large, white eye-patches, these stranded whales had tiny post-ocular eye markings.

For almost 50 years this kind of killer whale was not seen again. Because individual killer whales pods are usually all related to the matriarch in the pod, it was thought that maybe a mutant gene had been passed along among the group and that this was a one-off occurrence and therefore considered a genetic anomaly.

Around 2005, scientists began collecting photographs of killer whales from the Southern Ocean waters to learn about the distribution of three ecotypes of killer whales that they had described from Antarctica (Pitman and Ensor 2003). Among the thousands of photographs that they received, there were several  of  killer whales with the same features as in the New Zealand stranding, and it  became clear that they were dealing with a distinctive,  undescribed form of killer whale that was essentially unknown to science.

dsc_7567

All the orcas of the world are currently still grouped together as one species under the scientific name Orcinus orca and could be considered abundant in the planet’s oceans. A few years ago, this led to a request to delist the southern resident orcas of the Salish Sea as “there were plenty of orcas elsewhere”. Luckily this attempt failed, partly based on what scientists have known for a while now, that orcas differ in morphology, social structure, (acoustic) behavior and prey preferences, especially at high latitudes.

dsc_7565

Best known and longest studied is the example from the Pacific North West coast of North America where salmon-eating ‘residents’, mammal-eating ‘transients’ (or Bigg’s killer whales) and pelagic ‘off-shores’ roughly share the same area, but are quite distinct from each other and never mix, let alone interbreed.

A similar division might exist in the West Pacific waters around Kamchatka, the Commander Islands and other parts of the Russian Fareast.

Recent studies of killer whales in the UK and North Atlantic waters, based, among other things, on tooth wear, also point to at least two different types: The smaller type-1 that subsists mainly on herring and mackerel (but might eat seals too) and type-2, a generalist feeder, that may largely prey on cetaceans. Fish can be sucked in whole while cetaceans have to be ripped apart and chewed, hence a difference in dental wear. Type 2 adult males are almost two meters larger than type 1 adult males.

dsc_7562

The term ecotype was originally defined as the “result of the genotypical response of an ecospecies to a particular habitat”, but has more recently become to mean “con-specific individuals or groups of individuals, with similar ecological adaptations regardless of genealogical relationship.” Less scientific, this means that animals diverge from a common ancestor because of their adaptations to different ecosystems. Another way to express this is by calling the ecotypes “evolutionary significant units”.

An ecotype designation could be seen as the antechamber for separate species or subspecies recognition until all the evidence is in.

dsc_7560

In Antarctic waters there are three readily identifiable ecotypes: type-A (a large, open water, marine mammal hunter, mainly preying on Antarctic minke whales) and type-C (the Ross Sea killer whale, a fish eater, particularly preying on Antarctic toothfish). The original ecotype-B is now subdivided in a small (the Gerlache killer whale, a penguin hunter) and a large (the pack ice killer whale, a pinniped hunter) type.

Despite these tentative divisions, there might still be variations in both prey and morphology within these ecotypes and there are reports that some Southern Ocean orcas don’t really fit any box.

The ecotype-D killer whale was first described in 2007. Based on the compiled sightings, type D killer whales occurred around the entire continent of AntarcticaEcotype-D’s geographic range appears to be circum-global in waters between latitudes 40 S and 60 S, which led to the proposed name of ‘sub-Antarctic killer whale’.. They also seemed to be associated with the Polar Front, and as such, the scientist suggested the name: subantarctic killer whale, for the animal (Pitman et al. 2011).

dsc_7559

On December 26, 2014, the Sea Shepherd ship, Bob Barker, encountered a pod of orcas in stormy weather, while passing between the Crozet and Kerguelen archipelagos in the South Indian Ocean, in pursuit of the toothfish-poaching vessel Thunder. At that time the Bob Barker had been following the Thunder for just ten days. The vessel had left their illegal driftnets behind and after taking the chase first through ice, this was now the second patch of foul weather the Thunder had led the Sea Shepherd ship into in an attempt to loose it.

By the time the Thunder’s officers sank their own vessel, far away from the Antarctic in tropical waters off the West African island-nation Sao Tomé in an attempt to destroy the evidence (ship, fish cargo, fishing gear, etc.), we had been following the fishing vessel for 110 days, the longest ocean pursuit in maritime history.

dsc_7556

I joined the Bob Barker as chief engineer a few weeks before her departure from Williamstown, Australia. I had worked in that capacity on the polar expedition-cruise ship Plancius in the years before, so had seen the ecotype-A and -B orcas regularly in the south and got a few glimpses of the North Atlantic orcas en route to Spitsbergen. That’s how I knew about the existence of the ecotype-D and how seldom they are seen.

When not at sea, I lived with my girlfriend in Friday Harbor, San Juan Island, where the ‘residents’ and ‘transients’ lived almost right on our doorstep. I volunteered there with the Whale Museum’s boater education program ‘Soundwatch’, so I had spent quite a bit of time on the water with these orca ecotypes as well.

dsc_7555

As rare as the type-D’s are, they’re also the visually most distinct and easiest to identify. When they popped up right next to the Bob Barker that Boxing Day, even in the 6-meter waves and 8 BF winds, I sensed immediately that there was something different about these orcas and soon the distinct bulbous forehead of an adult male, like no other orca, and the tiny white eye-patch accompanying it, confirmed the extra-specialness of this ‘visit’.

dsc_7550

The encounter was photographed and filmed, and images of the encounter were forwarded to Marine Ecologist and (Antarctic) Orca expert, Robert L. Pitman, of Southwest Fisheries Science Center of the National Oceanic and Atmospheric Administra­tion in the USA and to Paul Tixier, who holds a similar position in France, for review.

dsc_7548

The most impressive thing about the encounter was that, while we as spectators had to hold on with both hands to our pitching and rolling ship, our lifebuoy in an environment hostile to us humans, the orcas surfed the waves across our bow with ease. The seemingly effortless surfing combined with tail-slaps and breaches could only be described as play and the crew watched the 13 killer whales, including a small juvenile and a large male, in awe for almost an hour.

dsc_7546

With 29.000 ‘likes’ the first post of photos on Facebook was one of the most popular posts ever on the Sea Shepherd Global site, only matched by the ICJ ruling against Japanese ‘scientific’ whaling of March that same year. The comments, even when people did not realize how rare the encounter was, reflected their joy of seeing wild orcas and their disgust with captivity. The circumstances in which we saw these orcas can never be recreated in a pool. Keeping orcas and other cetaceans in captivity is a crime.

dsc_7541

This new ecotype had only 6 confirmed at-sea sightings, when it was presented to the world in a scientific paper in August 2010. The re-occurring sightings of some 40 different individuals since 2003 around Crozet Island toothfish longliners were counted as one.

There are now at least 13 sightings, the Bob Barker one among them, what is still very few for such a large, distinctive whale.

dsc_7539

No feeding or hunting of this killer whale type has ever been observed, but as they have been seen associating with toothfish longliners near Crozet, scientist cautiously assume their diet includes (tooth)fish.

At Crozet, the type-Ds have never been encountered in inshore waters like the other orca types (A & C) visiting the island archipelago, so we can carefully assume that these are open ocean, deep water orcas.

dsc_7537

With only a dozen sightings, biopsy DNA material of type-D orcas does not exist yet, but one of the skeletons of the 1955 stranding was preserved in Wellington’s Te Papa Tongarewa museum. The study of the DNA from dried soft tissue on the skull and powdered tooth from this 50-year old skeleton revealed that type-D’s genetic differences point at a divergence from other orcas about 390.000 years ago. This makes ecotype-D the second oldest orca type, and most genetically divergent, after the ‘transient’ ecotype of the Northeast Pacific Ocean. Although the sample was somewhat degraded, it was clear that this was a very different type of killer whale and very possibly a different species (Foote et al. 2013).

“This study provides the first genetic support of Type-D potentially being a distinct subspecies or species of killer whale,” the researchers wrote in their paper.

dsc_7536

Ecotypic variation will likely result in speciation if the divergence in morphology, physiology and behavior (in essence evolution through natural selection for adaptive advantages), results in reproductive isolation, which seems to be the case for most ecotypes. This possibly means we have not just one species of orca, but multiple species or subspecies.

This could radically change the conservation status from abundant worldwide to rare for some of these new (sub)species. Determining how many species of killer whales there are is key to establishing conservation measures and to better understand the ecological role of this apex predator in the world’s oceans.

Ross Sea killer whales, for instance, were regularly seen in McMurdo Sound with Antarctic toothfish dangling from their jaws. Ten years after the Ross Sea fisheries started for this toothfish in 1996, the toothfish had disappeared from McMurdo Sound. If the Antarctic toothfish was the main prey for ecotype-C orcas they now would have to find something else to eat, like large quantities of sardine-size Antarctic silverfish, or perish.

Around the Salish Sea the southern resident orcas appear to be starving due to a lack of (Chinook) salmon. Their numbers never recovered from the decimating impact the captive industry had on this population.

Around the French sub-Antarctic island of Crozet orcas that are known to depredate Patagonian toothfish longlines, ”have undergone a marked decline in both their abundance and survival rate (Tixier, 2008; Poncelet et al., 2009).” The reasons are not clear, but back in the 1990s, the killer whale population there suffered from lethal interactions with toothfish poaching vessels that repelled the whales using guns and explosives during fishing operations. Poachers might still be causing the current unexplained mortality in these killer whale pods.

dsc_7536

We know too little bout the ecotype-D orcas to be able to establish a population estimate or trend, but if they are fish eaters it is almost inevitable they are competing with humans.

dsc_7534

Marine ecologist and (Antarctic) orca expert Robert L. Pitman, author of the above mentioned August 2010 scientific paper and co-author of the paper on the 1955 DNA, examined the photos from the Bob Barker encounter. He said: “my guess is they turn out to be a new species of killer whale.”

Het told the website TakePart: “Type D killer whale is the most different-looking killer whale that we know of; it could easily be a new species of killer whale, which would make it a candidate for the largest undescribed species of animal we have left on the planet”.

dsc_7531

The sighting occurred roughly midway between the Crozet and Kerguelen archipelagos at 49 55S 053 50E, 2014.12.26 09:50 UTC.

dsc_7526

A video of the encounter can be seen at: https://www.youtube.com/watch?v=i7fLDYT0PM0

dsc_7524

dsc_7523

dsc_7518

dsc_7517

 

References:

Interactions of Patagonian toothfish fisheries with killer and sperm whales in the Crozet islands Exclusive Economic Zone: an assessment of depredation levels and insights on possible mitigation strategies, P. Tixier1, N. Gasco, G. Duhamel, M. Viviant, M. Authier and C. Guinet

Killer whale ecotypes: is there a global model? J. Nico de Bruyn, Cheryl A. Tosh and Aleks Terauds

Observations of a distinctive morphotype of killer whale (Orcinus orca), type D, from subantarctic waters, Robert L. Pitman, John W. Durban, Michael Greenfelder, Christophe Guinet, Morton Jorgensen, Paula A. Olson, Jordi Plana, Paul Tixier, Jared R. Towers

Type-D killer whales Crozet Islands Photo-Identification Catalogue 2014, Paul Tixier, Nicolas Gasco, Timothée Poupart, Christophe Guinet

Durban, J. W., H. Fearnbach, D. G. Burrows, G. M. Ylitalo, and R. L. Pitman. 2016. Morphological and ecological evidence for two sympatric forms of Type B killer whale around the Antarctic Peninsula. Polar Biology DOI 10.1007/s00300-016-1942-x

Foote, A. D, P. A. Morin, R. L. Pitman, M. C. Ávila-Arcos, J. W. Durban, A. van Helden, M. H. S. Sinding, T. P. Gilbert. 2013. Mitogenomic insights into a recently described and rarely observed killer whale morphotype. Polar Biology 36:1519-1523.

Pitman, R.L. and P. Ensor. 2003. Three different forms of killer whales in Antarctic waters. Journal of Cetacean Research and Management 5(2):131-139.

Pitman, R. L., J. W. Durban, M. Greenfelder, C. Guinet, M. Jorgensen, P. A. Olson, J. Plana, P. Tixier, J. R. Towers. 2011. Observations of a distinctive morphotype of killer whale (Orcinus orca), type D, from subantarctic waters. Polar Biology 34:303-306

 

 

 


2 thoughts on “An encounter with rare ecotype-D orcas

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s