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Killer Whale Research References

I recently had a request to share some the resources that I have used throughout the years for killer whale research and thought I would share them publicly too for anybody who wants to get more in-depth knowledge of killer whale biology, ecology, culture, and evolutionary history. The best information comes from from primary sources––these will almost always be published peer-reviewed research articles. Unfortunately, they can be difficult to access outside academia thanks to paywalls and complex language/topics can make it difficult for people without background in the paper’s topic to fully understand. Worry not though! As a university student, I have access to most research papers and am more than happy to email them to you if needed. If you are having difficulty understanding what the paper is talking about, check out these resources on how to read scientific papers: 

How to (seriously) read a scientific paper

How to Read and Understand a Scientific Paper

If you are still having difficulty grasping the main concepts, shoot me a message and I’d be more than happy to explain them to you! Another note: it is important to understand that scientific research is always changing and that older papers, though they often contain the founding principles of a research topic, can sometimes have inaccuracies due to their age. Always be aware of this while reading older research. 

*Note: This is NOT a comprehensive list of all killer whale research papers. This is a list of key papers/studies I believe are good starting points for people who are interested in getting more in-depth knowledge of killer whales.*

Life History

Social Organization and Genealogy of Resident Killer Whales (Orcinus orca) in the Coastal Waters of British Columbia and Washington State (1990)

Life history and population dynamics of resident killer whales Orcinus orca in the coastal waters of British Columbia and Washington (1990)

Population structure and mating patterns of Killer Whales (Orcinus orca) as revealed by DNA analysis (2000)

Killer whales: The natural history and genealogy of Orcinus orca in the waters of British Columbia and Washington (2000) (Note: this is a book)

Adaptive Prolonged Postreproductive Life Span in Killer Whales (2012)

Life history and population dynamics of southern Alaska resident killer whales (Orcinus orca) (2013)

Reproductive Conflict and the Evolution of Menopause in Killer Whales (2017)

 Evolution

Note: most of these papers are heavy in genetic concepts and methods––they are difficult to understand and I recommend focusing on the introduction/abstract and discussion/conclusions for clarity. 

Complete mitochondrial genome phylogeographic analysis of killer whales (Orcinus orca) indicates multiple species (2010)

Phylogenomics of the killer whale indicates ecotype divergence in sympatry (2015)

Genome-wide SNP data suggest complex ancestry of sympatric North Pacific killer whale ecotypes (2016)

Foraging

Dietary specialization in two sympatric populations of killer whales Orcinus orca in coastal British Columbia and adjacent waters. (1998)

Foraging strategies of sympatric killer whale, Orcinus orca, populations in Prince William Sound, Alaska (2000)

Shark predation and tooth wear in a population of northeastern Pacific killer whales (2011)

You Are What You Eat: Foraging Specializations and Their Influence on the Social Organization and Behavior of Killer Whales (2014)

Culture & Behavior

The mixed blessing of echolocation: differences in sonar use by fish-eating and mammal-eating killer whales (1996)

The vocal behaviour of mammal-eating killer whales: communicating with costly calls (2005)

Cultural traditions and the evolution of reproductive isolation: Ecological speciation in killer whales? (2012)

Kin-directed food sharing promotes lifetime natal philopatry of both sexes in a population of fish-eating killer whales, Orcinus orca (2016)

Gene–culture coevolution in whales and dolphins (2017)

Infanticide in a mammal-eating killer whale population (2018)

Misc. Articles (Not Primary Literature)

Primary sources are always best but there are also good articles and sources outside of peer-reviewed literature that contain good information as well!

Whalewatcher: Killer Whale (HIGHLY recommend reading this)

Orcazine

Encyclopedia of Marine Mammals

Marine Mammals of the World

[flukeprintphotography-deactivat]

When you hear “diatoms” and “killer whales,” you probably immediately think of type B or C killer whales, so covered in algae they turn slimy and yellow. But don’t be fooled—northern hemisphere killer whales carry diatoms on their skin as well! Diatoms are tiny types of algae that thrive in polar and sub-polar waters. They are often found attached to the skin of whales and dolphins, leaving a yellowish brown color. A few genera of diatoms seem to be found exclusively on cetaceans, but very little is known about them as they are not studied much today. Because some are unique to cetaceans and found nowhere else, they likely have developed adoptions to dealing with extreme fluctuations in light, depth, and temperature as their cetacean hosts dive and move around.

Here are a few photos I took of some Alaskan diatoms under 400x magnification! Note: while I don’t know the species of these diatoms, they are most likely not the ones found on cetaceans—cetacean diatoms have not been found in plankton tows, where these samples came from.

[flukeprintphotography-deactivat]

Killer Whale Research References

I recently had a request to share some the resources that I have used throughout the years for killer whale research and thought I would share them publicly too for anybody who wants to get more in-depth knowledge of killer whale biology, ecology, culture, and evolutionary history. The best information comes from from primary sources––these will almost always be published peer-reviewed research articles. Unfortunately, they can be difficult to access outside academia thanks to paywalls and complex language/topics can make it difficult for people without background in the paper’s topic to fully understand. Worry not though! As a university student, I have access to most research papers and am more than happy to email them to you if needed. If you are having difficulty understanding what the paper is talking about, check out these resources on how to read scientific papers: 

How to (seriously) read a scientific paper

How to Read and Understand a Scientific Paper

If you are still having difficulty grasping the main concepts, shoot me a message and I’d be more than happy to explain them to you! Another note: it is important to understand that scientific research is always changing and that older papers, though they often contain the founding principles of a research topic, can sometimes have inaccuracies due to their age. Always be aware of this while reading older research. 

*Note: This is NOT a comprehensive list of all killer whale research papers. This is a list of key papers/studies I believe are good starting points for people who are interested in getting more in-depth knowledge of killer whales.*

Life History

Social Organization and Genealogy of Resident Killer Whales (Orcinus orca) in the Coastal Waters of British Columbia and Washington State (1990)

Life history and population dynamics of resident killer whales Orcinus orca in the coastal waters of British Columbia and Washington (1990)

Population structure and mating patterns of Killer Whales (Orcinus orca) as revealed by DNA analysis (2000)

Killer whales: The natural history and genealogy of Orcinus orca in the waters of British Columbia and Washington (2000) (Note: this is a book)

Adaptive Prolonged Postreproductive Life Span in Killer Whales (2012)

Life history and population dynamics of southern Alaska resident killer whales (Orcinus orca) (2013)

Reproductive Conflict and the Evolution of Menopause in Killer Whales (2017)

 Evolution

Note: most of these papers are heavy in genetic concepts and methods––they are difficult to understand and I recommend focusing on the introduction/abstract and discussion/conclusions for clarity. 

Complete mitochondrial genome phylogeographic analysis of killer whales (Orcinus orca) indicates multiple species (2010)

Phylogenomics of the killer whale indicates ecotype divergence in sympatry (2015)

Genome-wide SNP data suggest complex ancestry of sympatric North Pacific killer whale ecotypes (2016)

Foraging

Dietary specialization in two sympatric populations of killer whales Orcinus orca in coastal British Columbia and adjacent waters. (1998)

Foraging strategies of sympatric killer whale, Orcinus orca, populations in Prince William Sound, Alaska (2000)

Shark predation and tooth wear in a population of northeastern Pacific killer whales (2011)

You Are What You Eat: Foraging Specializations and Their Influence on the Social Organization and Behavior of Killer Whales (2014)

Culture & Behavior

The mixed blessing of echolocation: differences in sonar use by fish-eating and mammal-eating killer whales (1996)

The vocal behaviour of mammal-eating killer whales: communicating with costly calls (2005)

Cultural traditions and the evolution of reproductive isolation: Ecological speciation in killer whales? (2012)

Kin-directed food sharing promotes lifetime natal philopatry of both sexes in a population of fish-eating killer whales, Orcinus orca (2016)

Gene–culture coevolution in whales and dolphins (2017)

Infanticide in a mammal-eating killer whale population (2018)

Misc. Articles (Not Primary Literature)

Primary sources are always best but there are also good articles and sources outside of peer-reviewed literature that contain good information as well!

Whalewatcher: Killer Whale (HIGHLY recommend reading this)

Orcazine

Encyclopedia of Marine Mammals

Marine Mammals of the World

[delphinidae-info]

Sonar Can Literally Scare Whales to Death, Study Finds

Sonar's disruptive signal can harm beaked whales, in some cases causing their deaths.

[csnews]

Why do Beaked Whales Keep Returning to a Navy Sonar Range?

MAREX - January 29, 2019

Scientists have determined that beaked whales prefer to feed within parts of a Navy sonar test range off Southern California that have dense patches of deep-sea squid and that these prey hotspots are needed to survive. Similar patches do not exist in nearby sonar-free areas.

For decades, the U.S. Navy has used high-powered sonar during anti-submarine training and testing exercises in various ocean habitats, including the San Nicolas Basin off Southern California. Beaked whales are particularly sensitive to these kinds of military sonars, which the researchers say have sometimes resulted in mass stranding events. Following legal action from environmental activists related to these risks, the Navy modified some training activities, created sonar-free areas, and spent more than a decade and tens of millions of dollars trying to find ways to reduce the harm to beaked whales and other mammals.

Keep reading

[flukeprintphotography-deactivat]

Eyepatches can be a good tool for identifying killer whales, especially when they are photographed in positions when the saddle patch isn’t visible, like during spyhops. Note the uniqueness of each patch—no two are the same, not even on the same killer whale! Eyepatch photo-identification can be a lot harder, however, as it requires a photographer to capture clear images of both the left and right eye patch of a whale that was already identified via saddle patch. Unlike saddle patches, eyepatches are not always fully visible when a whale surfaces. For this reason, it is not used as a primary method of identification and instead as a supplementary tool.

[csnews]

Pod of orca swimming ‘strongly’ after being stranded in Kaipara Harbour, north Auckland

Mandy Te and Nicole Lawton - February 1, 2019

A pod of stranded orca looked like they “were on their way out” until some fishing friends spent three hours rescuing the animals in Kaipara Harbour, north Auckland. The group of friends had spent the day fishing and were on their way back to shore when they saw nine orca - seven adults and two calves - stranded on sand banks on Friday afternoon. Aucklander Marnix Kelderman​ was on an Ali-Kat charter boat - run by Wayne and Sharon Kostanich​  - with his friends when he said they spotted some dorsal fins “a bit high in the water” in the middle of the harbour.  

“The skipper knew that there were large sand banks there so he knew that could be a problem so he turned the boat and went out to have a look,” Kelderman said.

“Then we realised [the orca] were stranded on a large sand bank in the middle of the harbour.”

Keep reading

[flukeprintphotography-deactivat]

J1 Ruffles, The Iconic Bull from J Pod…Was an L Pod Whale!

Things are not always as they seem in killer whale population biology. J1, known to the public as Ruffles, was a keystone member of the southern resident killer whale population. He was most often seen traveling with J2 Granny, famous for her purported age of 100+ (spoiler: she probably was around 60-80 years old). Because of their close relationship, researchers assumed J1 was the final calf of J2, who had not given birth since killer whale population studies started in the 70s. Doing a bit of math and back calculating, they came to the conclusion that since J1 must be her final calf, J2 must have been born around 1911. 

A study on the paternity and reproductive success in the southern residents, published in 2011, revealed that this long-held assumption was completely wrong. You have to dig a little bit into the supplementary material/appendix, but it is there, clear as day: genetic testing showed J2 was not the mother of J1. His mother was listed as an unknown female that had not been sampled at that time. This essentially invalidated J2′s age estimate of 100+ years as it had been based on the assumption J1 was her final offspring. However, everyone still assumed J1 belonged to J pod. After all, why wouldn’t he be? He travelled with them all of the time. He was an iconic member of J pod. 

That, too, was wrong. Further genetic studies published in 2018  by Ford et al. dropped a bombshell that went largely unnoticed until recently. Again, looking into the supplementary material of that paper, we can see more information about paternity and maternity of the southern residents. And the most interesting fact to emerge was the identity of J1′s true mother: L45 Asterix. Additionally, it was revealed that L57 Faith, another large bull, was J1′s half-brother. J1 was in fact a true member of L pod. 

But the surprises don’t stop there. 

J1 was traveling with J2 as an integrated member of J pod when studies on the southern resident population began. His real mother, J45, however, was still very much alive and did not pass away until 1995. There are instances when orphaned males will transfer to a new pod and become “adopted” by other females (this is the situation with L87, currently living with J pod, who also was adopted by J2 Granny). But J1 wasn’t orphaned. His mother was alive and well. Why wasn’t he traveling in his birth pod with his birth mother? This new information raises the possibility that J1 could have been rejected or otherwise abandoned by his mother, causing him to seek out companionship with females in J pod. Another possibility is that L45 had enough on her plate raising L57 and J1 went off in search of a better adopted mother/provisioner (which we know is critical to the survival of adult males). 

While the revelation of J1′s true identity is definitely startling for all those who followed him over the years, there is some good news as well. J1 was a very successful father and sired dozens of calves, many of whom are in J pod. This raised concerns about inbreeding as pod members, even if they are not in the same matriline, are usually related. Typically, whales try to breed outside the pod by mating with individuals whose vocalizations are most different from their own––this indicates they are not closely related. Knowing that J1 was genetically an L pod whale means that the genetic viability of J pod is perhaps not as bad as once thought. It also raises interesting questions about culture and learning in killer whales––did J1 use J pod vocalizations or L pod vocalizations? How did this impact mate choices? 

This new discovery shows that with improvements in genetics, there are facets of killer whale biology which we currently accept as fact that might require a closer look. I, for one, love this aspect of science. There is always more to learn.

Check out @derangedhyena-delphinidae recording of the Way of Whales Workshop in which this information is discussed!

Photo source: Center for Whale Research.

[flukeprintphotography-deactivat]

AP18 is the biggest and oldest bull in his pod.

Though he will not sire any calves within his own pod, his sheer size and old age means he (barring any reproductive problems) has likely sired many calves in other pods. For reasons we still don’t totally understand, female killer whales prefer to mate with with old, large bulls. There is likely some aspect of mate choice but recent evidence of infanticide in other killer whale populations suggests that females may not have much say in some instances.

Due to the fact they spend nearly their entire lives underwater, we know virtually nothing about the reproductive behaviors and courtship of killer whales!

[flukeprintphotography-deactivat]

The peachy hue of newborn killer whales is one of the most curious things about killer whale physiology. Killer whales sport an orange tint on their eye patches and bellies for about a year and then gradually begin to take on their normal black white coloration. Surprisingly, the exact cause of this phenomenon is not known. Many people claim that the orange color is caused by the calf’s thin blubber layer—the thought being that the blood vessels are closer to the skin, imparting a peach color. However, it’s very unlikely this is true. After all, emaciated adult killer whales do not take on an orange color despite their thin blubber layer. Instead, there are two hypotheses that could explain their unique coloration:

1. Baby killer whales may be jaundice at birth. Other species of cetaceans, such as bottlenose dolphins and rough-toothed dolphins, often look yellowish at birth; studies have shown that these neonates have high levels of bilirubin, as their livers are working overtime to recycle old fetal blood cells. This would cause an orange-yellow tint in newborns that fades over time. This is currently the leading hypothesis according to Dr. Joseph Gaydos, a wildlife veterinarian   studying killer whales with the SeaDoc Society. 

2. The orange coloration may be the result of amniotic fluid staining the skin. Some early studies with newborn harbor porpoises show a layer of yellow skin that can be peeled off, revealing white skin underneath. This may explain why killer whales get a patchy appearance after a few months and show a mix of peach-colored and white skin.

Ultimately, many more studies will be needed to understand exactly why baby killer whales are so orange at birth!

[csnews]

South Australia plan to implement a speed limit for boats in Dolphin Sanctuary

November 21, 2018

Marine Connection on facebook:

Positive news - government of South Australia plan to implement a speed limit for boats in the Adelaide Dolphin Sanctuary. Boats will be held to a speed limit of seven knots (12.96 km per hour) to help prevent any future dolphin deaths. Seven dolphin calves born in the sanctuary in 2017 died as a result of “blunt trauma” - 17 out of 35 adult dolphins deaths in the region were also a result of “blunt trauma”. Boat strikes are by far the most probable cause of deaths.

[csnews]

More Than 140 Whales Die in New Zealand After Mass Beaching

Charlotte Graham-McLay - November 26, 2018   

More than 140 pilot whales died after beaching themselves in southern New Zealand, with half being euthanized by conservation workers in a “deeply saddening” decision after their discovery came too late to rescue them, officials said Monday.

The stranding, in an isolated part of Stewart Island, off the coast of the South Island, was the largest in New Zealand since 250 pilot whales died last year in one of the worst such incidents in the country’s history.

The beached whales on Stewart Island were discovered in two separate groups, or pods, just as several other whale deaths and strandings were reported around the country over the weekend.

The Department of Conservation said Monday that as many as 145 whales beached themselves at Mason Bay, on the island’s west side, where they were discovered by a hiker on Saturday afternoon.

Keep reading

[csnews]

Fishing methods are devastating seas

Alex Hubberstey - November 20, 2018

Vaquita isn’t a name many people will be familiar with, although it is the world’s most endangered cetacean. The endemic species, Phocoena sinus, resides in the northwest section of the Gulf of California.

Ever since the Baiji, or Yangtze River Dolphin went extinct in 2006, the vaquita took its place at the top of the critically endangered list. According to some sources, in 2017 there were less than 30 individuals left in the wild. What is more worrying is the estimate that only 12 individuals now remain. With a low fecundity (they produce one off-spring every two years), their future looks bleak.

But what is the reason for this species’ decline? P. sinus’ home range includes areas in which there are high levels of fishing with gill nets. These are nets which are designed to catch everything, if a fish swims into the mesh it becomes caught by its gills and cannot escape. The gillnets aren’t set to catch the cetacean. They are set to catch totoaba (Totoaba macdonaldi); they are highly sought after for traditional Chinese medicine, or more specifically, their swim bladder is. Even though the trade in totoaba swim bladders is illegal, a large enough organ can receive a very high price, and the black-market industry for them is now a multi-billion-dollar enterprise.

Keep reading

[csnews]

U.S. Court Upholds Seafood Import Ban to Protect Vaquita

MAREX - October 22, 2018

The U.S. Court of International Trade has denied the Trump administration’s request to lift a ban on certain seafood imports caught with gillnets that kill the critically endangered vaquita porpoise. In July, the court ordered the government to ban such imports from Mexico’s Gulf of California and this ruling upholds the earlier decision.   As few as 15 vaquita remain, and almost half the population drowns in fishing gillnets each year. Absent immediate additional protection, the tiny porpoise could be extinct by 2021.

The import ban covers all fish and fish products from Mexican commercial fisheries that use gillnets within the vaquita’s range in the Upper Gulf of California. This includes shrimp, corvina (drum fish), sierra (Spanish mackerel) and chano (bigeye croaker) from the area. Gillnets are fishing nets that hang in the water, indiscriminately catching both target fish and other marine creatures, including vaquita. It is estimated that in 2017 alone more than 1,400 tons of the now-banned gillnet-caught fish and shrimp, valued at roughly $16 million, crossed the border to be consumed in the U.S.

Keep reading

[cetacean-nation]

Why the Long Face, Extinct Dolphin?

A changing climate could have driven the evolution of bizarre species with snouts five times longer than the rest of their skulls.

[flukeprintphotography-deactivat]

New Insight into Killer Whale Skin Microbiomes and “Spa Trips” to the Subtropics

In 2012, biologists Robert Pitman and John Durban published a paper on the long-distance movements undertaken by type B Antarctic killer whales. They discovered something fascinating: the whales, tracked by satellite tags, swam virtually non-stop nearly 9,400 kilometers round-trip to the subtropical waters off Uruguay and Brazil! Though there are many distinct variations of killer whales, as a whole, the species displays very little regular long-distance movements. So what is going on with the type B killer whales?

The tags on the whales revealed that although they swam at slower speeds in these sub-tropical waters, they did not display any kinds of movements that were indicative of foraging or giving birth, the two most common reasons for migrations in animals. With these behaviors ruled out, biologists concluded there was likely only one explanation for these extreme sprints to the subtropics: the killer whale equivalent of a spa treatment.

Photos: John Durban/NOAA

The above photos are of the same individual type B killer whale. In the first photo, the whale has a yellow tint caused by the accumulation of diatoms, tiny single-celled algae. Killer whales living in extremely cold Antarctic waters likely prioritize blood flow to vital parts of their body, such as their core, in order to stay warm and functional. However, skin regeneration requires constant blood flow to the epidermis, and thus it likely occurs at a slow rate in these whales, allowing diatom buildup to occur. However, in the second photo, the whale is now “clean” and free of the algae! How did this happen?

Biologists suspect type B killer whales undergo intermittent migrations to the warm subtropics in order to speed up the process of skin regeneration and get rid of the diatoms.

But why shed the diatoms anyway? Why travel such long distances only to turn around and come right back? Migrations like these are almost certainly energetically costly as they are probably not stopping for food along the way.

New research published in the journal Molecular Ecology may hold some of the answers. A team of biologists went through the tedious process of examining and identifying the types of microbes that live on killer whale skin. They had samples from resident killer whales and transient killer whales in the North Pacific as well as samples from type B and C killer whales in Antarctica. They were able to provide genetic evidence from the microbiome of killer whales that supports Durban and Pitman’s hypothesis on type B killer whale movements. Even more interesting, they found that killer whales with high diatom loads also had high levels of a bacteria known as Tenacibaculum dicentrarchi, a pathogen that is known to cause skin lesions and skin rot in fish. They also noted that whales with high diatom loads sometimes were in poor health and had peeling skin and lesions, such as the one below documented in this study: 

Photo: Hooper et al. (2018)

However, other cetaceans are known to carry Tenacibaculum sp. without any apparent negative health effects, and more research will be needed to definitively conclude if this bacteria causes poor health in killer whales. 

This study provided more support for the “physiological maintenance” hypothesis proposed by Durban and Pitman, and showed some tentative links to a potentially pathogenic bacteria associated with heavy diatom loads. The benefits the whales get from ridding themselves of these diatoms and the bacteria associated with them may outweigh the energetic costs of these long migrations to the subtropics. 

References: 

J. W. Durban, R. L. Pitman. Antarctic killer whales make rapid, round-trip movements to subtropical waters: evidence for physiological maintenance migrations? Biol. Lett. 2012. DOI: 10.1098/rsbl.2011.0875. 

Host‐derived population genomics data provides insights into bacterial and diatom composition of the killer whale skin. Mol. Eco. 2018. DOI: 10.1111/mec.14860

[delphinidae-info]

Researchers Had ‘No Idea’ Killer Whales Could Dive This Deep

South Atlantic killer whales have destroyed their own record for deep dives—by 1,000 feet.