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Why Killer Whales Go Through Menopause But Elephants Don’t

Last summer, I met Granny. I was on a whale-watching boat that had sailed south from Vancouver Island, in search of a famous and well-studied group of killer whales (orcas). Two hours after we set off, we started seeing black fins scything through the unusually calm and glassy water. We saw a dozen individuals in all, and our guide identified them by the shape of their fins and the white saddle patches on their backs. Granny, for example, has a distinctive half-moon notch in her dorsal fin.

Seeing her, I felt an intense and solemn respect. She is the oldest member of the group, perhaps the oldest orca on the planet. Her true age is unknown, but a commonly quoted estimate puts her at 103, which would make her a year older than the Titanic, and far more durable. Imagine all that she has seen in that time: the generations of her children and grandchildren; the countless pursuits of fleeing salmon; the increasingly noisy presence of fishermen, scientists and gawking tourists. Decades of knowledge and wisdom live in her brain. Ad that knowledge might explain one of the most unusual features of killer whale biology—their menopause.

Animals almost always continue to reproduce until they die. There are just three exceptions that we know of: humans, short-finned pilot whales, and killer whales. In all three species, females lose the ability to have children, but continue living for decades after. That’s menopause. Female killer whales go through in their 30s or 40s. Why? Why sacrifice so many future chances to pass on your genes to the next generation?

One of the most compelling explanations is called the grandmother hypothesis. Proposed in 1966, it suggests that older females forgo the option to bear more children so they can support their existing ones. By helping their children and grandchildren to survive and thrive, they still ensure that their genes cascade down the generations.

In 2012, Darren Croft at the University of Exeter found evidence to support this hypothesis. His collaborator Ken Balcomb had been studying the resident killer whales of the Pacific Northwest since the 1970s; his astonishingly thorough census had captured the lives, deaths, and family ties of hundreds of these whales.

By ploughing through the data, student Emma Foster showed that if a male orca’s mother died before his thirtieth birthday, he was three times more likely to die the next year. If she passed away after he turned thirty, he was eight times more likely to subsequently snuff it. And if mum had gone through menopause, his odds of dying went up by fourteen times. The data were clear: mothers help their sons well into adulthood, and older mums are especially helpful.

“But that left a big unanswered question,” says Croft. “Old females are keeping their offspring alive, but how? What is it that they’re doing to confer the survival benefit?”

One reasonable guess involves salmon. Salmon makes up 97 percent of the diet of these particular orcas, and salmon are unpredictable. “They’re not distributed equally in space,” says Croft. “There are hotspots that differ with season, year, tide.” So just like human fishermen, the orcas need to know when and where to go to catch their fish. Do they stay at sea or swim inland? Do they go up their inlet or that one? The oldest females might be better at making these decisions, thanks to their accumulated experience.

To test this idea, the team turned to video footage of the southern residents, which Balcomb’s team had captured between 2001 to 2009. Postdoc Lauren Brent analysed over 750 hours of video to work out which whales were swimming together, and who was following whom. She also collected data from nearby fisheries to work out how big the salmon stocks were at different times.

She found that adult females are more likely to lead a group than adult males, and older post-menopasual females (who make up a fifth of the pod) were more likely to lead than younger ones. This bias was especially obvious in seasons when salmon stocks were low. And, as Foster found, there was a sex bias—males were more likely to follow their mother than females were.

These simple trends support the idea that the post-menopausal orcas are “repositories of ecological knowledge”. They lead the others to food, and their skills are especially important at times when food is scarce. And in doing so, they help their young to survive, which offsets the costs of forgoing any further reproduction. “That doesn’t tell us why they stop reproducing,” says Croft. “You could share information while still being reproductive. Why did they stop? That’s the next question.”

The same principles apply to human menopause, too. Some scientists have suggested that human menopause is merely a side effect of our longer lifespans, brought about by medicine and sanitation. But that can’t be right. Among many hunter-gatherers, like the Ache of Paraguay or the Hadza of Tanzania, around half of women survive to 45, and continue living into their late 60s. Like killer whales, they live long after the stop reproducing. And like killer whales, the longer they live, the more they know. In 2001, anthropologist Jared Diamond wrote:

“Old people are the repositories of knowledge in preliterate societies. In my field studies of New Guinea birds, I start work in a new area by gathering the oldest hunters and quizzing them… When the hunters are stumped by my asking about some especially rare bird, they answer: “We don’t know, let’s ask the old man (or woman).” We go into another hut, where we find a blind and toothless old person who can describe a rare bird last seen 50 years ago. Some of that stored information is essential to the survival of the whole village, whose members include most living relatives of the old person. The information encompasses wisdom about how to survive dangers — such as droughts, crop failures, cyclones and raids — that occur at long intervals but that could kill the whole tribe if it did not know how to react.”

Why, then, don’t elephants go through menopause? They are also long-lived animals that stay in family groups, and the old females—the matriarchs—are vital. They are better at recognising friendly faces and they know the best anti-lion moves. They provide their herds with the same benefits that orcas like Granny bestow upon their pods.

But resident killer whales differ from elephants in one critical respect: their sons and daughters stay in the groups where they were born. This means that as a female grows older, her pod becomes increasingly full of her own children and grandchildren. Over time, she becomes increasingly related to her neighbours, and she shares more and more of her genes with her neighbours. This creates a powerful impetus to shift her efforts away from having more children, and towards helping her existing descendants.

That impetus doesn’t exist in elephants because their sons eventually leave their birth group to find new ones. Females become less related to their group-mates over time or, at least, no more related. A matriarch’s best bet, then, is to carry on reproducing until she dies.

And humans? Many anthropologists believed that we started off with female-biased dispersal—that is, daughters would leave to join new groups. “When she joins, she has zero relatedness to the rest of the group,” explains Croft. “But as she ages, she has offspring and her local relatedness increases.” Then again, other animals like hamadryas baboons and the Seychelles warbler also have female-biased dispersal and don’t go through menopause. “So, it’s not just about the dispersal patterns but also the role that old females can play in the group,” says Croft.

In killer whales, the old females might also be better at catching salmon, which they then share with their kin. Perhaps they understand the hierarchies and structures of other groups, and mediate fights between their sons and rivals. These ideas are harder to test. “We have so little information on them,” says Croft. “We see them at the surface and we know so little about their lives.”

Reference: Brent, Franks, Foster, Balcomb, Cant & Croft. 2015. Ecological Knowledge, Leadership, and the Evolution of Menopause in Killer Whales. Current Biology http://dx.doi.org/10.1016/j.cub.2015.01.037

More on menopause:

Why do killer whales go through menopause?

Did conflict between old and young women drive origin of menopause?

The heavy cost of having children

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The Tiny Culprit Behind A Graveyard of Ancient Whales

As the Pan-American Highway snakes its way through Chile, it passes through a place called Cerro Ballena. The site is in the middle of the driest desert in the world, and just an hour away from the mine where 33 unfortunate miners were trapped a few years back. That particular stretch of road is vital for ferrying the mining equipment and extracted minerals that are fuelling Chile’s economic surge. For that reason, a construction company was tasked with expanding the highway from two lanes to four.

But at Cerro Ballena, they unearthed something odd: the skeleton of a whale.

And then another. And another.

Dozens of them; different species; adults and juveniles. The construction crews had unearthed an entire whale graveyard.

“I wouldn’t wish a whale skeleton on anyone,” says Nick Pyenson, an expert on prehistoric marine mammals from the Smithsonian Institution. “You’re going to have to dig a lot.”

The dig site at Cerro Ballena. Credit: Nick Pyenson
The dig site at Cerro Ballena. Credit: Nick Pyenson

Pyenson first saw the graveyard in 2011 at the urging of his Chilean colleague Mario Suarez. He was amazed. Chile is famously rich in marine fossils anyway. The local tectonic plates push what was once ancient seafloor to more accessible heights and since the area is so dry, there is little vegetation and lots of erosion. But even in this place, which offers up its treasures with unusual abandon, the graveyard was something else.

But Pyenson was also troubled. The construction crews were treating the fossils with great care, jacketing the bones in plaster and transporting them to museums. But through their good work, they were also divorcing the bones from their surroundings. Without knowing where they were buried or the properties of the surrounding Earth, it would be impossible for scientists date them. And they’d never be able to answer the obvious and burning question: why had all these animals died in this same place?

Context was everything, and context was rapidly vanishing. The crews would finish their work by the end of 2011, and Pyenson knew that time was running out. “I remember literally looking at skeleton after skeleton and thinking, ‘Okay, what are we going to do? This is not what I signed up for.’”

Enter Adam Metallo and Vince Rossi. Pyenson calls them the laser cowboys. They are part of the Smithsonian’s 3-D digitisation team, and they flew over to Cerro Ballena with a smorgasbord of lasers and other scanning equipment. They worked continuously for several days, creating virtual models of the entire site and all its fossils, at extraordinarily high resolution. The bones have now all been removed, but their resting place lives on in a digital guise.

The laser jockeys at work. Credit: Nick Pyenson.
The laser jockeys at work. Credit: Nick Pyenson.

So far, the team have documented 40 separate skeletons, which are all between 6 and 9 million years old. Thirty-one of these were probably from the same species of rorqual whale—the family of giants that includes blues, fins and humpbacks.

There were other animals too, including a penguin, an extinct type of sperm whale, and two seals (one of which is new to science). There was a walrus-whale—a bizarre prehistoric dolphin with a tusked walrus-esque face.  There was even an aquatic sloth.

All of these specimens were found in an area of roadcut just 240 metres long and 20 metres wide. Pyenson estimates that there are hundreds of skeletons still buried in nearby areas that the construction teams didn’t touch. “What did they obliterate when they built the first two lanes of highway?” he wonders. “They must have dug up bone after bone.”

Most of the rorqual skeletons were complete, well-preserved, and belly-up. There was even a group of two adults and a youngster, log-jammed together and beautifully preserved. All of this suggests that they died at sea and were washed onto tidal flats, where they were quickly buried. And since the fossils were found in four separate layers, these mass strandings happened repeatedly in this same place.

La Familia--two adult whales and a calf. Credit: Nick Pyenson
La Familia–two adult whales and a calf. Credit: Nick Pyenson


What killed such a diverse group of animals, time and again? “Every explanation must work across all the taxa, and must also satisfy what you see about the bones and their arrangement,” says Pyenson. “And it has to explain the pattern four times.”

It probably wasn’t a virus, of the kind that’s killing off dolphins in the US. Such epidemics are usually species-specific, and unlikely to kill many different species including both mammals and birds. It wasn’t a tsunami either. A large wave wouldn’t have selectively killed larger animals and, besides, the surrounding rocks show that the area was mostly calm and stable.

Pyenson says there is only one cause that fits all the available evidence: these animals were poisoned by algae.

Algae thrive when coastal waters receive an unusual influx of nutrients, and some species release deadly toxins into the water. These ‘harmful algal blooms’ or ‘red tides’ are potent enough to kill whales and dolphins, which choke to death on the toxins.

At the end of 1987, fourteen humpback whales were stranded along the coastline near Cape Cod, USA, over a span of five weeks. Like the Cerro Ballena fossils, the strandees included males, females and calves. When scientists cut them open, they found plenty of Atlantic mackerel in their stomachs. And the mackerel, in turn, were loaded with algal toxins.

All the signs at Cerro Ballena suggest that those animals died in the same way. They showed no signs of injuries or bite marks. They ate a wide variety of diets but they were all at the top of their food webs, and such animals are more prone to algal poisoning.

There are also orange blotches on the bones, which Pyenson thinks are the remains of algal mats. On some specimens, he even found thousands of tiny spheres, which are exactly the right size to be dinoflagellates—the creatures behind harmful algal blooms. “It’s the closest we get to a smoking gun,” says Pyenson.

His theory is that iron minerals from the Andes in the east periodically washed into the ocean. This fertiliser was concentrated in the surface waters by upwelling currents, transforming the local algae into toxic blooms. Their poisons killed off local animals, which floated towards the coast and were stranded on the tidal flats.

This clearly happened many times in the past. Today, small whales and dolphins are often stranded en masse, but aside from the Cape Cod humpbacks, the large rorquals generally aren’t. Pyenson thinks that’s because so many of them have already died at the harpoons of whalers. Whale graveyards like Cerro Ballena may be a thing of the deep past, because we have turned the entire ocean into a whale graveyard.

Reference: Pyenson, Gutstein, Parham, Le Roux, Chavarria, Little, Metallo, Rossi, Valenzuela-Toro, Velez-Juarbe, Santelli, Rogers, Cozzuol & Suarez. 2014. Repeated mass strandings of Miocene marine mammals from Atacama Region of Chile point to sudden death at sea. Proc Roy Soc B. http://dx.doi.org/10.1098/rspb.2013.3316

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On Dolphins, Big Brains, Shared Genes and Logical Leaps

In 2012, a team of Chinese scientists showed that a gene called ASPM has gone through bouts of accelerated evolution in two very different groups of animals—whales and dolphins, and ourselves.

The discovery made a lot of sense. Many earlier studies had already shown that ASPM is one of several genes that affect brain size in primates. Since our ancestors split apart from chimps, our version of ASPM has changed with incredible speed and shows signs of intense adaptive evolution. And people with faults in the gene develop microcephaly—a developmental disorder characterised by having a very small brain. Perhaps this gene played an important role in the evolution of our big brains.

It seems plausible that it did something similar in whales and dolphins (cetaceans). They’re also very intelligent, and their brains are very big. Compared to a typical animal of the same size, dolphin brains are 4-5 times bigger than expected, and ours are 7 times bigger than expected. The Chinese team, led by Shixia Xu, concluded that “convergent evolution might underlie the observation of similar selective pressures acting on the ASPM gene in the cetaceans and primates”.

It made for a seductive story. I was certainly seduced. In my uncritical coverage of the study, I wrote: “It seems that both primates and cetaceans—the intellectual heavyweights of the animal world—could owe our bulging brains to changes in the same gene.”

Many other scientists were sceptical—check out the comments in my original post—and it seems they were right to be. Three British researchers—Stephen Montgomery, Nicholas Mundy and Robert Barton—have now published a response to Xu’s analysis, and found it wanting. “It’s a completely plausible hypothesis but they didn’t test it very well,” says Montgomery.

In the original paper, Xu’s team looked at how ASPM has changed in 14 species of cetaceans and 18 other mammals, including primates and hippos. ASPM encodes a protein, and some changes in the gene don’t affect the structure of the protein. These “synonymous mutations” are effectively silent. Other “non-synonymous mutations” do change the protein and can lead to dramatic effects (like microcephaly). The Chinese team claimed that a few cetacean families had a high ratio of non-synonymous to synonymous mutations in ASPM—a telltale sign of adaptive evolution.

But Montgomery’s team had two problems with this conclusion. First, it’s statistically weak. Second, it’s not unique to cetaceans. Xu’s team largely looked at brainy groups like cetaceans and primates, but the British trio found exactly the same signature of selection in other mammals, including those with average-sized brains. “It looks like ASPM evolved adaptively in all mammals,” says Montgomery. “It could be that ASPM is a general target of selection in episodes of brain evolution and isn’t specific to large brains.”

Xu’s team also failed to check if the changes they found in ASPM were actually related to differences in cetacean brains. If the gene is changing quickly under the auspices of natural selection, does that translate to equally fast changes in brain size? The Chinese team never explicitly addressed that question. Montgomery’s team did, and their answer was a resounding no.

“We felt a little bad picking on them because it’s quite a common problem,” says Montgomery. “People pick a gene to analyse because it’s linked to something interesting. They find that it’s got this pattern of evolution, and they infer that it’s doing what they thought it was doing. It’s a circular argument. “

“These analyses need to be followed up with experimental work (if that is possible) or treated with caution if not,” says Graham Coop from University of California, Davis. “At best, such studies can only act to generate hypotheses about the role of a particular gene in phenotypic evolution”. That’s because most genes do many jobs, “and we are profoundly ignorant of many of these roles and how they differ across organisms.”

ASPM, for example, isn’t a “brain gene”. It creates molecular structures that help cells to divide evenly. It’s activated in the embryonic cells that make neurons, so if it’s not working properly, fewer neurons are made and individuals end up with small brains. But ASPM is also activated in other parts of the body.

As Vincent Lynch pointed out in a comment to my earlier post, ASPM affects the development of the testes:

“This brain-testis connection was described by Svante Pääbo’s lab. They swapped the mouse and human ASPM genes, I assume hoping to breed a super-intelligent strain of mice, and surprisingly found that nothing happened. Bummer… But rather than uncovering a role for ASPM as a casual agent of increased brain size in the human lineage, these authors found ASPM was required for male fertility (yes, the jokes are obvious) and suggested that the signal of selection observed in humans and other primates is likely related to role in testis. It is on old observation that many testis expressed genes evolve rapidly, many under some form of positive selection.”

So, maybe ASPM’s fast evolution in primates is more a story about nuts than noggins. Then again, Montgomery’s team have indeed found that changes in primate ASPM are related to differences in the size of their brains but not their testes.

These conflicting results illustrate just how important it is to test hypotheses carefully, rather than finding bits of evidence that look nice together, and uniting them through conjecture. It’s a valuable cautionary note to both scientists and journalists alike.

Reference: Montgomery, Mundy & Barton. 2013. ASPM and mammalian brain evolution: a case study in the difficulty in making macroevolutionary inferences about gene–phenotype associations. Proceedings of the Royal Society B http://dx.doi.org/10.1098/rspb.2013.1743

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Biography Of A Blue Whale, Told Through Ear Wax

A few years ago, Stephen Trumble contacted the Santa Barbara Museum of Natural History and asked if they had some earwax from a blue whale.

They did.

In 2007, a large ship travelling off the coast of California collided with a male blue whale, ending its life at the tender age of 12. It was one of three similar strikes that year. The animal’s 21 metre carcass washed up on the beach, and scientists from the local museum examined and dissected it with machetes and excavators. They collected several tissues and organs, including a 25-centimetre tube of earwax.

Blue whale earplug, extracted from a dead individual. Credit: Michelle Berman- Kowalewskic, Santa Barbara Museum of Natural History, Santa Barbara
Blue whale earplug, extracted from a dead individual. Credit: Michelle Berman- Kowalewskic, Santa Barbara Museum of Natural History, Santa Barbara

Earplugs are common to blues and other large whales like fins and humpbacks. They are similar to the ones in your ears, although obviously much bigger. Each is an oily build-up of wax and fats that accumulates through the whale’s life. “It looks like a long candlestick that’s been beat up a bit,” says Sascha Usenko, Trumble’s colleague at Baylor University. “It’s not appealing-looking.”

A whale produces a lighter-coloured wax during the time of year when it’s feeding, and a dark-coloured version when it migrates. If you cut through the earplug, you can see these varieties as alternating light and dark bands. They’re like tree rings. And just like tree rings, you can use them to estimate a whale’s age. That’s why scientists often collect and store the wax from dead whales.

But Trumble and Usenko have shown that the wax can reveal much more. It also preserves a chemical biography of a whale’s life, from its birth to its untimely ship-inflicted death. It records some of the hormones that surged through its body and the pollutants that it absorbed.

Blue whale earplug, whole (top) and in cross-section (bottom). Credit: Trumble et al, 2013. PNAS.
Blue whale earplug, whole (top) and in cross-section (bottom). Credit: Trumble et al, 2013. PNAS.

The duo previously measured environmental contaminants in whale blubber, but they realised that the same chemicals also ought to build up in earwax, which is made of similar fatty substances. “It was really an ‘A-ha!’ moment,” says Usenko. To find fresh whale wax, they contacted Michelle Berman-Kowalewskic from the Santa Barbara Museum of Natural History, who handed over the earplug from the dead blue whale they had dissected in 2007.

The plug showed that the whale’s testosterone levels rose during its first three years of life, fell until it was nine, and then shot up by around 200 times. That’s almost certainly the point when it became sexually mature. When other scientists have tried to work out this age using body length, ovaries or blubber, they’ve come up with estimates ranging from 5 to 15 years. “We didn’t really know,” says Udenko. “Now, we’ve nailed that down with tight resolution for one animal, and it’ll be really exciting to do a bunch more.”

Meanwhile, the whale’s levels of cortisol—a stress-related hormone— rose steadily over the course of its life and peaked a year after its testosterone spike. This might reflect the need to compete for mates, or to interact with other mature whales. “I think about what I was like at that age,” says Udenko. “A raging bull, trying to figure out my place in the social order… I was pretty stressed out.”

In the earplug, the team also found traces of several contaminants. There were 16 pesticides, flame retardants and other pollutants that tend to persist in the environment for a long time, such as the long-banned insecticide DDT. These were most concentrated during the first six months of the whale’s life, suggesting that they were inherited from its mother, either through the womb or from her milk.

There was also a fair amount of mercury, which gradually accumulated over the whale’s life and peaked twice, once when it was five years old and again when it was ten. Human industries like gold-mining can release large amounts of mercury into the oceans. Perhaps this whale was caught in a few such surges during its travels past California.

Blue whales off the coast of Sri Lanka. Credit: Ed Yong
Blue whales off the coast of Sri Lanka. Credit: Ed Yong

The chemical contents of the whale’s blubber matched those within its wax, which assured Trumble and Usenko that their readings were accurate. But blubber has no rings, so it can only give you an overall picture of the whales’ life. Earwax can tell you what happened every six months. Blubber gives the sum of the whale’s chemical bill; the earplug shows the individual lines.

“I was surprised at how well [the technique] worked, not only for persistent chemicals but for hormones that typically rapidly degrade,” says Usenko. “It allows us to ask more complex questions that are difficult to get at, like: What are the impacts of contaminants or stress on these animals?”

To get the same sorts of readings, Usenko says that he would need to follow a blue whale around for years, and take tissue sample from it every six months. “You couldn’t do it,” he says. “People have tried, but it’s difficult and you have to be committed for 30 years. Here, we can go to a lab and reconstruct the same effort in a month.”

But the earplugs have several limitations, says John Wise, a toxicologist at the University of Southern Maine who specialised on marine mammals. They only capture certain pollutants that accumulate in fat, they don’t tell us how those pollutants affect the animal’s health, and they can only be extracted from a dead whale. “Nevertheless, it’s a new and useful part of our whale conservation toolbox as we seek to better understand ocean pollution,” he says.

And, of course, the team have only looked at one earplug from one whale. Usenko acknowledges this, and says the study is meant to be a proof-of-principle. “We want to encourage museums to keep and collect these samples,” he says.

Existing earplugs should already provide a trove of data. The Smithsonian Institute alone has hundreds of plugs in its collection, many of which have been traced back to specific whales. They’re not in pristine condition, but they could be useful. Charles Potter, who manages the institute’s marine mammal collection and is a co-author on the paper, is now thinking about how to preserve these waxy treasures.

Reference: Trumble, Robinson, Berman-Kowalewski, Potterd & Usenko. 2013. Blue whale earplug reveals lifetime contaminant exposure and hormone profiles. PNAS http://dx.doi.org/10.1073/pnas.1311418110

PS: In case anyone was wondering, it doesn’t seem that the earplugs prevent the whales from hearing. In fact, some scientists have suggested that the plugs might actually help to channel sound towards the eardrum.

And finally, this is a good chance to reprise my blue whale facts:

  • Blue whales are so big that each one can grow as large as a fully grown blue whale. That’s huge!
  • If you take all the blue whales in the world and put them on a giant weighing scale, you are on drugs.
  • A blue whale’s main artery is so big that a human could swim through it, but it’s generally not advised.
  • A blue whale’s heart is the size of a Volkswagen beetle, but its steering is rubbish.
  • If you take a blue whale’s intestines and lay them in a line, the whale will die. Also, what’s wrong with you, you sick bastard?

More on whales:

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Scientists Address Wild Dolphins By Their Natural “Names”

We have given names to many bottlenose dolphins, from Flipper to Darwin. But in the wild, these animals have their own badges of identity—signature whistles that they develop during their early years and that are unique to them.

These whistles seem a lot like human names. The comparison isn’t perfect, but it’s now stronger than ever after Stephanie King and Vincent Janik managed to address individual wild dolphins with recordings of their own signatures. The dolphins responded by calling back, but only when they heard their own whistle. “I think our results do present the first case of naming in mammals, providing a clear parallel between dolphin and human communication,” says King.

The evidence that dolphins use signature whistles like names has been building since they were first discovered in the 1960s. They can convey a dolphin’s identity, as well as its mood and motivation. Individuals invent their own whistles at a few months of age, possibly with some influence from their mums. They’ll keep the same call for decades, although males sometimes change theirs to resemble the whistle of a new ally.

The whistles are clearly important, since they account for half of all the calls that wild dolphins make. They can mimic each other’s signatures, but they usually call with their own, perhaps to broadcast their identity and keeping in touch while swimming.

Working out how dolphins actually use these signatures in the wild has been very hard. These are fast-moving animals, whose calls blend together into a cacophonous mess. But Janik has developed a way of identifying individual whistles based on their distinctive rhythms. He can now follow free-swimming pods, record their calls using underwater microphones, and parse out the signatures of different individuals.

In 2011, he used this technique to show that groups of bottlenoses exchange signature whistles when they meet up—a ritualised greeting, like saying hello or shaking hands. When I covered that study, I ended with: “[Janik] also wants to try some playback experiments – the cornerstone of animal communication research – to see if he can provoke a specific response by playing a chosen signature whistle.”

And: check.

The duo worked with a group of Scottish bottlenoses that Janik’s been studying since 1994. Once they spotted the group, they recorded its signature whistles and made computer-generated copies on the spot, filtering out other distinctive features of the animals’ voices. They then played the synthetic whistles back at the pod.

It wasn’t easy—dolphin groups fuse and split all the time, and if that happened, the duo had to start from scratch. “There were times when we had everything ready to start a playback, and the dolphin group separated and the playback had to be aborted,” says King.

But when it worked, it really worked. When the animals heard their own signature, they usually called back with the same whistle type within seconds. This hardly ever happened if they heard the signature of a dolphin from another group. “It was really interesting to see how strong the response was,” says King. “In most cases, when we played back a copy of an animal’s signature whistle, it replied quickly and sometimes multiple times.”

Of course, it’s impossible to say who’s actually replying—it could be the signature’s owner or another dolphin mimicking the same call. However, we know that wild dolphins don’t mimic each other’s signatures that frequently; it happens, but not nearly often enough to explain the strong responses that King and Janik saw.

“Our new study really demonstrates that signature whistles are used like names,” says King. “It’s now clear that signature whistles have meaning, in that they’re labels for particular individuals and can be used by animals to address a social companion.” (Admittedly, there’s still no direct evidence that dolphins are using these whistles to call to their peers, but given the evidence we have, that’s not an unreasonable assumption.)

So, dolphin signature whistles are exclusive to individuals, rather than being part of a shared repertoire. They’re social sounds, unlike bird songs which are largely used to attract mates or defend territories. And they’re learned; many animals like birds and monkeys use distinctive calls to refer to specific objects (like different types of predators), but these are innate and inherited behaviours. “The use of new or learned sounds to label an object or class of objects is rare in the animal kingdom,” says King.

This combination of traits makes the signature whistles unique in the non-human world, at least for now. It’s possible that parrots and other birds might use similar calls. Various species can learn new sounds and use them to label objects, mimic each other’s sounds, tell individuals apart based on their distinctive calls, or refer to family members with specific sounds. If we want to look for other examples of natural animal names, the parrots are a good bet.

Reference: King & Janik. 2013. Bottlenose dolphins can use learned vocal labels to address each other. PNAS http://dx.doi.org/10.1073/pnas.1304459110

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For 150 years, no one had seen a full spade-toothed whale. Then two washed up on a beach.

For almost 150 years, no one had seen a spade-toothed whale. That’s not to say that the animal had gone extinct – no one had ever seen one alive. The first clue to its existence came in 1872, when Scottish geologist James Hector described an unusual jaw that had been collected from New Zealand’s Pitt Island a year earlier. Two more partial skulls would follow: another from New Zealand’s White Island in 1950 and the other from Chile’s Robinson Crusoe Island in 1986. But still, no one had seen the animal in the flesh.

Then, in December 2010, two of them washed up on Opape Beach in New Zealand.


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NOC, the white whale that tried to sound like a human

Listen to this recording. It sounds like a drunkard playing a kazoo, but it’s actually the call of a beluga (a white whale) called NOC. Belugas don’t normally sound like that; instead, NOC’s handlers think that his bizarre sounds were an attempt at mimicking the sounds of human speech.

The idea isn’t far-fetched. Belugas are so vocal that they’re often called “sea canaries”. William Schevill and Barbara Lawrence – the first scientists to study beluga sounds in the wild – wrote that the calls would occasionally “suggest a crowd of children shouting in the distance”. Ever since, there have been many anecdotes that these animals could mimic human voices, including claims that Lagosi, a male beluga at Vancouver Aquarium, could speak his own name. But until now, no one had done the key experiment. No one had recorded a beluga doing its alleged human impression, and analysed the call’s acoustic features.


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Why do killer whales go through menopause?

Here’s yet another reason why humans are weird: menopause. During our 40s, women permanently lose the ability to have children, but continue to live for decades. In doing this, we are virtually alone in the animal kingdom. From a cold evolutionary point of view, why would an animal continue to live past the point when it could pass on its genes to the next generation? Or put it another way: why don’t we keep on making babies till we die? Why does our reproductive lifespan cut out early?

One of the most popular explanations, first proposed in the 1966, involves helpful grandmothers. Even if older women are infertile, they can still ensure that their genes cascade through future generations by caring for their children, and helping to raise their grandchildren.* There’s evidence to support this “grandmother hypothesis” in humans: It seems that mothers can indeed boost their number of grandchildren by stepping out of the reproductive rat-race as soon as their daughters join it, becoming helpers rather than competitors.

Now, Emma Foster from the University of Exeter has found similar evidence among one of the only other animals that shows menopause: the killer whale.


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Same gene linked to bigger brains of dolphins and primates

Every whale and dolphin evolved from a deer-like animal with slender, hoofed legs, which lived between 53 and 56 million years ago. Over time, these ancestral creatures became more streamlined, and their tails widened into flukes. They lost their hind limbs, and their front ones became paddles. And they became smarter. Today, whales and dolphins – collectively known as cetaceans – are among the most intelligent of mammals, with smarts that rival our own primate relatives.

Now, Shixia Xu from Nanjing Normal University has found that a gene called ASPM seems to have played an important role in the evolution of cetacean brains. The gene shows clear signatures of adaptive change at two points in history, when the brains of some cetaceans ballooned in size. But ASPM has also been linked to the evolution of bigger brains in another branch of the mammal family tree – ours. It went through similar bursts of accelerated evolution in the great apes, and especially in our own ancestors after they split away from chimpanzees.

It seems that both primates and cetaceans—the intellectual heavyweights of the animal world—could owe our bulging brains to changes in the same gene. “It’s a significant result,” says Michael McGowen, who studies the genetic evolution of whales at Wayne State University. “The work on ASPM shows clear evidence of adaptive evolution, and adds to the growing evidence of convergence between primates and cetaceans from a molecular perspective.”


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Argentinian gulls are eating whales (or at least bits of whales)

Photo by Mariano Sironi, Instituto de Conservación de Ballenas, Argentina, via BBC

Like most seagulls, the kelp gull is an opportunist. It will catch fish and other small prey, but it’s not above scavenging at landfill sites. And off the southern coast of Argentina, some kelp gulls have developed a taste for whale.

Between June and December, Southern right whales gather to breed in the waters off Peninsula Valdes in Argentina, and every year, thousands of tourists go out to watch them.  Kelp gulls are watching too. As the whales surface for air, the birds land and rip pieces of skin and blubber form their backs, inflicting gaping wounds up to 20 centimetres long. The whales violently arch their backs to submerge whatever they can below the water, before hurriedly swimming away.

The first of these attacks was documented in 1972, and they have been getting worse. In 1974, just 1 per cent of whales had gull-inflicted wounds. By 2008, 77 per cent of them carried such injuries.


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New organ helps whales coordinate world’s biggest mouthfuls

The world’s largest animals have been hiding something. The bodies of the giant rorqual whales—including the blue, fin and humpback—have been regularly displayed in museums, filmed by documentary makers, and harpooned by hunters. Despite this attention, no one noticed the volleyball-sized sense organ at the tips of their lower jaws. Nicholas Pyenson from the Smithsonian Institution is the first, and he thinks that the whales use this structure to coordinate the planet’s biggest mouthfuls.


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Dolphins that help humans to catch fish form tighter social networks

In the coastal waters of Laguna, Brazil, a shoal of mullet is in serious trouble. Two of the most intelligent species on the planet – humans and bottlenose dolphins – are conspiring to kill them. The dolphins drive the mullet towards the fishermen, who stand waist-deep in water holding nets. The humans cannot see the fish through the turbid water. They must wait for their accomplices.

As the fish approach, the dolphins signal to the humans by rolling at the surface, or slapping the water with their heads or tails. The nets are cast, and the mullet are snared. Some manage to escape, but in breaking formation, they are easy prey for the dolphins.

According to town records, this alliance began in 1847, and involves at least three generations of both humans and dolphins. Today, there are around 55 dolphins in the neighbourhood, and around 45 per cent of them interact with the fishermen.

Now, Fabio Daura-Jorge from the Federal University of Santa Catarina, Brazil studied Laguna’s dolphins to learn how their unusual collaboration has shaped their social networks. He spent two years taking photographs of the local dolphins, and noting where they travelled and who they were associated with. As is typical for bottlenose dolphins, the Laguna individuals formed a ‘fission-fusion’ society – they all belonged to the same large group, but they had specific ‘friends’ whom they would spend more time with.

The dolphins roughly split into two separate groups, based on their tendency to hunt with humans. Those that co-operated with the fishermen were more likely to spend time with each other than the uncooperative individuals. Likewise, the uncooperative dolphins showed a tendency to stick to their own clique.

One individual even seemed to act as a “social broker”, and spent time with individuals from both groups.

Of the two groups, the human-helpers seemed to form stronger social ties. It is not clear if helping humans means they spend more time together, or vice versa. But certainly, their close associations increase the odds that one dolphin will learn the hunting technique from its peers.

This fits with what we know about bottlenose dolphins. They are extremely intelligent animals and different populations have developed their own quirky foraging traditions by learning from one another. Some use sponges to guard their snouts when they root about the ocean floor for food. Others can prepare a cuttlefish meal by sequentially killing and stripping them.

Daura-Jorge now wants to understand why only some of the dolphins help the fishermen, given that doing so clearly provides them with benefits, and all of them have the opportunity to help. By analysing the dolphins’ genes, he hopes to piece together their family trees, and work out if mothers pass on the behaviour to their calves.


Reference: Daura-Jorge, Cantor, Ingram, Lusseau & Simoes-Lopes. 2012. The structure of a bottlenose dolphin society is coupled to a unique foraging cooperation with artisanal fishermen. Biology Letters http://dx.doi.org/10.1098/rsbl.2012.0174

Bonus: There are several cases around the world where dolphins feed on the discarded remains of fish thrown away by humans. But the Laguna animals do far more than that – the fisherman wouldn’t catch any fish at all without their help. A similar alliance takes place half a world away in Burma, where Irrawaddy dolphins also fish cooperatively with humans.

More on dolphin behaviour:

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Will we ever… talk to dolphins?

Here’s the fourth piece from my new BBC column

“What’s that Flipper? The treasure is over there?” So went a typical plotline for the popular TV series featuring the cute, bottlenosed dolphin who could communicate with his human guardians, and who – in the time-honoured fashion – used his animal powers to apprehend criminals.

The idea that animals like Flipper can communicate with humans is not just the preserve of the small and big screen. History is littered with celebrity animals who have communicated with human scientists, with varying degrees of success. Many apes, including Washoe and Nim the chimps, and Kanzi the bonobo, have learned to communicate by using sign language or symbols on a keyboard. Alex, an African grey parrot learned over 100 English words, which he could use and combine appropriately; his poignant last words to Irene Pepperberg, his scientist handler, were “You be good. I love you. See you tomorrow.”

Dolphins hold a particular fascination; we are captivated by their intelligence and beauty, and swimming with dolphins features regularly on lists of things to do before you die. Denise Herzing has a lifetime of such experiences. For the last 27 years, she has been swimming with a group of Atlantic spotted dolphins in Florida as part of the Wild Dolphin Project. She can identify every individual and they, in turn, seem to trust and recognise her. It is a solid foundation for the boldest attempt yet to talk with dolphins.

One-way chat

“Talk” is tricky to define. A SeaWorld trainer who prompts a dolphin to jump for fish is arguably communicating with it. But such simple one-way interactions are a far cry from the conversational world of Dr Doolittle. Here, the dolphin responds, but says nothing intelligible back. Herzing’s vision is much more ambitious – she wants to establish two-way communication with her dolphins, with both species exchanging and understanding information.

The idea of talking to dolphins has a long and chequered history. It was widely publicised in the 1960s by John Lilly, who argued that dolphins have such large brains that they must be extremely intelligent and have a natural language. All we had to do was to “crack the code”. Much of Lilly’s work was highly questionable. He once flooded a house to keep a captive dolphin, instigated failed attempts to teach them spoken English, and even gave the animals LSD (while taking the drug himself). But there is no denying his influence in popularising the idea of two-way dolphin communication. “He said that in a few years, we will have established complex dialogue with them,” says Justin Gregg from the Dolphin Communication Project. “And he was saying that every few years.”

Lilly was right about dolphin intelligence, but not dolphin language. A true language involves small elements that combine into larger chains, to convey complex, and sometimes abstract, information. And there is no good evidence that dolphins have that, despite their rich repertoire of whistles and clicks.

Little less conversation

Wild dolphin communication is hard to study. They are fast-moving and hard to follow. They travel in groups, making it hard to assign any call to a specific individual. And they communicate at frequencies beyond what humans can hear. Despite these challenges, there is some evidence that dolphins use sounds to represent concepts. Each individual has its own “signature whistle” which might act like a name. Developed in the first year of life, dolphins use these whistles as badges of identity, and may modulate them to reflect motivation and mood. This year, a study showed that when wild dolphins meet, one member of each group exchanges signature whistles.

But beyond this, dolphin chat is still largely mysterious. “To communicate with dolphins, we need to understand how they communicate with each other in the natural world,” says psychologist Stan Kuczaj at the University of Southern Mississippi. “We still don’t know basic things like what the units of dolphin communication are. Is a whistle the equivalent of a “word” or a “short sentence”? We don’t know.”

We may not be able to understand them yet, but we know that dolphins can learn to understand us. In the 1970s, Louis Herman taught an invented sign language, complete with basic syntax, to a bottlenose dolphin called Akeakamai. For example, if he made the gestures for “person surfboard fetch”, Akeakamai would bring the board to him, while “surfboard person fetch” would prompt her to carry the person to the board. His experiments showed that dolphins could understand hundreds of words, and how those words could be combined using grammatical rules.

What’s my motivation?

Herman’s work was groundbreaking, but this was still one-way communication. It focused on comprehension, not conversation. In the 1980s, Diana Reiss had more luck by showing that dolphins could use underwater keyboards to make basic requests. When they prodded keys with their snouts, a whistle would play and Reiss gave a reward like a ball. Eventually, the dolphins used the artificial whistles to ask for the associated rewards.

But as conversations go, these were shallow ones. “The dolphins were only really interested in communicating about needs that they had, like a tool they needed or a fish they wanted,” says Kuczaj, who was involved in a similar project at DisneyWorld’s EPCOT Center. “We hoped they would also comment on other things going on in the aquarium but they didn’t.”

It is difficult persuading dolphins to learn some arbitrary signals, like a whistle signifying a ball, and then use them in a social context, admits Gregg. “They don’t seem to run with it the same way that chimps or bonobos have. The big stumbling block is motivation. Dolphins don’t seem to care.”

Herzing disagrees. She notes that captive animals, which often lack stimulation, will respond to systems like the underwater keyboards. She thinks that these experiments disappointed because they were cumbersome. “The dolphins swim very fast and went to where they were requested, but humans are very slow in the water. There wasn’t enough real-time interaction.”

Chat line

Herzing is trying to solve that problem with Cetacean Hearing and Telemetry (CHAT) – a lighter, portable version of the underwater keyboards. It consists of a small phone-sized computer, strapped to a diver’s chest and connected to two underwater recorders, or hydrophones. The computer will detect and differentiate dolphin sounds, including the ultrasonic ones we cannot hear, and use flashing lights to tell the diver which animal made the call.

The CHAT device can also play artificial calls, allowing Herzing to coin dolphin-esque “words” for things that are relevant to them, like “seaweed” or “wave-surfing”. She hopes the dolphins will mimic the artificial whistles, and use them voluntarily. By working with wild animals, and focusing on objects in their natural environment, rather than balls or hoops, Herzing hopes to pique their interest.

Herzing emphasises that her device is not a translator. It will not act as a dolphin-human Rosetta stone. Instead, she wants both species create a joint form of communication that they are both invested in. She hopes that CHAT will tap into the “natural propensity” that dolphins have “for creating common information when they have to interact”. For example, in Costa Rica, distantly related bottlenose and Guyana dolphins will adopt a shared collection of sounds when they come together, using sounds that they don’t use when apart.

As with past projects, all of this depends on whether the dolphins play along. Kuczaj says, “It’s a remarkable challenge because she is working with wild dolphins so they’ve got the option to participate or not.” Here, Herzing has an edge, since the animals know her, and vice versa. “We’ve been observing them underwater every summer since 1985,” she says. “I know the individuals personally – their personalities and relationships. We’ve got a pretty good handle on what they’d be interested in.” Perhaps this combination of cutting-edge technology and old-school fieldwork will finally produce the conversations that have eluded scientists for so long.

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Giant squids’ huge eyes see the light of charging whales

The giant squid sees the world with eyes the size of soccer balls. They’re at least 25 centimetres (10 inches) across, making them the largest eyes on the planet.

For comparison, the largest fish eye is the 9-centimetre orb of the swordfish. It would fit inside the giant squid’s pupil! Even the blue whale – the largest animal that has ever existed – has measly 11-centimetre-wide eyes.

So why the huge leap in size? Why does the giant squid have a champion eye that’s at least twice the size of the runner-up?

Dan-Eric Nilsson and Eric Warrant from Lund University, Sweden, think that the squid must have evolved its eye to cope with some unique challenge that other animals don’t face – to spot one of the world’s biggest predators, the sperm whale.


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When meeting up at sea, bottlenose dolphins exchange name-like whistles

When we meet a group of strangers, one of the first things we’ll do is to introduce ourselves by name. Nicola Quick and Vincent Janik from the University of St Andrews have found that groups of bottlenose dolphins do something similar. When they meet one another in the wild, they exchange “signature whistles”. These whistles are unique to each individual, and they’re strikingly similar to human names. And it seems that they’re a standard part of a dolphin’s meet-and-greet etiquette.