The tale of how whales walked into the seas is one of the most celebrated in evolutionary biology. Even our own fossil backstory, of arboreal apes that eventually began to walk upright, seems relatively unimpressive compared to how little mammals that scampered along the beach on four legs began a transition that would result in oceanic leviathans. But the land-to-sea switch isn’t the only one whales have undergone.
Not all whales live in the ocean. River dolphins – long-snouted whales with tiny eyes – inhabit turbid freshwater streams in South America and Asia. For a time, before evolutionary biology began using molecular techniques, it was thought that all of these similar cetaceans belonged to a singular group, but, as it turns out, they represent different lineages that all independently gave up life in the seas for one in freshwater. Dolphins have done this over and over again in waterways around the globe for millions of years, and a newly-named prehistoric species from Panama adds a little more definition to the outline of when South America’s river dolphins made the switch.
The prehistoric dolphin, described by Smithsonian Institution paleontologist Nick Pyenson and colleagues, didn’t actually live in a river. The geologic context in which it was found made it clear that this whale swam out in the open ocean off the Caribbean coast of Panama between 6.1 and 5.8 million years ago. But, at that time, this stretch of sea was not as it was now. The ocean was brimming with plankton and supported a much richer collection of creatures, possibly thanks to upwelling from the deep Pacific, and the dolphin snapped up fish in this highly-productive stretch of sea before the Panamanian Isthmus fully closed. Pyenson and coauthors drew from this fact to give the creature its name – Isthminia panamensis.
Relatively little of Isthminia was left in the rock. Just a skull, lower jaws, right shoulder blade, and two flipper bones. Much of the skeleton probably eroded away before it could be excavated in 2011. But enough remained to allow Pyenson and colleagues to outline how this dolphin lived and who it’s related to. While the size of the cetacean’s eyes and the wear on its teeth are most similar to open-ocean dolphins, the details of its anatomy indicate that it’s an ancient relative of today’s South American river dolphins in the genus Inia. In short, Isthminia was an early “river dolphin” that lived at sea.
Even though today’s river dolphins had marine ancestors, however, how Isthminia fits into this picture isn’t totally clear. Paleontologists have uncovered the first wave of river dolphin invasion in South America as occurring between 16 and 11 million years ago – a group called platanistids that later disappeared from this continent (but is represented by the Ganges River dolphin today). Isthminia could represent the beginnings of the second wave as dolphins became increasingly adapted to nearshore life towards the end of the Miocene, or, Pyenson and coauthors note, the dolphin could mark a reversal. In this case, an even earlier and as-yet-unknown group of dolphins threaded into South America’s rivers and, while most stayed, the ancestors of Isthminia went back to sea.
Regardless of which hypothesis turns out to be correct, there was no straight-line transition from the sea to the rivers. Just like the initial invasion of the water by whales was a tangle of different lineages that took to the water in disparate ways. Into the sea, to the rivers, and maybe even back again, fossil whales remind us that transcendent change is never as simple as it first seems.
“Hey, look at this,” said Bob Shadwick. He and his team were working on the dissected remains of a fin whale, the second largest animal on the planet, when they noticed a white cord-like structure lying against a slab of muscle. Shadwick picked it up and jokingly stretched it. “It was like a bungee cord,” recalls A. Wayne Vogl who was part of the group. It extended to more than twice its original length before recoiling back.
The team initially thought it was a blood vessel, but they soon realised that it wasn’t hollow. They looked closer and noticed that it had a yellowish central core, surrounded by a thick white coating. “It was then that we realized it must be a nerve, unlike anything we had seen before,” says Vogl.
On one hand, that made no sense. In mammals, nerves have a little slack in them but if you extend them by 10 percent, they’ll stop carrying electrical signals properly. Extend them by 30 percent and they’ll snap. Stretch injuries are the most common type of nerve injuries in people, and can lead to shooting pains, loss of sensation, and paralysis. Simply put: nerves don’t stretch.
On the other hand, the fin whale’s stretchy nerve made perfect sense. This is an animal whose entire existence is built upon extreme feats of stretchiness.
The giant rorqual whales—fins, blues, humpbacks, minkes, and their kin—feed on tiny crustaceans called krill, which they swallow by the millions using a unique technique called lunge-feeding. A rorqual will accelerate towards a swarm of krill at high speed and suddenly open its gargantuan mouth to a right angle. The two bones of the lower jaw swing outwards, widening the mouth; the tongue inverts, creating even more room. The whole mouth balloons outwards, increasing in circumference by around 162 percent and engulfing an astonishing amount of krill and water. A blue whale can swallow around half a million calories in a single mouthful.
Long pleats in the whale’s mouth allow it to expand without tearing skin or muscle. But what about nerves? Large nerves course through the lower jaw, connecting to the tongue and blubber. Those have to stretch and, as Vogl and Shadwick showed, they do.
The strategy, Vogt writes, is “simple yet elegant”. Each nerve contains bundles of fibres, called fascicles, which sit at its core and are highly folded. The fascicles are surrounded by a thick wall made of two proteins: sturdy collage and stretchy elastin. When a whale lunges, the fascicles and collagen fibres unfold, while the elastin fibres stretch. Once the collagen fibres unfold fully, they become taut, stopping the nerve from stretching any further (and potentially breaking). As the whale closes its mouth after a lunge, the elastin fibres pull the nerve back into its original shape.
And that’s it. The nerve fibres themselves don’t actually stretch. It’s more that they unfold. But that still makes them special. Other nerves that reside in the neck and ribcage of a fin whale don’t have this property, and are barely more extensible than those in your face. Those in the whale’s face, by becoming stretchier, allowed it to evolve its extraordinary style of feeding and its record-breaking size. Without stretchy nerves, fin and blue whales would never have become the giants that they are.
This unexpected discovery highlights how little we know about the giant whales, which have captivated our imaginations for millennia. Just a few years ago, the same team behind this new study discovered that rorquals have a volleyball-sized sense organ at the tips of their lower jaws—and no one had ever seen it before. There are undoubtedly surprises still to come. “One of the big mysteries yet to solve is how these animals actually swallow the food they concentrate after a lunge,” says Vogl. “We still don’t know this.”
Whales can poop almost anywhere they want. They have the entire ocean to relieve themselves in, so most of the planet can theoretically be their toilet. Yet, despite having a near-universal lavatory pass, cetaceans often relieve themselves near the surface. In the words of marine biologists Joe Roman and James McCarthy, many whales feed in the deeper tiers of the sea to then return to the surface and release “flocculent fecal plumes” – cetacean clouds that may create what Roman and McCarthy call a “whale pump“.
The researchers laid out their logic in a 2010 PLOS ONE paper. Our planet’s seas are constantly recycling themselves. Showers of marine snow send organic matter cascading down to the sea floor, and zooplankton excrete poop full of nitrogren, phosphorus, and iron in deep water as they go about their regular up-and-down migration through the water column. This is a downward “pump” of resources. But other organisms can also bring some of these elements back from the deep. Whales and other marine mammals, Roman and McCarthy hypothesized, replenish the surface waters with their excrement.
The researchers based their case on an array of cetacean observations. Whales must surface to breathe, the physiological consequences of diving and surfacing make it likely that marine mammals will let it all go near the surface, and observations of crappy clouds have shown that they dissipate through the water rather than sink. And even though whales sometimes feed in the upper portion of the sea, they often dive deeper to reach dense pockets of fish and invertebrates. These hard-to-reach resources are key to Roman and McCarthy’s proposal. Whales feed on deepwater prey that are taking up elements from far below. After a bit of digestion, the whales then jettison some of those elements in shallower waters and leave plankton to recycle the slightly-used nitrogen.
Seals and sea lions might do their share, too. If you’ve ever smelled a pinniped colony at the height of breeding season, you’ve probably cursed your sense of smell. What the blubbery mammals spill onto the shore can be washed back into the sea, emanating the ecological reek of seal-processed fish and squid returning nitrogen to the water.
It’s one thing to theorize from an armchair, though, and quite another to get out on a boat and collect some whale feces. That’s exactly what Roman and McCarthy did to further investigate their idea, taking 16 samples of billowy poops from the Gulf of Maine. All of the samples contained significantly more ammonium – a nitrogen-rich waste product – than the surrounding water. Based on these analyses, Roman and McCarthy suggested that whales could be responsible for dumping 2,3000 metric tons of nitrogen into the Gulf of Maine every year. The amount was probably even higher before commercial whaling tried to sate its hunger for the massive mammals.
And seagoing beasts may only be continuing a trend that was in place long before they took to the water. At this past weekend’s PaleoFest at the Burpee Museum of Natural History, paleontologist Ryosuke Motani pointed out that marine reptiles were doing the dive-and-surface shuffle hundreds of millions of years before the hoofed ancestors of whales were even a glimmer in natural selection’s eye. Some of these marine reptiles – such as the fish-like ichthyosaurs – were some of the first deep-divers, Motani pointed out, and they could have played an ecological role similar to what Roman and McCarthy have suggested for whales. So perhaps it’s too narrow to talk about “whale pumps” or “marine reptile pumps” feeding the seas. Those are just more academically-acceptable ways of talking about “poop pumps”.
The inspiration for the study came from damaged bones. In 2012 Fahlke published a paper on a set of busted whale skulls from the 38-36 million year old strata of Egypt. Each of the four were from juveniles of a whale called Dorudon – a sinuous, fully-aquatic whale that still had differentiated teeth for gripping and shearing – and they all bore bite marks that matched the size and spacing of teeth belonging to the similar, but much larger, Basilosaurus. The bigger whales were grabbing the young Dorudon by the skulls, sometimes repositioning their prey before a final crunch.
The ancient toothmarks offered compelling evidence that, much like today’s orcas, Basilosaurus was a whale that ate other whales. But as a check on its biting power, Snively, Fahlke, and Welsh turned to an engineering technique called finite element analysis to run Basilosaurus through some virtual chomping.
Working from a skull belonging to a beautifully-complete specimen of Basilosaurus isis found in Egypt, the researchers found that the whale could bite with a force of over 3,600 pounds at the position of its upper third premolar. As suggested by Fahlke, this was the part of the mouth Basilosaurus used to crack open little Dorudon skulls and the estimated force is more than sufficient to penetrate through skin, muscle, and bone. And while the figure is undoubtedly influenced by the size of Basilosaurus, as Andy Farke points out, this is still the highest bite force yet estimated for a mammal.
Basilosaurus didn’t go right for a killing stroke, though. Some of the Dorudon skulls hint at initial capture with the conical, canine-like teeth at the front of the jaw first, and the researchers found that Basilosaurus could grip victims with over 2,300 pounds of force. With prey in place, Basilosaurus could then toss it back further along the jaw for a deadly shear bite. Crocodylians sometimes do the same with turtles and other hard-shelled prey, nabbing them with pointed teeth before obliterating their victims’ defenses with a back-tooth bite.
All that biting power allowed Basilosaurus to effectively dismantle large prey. The skulls of dead Dorudon and Basilosaurus teeth worn from scraping against bone attest to that grisly fact. And as Snively, Fahlke, and Welsh note, that Basilosaurus was capable of such shattering bites also fits with the picture of the whale as a consummate hunter.
The highest bite forces known – whether recorded from live animals or estimated from bones – belong to active predators, including carnivores like saltwater crocodiles, spotted hyenas, great white sharks, and Tyrannosaurus. Sure, powerful bites might let them take advantage of carrion from time to time, but the ability to deliver devastating chomps is also a critical skill for predators who must quickly disable their victims. What was true for spotted hyenas was likely true for Basilosaurus, making the ancient mammal one of the most frightening whales of all time.
Fahlke, J. 2012. Bite marks revisited – evidence for middle-to-late Eocene Basilosaurus isis predation on Dorudon atrox (both Cetacea, Basilosauridae). Palaeontologia Electronica. 16 (2), 1-16.
A few years ago, Carl Zimmer and I ran a workshop on science writing, where we talked, among other things, about explaining science without talking down to your audience. It apparently left an impression on Craig McClain, a marine biologist and blogger who was in the audience. “I made a comment about how I always wanted to write a post on how giant squid sizes are bullsh*t,” he recalls,” but that those always come off as an arrogant scientist telling the world that it’s wrong. And you said: You should write it, but you just need to find the right tone. That kicked me off.”
Rather than an angry blog post, McClain decided to put together a scientific paper that would accurately answer a simple yet slippery question: How big do the biggest animals in the ocean get?
The oceans are home to giants: blue whales and great white sharks; giant squids and giant clams; elephant seals and Japanese spider crabs. These creatures have no trouble capturing the public imagination, but scientists often have trouble capturing them. Many are rare, elusive, or live in inaccessible parts of the sea. Some are only measured when they wash ashore, after dry land distends or deflates their bodies. Some are so big that they are just plain hard to measure. And so, oceans are also home to exaggeration.
Take the giant squid. Umpteen media report claim that this nigh-mythic animal can grow up to 60 feet (18 metres) in length. That’s absurd, McClain thought. The vast majority are less than half that length. Many individuals are measured when they wash ashore, after decomposition loosens their muscles and eager humans stretch their tentacles. One size estimate even came from someone counting his paces next to a beached squid! Shoddy data had been unleashed upon the kraken.
McClain, together with Meghan Balk from the University of New Mexico, went after better sources. They recruited five keen undergraduate students and large team of colleagues, who divided a list of target species between them. They trawled the scientific literature for measurements. They combed through books, newsletters, and newspapers. They asked colleagues at museums to measure specimens in their collections. They contacted networks that rescue stranded turtles. They reeled in eBay records to find the measurements of giant clams and snail shells. And together, they found the best possible estimates for the maximum sizes of 25 ocean giants.
For some species, widely quoted figures were outrageously wrong. The largest verifiable giant squid was 12 metres long—giant, sure, but a damn sight smaller than 18 metres. The biggest known walrus weighed 1,883 kilograms, a far cry from the 2,500 kilogram titan that a hunter supposedly shot, and clearly embellished.
For some species, estimates were outdated—giant clam sizes all date to the 60s and 70s. For others, like the lion’s mane jellyfish and Japanese spider crab, the team found that accurate data just doesn’t exist.
And “some animals may just not be getting as big as they used to get,” says McClain. In 1885, fishermen in the Aleutian Islands caught a Giant Pacific octopus that was 9.8 metres from one arm tip to the next. “The two octopus experts who were with me on this paper say that they just don’t get that big any more,” says McClain. “It could be pollution or climate change.”
Hype and decline aside, the stats from the paper still tell of oceans that are full of impressive leviathans. There are giant barrel sponges, whose bodies are just two layers of cells sandwiching a jelly filling, but can nonetheless grow to 2.5 metres wide. There are 2-metre-wide Nomura’s jellyfish that can weigh 200 kilograms. In the depths, 3-metre-long giant tube worms thrive near hot, belching, volcanically heated vents, and giant isopods—a kind of undersea woodlouse on steroids—can reach 50 centimetres. Seven treacherous metres exist between the tip of a great white shark’s toothy snout and the end of its powerful tail.
The largest mammal, the blue whale, grows up to 33 metres long, and can swallow half a million calories in one mouthful. The longest fish—the star-backed whale shark—gets to 18.8 metres. The longest bony fish—the bizarre, serpentine oarfish—can reach 8 metres. The heaviest bony fish—the ocean sunfish, which looks like the decapitated head of a much larger fish—grows to just 3.3 metres long but weighs up to 2,300 kilograms. That’s much heavier than the biggest turtle (leatherback, 650 kg), a little heavier than the biggest walrus (1,883 kg), and not a patch on the heaviest seal (Southern elephant seal, 5,000 kg).
These measurements are all as accurate as possible; finding them often involved a labyrinth of references and phone calls. For the Australian trumpet—a beachball-sized monster of a snail—McClain found an issue of Hawaiian Shell News, in which a collector named Don Pisor holds up an enormous and supposedly 90-cm shell. But McClain also found a copy of the Registry of World Record Size Shells, which said that the record-holder was just 72 centimetres long. It was also attributed to Don Pisor. Were these the same specimens? Was this guy a charlatan? Or just phenomenally good at catching escargods? There was only one thing to do: McClain tracked down Pisor and asked him. It was just one specimen, he said, and he donated it to the Houston Museum of Natural Science. McClain called the museum. 72 centimetres, they said. Another data point for the list.
In a few cases, the team discovered new things about the giants. Andrew Thaler, who collected the data on giant isopods suddenly realised that males were, on average, much bigger than females. “That’s not something either of us knew before and both of us know everything there is to know about giant isopods,” says McClain.
And for several animals, the team managed to plot out the distribution of their sizes, rather than just the maximum. Scientifically, that’s more useful. People love to know how big animals can get, but that tells us very little about their typical lives. The biggest known giant squid was 12 metres long, but their average length is 7.3 metres, and most individuals are shorter than 9.2. Its archenemy, the sperm whale, has a recorded maximum size of 24 metres, but 95 percent of these whales are shorter than 15 metres.
As McClain—himself a bear of a man at 6’ 2”—points out, “individuals may reach these extraordinary large sizes through developmental or genetic defects.” The tallest human ever, Robert Wadlow, was 8 feet and 11 inches in height; he also needed leg braces to walk and died at 21 from an infection aggravated by an autoimmune disease. The tallest woman, Zeng Jillian, reached her lofty 8 feet and 1 inch because of a tumour in her pituitary gland; she died at 17. We are fascinated by extremes, but life mostly plays out in the middle.
Flippers, the need to breath air, the ability to give milk, and a streamlined shape. There are plenty of signs that let us immediately distinguish whales from fish and the other creatures of the sea. Yet, alone or in combination, the traits I just mentioned aren’t unique to whales. Seals and sea lions, for example, are also flippered, air-breathing, milk-giving, streamlined mammals. If you truly wish to draw out leviathan, you have to look beyond the blubber to a clue made of bone.
The secret is in the skull. Being mammals, whales have domes of bone on their skulls that enclose the middle ear. These are called tympanic bullae. But whales have a peculiar modification to these bony bulges. The inner edges of these bulbs are so thick and dense that they get their own name – the involucrum.
It’s not just modern whales that display this structure. An involucrum is a very, very ancient cetacean trait. When Philip Gingerich and Donald Russell first described the 55 million year old Pakicetus in 1981, for example, they were able to immediately recognize it as an early whale because of a partial skull preserving the thickened tympanic bullae on the bottom. Living and fossil, whales are united by a thick wall of bone over their ears.
But here’s where things get a little complicated. In 2007 Hans Thewissen and colleagues announced that Indohyus – a small, hoofed, 48 million year old mammal found in India – had an involucrum, too. A happy accident had broken open the beast’s middle ear and revealed a dense, thick margin just like that in whales. And while Indohyus wasn’t technically a whale – it belonged to a group called raoellids – the mammal was nevertheless an extremely close relative of the very first whales, providing paleontologists a proxy for what the ancestors of whales were like. Whales had inherited the involucrum from their deer-like ancestors and have kept it throughout their history, a rind of bone that whispers of the distant past.
Deep in the sea, on the denuded carcasses of whales, there live humble little scavengers. They’re the snotworms, better known to researchers as various species of the polychaete worm Osedax. They pursue a very dedicated lifestyle. Female snotworm larvae settle onto the exposed bones of dead whales, sending down “roots” to tap into the fatty substances locked in the cetacean’s skeleton. Together with mats of bacteria and other organisms, they’re part of a whale deconstruction crew that can totally break down the world’s largest animals.
And the snotworms have been at this for quite some time. Their distinctive pockmarks have been found on fossil whale bones dating back to about 30 million years ago. And even though they’re most famous for feeding on decaying whales, the snotworms can be food, too. In a new Lethaia paper, University of Otago paleontologists Robert Boessenecker and Ewan Fordyce describe divots and scratches on a 28-23 million year old whale that show fish and sharks gobbled snotworms.
The whale in question – of an as-yet-unnamed prehistoric genus and species – was found on New Zealand’s South Island. There was quite a bit of the mammal in the rock, including the skull, vertebrae down to the torso, ribs, and additional bones left at the site. And upon those prehistoric bones are trace fossils that testify to the presence of other organisms. Among the most numerous are clusters of small circular holes that are concentrated on well-preserved bone – these are the signs of prehistoric Osedax, the first fossil occurrence from the southern hemisphere.
But in some spots there are other marks that cut across the snotworm holes. The snotworm burrows on the skull bones are associated with shallow, parallel scrape marks. The most likely culprits, Boessenecker and Fordyce propose, are fish and sharks that dragged their jaws across the whale carcass to snaffle the snotworms, roots and all.
The Osedax feast continues today. Boessenecker and Fordyce point out that ratfish and crabs have been seen eating whale bone covered in snotworms, too. As long as there have been snotworms, other creatures have turned to them for food. It’s another indication that, rather than being silent undersea tombs, whalefalls are sites of vibrant life.
The southern right whale is a huge fortress of animal—50 feet and 60 tons of muscle and blubber. At its size, this giant should have nothing to fear from ocean predators, except possibly for killer whales. But in the waters around Argentina, southern rights have been so badly tormented by an unusual threat that they have been forced to take stealthy precautions.
Their nemesis is the kelp gull.
Kelp gulls, like most of their kind, are opportunists. They’ll pluck fish from the sea, and scraps from landfill sites. And those near Peninsula Valdes in Argentina have started stripping flesh from the backs of whales.
Thousands of southern rights gather in those waters to breed between June and December. As they come up for air, the gulls land on their backs and tear off chunks of skin and blubber, leaving 20-centimetre long wounds. As many as eight birds can target one unfortunate whale.
As I reported two years ago, scientists first documented these attacks in 1972. They were rare then, but have been getting steadily worse. By 2008, some 77 percent of the whales were swimming around with gull-inflicted gashes. Partly, that’s because gull populations have soared thanks to the food provided by human fisheries and dumps. They may also be learning the behaviour from each other.
“Nowadays, gull attacks are so widespread in waters surrounding Península Valdés that it seems that there is no place without this interaction,” writes Ana Fazio from CONICET, an Argentinian institution.
The wounds might riddle the whales with skin infections, especially if the gulls are sticking their faces in rubbish heaps beforehand. They might also be distractions. Fazio found that the whales spend a quarter of their daylight hours trying to avoid the gulls, which might exhaust them, while depriving them of feeding opportunities. The calves suffer most: some 80 percent of the gulls’ attacks are aimed at mother-calf pairs.
Local government authorities have recently decided to take action, prompted in large part by pressure from visitors and tour operators. They have kick-started a management programme to protect the whales, including everything from killing the attacking birds, to closing landfills and reducing the waste that sustains the large gull populations.
Meanwhile, the whales have started taking matters in their own flippers. Clearly, they’re not keen on being flayed alive by gulls. They react by flinching strongly, arching their bodies so their heads and tails come up while their backs submerge. Scientists have described this posture as the “galleon position” or “crocodiling”.
Then, in 2008, they started doing something new.
Usually, when they come up for a breath, they do so in a leisurely way, lying parallel against the water surface with much of their backs exposed. But in 2009, Fazio’s team saw that a few of the whales would instead rise at a 45 degree angle so that only their heads were exposed, and only up to their blowhole. Their breaths were shorter and stronger than usual, and they quickly submerged again.
This technique, which the team called “oblique breathing”, exposes as little flesh as possible to the marauding gulls. It’s especially common at a site called El Doradillo, where the gull attacks are especially common. In 2010, 3 percent of the whales in El Doradillo were using oblique breathing. By 2013, 70 percent were doing it, and the behaviour had spread to neighbouring tracts of water. And most recently, the whales have started doing it even when they aren’t attacked, possibly as a preventive measure or to teach the trick to their calves.
It looks like the whales have won this round, but Fazio notes that oblique breathing isn’t an easy technique. These animals are naturally buoyant at the sea surface, so it takes energy to keep their backs and tails underwater. The technique may be especially taxing for the calves and this, combined with the actual attacks, may explain why the calves of Peninsula Valdes are dying in higher numbers than expected.
The blue whale can swallow half a million calories in a single mouthful. When it spots its prey—shrimp-like creatures called krill—it lunges forward, accelerating rapidly and opening its jaws to an almost right angle. Its mouth expands, its tongue inverts, and it engulfs around 110 tonnes of water—about the same mass as another small blue whale. Over the next minute, it pushes the water through sieve-like plates, filters out the krill, and swallows. Then, having reloaded its face, it’s ready for another attack.
This sequence, known as lunge-feeding, is the signature move of the rorquals—the family of giant whales to which the blue belongs. It allows these animals to grow to huge sizes by feasting on huge volumes of miniscule prey.
But lunge-feeding didn’t evolve among titans. The fossil record tells us that the technique first arose in species in the size class of the modern minke whales—the smallest of the rorquals at a mere (!!) 5 metres long. To understand how and why lunge-feeding evolved, we need to understand how the minkes do it.
That should be easy, since minkes are the most common whales in the Antarctic. But they are also among the most elusive. Large rorquals like the blues will spend a reasonable amount of time at the surface recharging their lungs, allowing scientists to easily stick tags and recorders to them. But with minkes, “you see them for a breath or two and then they’re gone,” says Jeremy Goldbogen, a whale researcher at Stanford University. “You have a second to get it in the right spot.” No one had been able to tag one, and not for lack of trying.
That changed in February 2013. While trying to study humpbacks in Antarctica, a team led by Ari Friedlander at the Oregon State University found big groups of minkes, up to 40-strong, feeding around large floes of ice. They seemed to be socialising, and they were certainly relaxed enough for the team to sneak up in an inflatable boat. Friedlander sat on a pulpit at the front, carrying a long carbon-fibre pole with a suction-cup tag at the end. He waited, and eventually, one of the whales surfaced at just the right spot for him to stick the tag on. It was a first.
For 18 hours, the tag stayed on and recorded pressure, temperature and acceleration. A few days later, the team managed to tag a second animal, for a further 8 hours of data.
And what data! During that time, the two animals managed 2,831 lunges over 649 dives. While they were feeding, they lunged around 100 times every hour. That’s just over half a minute to accelerate a five ton body through water, swallow the equivalent of a king-size bed, filter out all the food within it, and be ready to go again. And again. And again.
The team also found that the minkes did something that other rorquals don’t: they made long, shallow dives under large floes of floating ice to feed on the swarms of krill beneath. No other predator can exploit this resource so efficiently. Blue, fin and humpback whales are too big, and they feed in more open, ice-free waters. Penguins and seals can dive under the ice, but they’re limited to picking off one prey at a time. The minke, by combining manoeuvrability with lunge-feeding, can consume the food beneath the ice in bulk.
Their feeding strategy is similar in kind to that of a blue whale, but very different in degree. Since they’re smaller, they can’t engulf as much water, but they also expend less energy on lunging. For a blue, lunging is a massively draining affair that pays off only because it guarantees the world’s most calorific mouthfuls. For a minke, lunging costs barely more energy than steady swimming. So while blues make a few gigantic gulps, minkes can take small gulps at a much faster rate. And that provides a clue about how lunge-feeding evolved.
Goldbogen thinks that the strategy helped early small rorquals to eat more efficiently, by swallowing large amounts of prey at once. That allowed some of them to become truly enormous, by using the same behaviour to consume vast quantities of prey in the open ocean. Others, like the minke, kept to a small size to exploit patchier swarms that their giant cousins couldn’t reach. “As body size evolved to bigger size classes, you got this niche partitioning,” says Goldbogen. “That’s our leading hypothesis.”
The study is a small victory for the team, not least because “Japan is still whaling minkes in the Antarctic,” says Goldbogen. “They claim it’s for scientific purposes but I don’t think anyone was fooled by that claim. Here we show that you can study whales without killing them. That was obvious before but providing some published accounts is important too.”
There’s more to come. The team has just developed a new class of tag that has cameras as well as the usual sensors. They’ve deployed it on five humpbacks and two blues, and they’re about to try it on some minkes in the coming months. “It’s pretty much a full flight recorder on top of a whale,” says Goldbogen. “We’ve been having a lot of fun.”
Reference: Friedlander, Goldbogen, Nowacek, Read, Johnston & Gales. 2014. Feeding rates and under-ice foraging strategies of the smallest lunge filter feeder, the Antarctic minke whale (Balaenoptera bonaerensis). Journal of Experimental Biology http://dx.doi.org/10.1242/jeb.106682
The magnificent pronged antlers growing from the skull of a male red deer are billboards. Their size reveals his strength and fighting ability to other males, and his health and quality as a mate to females. Similar horns, antlers and crests adorn the skulls of other animals, including giraffes, antelope, goats, cows, sheep, and dinosaurs like Triceratops. They’re all highly visible, as befitting their role in signalling. What use, after all, is a billboard that you can’t see?
But what if that wasn’t necessary? What if an animal had a way of “seeing” inside a rival’s body? Would antlers need to be visible at all?
Pavel Gol’din doesn’t think so. A zoologist at the National Academy of Sciences of Ukraine, Gol’din has been studying beaked whales—an elusive group of mammals known for their incredibly deep dives and their bizarre skulls. They look like someone glued on a variety of crests, ridges, and domes onto the skulls of more vanilla whales. Many of these structures are found only in males, and are signatures of single species. A few are made of spongy tissue; most are made of incredibly dense and compact bone.
Gol’din thinks that these structures are internal versions of a red deer’s antlers. They serve a similar purpose, signalling a male’s size, strength and health. The big difference is that, unlike antlers, these structures are largely invisible from the outside.
But that’s not a problem for the beaked whales. They navigate with echolocation, making high-pitched calls and seeing the world in the rebounding echoes. If they aimed this sonar at their peers, they should be able to distinguish the compact bone of the skull from the soft overlying tissues. They could effectively become living ultrasound scanners, seeing through each other’s heads and visualising the bones within. In this way, they could signal to each other using features that are hidden from sight.
Gol’din’s idea is still a hypothesis, and one that he hasn’t tested. But other scientists are certainly intrigued. “My first reaction was: Wow, what a cool idea! Why didn’t we think about that before?” says Olivier Lambert from the Royal Belgian Institute of Natural Sciences.
Lambert thinks that Pavel’s idea may not apply to all beaked whales, but seems convincing for many species, like the extinct Globicetus and Tusciziphius. “I clearly remember conversations with other colleagues about these crests. We were asking if a part of them could be visible from the outside for visual display. But this is not necessary for such specialized echolocating animals.”
These inner structures don’t wreck the whales’ streamlined bodies, as horns or external ornaments surely would. That’s important given how frequently they dive. With internal antlers, they could get the advertising space of a bus and the profile of a Ferrari at the same time.
Colin Macleod from the University of Aberdeen also likes the idea and has an unfinished paper in a drawer that explored a similar concept. “Pavel seems to have independently come to similar conclusions—always a good thing!” he says. But he notes that deer antlers aren’t just for display; males also use them to fight each other when stand-offs turn sour. Beaked whales may do something similar, using their skulls as weapons. “But because of echolocation, their skull structures can still serve a display function in the process of escalating aggression, despite being internal.”
“The multitude of scratches that appear on male beaked whales—often with just the right spacing to be from the tusks of another male—suggest that they use their teeth for fighting,” adds John Hildebrand from the University of California, San Diego. “Examining the interior of your rival’s skull with sonar may be another way to judge his ability to put up a good fight.”
Both ideas—fighting and signalling—certainly seem more plausible than the alternatives. Some scientists have suggested that the structures weigh the skulls down when the whales dive, but there’s no evidence that the males diver deeper than the females or youngsters. Others have hypothesised that the structures are like brass instruments that help the whales to make calls, but some of them sit in front of the sound-producing organs and would get in the way if anything.
Whales actually evolved from artiodactyls—the family of even-toed hoofed mammals that includes deer, cows, sheep, and antelopes. It’s not far-fetched to think that the same evolutionary forces that outfitted rams with their horns or stags with their antlers were also responsible for the textured skulls of beaked whales.
“But it will be a challenging hypothesis to test, and it may not be logistically possible at the moment,” says Nick Pyenson from the Smithsonian Institution. Museum specimens are few and far between, and “their deep-diving ecology makes them very tough to study at sea. It takes researchers going far off-shore and to remote places to even encounter them,” he says. For example, after scientists first found the bones of the spade-toothed beaked whale, it took 150 years before someone finally saw it in the (dead) flesh.
MacLeod agrees. “They are so difficult to observe that it’s hard to carry out the required observations to actually test them. We might never know for certain exactly how many of these structures are actually used.”
Reference: Gol’din. 2014. ‘Antlers inside’: are the skull structures of beaked whales (Cetacea: Ziphiidae) used for echoic imaging and visual display? Biological Journal of the Linnean Society. http://dx.doi.org/10.1111/bij.12337
Two years ago I was exploring the San Diego Natural History Museum when a fossil skull stopped me in my tracks. The Pliocene bones were clearly those of a toothed whale, but the specimen wasn’t quite like anything I had ever seen before. The porpoise’s lower jaw jutted far ahead of the upper – a thick, bony “chin” that would make Bruce Campbell jealous. What was that prodigious jaw for, and how did it evolve?
I wanted to know more, but the exhibit was short on details. The extinct whale hadn’t been officially named, and why a porpoise would have such a peculiar profile was anyone’s guess. That’s why I was thrilled to see that Yale University doctoral candidate Rachel Racicot and coauthors have now published answers to some of the questions that transfixed my mind when I first saw the skull.
The porpoise’s name, Racicot and colleagues decided, is to be Semirostrum ceruttii, the genus name following from the shortened appearance of the snout compared to the lower jaw and the species epithet honoring the man who found the skull, Richard A. Cerutti. There’s more of the cetacean – including vertebrae, ribs, pectoral girdle, and arm – but it’s the skull that makes the Pliocene porpoise an enigma.
Measured by Racicot and coauthors, the toothless, fused part of the porpoise’s lower jaw takes up at least 40% of the length of the entire lower jaw. The look is superficially similar to some species of fish and a bird called the black skimmer that does exactly as its name suggests as it tries to snag small meals from the surface of the water. The question is how the whale used this unusual protuberance as it swam the seas of southern California between 5.3 and 1.3 million years ago.
What a prehistoric creature was capable of doing and what that animal actually did is a persistent paleo puzzle. Fortunately, the skull of Semirostrum preserves a few delicate clues as to how this unusual whale made a living.
Along the stiff lower jaw of Semirostrum are numerous small openings. These are the end-points of canals that housed soft tissues and ran through the bone in life, indicating that the lower jaw was a very sensitive appendage. This was a specialized sensory structure.
But specialized for what? Racicot and colleagues propose that the porpoise’s jaw may have evolved to probe for prey hiding in the murky ocean bottom. And the cetacean’s teeth offer another reason to imagine Semirostrum tracking fish hiding beneath the surface. The porpoise’s teeth are worn down and polished, suggesting that a great deal of abrasive sediment was brushing by as the whale snatched small prey.
Not that the jaw would have been all about feeding. Such a sensitive jaw, Racicot and coauthors note, could have also been a bony antenna that helped Semirostrum communicate with each other in turbid or shadowy seas. If you could put yourself in the porpoise’s Pliocene waters, perhaps you would hear them click and buzz as they pointed each other to the best spots to swipe fish from the sand.
This is the story of a whale that tried something new and a monkey that fell in line.
It’s about how wild animals can create cultures and traditions just as we can, through the twin forces of innovation and conformity.
In 1980, a humpback whale in the Gulf of Maine started doing something different. All its neighbours would catch small fish by swimming in circles below them, blowing curtains of bubbles, and then lunging straight up at the corralled shoal. Then one individual, out of the blue, started smacking the water surface with its tail before diving down and blowing its bubbles.
This behaviour is called lobtail feeding, and no one knows why it works. Maybe it disturbs the water above the bubble curtains and discourages fish from jumping to safety. Whatever the benefit, it went viral. Just eight years after the first innovative whale started doing it, 20 percent of the Maine humpbacks had picked up the technique. Now, it’s more like 40 percent. What began as one whale slapping the water is now a tradition.
The obvious explanation is that the whales were learning from each other. But there could be other reasons. If the technique has a strong genetic basis, it could pass down family lines without any form of social learning. Or maybe environmental changes were responsible. The whales seem to use lobtail feeding specifically to catch small fish called sand lance, and the strategy only started spreading after populations of herring, another important prey species, crashed. Perhaps hunger drove the whales to individually develop a new technique for catching a different sort of prey.
Jenny Allen worked out how to tell these possibilities apart. As a masters’ student, she had worked on whale-watching boats in Maine, and knew that the Whale Center of New England (WCNE) had collected a huge data set of the local animals’ behaviour. Over 27 years, they had recorded almost 74,000 sightings. Allen was looking for ways of using this data when she joined Luke Rendell’s lab at the University of St Andrews as a PhD student. “I realised this was the lobtail-feeding population and asked whether it was still going on,” says Rendell. “She said, ‘Yes, it seemed to still be spreading’. I knew we were in business.”
The team used the Maine data to reconstructed the whales’ social network and simulate the spread of lobtail feeding under different mathematical models—some that included social learning and others that didn’t. The results were so clear that even Rendell was surprised. “It was very, very clear that cultural transmission was important in the spread of the behaviour,” he says.
The models which assumed that the whales were learning lobtail feeding from each other were a far better fit for the actual spread of the behaviour than those which assumed no social connection. “The weight of evidence was up to 23 orders of magnitude greater for these models,” says Rendell. “It’s the difference between the weight of a single person and the weight of planet Earth.”
By contrast, genetics was unimportant. “Having a lobtail-feeding mother makes virtually no difference to whether you will become one,” says Rendell. Ecology mattered more. Whales were more likely to learn the lobtail method in the specific region where the sand lances live, and during years when sand lance numbers were high.
This doesn’t detract from the importance of social learning, which was by far the more important factor in the strategy’s spread. Instead, it shows how useful it can be to pick up skills from your neighbours. “If a species is smart enough to innovate and transfer information socially, it could adapt very quickly to new environmental pressures. This is why humans are so successful,” says Michael Kruetzen from the University of Zurich. “I find this to be a highly convincing case for a foraging tradition in a cetacean,” adds Susan Perry, an anthropologist from the University of California, Los Angeles.
Critics might point out that Allen’s study relied only on observations rather than experiments, and incomplete observations that were limited by what boat crew could see. But the team took steps to account for this, adjusting their models to account for patchy sightings, or the fact that the most commonly spotted whales would repeatedly pull off the same behaviours. None of that changed the results.
And Rendell scoffs at the notion that you can never know anything for sure from observational data alone. “It would be great to look at this experimentally, but we’re talking about a population of wild humpback whales here,” he says. “Spock and Kirk were able to beam one up in The Voyage Home, but we aren’t going to be doing that any time soon. This is really the best approach we have, and the answer it gives is unequivocal.”
Meanwhile, thousands of miles away in South Africa’s Mawana Game Reserve, there lived a vervet monkey called Groot, who was a fan of blue corn. One day, two boxes of dyed corn kernels had mysteriously appeared. The pink ones tasted disgusting but the blue ones were tasty, and Groot’s entire group quickly learned to eat the blue ones. Then, as all male vervets do when they grow up, Groot left his family behind and moved to a new group. And when he did, he saw that his new companions liked pink corn instead. He watched, he processed, and he starting eating the pink corn too.
Groot didn’t know it, but he was part of an ambitious experiment by Erica van de Waal and Andrew Whiten from the University of St Andrews to study the spread of animal traditions. Recently, Whiten’s team has studied whether captive chimps and capuchin monkeys can learn from each other. The answer is yes. Tutors, who are taught new foraging techniques in isolation, can seed their groups with these new innovations when they are reunited.
This approach is impractical in the wild, because it’s very hard to isolate a tutor individual. Instead, scientists have studied differences in behaviour between groups of wild chimps, orang-utans and other species. These studies have been pivotal for our understanding of animal culture, but they’ve run against the same refrain that Rendell dislikes: they’re just observational, not experimental.
So, van de Waal tried something new—she seeded new traditions in entire groups rather than individuals. She gave four groups of wild vervets, which included 109 individuals between them, a choice between blue corn and pink corn. In each case, the group would only ever eat one colour because the other was coated with a repulsive extract from local aloe plants. (They tried vinegar and chilli powder, but the vervets happily ate those. Only aloe worked. “The experimenters tested the corn themselves and had the bitter taste for a whole day in their mouths,” said Whiten.)
Van de Waal took the corn away for 4 to 6 months and during that time, new babies were born into the vervet communities. The corn eventually returned and this time, both colours were tasty and palatable. Even so, it seems you can’t teach an old vervet new tricks, and the monkeys stuck with their existing colour preference.
More importantly, their infants, who had never seen dyed corn before, just ate whatever they saw their mothers eating. Those born into pink cultures ate pink corn. Those born into blue cultures ate blue corn.
It’s not surprising that infants follow their mothers, but the strength of their preferences caught the team off-guard. “Infants chose only what their mother ate despite there being right in front of them a box of perfectly edible corn of a different colour,” says Whiten. “Some even sat on that, to eat the ‘right’ colour of corn!”
Emigrating males also took up the traditions of their new groups. By sheer luck, during the experiment, ten males moved into a group that preferred a different coloured corn than their original group did. Seven of these newcomers seven immediately started eating whatever colour their new comrades preferred, and two more soon followed suit. The only exception was a male called Lekker who immediately took up a dominant rank in his new group, which may explain why he stuck to his old ways.
Perry praises the elegant experiments but notes that the numbers are quite small. “Seven out of ten is only 2 data points greater than chance preference for a particular colour,” she says. “I appreciate the difficulty in obtaining a larger sample—you have to wait for males to migrate—but I hope the authors will persevere in increasing that sample size.”
This degree of conformity is surprising especially for vervets, which “are often thought to be opportunistic”, according to Whiten. This “when-in-Rome” mentality makes sense. In the wild, foraging animals have to make decisions about the nutritional quality of potential foods and the presence of poisons. When moving into a new environment, it pays to copy what local experts are doing, even when it means overriding the knowledge you’ve gained in a different context.
The tendency to conform could also explain other social learning experiments have failed. Scientists have tried to teach new behaviours to wild tutor individuals, including vervets and meerkats, but found that these nascent traditions are difficult to spread. That may be because these traditions face an uphill struggle, says Whiten, “whereas, in our study, the naïve infants and immigrant males were already surrounded by a majority doing the same thing.”
The team now wants to see if the wild vervets will also learn more complicated behaviours from each other, such as techniques for dealing with their food. Based on work with captive monkeys, they think the answer is yes. It’s now time to take these experiments into the field.
Thanks to decades of research, it is now clear that animals can learn from each other in ways that create different cultures in the wild.
As Frans de Waal writes in a commentary accompanying these new studies, “The early debate about animal culture focused on the mechanism of behavioural transmission.” Are apes apeing each other in the way that humans can? When whales and dolphins imitate each others’ songs and actions, do they understand each others’ goals and methods? When blue tits peck open the tops of milk bottles, is it because they’ve picked up the technique from other tits, or because those birds just drew their attention to the bottles?
Now, studies of animal culture are moving beyond just asking whether it happens to probing why it happens and how strongly it does. The humpbacks show that new traditions can easily spread within a group, but the vervets show that the conformity can also suppress new behaviours in favour of old rituals. We see the same tension between innovation and conformity in our own societies, and it’s fascinating to see the same patterns in animal groups.
All of this requires intensive field work and long-term studies. To watch the vervets from the comfort of nearby chairs, de Waal and Whiten had to spend over a year with the monkeys, getting them used to their presence and learning how to recognise over 100 individuals by eye. To understand what the whales were doing, Allen and Rendell had to use a 27-year set of data. “That shows how important it is to have long-term research so you can create these data sets,” says Kruetzen “If people had just gone there for a year or two, it would have been very hard to document these changes.”
Of all the baleen whales in the sea, the pygmy right whale is arguably the most mysterious. Technically-known as Caperea marginata, this 20-foot cetacean is rarely seen in its South Ocean habitat. And even when a stranded specimen turns up, the whale continues to vex scientists. Molecular and anatomical data conflict about just what sort of baleen whale Caperea marginata actually is, and the frustrating marine mammal has often been regarded as the sole member of its own subfamily. Yet University of Otago whale experts Ewan Fordyce and Felix Marx have proposed a startling solution to the question of the pygmy right whale’s identity.
Zoologists have long known that “pygmy right whale” is a misnomer. As Fordyce and Marx point out in the paper, Caperea marginata “differs from right whales … in its external form and osteological features in all parts of the skeleton.” The small, southern whale just happens to superficially resemble the larger, better-known right and bowhead whales. Indeed, as Fordyce and Marx found when they reviewed a “wealth” of Caperea marginata in New Zealand museum collections, the whale appears to be a cetothere – a variety of baleen whale that was thought to have gone extinct about 2 million years ago.