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Fast-Swimming Swordfish Automatically Lubricate Themselves

Broadbill Swordfish in the Mediterranean Sea off Italy.
Broadbill Swordfish in the Mediterranean Sea off Italy.
PHOTOGRAPH BY BRIAN J. SKERRY, NATIONAL GEOGRAPHIC CREATIVE

Swordfish steaks frequently appear on menus and dinner plates around the world. But even though many people have hooked, hacked apart, and devoured these majestic fish, few truly understand their bodies. Indeed, until John Videler from Leiden & Groningen University started studying swordfish, no one knew that they had a fist-sized gland in their heads, which slathers lubricating oil over their famous pointed snouts.

Videler has been studying the physics of swimming fish for most of his career, and swordfish were particularly intriguing to him because they’re such superlative swimmers. It’s commonly said that they can reach speeds of 100 kilometres per hour (62 miles per hour), and although the provenance of that estimate is dubious, there’s little doubt that they are really, really fast. So in 1994, while teaching a diving course in Corsica, he bought a swordfish bill from a local fisherman and started studying it.

When a swordfish swims, layers of water flow along the surface of its bill. As it picks up speed, these currents threaten to break away, creating swirling areas of turbulence that increase the drag upon the animal.

But Videler found that the bill is rough, like sandpaper. This limits any turbulence to a thin layer close to the bill, and prevents the larger, destabilising eddies from forming. The bill is also pitted with small, interconnected holes near its tip, which stop water pressure from building up at the fish’s front end—again, this reduces drag by preventing turbulence.

By then, Videler was hooked. He got two more swordfish from the same fisherman, and persuaded Ben Szabo—the head of radiology at Groningen University—to put them in a medical MRI scanner. The team scanned the fish heads between 2 a.m. and 5 a.m., when the machine was available.

At first, the images were confusing and hard to interpret. But when Videler dissected the heads themselves, he noticed a large oily gland above the base of the bill and between the animal’s eyes. And sure enough, there it was on the scans.

He thought nothing of it until 2005, when a student named Roelant Snoek came to him with an interest in swordfish. Videler told him about the gland, and suggested that it might connect to the fish’s olfactory system, influencing its sense of smell. But Snoek couldn’t find any such connections.

After much frustration, he finally worked out the gland’s true purpose by accident. While taking photographs of a swordfish head, he accidentally dropped a lightbulb onto it. The bulb illuminated a web of tiny blood vessels inside its skin, and Snoek showed that these were connected to the gland. The vessels then open out into the fish’s skin via tiny pores, each just a fraction of a millimetre wide. Snoek proved this by heating the gland with a hair-dryer; once hot, the congealed oil became liquid and oozed out the fish’s pores.

So Videler thinks that the gland is yet another drag-reducing adaptation. Its oil repels water and allows incoming currents to flow smoothly over the surface of the bill. That depends on the oil staying warm, but swordfish have a solution for that, too. They have modified some of their eye muscles into heat-producing organs that warm their blood and sharpen their vision as they hunt. This same heating effect could liquefy the drag-reducing oil, allowing it to ooze out of the glands just as the fish have the greatest need for speed.

The oil might explain another weird feature of swordfish anatomy. They are among the only fish with a concave hollow at the front of their heads—an slight inward-curving bowl that, counter-intuitively, ought to increase drag. “I’ve been puzzling about that for years,” says Videler. He now thinks that the hollow is shaped so that water flowing past it creates an area of low pressure, which sucks the oil out of the fish’s gland.

If he’s right, it means that a fast-swimming swordfish automatically lubricates itself.

This makes a lot of sense, but it’s still a hypothesis. “We still have to find some way of doing experiments to visualise the flow of water [over the bill],” Videler admits. “We can’t do that on live swordfish,” since these animals are impossible to keep in captivity. But he hopes that other scientists could run fake swordfish—sandpaper skin, pores, oil, and all—in water tunnels to see how they perform.

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Butterflies Behaving Badly: What They Don’t Want You to Know

Small Grass Yellow butterflies feed on fresh elephant dung in Kenya's Tsavo West National Park.
Small grass yellow butterflies feed on fresh elephant dung in Kenya’s Tsavo West National Park.
Photograph by Nigel Pavitt, Getty

Butterflies have had us fooled for centuries. They bobble around our gardens, all flappy and floppy, looking so pretty with their shimmering colors. We even write odes to them:

Thou spark of life that wavest wings of gold,
Thou songless wanderer mid the songful birds,
With Nature’s secrets in thy tints unrolled
Through gorgeous cipher, past the reach of words,
Yet dear to every child
In glad pursuit beguiled,
Living his unspoiled days mid flowers and flocks and herds!
Ode To A Butterfly, by Thomas Wentworth Higginson

But butterflies have a dark side. For one thing, those gorgeous colors: They’re often a warning. And that’s just the beginning. All this time, butterflies been living secret lives that most of us never notice.

Take this zebra longwing, Heliconius charithonia. It looks innocent enough. 

The zebra longwing butterfly was made Florida's state butterfly in 1996.
The zebra longwing butterfly was made Florida’s state butterfly in 1996.
Pixabay, CC0

But it’s also famously poisonous, and its caterpillars are cannibals that eat their siblings. And that’s hardly shocking compared with its propensity for something called pupal rape.

Once you know that a pupa is the butterfly in its chrysalis—in between being a larva and an adult—then pupal rape is pretty much what it sounds like. As a female gets ready to emerge from her chrysalis, a gang of males swarms around her, jostling and flapping wings to push each other aside. The winner of this tussle mates with the female, but he’s often so eager to do so that he uses his sharp claspers to rip into the chrysalis and mate with her before she even emerges.

Since the female is trapped in the chrysalis and has no choice in the matter, the term pupal rape came about, though some biologists refer to it more charitably as “forced copulation” or simply pupal mating. Whatever you call it, it’s hardly the stuff of children’s books.

The zebra longwing is certainly pretty, though. Maybe that’s how it got to be Florida’s state butterfly.

And don’t think for a minute that zebra longwings are an anomaly—plenty of their kin are bad boys, too.

One day in Kenya’s North Nandi forest, Dino Martins, an entomologist, watched a spectacular battle between two white-barred Charaxes. A fallen log was oozing fermenting sap, and while a fluffy pile of butterflies was sipping and slowly getting drunk, the two white-barred butterflies showed up and started a bar fight. Spiraling and slicing at one another with serrated wings, the fight ended with the loser’s shredded wings fluttering gently to the forest floor.

A green-veined Charaxes dines on animal poop.
Photograph by Dino Martins

Martins, a former National Geographic Emerging Explorer, wrote about Charaxes, or emperor butterflies, in Swara magazine, published in East Africa where he is now Director of Kenya’s Mpala Research Centre.

“They are fast and powerful,” he writes. “And their tastes run to stronger stuff than nectar: fermenting sap, fresh dung and rotting carrion are all particular favourites.”

That’s right; don’t get between a butterfly and a freshly dropped pile of dung. It drives them wild. They uncoil their probosces and slurp away, lapping up the salts and amino acids they can’t get from plants.

It’s called mud-puddling, and it’s very common butterfly behavior. It doesn’t have to be dung, although that’s always nice; you may see flocks of butterflies having a nip of a dead animal (as depicted in this diorama of butterflies eating a piranha), drinking sweat or tears, or just enjoying a plain old mud puddle.

(VIDEO: Did You Know Butterflies Drink Turtle Tears? Watch to find out why.)

But still, butterflies are harmless, right?

Sorry, kids—not always. Butterflies start life as caterpillars, which are far from harmless if you’re a tasty plant, and can be carnivorous. Some are even parasites: Maculinea rebeli butterflies trick ants into raising their young. The caterpillars make sounds that mimic queen ants, which pick them up and carry them into their colonies like the well-to-do being toted in sedan chairs. Inside, they are literally treated as royalty, with worker ants regurgitating meals to them and nurse ants occasionally sacrificing ant babies to feed them when food is scarce. Butterflies invented the ultimate babysitting con.

So, let’s review. Here are seven not-so-nice things butterflies are into:

  • Getting drunk
  • Fighting
  • Eating meat
  • Eating poop
  • Drinking tears
  • Tricking ants
  • Raping pupae

Don’t get me wrong—I like butterflies. In fact, I like them more knowing that they have a dark side. They’re far more interesting, more weird, than any ode to pretty colors could convey.

Happy Learn About Butterflies Day!

 

Reference:
Dino Martins. Flitting Emperors – and Forest Queens. SWARA Vol. 27 No. 2 / April–June 2004; pp. 52-55. No link available.

Dino Martins. ‘Mud-Puddle’ — or Be Damned. SWARA January—March 2006; pp. 66-68.

Queen Ants Make Distinctive Sounds That Are Mimicked by a Butterfly Social Parasite. Science: Vol. 323, Issue 5915, pp. 782-785. 2009.

Giant Flesh-Eating Koala of Legend Was Real

The skeleton of Thylacoleo in Naracoorte Caves National Park. Photo by Karora.
A skeleton of Thylacoleo in Naracoorte Caves National Park. Photo by Karora.

If you ever go on a camping trip to Australia, you might be told to beware the dreaded drop bear. There won’t be a chase. You’ll just be walking along, minding your own business, when a dark shape plummets onto you from above, pinning you down before your realize that you’re being eaten alive by an overgrown koala. The only way to protect yourself, the locals will advise, is to slather yourself in Vegemite and speak in an Australian accent. The efficacy of changing your name to Bruce is unknown.

This is all nonsense, of course. There are no carnivorous koalas with a taste for tourists hanging around the eucalyptus trees of Australia. Yet, despite the fact that the drop bear is a modern hoax, I’m still tickled by the fact that the mythical animal’s description closely matches a very real animal that prowled Australia during the last Ice Age. Paleontologists and fossil fans know this beast as Thylacoleo carnifex, the “marsupial lion.”

Despite the mammal’s name, Thylacoleo doesn’t hold much leonine resemblance. The carnivore’s skull is a modified version of a koala’s or wombat’s, just with cleaver-like shearing teeth at the cheek instead of grinders. That fits given that Thylacoleo belonged to the group of marsupial mammals called the diprotodonts, which includes kangaroos, wombats, koalas, and possums today. Thylacoleo was closer to being a carnivorous koala than a pouched cat.

The kinship of Thylacoleo is only half of the drop bear equation, though. The other has to do with its hunting habits. Back in 2010, paleontologist Roderick Wells and colleagues found that the paws of this marsupial predator would have been just as useful for climbing trees as grappling with the large prey of its era. Now Samuel Arman and Gavin Prideaux have forwarded even more evidence that Thylacoleo was a skilled climber: thousands of scratch marks in the lair of Australia’s real drop bear.

Southwestern Australia’s Tight Entrance Cave yielded the essential clues. In addition to a bonebed cradling the bones of both living and extinct marsupial species, the main chamber of the cavern is marked here and there by V-shaped scratch marks. Only one animal in the cave matches the size and anatomy required to make the largest scratches: Thylacoleo. And while Arman and Prideaux concede that some of the smaller scratches could have been made by other animals trying to find their way out of the cave, from possums to Tasmanian tigers, their preferred interpretation is that most of the smaller scratches were left by Thylacoleo joeys who were reared in the safety of the cave.

Scratches likely made by Thylacoleo in Tight Entrance Cave. From Arman and Prideaux, 2016.
Scratches likely made by Thylacoleo in Tight Entrance Cave. From Arman and Prideaux, 2016.

The nature of the bones in Tight Entrance Cave bolsters this vision of Thylacoleo hunkering down in the dark. Relatively few of the bones in the cave show bite marks. This means that the cave was not the habitat of bone-eaters, like Tasmanian devils, and might indicate that Thylacoleo was much like a cat in primarily dining on flesh and viscera, leaving bones mostly intact.

At different times, off and on between 140,000 and 51,000 years ago, Thylacoleo apparently used the cave as a refuge. And from where the claws marks are situated among the inclines and boulders, it seems that these predators had qualms about taking difficult routes through the dark. “Many claw marks within TEC are located on steep surfaces, despite more gradual inclines being available on other sides of the central rock pile and boulder,” Arman and Prideaux write, and the entrance to the cave itself appears to have been a steep deadfall for other creatures. This suggests that Thylacoleo was a skilled and confident climber, clambering in and out of a cave that trapped other species. And if Thylacoleo could haul itself around rocky caves, it could almost certainly scale trees.

Humans undoubtedly saw Thylacoleo. The mammal was still very much alive when people arrived on Australia around 50,000 years ago, and there may even be Pleistocene art of the mammal. The mythical drop bear, however, didn’t appear as a tall tale until the 20th century, so there’s no link between what people actually saw and stories used to make tourists shudder at the sound of a creaking branch in the night. It’s convergence, but it’s a wonderful sort of convergence. So much of prehistoric life was so strange that we could have never imagined those species if we hadn’t come across their remains. The drop bear is a rare case when our species, in jest, stumbled upon something real and just as scary as our  imaginations can muster.

Bonus: In response to a piece I wrote for Slate about real creatures that could inspire Hollywood monsters, artist Ted Rechlin made this wonderful poster for a Drop Bear movie starring Thylacoleo.

Reference:

Arman, S., Prideaux, G. 2016. Behaviour of the Pleistocene marsupial lion deduced from claw marks in a southwestern Australian cave. Scientific Reports. doi: 10.1038/srep21372

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This Animal Tears Its Face Off to Open Its Mouth

There’s a small, tentacled freshwater animal called a hydra, whose mouth disappears every time it closes.

I really mean that: it disappears. When your mouth closes, the two halves are still distinct. No matter how tightly you purse your lips together, they’re still separate bits of flesh. The same is true for the enormous mouths of whales and the tiny ones of mice, the beaks of birds and the expandable jaws of snakes. But not a hydra—its closed mouth fuses shut to form a continuous, sealed sheet. In the words of one scientist,  “when a hydra closes its mouth, it obliterates it.”

Which means that whenever a hydra opens its mouth, it must tear itself apart.

In Greek mythology, Hydra was a venomous, many-headed snake monster with amazing powers of regeneration. Real hydras… aren’t actually that far off. They’re small and not that terrifying, but their shape—a tubular body crowned by wavy tentacles—recalls the beast of mythology. Like their cousins, the jellyfish, sea anemones, and corals, they’re armed with stinging cells that fire venomous harpoons. And they do regenerate with incredible skill; some biologists have even suggested that they’re effectively immortal.  They are amazing creatures, which feature (along with their microbes) in my upcoming book, I CONTAIN MULTITUDES. But until recently, I had no idea about their weird mouths.

Hydra viridissima.
Hydra viridissima.
Frank Fox CC BY-SA 3.0

In the 1970s, scientists saw that hydras can open their mouths wider than the diameter of their own bodies, allowing them to swallow prey far larger than themselves. They also noticed that the mouth seemed to disappear whenever it closed. They couldn’t see it, not even with powerful microscopes.

In 1987, Richard Campbell from the University of California, Irvine discovered why: a hydra mouth is not a permanent opening. It constantly forms and vanishes. When it closes, a wide ring of cells around the edge of the mouth collapses into a small mound called a hypostome, with a rosette of 6 to 12 cells at its centre.  These cells are stapled together by small junctions, so that not even a tiny pore remains between them.  In many ways, Campbell wrote, closing the mouth is very much like healing a wound.

When a hydra opens its mouth, these rosette cells slowly stretch and flatten over a minute or so. Finally, a small rupture appears between them. As soon as this happens, the mouth quickly snaps open. Within half a second, a gap that extends between two or three cells becomes a gaping maw with hundreds of cells around its margin.

Campbell described this process in huge detail using careful microscopy but there was still a lot he didn’t understand. Now, three decades later, Eva-Maria Collins from the University of California, San Francisco has discovered more about this process, by studying genetically engineered hydra that have glowing molecules in their heads.

Hydra’s hypostome contains contractible filaments called myonemes, which are arranged in rings and spokes, much like a spider web. Collins proved that the mouth opens when the spokes contract, and presumably closes when the rings do. (A similar process dilates and constricts the pupils in your eyes.) Her team also showed that the cells around the opening mouth don’t rearrange themselves, as Campbell suggested. Instead, they just change shape, becoming longer and narrower to accommodate the creature’s widening gape.

Of course, none of this explains why the hydras have evolved such a weird way of opening and closing their mouths. Slaying the mythical Hydra was the second of Hercules’ great labours. And understanding the biology of real hydras is proving to be no less a feat.

Prehistoric Animal Bit Like a Sabercat, Crunched Like a Bear

The skull of Kolponomos, with jaw muscles in red. From Tseng et al., 2016.
The virtual skull of Kolponomos, with jaw muscles in red. From Tseng et al., 2016.

Stroll through any museum hall well-stocked with fossil mammals and it’s tempting to look at the extinct beasts as variations on familiar themes. There’s a sloth, but bigger. There’s a camel, but smaller. I guess that weirdo in the corner looks something like a pig. We shove the remains of the extinct into expectations of the familiar even if the fit isn’t particularly good. And that’s a shame. Fossil mammals were stranger than we often give them credit for, and they often behaved in ways that no modern animal does. Just look at Kolponomos.

In the wide spread of the mammal family tree, Kolponomos was a carnivoran. That’s the group that includes cats, seals, bears, civets, and the dog snoring on the couch next to me as I write this. From there the phylogenetic haze sets in, however, with the 20 million-year-old Kolponomos fitting in somewhere around bears and their extinct relatives the bear-dogs, but not really belonging to either line. Regardless of which group can claim Kolponomos, however, what makes this beast so strange was the way it fed. This almost-bear bit like a sabertoothed cat, crunching mollusks in grizzly-like jaws studded with otterish teeth.

The idea that Kolponomos fed on shellfish has been around for a while. The mammal has been found in marine rocks from Oregon, Washington, and possibly Alaska, and the cheek teeth of these fossils show extreme wear from a diet of hard foods. In fact, Kolponomos so regularly dined on clams and mussels that the blocky crushing teeth are often “lakes” of softer dentine with the harder enamel fencing them in. Yet no one had tested this idea, nor how Kolponomos went about prying its food up from rocky shores. Now paleontologist  Jack Tseng and colleagues have finally looked Kolponomos in the mouth.

A restoration of Kolponomos by
A restoration of Kolponomos by Ken Kirkland.

From the anatomy of the shoreline mammal’s jaws, Tseng and coauthors expected that it shared a habit in common with saber-toothed cats. The front of the jaw in Kolponomos is deep and buttressed, giving it a prominent chin just like the famous sabercat Smilodon. In the cats this condition is thought to reflect an attack strategy of anchoring the head with the lower jaw and then using the leverage to drive the famous canines through their prey with a powerful contraction of neck muscles. Kolponomos was no sabertooth, but Tseng and coauthors thought that the mammal could have used the same strategy to detach mollusks from their beds.

To find out, Tseng and colleagues took a multi-pronged approach involving virtual models of Kolponomos, Smilodon, and five other carnivorans to examine bone stress during simulated bites and compare shape, adding examination of tooth wear patterns to see how the hypothesis held up. What they found was that Kolponomos fed like no mammal alive today.

Kolponomos bite sequence. Courtesy Jack Tseng.
Kolponomos bite sequence. Courtesy Jack Tseng.

Tseng and coauthors were on the mark with their Smilodon suspicion. Despite being distant relatives and feeding on entirely different prey, the lower jaws of both Kolponomos and Smilodon were extremely similar in their anatomy, shape, and response to anchor bite stress. The anchor bite was the key. More than that, the researchers found that even though the teeth of Kolponomos resemble those of sea otters the crushing portion of the extinct mammal’s jaw was actually much more like that of a bear in being stiffer but with less mechanical efficiency. Otters show the opposite condition, indicating that there’s more than one way for a carnivoran to be a shell-crusher as far as lower jaws are concerned. This makes the jaws of Kolponomos a multitool, the front strengthened for prying up shellfish and the back stiffened to crush through those defenses.

So if you were to visit coastal Washington about 20 million years ago, you might have seen something almost like a bear, but not quite like a bear, ambling along the rocky shorelines. Sniffing out a shellbed, the burly carnivore opens its jaws to jam its lower teeth into the colony of clams, biting and jerking its neck. The first shove doesn’t work, but the beast bites again and with another spasm the clam comes free with an audible pop and a little arc of spray as Kolponomos tosses its head back. There’s no hope for the bivalve now – with a swipe of its tongue the mammal shoves the snack to its cheek, and you can hear the shell give way beneath molars flattened through repetition. A quick swallow and the mammal’s snout is back in the shallows, ready to pry out another morsel as well as our preconceived notions about what fossil mammals were really like.

Reference:

Tseng, Z., Grohe´, Flynn, J. 2016. A unique feeding strategy of the extinct marine mammal Kolponomos: convergence on sabretooths and sea otters. Proceedings of the Royal Society B. doi: 10.1098/rspb.2016.0044

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Amazing Video Reveals Why Roaches Are So Hard to Squish

No door will stop them: American cockroaches can squeeze through a space just three millimeters high.
No door will stop them: American cockroaches can squeeze through a space just three millimeters high.
Photo Credit Tom Libby, Kaushik Jayaram and Pauline Jennings. Courtesy of PolyPEDAL Lab UC Berkeley

 

Have you ever stomped a roach, just to have it skitter away unscathed?* Or seen one disappear into an impossibly small crack?

Now scientists have figured out how they do that, and the results are terrifying.

The American cockroach (Periplaneta americana, aka “the big ones”) can squeeze through a crack the height of two stacked pennies in about a second—a fact newly discovered by two brave scientists who are probably still seeing roaches squeezing under the doors of their nightmares.

See for yourself:

Not only can roaches fit through tight spaces by flattening their flexible exoskeleton and splaying their legs to the side, the researchers found, they can keep running nearly as fast while squished, the team reports Monday in the Proceedings of the National Academy of Sciences. (In roach terms, top speed is 1.5 meters, or 50 body lengths, per second. Scaled up, that’s equivalent to a human running 200 miles per hour.)

Robert Full and Kaushik Jayaram at Berkeley built tiny tunnels and used a roach-squishing machine to test the animals’ limits. (No roaches were harmed—Full says “we only pushed them to 900 times their body weight, and they could still do that without being hurt.” In fact, they ran just as fast afterward.)

“We find them just as disgusting and revolting as everybody else,” Full says. But he also thinks they’re amazing, and is designing roachy robots that can squeeze and scuttle just like the real thing. The robots take inspiration from roaches’ jointed exoskeletons, with a design similar to folded origami.

A new compressible robot, nicknamed CRAM, is inspired by the flexible yet tough cockroach.
A new compressible robot, nicknamed CRAM, is inspired by the flexible yet tough cockroach.
Photograph by Tom Libby, Kaushik Jayaram and Pauline Jennings. Courtesy of PolyPEDAL Lab UC Berkeley

Full sees roaches and other arthropods—insects, spiders, and the like—as the next big thing in robots inspired by nature. Unlike other soft robots inspired by worms or octopuses, insect-bots with hard exoskeletons and muscles could run fast, jump, climb, and fly, while still remaining flexible.

“We know that cockroaches can go everywhere. They’re virtually indestructible,” Full says. For roaches, being able to scuttle quickly through small spaces has allowed them to spread into virtually every habitat imaginable and outrun their competition. Other insects probably have their own versions of these super-squishing superpowers, too, he says.

(For more on the positive side of roaches, learn why cockroaches made it onto our list of “All-Star Animal Dads.”)

The new roach study “transformed how I view a seemingly ‘hard’ animal,” says Daniel Goldman of Georgia Tech, who studies the physics of animal movement.  

“Their idea to create a “soft” robot out of deformable “hard” parts is great, and should transform how we think of creating all-terrain robots,” Goldman says.


*If you would never, ever, stomp on a roach, and are horrified at the suggestion, you’re a kind person and a sensitive soul. Keep watching the video though—it may surprise you.

Paleo Profile: Alcide d’Orbigny’s Dawn Beast

From de Muizon et al., 2015.
The nearly-complete skeleton of Alcidedorbignya inopinata. From de Muizon et al., 2015.

Vertebrate paleontology has a sample size problem. Only a fraction of all the creatures that ever lived became preserved in the fossil record, and an even tinier sliver of that array has been discovered, cleaned, and studied. Even the most famous animals, like the fearsome Tyrannosaurus, are known from a (figurative) handful of individuals scattered through swaths of rock spanning a million years or more. Finding enough fossils to even start to pick at the biology of an extinct species is a tall order.

But every now and then paleontologists strike just the right spot. One such locality, near Tiupampa, Bolivia, is simply known as “The Quarry”, but don’t be fooled by the lackluster name. This is one of the best places in the world to find the skeletons of the mammals that thrived just a million years after a wayward asteroid closed the Age of Reptiles for good, and, as paleontologist Christian de Muizon and colleagues report in a massive monograph, this place has supplied an exquisite record of one of the earliest placental mammals to skitter around in the end-Cretaceous aftermath.

de Muizon and Larrry Marshall named the mammal Alcidedorbignya inopinata in 1992. Back then, it was mostly known from teeth and pieces of jaw. But in the years since the initial finds paleontologists have uncovered a nearly-complete skeleton, several partial skulls, and hundreds of other scattered elements. With all this new material, de Muizon and colleagues set about piecing together this dawn beast in greater detail than possible before.

There’s not an exact modern equivalent for what Alcidedorbignya was. It was a tiny member of a totally-extinct group of mammals called pantodonts that thrived in the earliest days of the Paleocene. And unlike its larger relatives, Alcidedorbignya was a nimble little beast that was probably adept at running through the trees as well as scampering around on the ground, able to stand up on its hind legs to have a look around or grab a morsel when necessary. The restoration of the mammal by Justine Jacquot-Haméon makes me think “cat squirrel” isn’t too far off, although the beast wasn’t closely related to either.

What’s still unclear is what led so many Alcidedorbignya to become buried in the same place. Especially strange is that The Quarry has yielded 33 jaws of juvenile animals and 35 jaws from adults, raising the prospect that these were gregarious mammals or that the youngsters hung around with their parents. Were these mammals social, or did the a local flooding event hit at just the wrong time of the year, taking out the next generation as well as their parents? The case remains open. With so many bones of Alcidedorbignya to compare and scrutinize, though, this little mammal offers one of the best chances we have to envision the world just after it was freed from the claws of the “terrible lizards.”

Caption
Alcidedorbignya in its Paleocene environment. Art by Justine Jacquot-Haméon.

Fossil Facts

Name: Alcidedorbignya inopinata

Meaning: The genus name honors French naturalist Alcide d’Orbigny.

Age: About 65 million years old.

Where in the world?: Tiupampa, Bolivia.

What sort of critter?: A pantodont, one of the mammals that proliferated after the demise of the non-avian dinosaurs.

Size: About the size of a large squirrel.

How much of the creature’s body is known?: Multiple fossils including a nearly-complete skeleton, at least three juvenile skulls, several hundred dental specimens, and more.

Reference:

de Muizon, C., Billet, G., Argot, C., Ladevèze, S., Goussard, F. 2015. Alcidedorbignya inopinata, a basal pantodont (Placentalia, Mammalia) from the early Palaeocene of Bolivia: anatomy, phylogeny, and palaeobiology. Geodiversitas. doi: 10.5252/g2015n4a1

Previous Paleo Profiles:

The Unfortunate Dragon
The Cross Lizard
The South China Lizard
Zhenyuan Sun’s dragon
The Fascinating Scrap
The Sloth Claw
The Hefty Kangaroo
Mathison’s Fox
Scar Face
The Rain-Maker Lizard
“Lightning Claw”
The Ancient Agama
The Hell-Hound
The Cutting Shears of Kimbeto Wash
The False Moose
“Miss Piggy” the Prehistoric Turtle
Mexico’s “Bird Mimic”
The Greatest Auk
Catalonia’s Little Ape
Pakistan’s Butterfly-Faced Beast
The Head of the Devil
Spain’s Megatoothed Croc
The Smoke Hill Bird
The Vereda Hilarco Beast
The North’s Sailback
Amidala’s Strange Horn
The Northern Mantis Shrimp
Spain’s High-Spined Herbviore
Wucaiwan’s Ornamented Horned Face

How Jaguars Survived the Ice Age

A jaguar at the St. Louis Zoo. Photo by Brian Switek.
A jaguar at the St. Louis Zoo. Photo by Brian Switek.

The mastodons, ground sloths, and sabercats are all gone. They all slipped into extinction around 10,000 or so years ago, along with an even wider variety of fantastic beasts and birds that fall under the category “megafauna.” But not all the Ice Age megamammals died out. We spend so much time mourning the losses that we often forget the survivors that carry whispers of the Pleistocene world. Among these resilient beasts is the jaguar.

Jaguars are old cats. They first evolved in Eurasia sometime around three million years ago before spreading both west and east, eventually inhabiting a range from southern England to Nebraska and down into South America. Today’s range of southern Arizona to Argentina—over 3.4 million square miles—is only a sliver of their Ice Age expansion. And it wasn’t just the jaguar’s range that shrunk. Today the spotted cats are about fifteen percent smaller than their Pleistocene predecessors.

Nevertheless, jaguars survived while the American lion, the sabercats, and other predators vanished. How? In order to investigate this question, biologist Matt Hayward and colleagues looked at the jaguar diet and how the cat’s prey preferences changed over time.

Drawing from 25 published studies documenting 3,214 jaguar kills, Hayward and coauthors found that jaguars are pretty finicky for apex predators. The big cat’s menu spans 111 species—ranging from cattle to rodents to monkeys to turtles—but, contrary to what has often been written about the cat, the jaguar is not really a generalist that hunts anything and everything.

The most common parts of the jaguar diet, Hayward and colleagues found, are capybara, wild pig, caiman, collared peccary, nine-banded armadillo, giant anteater, and white-nosed coati. These species account for 16-21% of the jaguar diet. The stats also showed that prey including peccaries, brocket deer, giant anteaters, and coatis which were hunted 85% of the time when they were present in the jaguar’s range. Crunching the numbers a bit further, the zoologists found that jaguars seemed to especially target capybara and giant anteater. On the other hand, jaguars never preyed upon tapirs and almost never touched primates.

Jaguars come out of all this as a paradox. They are burlier than leopards, yet they prefer to hunt a narrow range of prey that falls in the shallow end of what jaguars should be able to tackle. This might have something to do with why the cats have shrunk. Jaguars aren’t large enough to take on tapirs alone, yet human hunting on mid-range prey—such as deer—has made such herbivores too rare to rely upon. So despite their size, jaguars responded by picking out smaller prey which Hayward and coauthors dub “suboptimal” for what the cats initially evolved to do.

The jaguar’s not alone in this. Coyotes have gone through similar changes. The scrappy canids are Ice Age survivors, too, and they were significantly larger during the Ice Age. When all their competition disappeared, coyotes became smaller and ended up living on the fringes in a world heavily influenced by humans.

Flexibility made all the difference for these carnivores. Even though jaguars no longer prowl as much of the world as they once did, and are currently listed as “near threatened” on the IUCN Red List, they were able to persist where so many other carnivores perished by shifting their diets. “It may be that jaguars survived this mass extinction event by preferentially preying on relatively small species,” Hayward and coauthors write. The fossil record of cougars tells a similar story: By eating parts of carcasses other cats didn’t want, mountain lions were able to survive the tough times. And even though the cause of the loss of many Ice Age celebrities remains debated, the survivors are truly the animals we should be looking at in greater detail. How they succeeded may hold the secrets to why so many other species failed.

Reference:

Hayward, M., Kamler, J., Montgomery, R., Newlove, A., Rostro-García, S., Sales, L., Van Valkenburgh, B. 2016. Prey preferences of the jaguar Panthera onca reflect the Post-Pleistocene demise of large prey. Frontiers in Ecology and Evolution. doi: 10.3389/fevo.2015.00148

AUV Shows What Great White Sharks Do All Day

A great white shark off Guadalupe Island. Photo by Terry Goss, CC BY 2.5.
A great white shark off Guadalupe Island. Photo by Terry Goss, CC BY 2.5.

No creature has a reputation more fearsome than the great white shark. Despite all we’ve learned about them, including how they really don’t have much interest at in all eating us, movies and basic cable documentaries still show them as “machines” that do little more than “swim and eat and make little sharks.” And that’s not to mention the various video games where your goal as a great white is to chomp everything in sight in as little time as possible.

But what do great white sharks really do all day? It’s easy for the mythology of these predators to overshadow their real biology because it’s difficult to spend an extended amount of time following and observing animals that live beneath the waves and can cross entire oceans. We mostly see these burly sharks when they’re near the surface, and, while ingenious, strategies like Crittercam have literally been limited in scope and what can be recorded. That’s why shark researcher Gregory Skomal and colleagues turned to a different technology to see what the great fish are up to.

Thanks to documentaries and celebrity sharks like “Deep Blue“, Guadalupe Island off the coast of Mexico has become known as a great white hotspot. Yet, despite the abundance of sharks and observers – including cage divers – in the area, no one has seen how these sharks go about getting their meals. At locales off California and South Africa great white sharks make the most of their natural countershading to hide their outline against the bottom while looking up to the surface for seals to surprise. Some propel themselves with such power that they actually launch themselves out of the water in the process. But no one has seen behavior like this at Guadalupe Island.

The great white sharks of Guadalupe Island feed on the fur seals, elephant seals, and sea lions that loll about in the shallows there. Sharks have been seen feasting on the blubbery mammals at the surface. But the initial strikes have never been seen. Given the waters around Guadalupe Island rapidly drop off from the shoreline, Skomal and coauthors write, some researchers expect that the sharks are attacking their prey at depth and follow the carcass up the water column as it bobs to the surface.

To find out, the ichthyologists turned to an autonomous underwater vehicle or AUV. It looks like a shark-seeking torpedo, except with cameras and scientific equipment rather than explosives. So after tagging a shark with a device that would allow the researchers to follow the location of the fish remotely, the researchers launched the AUV to follow the shark and hopefully catch one in pursuit of mammalian prey.

Unfortunately, none of the four sharks actively tracked in the study felt particularly peckish. Or, at least, the AUV couldn’t see it. Some of the predators dove much deeper than the limits of the AUV, sometimes spending the bulk of their tracked time down below. But Skomal and colleagues propose that they were able to catch a different sort of predatory behavior on camera.

Sharks testing out the AUV. From Skomal et al., 2015.
Sharks testing out the AUV. From Skomal et al., 2015.

Even though the team actively tracked four sharks over six sessions, the cameras picked up at least eight other great white sharks in the area. Some of these sharks apparently didn’t take too kindly to the AUV. Altogether, great white sharks approached the AUV 17 times, bumped it four times, and bit it nine times. These interactions sometimes went beyond gentle, exploratory mouthings. During one mission, the tracked shark was down near the bottom while another swam up from below and behind and bit the AUV for 11 seconds, returning to bite it four more times over the next eight minutes. Then a different shark came by a half an hour later and chomped the device so hard that she breached the AUV’s hull.

Being that none of us know the mind of a shark, it’s difficult to say for sure what these fish were doing. Were they truly considering the AUV as prey, or were they frustrated with the buzzing oddity making a ruckus on their turf? There may not be a conclusive answer, but Skomal and coauthors argue that at least some of these sharks were biting to kill. When great whites fight they tend to bite each other around the pectoral fins and heads, but they tend to target the rear of creatures they aim to eat – biting off the rear flippers is one way to immobilize a seal. The fact that most of the sharkbite damage to the AUV was to the rear suggests that the sharks were trying to use the same strategies they employ to kill seals, regardless of what their motivation was.

But it’s not as if all the sharks in the area immediately descended on the AUV to snap it in half. For the most part, the observed sharks just… swam around. They followed the coast, dove deep for a while, swam by other sharks, and just generally propelled their bulk through the water with swishes of their crescent-moon tails. Some were even curious about the AUV, popping up and down from deeper water to investigate the weird object. In a mammal, we’d probably have no qualms about calling this curiosity. So even though the researchers didn’t exactly get what they were hoping for, they picked up something different – the mostly-peaceful and inquisitive ramblings of some of the greatest predators in the sea.

Reference:

Skomal, G., Hoyos-Padilla, E., Kukulya, A., Stokey. R. 2015. Subsurface observations of white shark Carcharodon carcharias predatory behavior using an autonomous underwater vehicle. Journal of Fish Biology. doi: 10.1111/jfb.12828

What Hyena Giggles Really Say

A spotted hyena in Kenya. Photo by Liaka ac, CC BY-SA 2.0.
A spotted hyena in Kenya. Photo by Liaka ac, CC BY-SA 2.0.

Spotted hyenas may be the chattiest carnivores on the planet. They whoop, rumble, low, and laugh, announcing their presence wherever they go. But what do all these calls mean?

Zoologist Kay Holekamp laid out the spotted hyena repertoire in a 2011 New York Times field journal. So far as we humans are able to understand, each category of call carries a general meaning that can be modulated by the sender to varying effect. Spotted hyenas low when they want to team up, “alarm rumble” to raise a red flag to approaching danger, and groan to greet cubs at a den, who then “squitter” to demand milk from mom. And their trademark giggle? That’s nervous laughter. Spotted hyenas usually titter when they’re being attacked, harassed by another member of their clan, or frustrated.

But there are more details embedded in hyena calls than we usually pick up on. In a 2007 study, Holekamp, Kevin Theis, and colleagues reported that spotted hyena whoops – their haunting, long-distance calls – reflect details about the age, and sometimes sex, of the hyena sending the signal. By looking at the acoustic details of 117 whoop bouts from 60 different hyenas, the researchers were able to discern that whoops become deeper with age and that the calls of non-juvenile males and females could be distinguished from each other (perhaps because the larger females have bigger chests that give them a deeper pitch). If you were a hyena, your whoop would carry essential information about who you are.

Mother hyenas grunt to draw their cubs out, and those cubs "squitter" to beg for milk. Photo by Budgiekiller, CC BY-SA 2.5.
Mother hyenas grunt to draw their cubs out, and those cubs “squitter” to beg for milk. Photo by Budgiekiller, CC BY-SA 2.5.

A hyena’s giggle is even more distinctive. A 2010 study by Nicolas Mathevon and colleagues on 695 giggles made by the University of California, Berkeley’s captive hyena clan (shuttered last year, sadly) found that the carnivore’s characteristic laugh carried cues about the sender’s age, status in the clan, and perhaps individual identity. This is all critical information for a social predator. If you’re going to work as a group, you need to know who’s talking as well as what’s being said.

And while some of these details might be lost on other species, hyena chatter can carry critical information for their carnivorous neighbors. Cheetahs, zoologist Sarah Durant discovered through playback experiments, will leave an area if they hear the sounds of lions or hyenas. In fact, Durant observed, the sleek cats were even less likely to go on the hunt after hearing the calls from their competitors. What was the point of bringing down dinner if a hyena might swoop in and steal it?

Lions are another matter. Despite their regal reputation, these burly felids often play the part of kleptoparasites. Lions have no qualms about bullying weaker carnivores off their kills, and, as argued by Hugh Webster and colleagues after playback experiments, lions will eavesdrop on the calls of other species to zero-in on an easy meal. Wild dog calls always generated interest, the researchers found, but male lions or mixed groups of male and female lions would also approach spotted hyena vocalizations in the hope of some grub on the go. At least hyenas can mitigate the risk of losing their lunch. One population in Zimbabwe started traveling in mid-size groups, rather than forming large foraging parties, in response to an influx of lions.

Short of a Babel fish, we’ll never be able to translate hyena giggles down to the level of “Hey! That’s my wildebeest leg!” or “Get lost, you mangy lion!” But hyenas don’t need the broadened vocabulary we have to keep their clans together. Their set of a dozen or so calls seems to suit them fine, with each hyena adding their own unique voice to the chorus.

References:

Durant, S. 2000. Living with the enemy: avoidance of hyenas and lions by cheetahs in the Serengeti. Behavioral Ecology. doi: 10.1093/beheco/11.6.624

Mathevon, N., Koralek, A., Weldele, M., Glickman, S., Theunissen, F. 2010. What the hyena’s laugh tells: sex, age, dominance and individual signature in the giggling call of Crocuta crocuta. BMC Ecology. doi: 10.1186/1472-6785-10-9

Theis, K., Greene, K., Benson-Amram, S., Holekamp, K. 2007. Sources of variation in the long-distance vocalizations of spotted hyenas. Behaviour. doi: 10.1163/156853907780713046

Webster, H., McNutt, J., McComb, K. 2010. Eavesdropping and risk assessment between lions, spotted hyenas, and African wild dogs. Ethology. doi: 10.1111/j.1439-0310.2009.01729.x

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Tool-Using Parrots Use Pebbles to Grind Seashells

In the spring of 2013, Megan Lambert noticed the greater vasa parrots of Lincolnshire Wildlife Park doing something odd. They looked like they were licking the cockle shells that lined the floor of their outdoor enclosure. But when Lambert looked closer, she noticed that they were holding a pebble or date pit in their beaks, and rubbing these against the shells.

They were using tools.

Several birds can use tools. Woodpecker finches prise grubs from wood with twigs, New Caledonian crows do the same, Egyptian vultures drop rocks onto eggs to crack them open, and rooks can raise the water level of a pitcher by dropping stones into it, Aesop-style. But among the 300 species of parrot, tool use is relatively rare. Black palm cockatoos use rocks to drum on tree trunks, while hyacinth macaws use sticks to prise open nuts. The kea, a delightfully mischievous New Zealand parrot, can use and make tools in the lab, but no one knows if they do so naturally.

Thanks to Lambert’s observations, the greater vasa parrot joins this exclusive club. Native to Madagascar, the greater vasa is a bit of a goth parrot, eschewing the vibrant hues of its relatives in favour of black and dark grey plumage. They’re sociable and inquisitive, and will often explore and manipulate objects in captivity; while watching them, Lambert saw one thread a twig through the open links of a chain. That seemed like play. By contrast, the thing with the seashells was probably more purposeful.

Seashells are made of calcium carbonate, and birds need calcium to build the shells of their eggs. Lambert thinks that the vasas were using the pebbles and pits to grind down the cockles and liberate the calcium within them. Other egg-laying animals, including sandwich terns and gopher tortoises, have been seen eating seashells, presumably for the same reason. But the vasas are the only ones known to process the shells. “That’s particularly interesting because humans are the only other animals known to use tools for grinding,” says Lambert.

But if that’s the case, why is it that only male parrots ground the seashells? If they’re trying to get at calcium for egg-laying, surely the females should be at it? Possibly, but during courtship and sex, vasa males spend a lot of time feeding females with regurgitated meals. Perhaps the calcium content of those fluids is a signal of the male’s quality as a mate?

Regardless, the behaviour is certainly common. Over a few months, Lambert saw all ten of the park’s greater vasa parrots interacting with the seashells, and at least five of them grinding the shells with pebbles or pits. One particular bird, a male named JD, was an especially prolific tool-user.

He was also a prolific tool-donor. On 16 occasions, Lambert saw one of the female parrots nicking a tool from another—usually JD, who tolerated the “theft”. “It’s quite unique that tools are transferred directly between birds, as this is not commonly observed in the animal kingdom and may provide clues as to how this behaviour came about in the first place,” says Lambert.

So far, Lambert and her colleagues haven’t done any experiments with the parrots, which leaves a lot of unanswered questions. Do the birds learn to use the tools themselves, or do they pick it up from their peers? What’s the purpose of the behaviour, and does it actually influence the birds’ reproductive success? Do the parrots grind seashells, or use other tools, in the wild? And what else are these animals capable of?

When Lions Abound, Hyenas Pick a New Menu

Hyenas and a jackel at a lion kill in Kenya. Photo by Roger Smith,
Hyenas and a jackal at a lion kill in Kenya. Photo by Roger Smith, CC BY-NC 2.0.

For as long as there have been lions and spotted hyenas, the carnivores have competed with each other. The gore-flecked conflicts over carcasses on the African grassland are just the latest skirmishes in a carnivoran competition that has been going on since the Pleistocene.

I root for the hyenas. There’s something strangely charming about the tittering predators, and their dining habits are incredibly flexible. Despite their public image as desperate scavengers, clans of hyenas are capable of taking down prey as large as juvenile elephants as well as reducing carcasses to piles of splinters with their exceptionally powerful jaws. This combination of skills has allowed them to thrive in lands stalked by their Ice Age competitors. As Stéphanie Périquet and colleagues have found during a long-term study of hyenas in Zimbabwe’s Hwange National Park, when too many lions are around the hyenas simply change what’s on the menu.

The new study came out of observations of the park’s hyenas carried out between 1999 and 2013. And it was during the later part of this span, between 2005 and 2008, that lions made a minor comeback. A ban on lion trophy hunts around the park borders let the big cats proliferate and prowl the park in greater numbers than before, coming into greater competition with hyenas. You can see it in what the hyenas ate.

Over two study periods – one before and one during the lion surge – researchers followed groups of hyenas as they foraged and collected scat for analysis of the prey remnants inside. (The process for this latter effort involved soaking each turd in water and bleach for thirty minutes in a nylon stocking to extract the hairs inside, sun-drying those contents, and picking through them to match hair to prey species.) What the zoologists found didn’t match their expectations.

During the first period, when there were fewer lions, the hyenas focused on hunting mid-size and large prey like zebra, kudu, and buffalo, supplemented by smaller species. Périquet and coauthors thought that competition with lions would drive hyenas to focus on small prey. That way the hyenas could finish their meals before lions would have a chance to find them and steal the carcasses. Instead, however, the zoologists discovered that hyenas started traveling in mid-sized groups and started to avoid hunting zebra and kudu in favor of feasting on elephant and giraffe carcasses.

The strong jaws of spotted hyenas make them adept at both hunting and processing carcasses. Photo by Brian Switek.
The strong jaws of spotted hyenas make them adept at both hunting and processing carcasses. Photo by Brian Switek.

These changes were not in proportion to the availability of prey species. The number of giraffes actually declined between the two study periods, yet the hyenas were consuming giraffe more often. Lions may have been inadvertently supplying them. While the hyenas likely killed some of the giraffes, other times the carnivores acted as scavengers. This didn’t necessarily involve running the cats off their kills. Even when they pick a body “clean”, lions still leave a wealth of meaty morsels and marrow-filled bones on a carcass. All hyenas have to do is show up as a clean-up crew.

The scavenging shift may be attributable to the way hyenas hunt. Hyenas are pretty noisy when taking down prey, Périquet and colleagues note, and this makes it all the easier for lions to find them and snatch their kills away. By traveling in smaller groups and hunting less the Hwange National Park hyenas were able to go dark and avoid risking fights with enraged lions.

And the change worked. The hyena population, Périquet and coauthors note, remained stable even as lions moved in. Hyenas didn’t go from apex predators to dangling at the bottom of the food chain. Their magnificent jaws offered them another option, giving them plenty of reason to laugh at those pushy lions.

Reference:

Périquet, S., Valeix, M., Claypole, J., Drouet-Hoguet, N., Salnicki, J., Mudimba, S., Revilla, E. Fritz, H. 2015. Spotted hyaenas switch their foraging strategy as a response to changes in intraguild interactions with lions. Journal of Zoology. doi: 10.1111/jzo.12275

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How a 5-Ounce Bird Stores 10,000 Maps in Its Head

It weighs only four or five ounces, its brain practically nothing, and yet, oh my God, what this little bird can do. It’s astonishing.

Photograph by Diana Tomback
Photograph by Diana Tomback

Around now, as we begin December, the Clark’s nutcracker has, conservatively, 5,000 (and up to 20,000) treasure maps in its head. They’re accurate, detailed, and instantly retrievable.

A Clark's nutcracker with a thought bubble full of maps
Photograph by Glenn Bartley, Alamy; Maps courtesy of jaffne, Flickr; GIF by Becky Harlan

It’s been burying seeds since August. It’s hidden so many (one study says almost 100,000 seeds) in the forest, meadows, and tree nooks that it can now fly up, look down, and see little x’s marking those spots—here, here, not there, but here—and do this for maybe a couple of miles around. It will remember these x’s for the next nine months.

How does it do it?

32 Seeds a Minute

It starts in high summer, when whitebark pine trees produce seeds in their cones—ripe for plucking. Nutcrackers dash from tree to tree, inspect, and, with their sharp beaks, tear into the cones, pulling seeds out one by one. They work fast. One study clocked a nutcracker harvesting “32 seeds per minute.”

These seeds are not for eating. They’re for hiding. Like a squirrel or chipmunk, the nutcracker clumps them into pouches located, in the bird’s case, under the tongue. It’s very expandable …

Drawing of one clark's nutcracker bird without seeds in its cheeks, and another clark's nutcracker with its cheeks full of seeds
Drawing by Robert Krulwich

The pouch “can hold an average of 92.7 plus or minus 8.9 seeds,” wrote Stephen Vander Wall and Russell Balda. Biologist Diana Tomback thinks it’s less, but one time she saw a (bigger than usual) nutcracker haul 150 seeds in its mouth. “He was a champ,” she told me.

Next, they land. Sometimes they peck little holes in the topsoil or under the leaf litter. Sometimes they leave seeds in nooks high up on trees. Most deposits have two or three seeds, so that by the time November comes around, a single bird has created 5,000 to 20,000 hiding places. They don’t stop until it gets too cold. “They are cache-aholics,” says Tomback.

When December comes—like right around now—the trees go bare and it’s time to switch from hide to seek mode. Nobody knows exactly how the birds manage this, but the best guess is that when a nutcracker digs its hole, it will notice two or three permanent objects at the site: an irregular rock, a bush, a tree stump. The objects, or markers, will be at different angles from the hiding place.

a drawing of clark's nutcracker looking at a tree stump and a mountain in the spring, with arrows pointing between the bird, the mountain, and the stump
Drawing by Robert Krulwich

Next, they measure. This seed cache, they note, “is a certain distance from object one, a certain distance from object two, a certain distance from object three,” says Tomback. “What they’re doing is triangulating. They’re kind of taking a photograph with their minds to find these objects” using reference points.

Psychologist Alan Kamil has a different view. He thinks the birds note the landmarks and remember not so much the distances, but the angles—where one object is in relation to the others. (“The tree stump’s 80 degrees south of the rock.”) These nutcrackers are doing geometry more than measuring.

a drawing of clark's nutcracker looking at a tree stump and a mountain in the rain, with arrows pointing between the bird, the mountain, and the stump
Drawing by Robert Krulwich

However they do it, when the snow falls and it’s time to eat, they’ll land at a site. “They will perch on a tree,” says Tomback, “on a low branch, [then light onto the ground, where] they pause, look around a bit, and they start digging, and in a few cases I’ll see them move slightly to the right or to the left and then come up again.”

She’s convinced that they’re remembering markers from summer or fall and using them to point to the X spot—and, “Lo and behold, these birds come up with their cracked seeds,” she says. “And it’s really pretty astounding.”

In the 1970s, Stephen Vander Wall ran a tricky little experiment. He shifted the markers at certain sites, so that instead of pointing to where the seeds actually were, they now pointed to where the seeds were not. Like this …

Picture of a clark's nutcracker standing between two X's and looking confused
Drawing by Robert Krulwich

And the birds, as you’d expect if they were triangulating, went to the wrong place.

But at sites where he left the markers untouched, the birds got it right. That’s a clue that each of these birds has thousands of marker-specific snapshots in their heads that they use for months and months. When the spring comes and the birds have their babies, they continue to visit old sites to gather seeds until their chicks fledge.

The mystery here, the deep mystery, is how do they manage to store so much data in their heads? I couldn’t possibly do what they do (I can’t even remember all ten digits in a phone number, so I’d be one very dead nutcracker in no time). Is their brain organized in some unique way?

Is their brain plastic? Can it grow more neurons or more connections when it needs to? Chickadees are also food hiders, and they do grow bushier brains when they need to, expanding in the “remember this” season and contracting afterward. Do Clark’s nutcrackers do that? We don’t know.

Whatever it is they do, I want what they’ve got.

Sabercats and Other Carnivores Kept the Ice Age World Green

A Smilodon angles to get a better bite on a sloth at the La Brea Tar Pits and Museum. Photo by Brian Switek.
A Smilodon angles to get a better bite on a sloth at the La Brea Tar Pits and Museum. Photo by Brian Switek.

The huge herbivores of the Ice Age were ecosystem engineers. Wherever they went, mastodons, sloths, bison, and their ilk changed the landscape by eating, defecating, trampling, and otherwise going about their plant-mashing business. But they were not isolated agents. Following out the engineer analogy, the megaherbivores of times past had managers. These were the sabercats, hyenas, wolves, and other predators past.

Many Pleistocene carnivores certainly look menacing enough. The long fangs of Smilodon have made it a staple of museum halls as well as schlock horror, and the thought of staring down a giant hyena is enough to send a shiver down my spine. So given that some prehistoric predators had such impressive weapons it’s not surprising that we’ve often imagined them setting into mammoths and other Ice Age giants. Bigger prey requires bigger cutlery, right?

Well, not quite. Many of the most iconic Ice Age herbivores were simply too big to kill. It’s the same reason why lions don’t chase after adult elephants. Clawing into a pachyderm is a high-risk scenario, even considering the fleshy reward, and fossil evidence has suggested the same pattern held in the Pleistocene. Smilodon didn’t take on adult mammoths and Megatherium, for example, but often targeted camels and bison instead. Large size was a refuge was most Pleistocene giants. But their offspring were a different story.

In a new study surveying the effects of large carnivores stalking the Ice Age landscape, University of California, Los Angeles paleontologist Blaire Van Valkenburgh and colleagues found that the young of many large Pleistocene herbivores would have been right in the sweet spot for hungry carnivores.

Part of the analysis involved sizing up the predators themselves. For starters, Van Valkenburgh and coauthors point out, not only were many extinct Pleistocene carnivores significantly larger than the predators that survived them, but each “carnivore guild” in the sample included a greater number of species in the past than comparable ecosystems today.

Even just looking at the felids, the researchers write, “nearly all Pleistocene predator guilds found outside of Australia included at least one and often two species of large sabertooth cat.” This pattern is directly related to the number of big herbivores there were to eat. Even in modern ecosystems, Van Valkenburgh and colleagues point out, the likelihood that three or more large carnivores might be present steadily increases. In addition to the herbivores creating more open habitat that give predators the opportunity to hide along the forested margins, there’s simply more meat to carve up.

Much of that flesh came in the form of juvenile giants. Even though we tend to think of adult specimens embodying any given fossil species, all prehistoric animals had to grow up. And just as with modern species – like the 74 juvenile elephants taken by lions over a four year period in Botswana – the little ones are vulnerable. Juveniles would have been even more at risk in the Ice Age, when apex predators were larger and there were far more of them.

Baby mastodon - like this one at the La Brea Tar Pits and Museum - would have been vulnerable until they reached about six years of age. Photo by Brian Switek.
Baby mastodon – like this one at the La Brea Tar Pits and Museum – would have been vulnerable until they reached about six years of age. Photo by Brian Switek.

Drawing from data on prey selection by modern carnivores, Van Valkenburgh and colleagues applied the same ecological arithmetic to the fossil record. While a solitary extant lion probably can’t capture even a two-year-old baby elephant, the paleontologists found, a lone Smilodon, Homotherium, cave lion, or other large cat would have been capable of hunting a baby mammoth or mastodon in the two-to-four-year-old range. (A sabercat den full of baby mastodon bones in Texas supports this contention.)  The chances of the Pleistocene predators only got better if they formed a pride, and social strategy was a boon to packs of wolves and clans of hyenas, too.

So while none of the Ice Age carnivores could have taken on an adult mammoth or mastodon, all of them – especially if they were social predators – were capable of tearing into the young. The big proboscideans would have been vulnerable until they were about six years old, which is a long time to have to be looking out for hungry eyes peering through the brush.

This is how the landscape was shaped by the subtle paw of the carnivores. Many paleontologists previously thought that Ice Age herbivores were too big to fail. That they existed at “saturation levels” because their size made them immune. But now Van Valkenburgh and coauthors have made a solid case that carnivores greatly influenced herbivore populations by preying on the young. This was violent, and even sad, but all a part of the constant ecological shuffle. Unchecked by carnivores, large herbivores can proliferate to destructive levels until they start eating themselves out of house and home. Smilodon, dire wolves, and other beasts of prey actually defended the plants – vegetation has no greater friend than a predator. That’s how large carnivores have been keeping the world green for millions of years , and I hope that our species can yield them the space to keep doing so.

Reference:

Van Valkenburgh, B., Hayward, M., Ripple, W., Meloro, C., V. Roth. 2015. The impact of large terrestrial carnivores on Pleistocene ecosystems. PNAS. doi: 10.1073/pnas.1502554112

 

Did Dakotaraptor Really Face Off Against Tyrannosaurus?

Dakotaraptor pulls feathers from Ornithomimus it killed. Art by Emily Willoughby.
Dakotaraptor pulls feathers from Ornithomimus it killed. Art by Emily Willoughby.

By now you’ve probably heard about the giant “raptor” uncovered in South Dakota. The dinosaur’s discovery came as quite a shock. For the past century Tyrannosaurus rex has dominated our imaginations as the sole apex predator of the Hell Creek Formation, but Dakotaraptor steini, as Robert DePalma and coauthors dubbed the dinosaurs, was large enough to compete for flesh with young tyrannosaurs.

With scenes from the Jurassic Park franchise still stomping through our imaginations, it’s tempting to pit packs of 18-foot-long Dakotaraptor against the heavyweight champion T. rex, mobbing the bulky carnivore off its kills. DePalma has suggested as much, calling Dakotaraptor “the most lethal thing you can possibly throw into the Hell Creek ecosystem.”

But before we get too carried away and start commissioning murals of giant raptors slashing the flesh of Tyrannosaurus Age of Reptiles style, it’s worth thinking about what the world of dinosaurs was really like.

The known elements of Dakotaraptor and a reconstructed skeleton. From DePalma et al., 2015.
The known elements of Dakotaraptor and a reconstructed skeleton. From DePalma et al., 2015.

Dakotaraptor ups the diversity of dinosaurs known from the Hell Creek Formation. It’s an increase of one new species. And finding a new species means that there must have been a population of these big dromaeosaurids running around that paleontologists have missed up until now. (Although the idea of cooperative raptor packs rests on only the barest sliver of evidence right now.) But this doesn’t mean that where there was Tyrannosaurus, Dakotaraptor followed. What I’m getting at is a concept ecologists call species evenness.

Let’s take an avian dinosaur’s-eye view of the big Hell Creek Formation carnivores. We’ll cover Tyrannosaurus first. This dinosaur is known from about 50 partial-to-nearly-complete skeletons found in rocks between 68 and 66 million years old spanning Saskatchewan to New Mexico, at the very least. Dakotaraptor, on the other hand, is only known from a partial adult individual found near the top of the Hell Creek Formation in South Dakota and a smattering of other isolated elements from that area.

The fossil record is biased, of course. What’s preserved in the rocks is not a perfect record of life as it once was, and there are various other reasons why Dakotaraptor is so rare. Perhaps the dinosaur was the wrong size to be preserved as often as Tyrannosaurus. Maybe teeth and other pieces of this dinosaur were found before but could not be recognized as belonging to a giant raptor until now. Or the commercial fossil market could have snaffled up some of the relevant bones, making them inaccessible to paleontologists.

Future finds will inform what we know about the abundance and distribution of Dakotaraptor. But what if it took so long to find this predator because it truly was a rare animal with a relatively limited range? In terms of species evenness, in other words, the current spread of what we know is heavily imbalanced. Tyrannosaurus was extremely abundant and widespread while Dakotaraptor seems elusive, even by mid-size dinosaur standards.

This isn’t a knock against Dakotaraptor. Quite the opposite. If the dinosaur’s rarity isn’t stemming from a biased fossil record or a problem with sampling, then Dakotaraptor might eventually yield some new information about Hell Creek Formation ecology.

"Jane" is our best look at a juvenile T. rex. Photo by Brian Switek.
“Jane” is our best look at a juvenile T. rex. Photo by Brian Switek.

Up until now, Hell Creek Formation carnivores seemed to be widely split. There wasn’t a gradient from the small to the gargantuan as there was in the Late Jurassic Morrison Formation, but a wide gap between little nippers like Acheroraptor and the lone giant, Tyrannosaurus. What was in the middle, then, were juvenile Tyrannosaurus – lithe, leggy youngsters that had jaws better-suited to stripping flesh than to delivering crushing bites.

Dakotaraptor changes that picture. At least one other mid-sized predator was able to evolve and survive within the domain of Tyrannosaurus. Yet Dakotaraptor may have been so elusive because Tyrannosaurus still maintained a disproportionate presence on the landscape, or perhaps because Dakotaraptor typically lived in upland environments that weren’t preserved as often as the wet lowlands Tyrannosaurus frequented. So even though it’s possible, even probable, that Dakotaraptor and young Tyrannosaurus faced off over carcasses from time to time, it’s not as if Hell Creek Formation time was an era of constant shrieks, roars, and ruffled feathers.

Ceratosaurus was rare compared to Allosaurus. Photo by Brian Switek.
Ceratosaurus was rare compared to Allosaurus. Photo by Brian Switek.

This wouldn’t be the first time carnivorous dinosaur tallies have come out uneven. At the Late Jurassic Cleveland-Lloyd Dinosaur Quarry, for example, the remains of at least 48 Allosaurus have been uncovered while the same site has yielded only a single Ceratosaurus, a few Torvosaurus bones, and single-digit counts of the medium-sized carnivores Marshosaurus and Stokesosaurus. This pattern holds at a wider, rougher view, as well. Allosaurus was the most common large carnivore of the Morrison Formation with Ceratosaurus trailing behind in count and range, followed by even rarer and more restricted Torvosaurus, Stokesosaurus, and Marshosaurus. So, with a count of at least five, we can say that the upper part of the Morrison Formation had a diverse array of mid- to large-sized carnivorous dinosaurs, but that their numbers were not at all even.

Why different dinosaurs were unevenly spread in a given habitat or formation isn’t something that’s well-understood. It’s difficult to study an ecosystem that’s been dead for at least 66 million years. Answers could range from how we sample the fossil record to instances of niche partitioning like habitat preference or seeking particular food sources. There’s still plenty of rock to shift and dinosaurs to count. But if we’re ever going to fully understand dinosaurs, we need to step back from the carnivore vs. carnivore fights we used to imagine in the sandbox and try to understand them as animals that were each part of ever-shifting ecosystems. Dinosaurs weren’t monsters stalking around on unimportant backdrops. The endpoint of raising their bones in the first place is to envision how they fit into lost worlds.

Reference:

DePalma, R., Burnham, D, Martin, L., Larson, P., Bakker, R. 2015. The first giant raptor (Theropoda: Dromaeosauridae) from the Hell Creek Formation. Paleontological Contributions. doi: 10.17161/paleo.1808.18764