A Blog by

This Plant Bleeds Sweet Nectar To Recruit Ant Bodyguards

A bittersweet nightshade plant, Solanum dulcamara.
A bittersweet nightshade plant, Solanum dulcamara.
Photograph by Joel Sartore

Six years ago, Anke Steppuhn noticed that the bittersweet nightshade, when attacked by slugs and insects in a greenhouse, would bleed. Small droplets would exude from the wounds of its part-eaten leaves. At the same time, Steppuhn and her colleagues saw that the wild plants were often covered in ants.

These facts are connected. Steppuhn’s team from the Free University of Berlin, including student Tobias Lortzing, have since discovered that the droplets are a kind of sugary nectar, which the beleagured nightshade uses to summon ants. The ants, in return for their sweet meals, attack the pests that are destroying the plant. And this discovery provides important clues about the evolution of more intimate partnerships between ants and plants.

Acacia trees, for example, are masters at recruiting ant bodyguards. The insects protect the trees from plant-eaters and even prune back invading vines. In return the trees provide them with shelter in the form of swollen thorns, snack stations that look like orange berries, and drinks in the form of nectar. The latter come from small green lumps called extrafloral nectaries, which the ants sip from.

Some 4,000 species of plants have extrafloral nectaries, which vary considerably in their shape. Some are obvious structures, like those of the acacia. Others are mere pits or hollows. But whatever their form, their benefits are invaluable. They are not only ant rewards, but also ant concentrators.

“Ants often appear to be whimsically inefficient plant defence agents,” says Elizabeth Pringle from the Max Planck Institute for Chemical Ecology. “They wander to and fro, haphazardly nipping at anything that happens to be in their way, which gives plenty of time for something with a hard exoskeleton and wings, like an adult flea beetle, to escape and happily land somewhere else to feed. But concentrate lots of ants around a sugar source, and pretty soon nothing soft and slow stands a chance. This is the value of extrafloral nectaries.”

The bittersweet nightshade’s oozing droplets have almost all the characteristics of extrafloral nectaries. It’s a sweet liquid, obviously. But Lortzing showed that it’s not just fluid that passively leaks from a damaged leaf. When he cut the nightshade with a clean scalpel, the nectar droplets didn’t appear. They did emerge, however, if Lortzing first coated his scalpel in jasmonic acid—a hormone that plants release upon insect attack.

Sweet nectar oozes from a wounded bittersweet nightshade.
Sweet nectar oozes from a wounded bittersweet nightshade.
Photograph by Tobias Lortzing

He also showed that the nectar is chemically distinct from the plant’s actual sap—full of sweet sucrose, and deficient in almost everything else. Clearly, it is actively produced and secreted by the plant.


To find out, the team added droplets of either sucrose or water to wild undamaged nightshades. After a month, they saw that the sucrose-treated plants were patrolled by more ants, and had suffered half as much damage to their leaves. To their surprise, the ants even seemed to protect the nightshades against slugs. That’s new. Ants have been known to defend plants against other insects and mammals, but never before slugs or snails.

More bizarrely, the ants didn’t seem to attack adult flea beetles—the nightshade’s greatest enemies. They seemed like poor defenders, until Steppuhn’s team realised that the ants were focused not on the beetle adults, but on their larvae. The larvae hatch from eggs in the soil, climb up the nightshade’s shoots, and bury themselves in its stem.

Ants will pick up the larvae and carry them into their nests, never to be seen again. The ants might ignore the adults, but they stop the next beetle generation from causing even greater harm.

So, the nectar droplets, being actively produced, chemically distinct, and efficient at summoning guardian ants, are very much like the extrafloral nectaries of other plants. The only difference is that they’re not associated with any specific structure—no obvious lump or pit. It’s the “most primitive extrafloral nectary that has been discovered so far and shows how little is needed to make a functioning nectary,” says Martin Heil from CINESTAV in Mexico.

Although such structures are common throughout the plant world, every group with nectary-bearing species also has nectary-less members. “This means that extrafloral nectaries appear and disappear quickly, in evolutionary terms,” says Heil. And Steppuhn’s discovery “helps us understand why and how these nectaries can evolve out of nowhere.”

Perhaps, at first, fluids that passively leak from wounds are visited by ants. Gradually, plants evolve to recruit the ants more effectively by controlling those leaks and tweaking the liquids that emerge, as the nightshade has done. Eventually, they develop specialised structures.

But nectaries are lost so frequently among plant families that they clearly incur some cost, says Pringle. It takes a lot of up-front investment to build the dedicated structures and to keep them constantly brimming with nectar. By contrast, the nightshade’s droplets show that plants can summon ants in a more ad hoc and less effortful way.

Whether plants go for that cheaper option, or head towards full-blown nectaries, probably depends on how badly they’re threatened by plant-eaters, how effective ants are, and how much energy it takes to summon and reward them. Nothing in nature comes for free, and evolution is the ultimate arbiter of costs and benefits.

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.


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

A Crushing Bite Gives Sea Otters Their Cute Mugs

A southern sea otter off Piedras Blancas, California. Photo by Brian Switek.
A southern sea otter off Piedras Blancas, California. Photo by Brian Switek.

All otters are adorable. That’s as much of a fact as the existence of gravity. But among the 13 or so living otter species, none generate as many “Aww”s as Enhydra lutris, the sea otter. These fuzzballs are so cute, in fact, that we often overlook their bad behavior. But what is it that sets them apart? There’s the dense coat of fur and their fastidious dining habits, of course, but they also look a bit different from most other otters. Sea otters have short, round faces compared to their relatives, and that’s all because of their specialist diet. To put it bluntly, I think a crushing bite has given sea otters an edge over their cute competition.

This epiphany came after reading a new paper by Texas A&M zoologists Lori Timm-Davis, Thomas DeWitt, and Christopher Marshall on the two major ways that otters feed. Some otters, like giant and North American river otters, primarily catch fish and other squirmy prey with their jaws, while otters such as Asian small-clawed otters and sea otters often nab mollusks, echinoderms, and other hardened prey with their dexterous hands before crushing through those exterior defenses with expanded cheek teeth. And given that there are trade offs between speed and power in any bite, Timm-Davis and colleagues expected that the differences between these two feeding styles would be visible in the shape of the otters’ skulls. With that in mind, they measured and estimated the bite mechanics for 150 otter skulls representing four different species, as well as parsing out three different populations of sea otters.

The skull of a southern sea otter at Año Nuevo State Park, California. Photo by Brian Switek.
The skull of a southern sea otter at Año Nuevo State Park, California. Photo by Brian Switek.

The otters generally met the researchers’ expectations. Giant and North American river otters, which subsist primarily on fish, have longer, narrower skulls capable of fast bites. Just the sort of setup for snapping at slippery and fast-moving prey. The Asian small-clawed and sea otters, which more often rely on plucking up slow-moving invertebrate morsels, have wider, shorter skulls and jaws, delivering a slower but more more powerful bite. Sea otters take this to the extreme, with wide, rounded cheek teeth best suited to pulverizing hard foods.

Not that all sea otters behave the same way, though. When Timm-Davis and coauthors looked at the differences between isolated Russian, northern, and southern sea otters they found that the skulls of each population clustered together in slightly different shapes. This appears to be because of diet. Northern and Russian sea otters diversify their diet a bit by eating more fish than their southern cousins, and this difference shows up in the anatomy of their jaws. Among other variations, the southern sea otters had about 19.1% more crushing surface on their cheek teeth – the better to mash up sea urchins with. These relatively recent changes reflect how quickly differences in diet can start to affect the shape of otter evolution.

For the most part, though, even sea otters with more cosmopolitan tastes still share the deep, short, and wide skull shape that distinguishes them from their lithe relatives. Sure, all that fur, the little nose, and oildrop eyes complete the package, but the mammal’s lutrine looks go down to the bone. Their cuteness comes from their ability to crush.


Timm-Davis, L., DeWitt, T., Marshall, C. 2015. Divergent skull morphology supports two trophic specializations in otters (Lutrinae). PLOS ONE. doi: 10.1371/journal.pone.0143236

Filter Feeder Was the First of its Kind on Earth

Fossils and a reconstructed model of Tribrachidium. From Rahman et al., 2015.
Fossils and a reconstructed model of Tribrachidium. From Rahman et al., 2015.

If you like enigmatic blobs, then you would have loved the Ediacaran. Back then, between 575 and 541 million years ago, much of life came in a range of fronds, pancakes, and medallions that have puzzled and inspired paleontologists for decades. Some of them were animals. Others were forms of life that defy categorization. But even though mysteries still abound, paleontologist Imran Rahman and colleagues have solved one aspect of how a particular species of Ediacaran oddball fed and what that meant for the evolution of our seas.

Rahman and coauthors settled on a tiny button of an organism named Tribrachidium heralicum. This circular, triple-ridged species has been found in marine rocks in South Australia, Russie, and Ukraine dating between 555 and 550 million years old. No one knows exactly what the organism is – the species has triradiate symmetry, which no animal possesses today – but, through fluid dynamics experiments, Rahman and colleagues were able to determine that Tribrachidium now holds the title of the oldest filter-feeder yet known.

Water flow over the surface of Tribrachidium. Image: I.A. Rahman
Water flow over the surface of Tribrachidium. Image: I.A. Rahman

Up until now, most Ediacaran critters were thought to be osmotrophs. That means they passively absorbed organic particles that they either shuffled over or that fell upon them. But Rahman and coauthors found that current flow over the surface of Tribrachidium directed water towards the apex of the organism, over small branches called a “tentacular fringe” and into specialized pits. As water carrying little organic tidbits flowed over Tribrachidium, in other words, the organism’s shape directed that water upwards to a spot where the flow lost some of its speed and dropped the tiny organic morsels to a place where they could be consumed.

That food didn’t just fall from above. Tribrachidium lived during a time when expansive organic mats covered much of the seabottom, Rahman and colleagues point out, and when currents shook up all that muck some of the organic particles were thrown back up into the mix. The fact that the shape of Tribrachidium had the same filtering effect regardless of current direction is a sign that it made the most of habitats where water frequently sloshed the organic debris around.

At about 10 million years before the onset of the “Cambrian explosion“, when animal life ran riot for the first time, this new discovery adds a new dimension to how life changed the seas.  Tribrachidium was likely an “ecosystem engineer”, Rahman and coauthors write, removing organic material from the water column that helped more light shine in and oxygenated the water column. This early pop could have been important in setting up one of evolution’s most explosive chapters.


Rahman, I., Darroch, S., Racicot, R., Laflamme, M. 2015. Suspension feeding in the enigmatic Ediacaran organisms Tribrachidium demonstrates complexity of Neoproterozoic ecosystems. Science Advances. doi: 10.1126/sciadv.1500800

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.


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

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.


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.


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

Death of Ice Age Giants Shaped Today’s Landscapes

The extinct Bison antiquus at the Page Museum. Photo by Brian Switek.
The extinct Bison antiquus at the Page Museum. Photo by Brian Switek.

I can’t help the impulse. Whenever I’m hiking through the western forests, prairies, and deserts, my mind conjures up images of Ice Age beasts. I guess I keep engaging in the fantasy because I know I just missed them. Ten thousand years is nothing from a geologic perspective. Shasta ground sloths wouldn’t seem out of place shuffling through groves of Joshua trees, mastodons should still be cracking conifer boughs in the woods, and the grasslands were so recently the place where deer, antelope, and camels played.

But the places I scuff my boots aren’t the same as they were back in the heyday of North America’s enormous herbivores. While there have only been a few clicks of the Cosmic Clock since the end of the Pleistocene, the world hasn’t remained in stasis as if waiting for the return of our missing megafauna.

In fact, as Elisabeth Bakker, Jacquelyn Gill, and others argue in a recent review, the extinction of the great Ice Age beasts has created a world dramatically different than the one roamed by shaggy proboscideans and enormous sloths.

Herbivores are plant predators. It might be strange to think of them that way. A horse plucking up grass or an elephant chawing a mouthful of leaves isn’t as violent or gory a spectacle as a pack of wolves taking down an elk. Yet ecologists call the feeding habits of herbivores “predation” for good reason. The interactions may be slower and harder to see, and there is cooperation in addition to competition, but there are still arms races between herbivores and the plants they rely on. And this constant shuffle is what helps create the landscapes we see all around us.

Consider the American mastodon. This “bubby toothed” elephant was a browser, preferring tree branches and other woody vegetation to the diet of grass enjoyed by its distant cousin, the woolly mammoth. But the mastodon didn’t just eat trees and shrubs. The beast would have trampled down paths through the woods and scraped its tusks against tree trunks, further altering the landscape around it by stamping out some young plants and hindering the growth of others. Mammut americanum wasn’t just a big vegetarian.

The beast, Bakker and coauthors write, was an ecosystem engineer.

The same was true of many other herbivores that lived around the world until very recently. Up until about 600 years ago, for example, giant, flightless birds called moas browsed in the forests of New Zealand, helping to create openings in the woodlands that allowed light-sensitive plants to thrive in the patches they opened up. Since their disappearance, however, the forest has closed, with wire plants—whose springy anatomy made them resistant to moa depredations—spreading in greater numbers.

Imagine the damage the claws of Harlan's ground sloth could have done to Pleistocene trees. Photo by Brian Switek.
Imagine the damage the claws of Harlan’s ground sloth could have done to Pleistocene trees. Photo by Brian Switek.

Modern, short-term experiments have shown the same pattern. When big herbivores or either eliminated or excluded from an area, Bakker and colleagues write, the woodlands start to close up. Not as many young plants are being pulled up and fewer adult plants are having to struggle to put out leaves against the onslaught of big browsers.

For example, experimental studies have shown that areas where African elephants have been excluded can host 42% more trees than when the mammals are stripping them and pushing them over. Through extinction and the restriction of our last few megaherbivores to parks and game reserves, we’re playing out a miniature version of what happened when the Pleistocene’s major plant predators went extinct.

So when I set out from my Salt Lake City apartment and climb up above the level of the Lake Bonneville shoreline, to where my Ice Age inspirations used to roam, I need to do more than picture Harlan’s ground sloth or a mastodon trundling through the stands of oak and aspen. I need to think about what those herbivores did. Of branches stripped bare, toppled trunks, and wide paths through the woods pressed down by the hungry herbivores.

The lost megafauna weren’t just charismatic characters from a closed act in Earth’s history. They helped make the world what it was. I am only sorry that I can’t see what they created.

Bakker, E., Gill, J., Johnson, C., Vera, F., Sandom, C., Asner, G., Svenning, J. 2015. Combining paleo-data and modern exclosure experiments to assess the impact of megafauna extinctions on woody vegetation. PNAS. doi: 10.1073/pnas.1502545112

A Blog by

Nudging Kids Into Wonder—Then Science

They never met, Rachel Carson and Cecilia Cruz.

Diptych of portrait of Rachel Carson and an illustration of Celia Cruz
(Left) Photograph by CBS Photo Archive, Contributor, Getty (Right) Illustration detail by Gavin Aung Than, Zen Pencils

Cecilia, as you’re about to learn, is a little girl who lives indoors. She doesn’t get out much, doesn’t want to, but she has a mom, and that mom coaxes her out the door, across the yard and onto a beach that looks….. totally empty, totally boring—and then, something happens. Something extraordinary.

Actually, reading this cartoon strip, two amazing things happen, or happened to me. The words come from Rachel Carson, the famous marine biologist and author of the world-changing Silent Spring. The text is only 340 or so words, lifted from an essay she wrote about taking her little nephew to explore woods and beaches. It’s about childhood wonder.

The opening spread of Rachel Carson's ''The Sense of Wonder''
Photograph by Becky Harlan

Carson writes well enough, but for me the real kick comes from Gavin Aung Than’s pictures. He’s an Australian illustrator, and he doesn’t change a word. But he improvises. Instead of a boy, Than draws a girl, an imaginary “Cecilia.” He substitutes the girl’s mother for Carson. And instead of woods and shells, he gives Cecilia a moment on the beach that thrills her and changes her life.

None of the scenes drawn here were in Carson’s head, but what Than has imagined is the graphic equivalent of a movie score—he enhances, he underlines, and every so often he gives her words a crazy, topsy-turvy joy. Maybe you’ll disagree. Why don’t you to take a look?

Comic illustrating words by Rachel Carson about encouraging a sense of wonder in children

Comic illustrating words by Rachel Carson about encouraging a sense of wonder in children
Comic by Gavin Aung Than, Zen Pencils

Than does a lot of these illustrated passages. His blog is called Zen Pencils. A few years ago, he was toiling away in an Australian ad agency, hating his job, hating his days, and I don’t know what broke him, but finally he said “enough,” sold his house, resigned his job, and decided to throw himself into this project, taking quotations (from presidents, scientists, statesmen, writers, celebrities) and annotating them with drawings. Now it’s a pair of books.

What he does is not translation; there’s nothing literal about his strips. He’s inventing, augmenting, reshaping. In the Carson passage, the mother worries that she doesn’t know enough to teach her child true things about nature. “It is not half so important to know,” Carson writes, “as to feel.”

So how does he sell that line? He shows us, wordlessly, all these little turtles heading off to sea, lit by a rising sun. Feelings follow. Later, he gives Cecilia a 500-pound swimming companion to keep her company. Yes, it’s sentimental. But hey, he’s got a brush in his hand, a mood in his head, and he knows how to make us see what those sentences are saying. Or what he thinks those sentences are saying.

As Carson suggests, science is a discipline. It needs data, numbers, replication, pattern. But to get there, to get started, scientists need astonishment, mystery, and an intuitive feel for beauty. So feelings matter. And Gavin Aung Than has a feel for feelings.

As good as the Rachel Carson strip is, I think my all-time favorite is Than’s take on a passage by Loony Tunes cartoonist Chuck Jones (of Elmer Fudd and Bugs Bunny fame) talking about his first few (horrible) days in art school, which was a total nightmare until his uncle gave him some simple, cool advice. This involves dancing. Much dancing. You’ll find it here.

A Blog by

Yes, Rats Can Swim Up Your Toilet. And It Gets Worse Than That.

They eat our food. They furnish their nests with our detritus. They chew through our sheet metal, our lead pipes and our concrete. They outsmart us at every turn. They are our shadow, our enemy, our next door neighbor.    —”Rat City!Spy magazine, 1988

“You have to think like the rat,” my new friend Gregg told me. At the time, we were pushing Gregg’s homemade rat detector through a small hole in my basement ceiling. He had bought an endoscope camera online—the kind a doctor uses to hunt for polyps in one’s nether regions—and attached it to a bent wire coat hanger. The camera’s images would be displayed on his laptop.

Gregg became obsessed with rats when they took over his girlfriend Anne’s house, across the street from mine. Having tracked and conquered her rats, he was eager to bring his rat-buster skills and tools to my infestation. Gregg showed up on a Sunday afternoon with the endoscope and a two-gallon bleach sprayer and explained my role: Simply turn the endoscope’s light up or down on his command as he threaded the coat hanger through ceilings and walls.

In the ceiling space above the basement bathroom, we hit the mother lode: towering piles of little black rat turds appeared on the laptop screen. “Here’s your nest,” Gregg proclaimed, our first small victory in what had been a long, losing battle. As I wrote in May, I had already suffered an invasion of live rats, followed by stinking dead rats and a Flymageddon of bottle flies and flesh flies that hatched out of their carcasses.

I had learned a few things about rats by this point: They are creatures of habit. They establish trackways through a house, following the same paths each day: in, out, to food, to nest. And they can, in fact, rise up from the sewers.

VIDEO: WATCH OUT! A rat’s super swimming ability and flexibility enable it to make its way easily from the city streets to your toilet. See how they do it.

This last point became central to my investigation. When my husband, Jay, cut out a section of the bathroom ceiling where Gregg’s endoscope had led us, we found that our rat nest was centered around an old sewer drain pipe that, unbeknownst to us, had been cut but never capped during the removal of an upstairs toilet. Dark oily smudges marked the rim where rats had climbed up from the sewers and dropped into my basement ceiling space.

Upon further research, I found that not only is it pretty easy for a rat to climb up a three-inch toilet drain pipe (most of the time there’s not even water in it), but I live in a part of D.C. with a combined sewer system, so the storm drains on the street and the pipes from the toilets run to the same place. A combined sewer is one big, happy, Rat Central Station. 

Having figured out how our rats were getting in, and assuming that any remaining rats would have been scared away by our noisy labors and hole-poking, Jay capped the pipe, and we congratulated ourselves on a mystery solved.

Maybe you read my last post, and you can see where this is going.

One With the Rats

Rats’ superpowers are near-mythical: They can swim for three days. They can fit through holes the size of a quarter. They’ve even been said to have no solid bones, just cartilage (definitely false, and I can’t confirm whether they can collapse their ribcages). I looked to science for the truth. But I was surprised by the dearth of studies on the Norway rat—the common city rat, Rattus norvegicus—in the wild (the wild in this case being any city on Earth). Despite our long human history with lab rats, we know very little about the lives of the rats in our homes.

In fact, as veterinary scientist Chelsea Himsworth told me, “We probably know more about the ecology of polar bears than we do about rats.” Himsworth is studying how rats spread disease in cities as part of the Vancouver Rat Project.

“The interesting thing about Norway rats is they don’t exist in the wild,” Himsworth said. Their migrations—through Asia, over continents and across oceans—are our migrations. They’ve been in contact with humans for so long that they not only live with us, they depend on us almost entirely for food.  

They don’t stray far from our homes. One of the most important findings of the Vancouver Rat Project has been that rats form highly stable family groups or colonies, block by block in a city. And when people break up rat families, say by indiscriminate trapping or poisoning, the remaining rats are forced to move—and that’s when they tend to spread disease.

Sewer Rats

I was, of course, trying not to be indiscriminate at all. I wanted to kill them all—the whole rat family.

I told this to Robert Corrigan, who was described to me as the “rat king of New York City.” He seems okay with the title. Corrigan has spent his career fighting rats up and down the Eastern Seaboard, which—with its dense population, waterways, and old pipes—is pretty much rat heaven.

Corrigan said he agreed with Gregg in part: To wipe out an infestation you have to think like a rat. “But I also think it’s not difficult to out-think a rat,” he said. Unlike many animals, a rat must have both food and water every single day to survive. No skipping meals.


“If it doesn’t have food and water, it goes into this kind of ‘crazy mode,'” Corrigan said. Rats have a very low tolerance for hunger—so to get rid of them simply ask where they’re getting food and eliminate the source.

But what about my rats?, I asked him. How were they getting food? Clearly they were coming up an old toilet pipe from the sewer, and there wasn’t any food in my basement ceiling.

That’s where it got a little ugly. I was right about the combined sewer system, Corrigan said; it does make it easier for rats to get into toilets. As if to make the point, the day after we capped our toilet pipe, a rat popped up in my next-door neighbor’s toilet.

Plus, toilet drainage turns out to be a boon for sewer rats. “Lots of food gets flushed,” Corrigan pointed out. (This remains hard for me to fathom, but I do recall a landlord once complaining about a tenant who always flushed chicken bones down the toilet.)

“Also, if push comes to shove, human feces and dog feces contain undigested food,” Corrigan said.

“They don’t turn up their nose at anything that floats by.”

Let’s pause on that for a moment. What Corrigan is saying is that the rats in my basement ceiling were climbing up and down a toilet pipe into the sewer every day, whereupon they ate and quite possibly dragged back up caches of food that may or may not have included human excrement.

“That’s repulsive to humans, but it’s called coprophagy, and it’s part of the reason rats are so successful,” he said. “They don’t turn up their nose at anything that floats by.” 

Not Again

So it was smart of us to cap the sewer pipe. But little did I know when we cut off the entrance and exit to the basement ceiling, that at least two more rats remained in the ceiling—or that only one would survive. Survivor Rat chewed its way out of the house, leaving in its wake a gnawed-off condensation tube spewing water into the basement ceiling. Loser Rat didn’t hold out long enough and died in unknown quarters, spawning a new flock of flesh flies.

When the big striped monsters began to emerge and cruise the basement skies, I pretty much lost it. I Can’t. Do. This. Again.

Caving to the chemical solution, I bought a bug-fogging bomb and waited until I thought most of the flies would be emerging from their pupal cases—when I’d have the best chance of killing them. (Check out this video of  house flies emerging.)

I approached a hole we’d cut in the ceiling where I’d observed flies emerging. Using salad tongs, I pinched the plastic cover and pulled it back an inch. A rain of black flies drip-dropped from the hole onto the floor, buzzing. They had emerged from their cases but couldn’t quite fly yet. Perfect. I yanked the cover the rest of the way off, jumped back as a mass of flies hit the ground, some taking wing, and hit the button on the fogger.

Then I dropped my tongs and ran.

Those are dead flies. Multiply by entire basement.  Photo by Erika Engelhaupt
Those are dead flies. Multiply by entire basement. Photo by Erika Engelhaupt

Here is what I came home to.

It wasn’t as bad as Flymageddon.

Hot Fossil Mammals May Give a Glimpse of Nature’s Future

The present is the key to the past. Every geologist worth their sodium chloride knows this. The famous phrase, a distillation of the principle of uniformitarianism, can be seen emblazoned on mugs, bumper stickers, and more in college geology departments around the country. But while it’s true that phenomena currently in action can help us understand what transpired during prehistory, the flow of clues isn’t one way. The past may very well be the key to the future, especially when we want a preview of what can happen during periods of rapid climate change (like the human-caused one we’re in now). The latest study in this emerging area of research centers on the fate of ancient mammals that went through a period of warming similar to the one we’re starting to experience now.

During the dawn of the “Age of Mammals”, around 56 million years ago, the global temperature rapidly stabbed upwards. In about 100,000 years temperatures rose over 40 degrees Fahrenheit. Paleontologists know this as the Palaeocene/Eocene Thermal Maximum (PETM for short), and there’s hardly a better place to see its effects than the deserts of Wyoming. The fossil localities here are famous for producing a detailed sequence of species from this time, recording how life responded to rapid climate change.

Insects, for example, fared quite well. So much so that plant fossils from the PETM show a spike in holes and divots created by hungry, hungry arthropods. And then there are the mammals. The mammals that lived in the ancient Wyoming basins during the heat wave were smaller than those that came before or after. The fauna seem to have shrunk in the heat.

But what does this change really mean? Up until now, paleontologists have considered two hypotheses. It could be that the larger mammal species evolved to become smaller over time in a straight-line fashion called anagenesis. Then again, the smaller species could be closely-related immigrants that had lived in warmer habitats and were able to thrive as the larger species went extinct. Either way, the hypothesis is that smaller-bodied mammals were probably better able to shed heat and cope with altered nutritional values of plants that go along with high CO2 levels.

But the new study by Brian Rankin and colleagues looks at another possibility – species selection. The logic is the same as that of natural selection, but bumped up one level. Just like individuals, the argument goes, some species will vary in ways that make them more successful in splitting off descendant species than others. In this case, large-bodied mammal species would have suffered in the hothouse world, while the species that were already small would have spun off an increased number of new lineages. While the large species went extinct, the small species would have proliferated.

Fortunately the Bighorn and Clarks Fork Basin faunas have been so extensively studied that paleontologists have been able to reconstruct body sizes, ancestor-descendant relationships (which is a rare feat), and identify immigrant species. This is what decades of fieldwork leads up to – a dataset of over 2,000 localities, 5,000 specimens, and 50 species carefully arranged according to the times and places those mammals lived. Plugging all that into a modified version of what naturalists call the Price equation, Rankin and colleagues were able to parse why the ancient beasts became downsized.

There wasn’t a single reason why mammal body size changed during this narrow span of Cenozoic time. The primary cause, Rankin and colleagues conclude, is the immigration of small species into the Bighorn and Clarks Fork Basins as the large native species disappeared. These were mammals like the archaic hoofed herbivore Ectocion parvus and the primate Teilhardina brandti. The paleontologists also found evidence for some native species, such as the carnivore Viverravus politus, becoming smaller with time.

But here’s the strange part. The paleontologists found some influence of species selection in these basins, but it was in favor of larger mammals. This was a one-two punch of extinction and evolution. Some small animals, like the early primate Carpolestes simpsoni, went extinct at the same time that large ones, such as the superficially rodent-like Azygonyx, were leaving big descendant species.

Without species selection causing some large species to more successfully leave big-bodied descendants, the mammal fauna of the PETM would have been even smaller than what was left behind in the rock. And as the simmering heat decreased, species selection still favored larger species, with anagenetic change and immigration being less important. This might mean that species selection was a relative constant during the days of the Palaeocene and Eocene but became briefly suppressed when intense heat threw a brief advantage to smaller mammals.

Similar influences may soon come into play, if they haven’t already. During very short time frames, Rankin and coauthors write, the influence of climate change can be see within species. But in the long term – the extended effects that we can see coming down the line from anthropogenic climate change – species selection starts to come into play. Which species go extinct and which are able to keep spinning off descendants begins to shape the world in new ways. There’s no set path to evolution. No destiny. But by looking to the deep past, maybe we can begin to perceive the rough outlines of the new world we’re inadvertently creating.

For more, check out Shaena Montanari’s post on the same study, as well as this interview with study author Jessica Theodor I filmed at the Society of Vertebrate Paleontology meeting last fall:


Rankin, B., Fox, J., Barron-Ortiz, C., Chew, A., Holroyd, P., Ludtke, J., Yang, X., Theodor, J. 2015. The extended Price equation quantifies species selection on mammalian body size across the Palaeocene/Eocene Thermal Maximum. Proceedings of the Royal Society B. doi: 10.1098/rspb.2015.1097

A Blog by

Should You Put a Baby Bird Back in the Nest? Depends If It’s Cute

Ah, the first days of summer—the smell of cut grass, kids on vacation… and baby birds falling out of trees.

Every year, I see a new flock of people rescuing fallen birds, and then arguing on Twitter and Facebook about whether it’s OK to put them back in the nest.

Some are adamant that if you handle a baby bird, its mother will reject it. Others say it’s fine; just put the bird back.

A lot of people face this dilemma at the beginning of summer, when many baby birds are taking their first flight from the nest—in bird-nerd speak, they’re fledging. I was in Mississippi in early June, and it seemed like it was raining dead baby birds there. One fell from its nest onto my car, and another mysteriously turned up on the porch steps. It was too late for those birds, but what do you do when faced with a little peeper like this?

First, you should ask yourself how cute the bird is.

Okay, that sounds cruel and judgmental. But it’s basically true. The Cornell Lab of Ornithology gives excellent advice: The first thing you need to know is whether the baby is a nestling or a fledgling. Most of the birds people find are fledglings. Fledglings have feathers, can hop, and are “generally adorable and fluffy, with a tiny stub of a tail.”

“When fledglings leave their nest they rarely return, so even if you see the nest it’s not a good idea to put the bird back in—it will hop right back out. Usually there is no reason to intervene at all beyond putting the bird on a nearby perch out of harm’s way and keeping pets indoors.”

And if you’ve got an ugly little unfeathered friend?

“If the baby bird is sparsely feathered and not capable of hopping, walking, flitting, or gripping tightly to your finger, it’s a nestling.

If you can find the nest (it may be well hidden), put the bird back as quickly as possible. Don’t worry—parent birds do not recognize their young by smell. They will not abandon a baby if it has been touched by humans.”

So leave the cute ones alone, and put the little ratty-looking ones back in the nest.

And if you don’t stumble across any fledglings this year, the Cornell Lab of Ornithology has a website where you can watch live video of baby birds on Birds Cams.

There are plenty of adorable Bird Cam moments, like this fledgling hawk returning to the nest and checking out the camera.

But it wasn’t all pretty. “This has been probably our toughest year on record,” says Charles Eldermire, who runs the Bird Cams program. The ospreys were hit by dime-sized hail a week before their eggs were to hatch, cracking all the eggs. A baby owl died, and the parents fed it to its siblings. Eldermire even had to put up warnings that viewers had to click on before watching particularly bad things happening.

“We started this project in part to help people learn about what happens in nature,” Eldermire says. “We’re aware that many have never had an unfiltered view of what happens in nature.”

The Bird Cam folks make a point of not interfering. “We can learn by letting it play out. Any intervention could have a negative impact; if we feed that baby owlet to save it, maybe it’s sick, or maybe the environment won’t support another barn owl.”

I love what Eldermire said next. Think about this as you watch the ospreys in the video above hunker over their eggs in a hailstorm: “The struggles that we go through as people in our own lives aren’t all that different from the animals on the screen.”

“The truth is we can’t control everything in our lives. One thing we can all learn from watching wild things and how they survive is that sense of resilience that is really at the core of any wild thing.”

Hothouse Climate Slowed Dinosaurs’ Rise

It gets hot at the Hayden Quarry. Hot enough to keep away the biting gnats – eternal foe of the field paleontologist – and to require a brief siesta every afternoon in the cool of a nearby streambed. The August monsoons do little to help. The New Mexico desert greedily slurps every drop of moisture and within a few hours you forget that water ever falls from the sky. But that’s as it should be. It helps get you in the mindset of creatures that lived and died in the spot over 211 million years before, back when ancient aridity kept early dinosaurs down.

We often think of the Mesozoic as an endless summer when reptilian monsters stalked jungles and swamps choked with vegetation. Some dinosaurs really did live that large. But the Hayden Quarry tells a very different story. It’s from a time when the “Age of Dinosaurs” hadn’t truly begun. When tropical heat created wildly-fluctuating habitats repeatedly scorched by wildfire.

Paleontologist Adam Pritchard excavating part of the Hayden Quarry in August 2011. Photo by Brian Switek.
Paleontologist Adam Pritchard excavating part of the Hayden Quarry in August 2011. Photo by Brian Switek.

The signs of the Triassic blazes are easy to spot. Chunks of charred wood are scattered amongst the black Hayden Quarry bones, sometimes leading to moments of nervous excavation when it’s not clear whether you’re uncovering part of a little phytosaur jaw or the burnt remnants of a prehistoric conifer. (When in doubt, treat a fossil like it’s bone until you’ve proven otherwise.) And while they seem rather mundane next to the skulls, limb bones, and other vertebrate fossils that pack the quarry, the crispy remnants of prehistoric plants are what truly set the stage for this slice of time.

University of Southampton geologist Jessica Whiteside and colleagues tell the tale in a new paper in PNAS. By turning to the burnt plants, fossil pollen, and carbon isotopes of the Hayden Quarry, the researchers were able to piece together what this spot in northern New Mexico was like 211 million years ago. The site, which was then within the tropics, was a hot, arid place continuously tossed between wet and dry seasons (roughly similar to the seasonal shifts that bake the quarry today). It was so persistently dry that the local foliage often turned to tinder. Dessicated and dead plants provided the fuel for frequent wildfires that raged between 320 and 680 degrees Celsius.

Those fires altered the plant communities from season to season. Even though the forests hosted an increasing number of conifers alongside the more archaic seed ferns, Whiteside and coauthors found, the plant species present kept changing as wildfires reshuffled the ecological deck. Later the rains returned to batter that blackened ground, washing loose soil, singed wood, and bones together into the stream channels that now preserve this snapshot of Triassic life.

Dinosaur distribution in the Late Triassic. Only small carnivores managed to get a toehold in the tropics. From Whiteside et al., 2015.
Dinosaur distribution in the Late Triassic. Only small carnivores managed to get a toehold in the tropics. From Whiteside et al., 2015.

Yet, despite all this ecological chaos, the animals of the age lived in stable communities. They were resilient creatures that were able to carve out a living in the shifting landscape. The most diverse and disparate creatures of the tropical Triassic were pseudosuchians – crocodile cousins that included bipedal “dinosaur mimics”, huge carnivores, heavily-armored omnivores, and more. Dinosaurs, meanwhile, were only represented by a few small, sleek carnivores. There were no giant herbivores, like the long-necked sauropodomorphs found at higher latitudes, or, in fact, plant-eating dinosaurs of any kind. The plant communities in the low latitudes were too changeable to support dinosaurs that required a great deal of forage to keep their metabolisms running hot. Only little hunters could eke out a living here.

What Whiteside and colleagues found at the Hayden Quarry holds across the planet. Dinosaurs didn’t dominate the Triassic tropics. The increased carbon dioxide in the atmosphere created a hothouse climate where the sharp swings between the seasons prevented dinosaurs from getting any more than toehold at low latitudes. It was only in the wetter, lush regions away from the equator that dinosaurs started to get big and diversified. These were the centers of dinosaur evolution that produced the diversity which later took over the planet when a mass extinction decimated the protocrocs at the end of the Triassic. The true “Dawn of the Dinosaurs” didn’t start until the world had turned in their favor.

[Note – I’ve previously volunteered on Hayden Quarry excavations with several of the study authors, and will be returning there this coming August.]


Whiteside, J., Lindström, S., Irmis, R., Glasspool, I., Schaller, M., Dunlavey, M., Nesbitt, S., Smith, N., Turner, A. 2015. Extreme ecosystem instability suppressed tropical dinosaur dominance for 30 million years. PNAS. doi: 10.1073/pnas.1505252112

A Blog by

How Do African Grasslands Support So Many Plant-Eaters?

Across the savannahs of Africa, millions of stomachs are busy converting plant tissue into animal flesh. The continent’s leaves and grasses are under constant assault from impala, wildebeest, buffalo, zebra, gazelles, and giraffes. Even acacia trees get bulldozed by elephants. There can be up to 25 species of these large plant-eaters in a given place, and many of them gather in gargantuan herds. How do they co-exist?

“It’s not obvious why competition for food doesn’t whittle the number of species down to just a few dominant competitors,” says Tyler Kartzinel from Princeton University. The prevailing idea says that different species have different food preferences. Grazers like zebra and wildebeest eat grass and little else. Browsers like dik-diks and giraffes nibble on leaves and shrubs—collectively called “browse”. Some animals, like elephants and impala, go for both.

Within each category, animals partition themselves in space. Zebras eat the tallest grasses; wildebeest munch the shorter ones. Dik-diks browse on the lowest leaves; impala take the mid-level; and giraffes pluck the loftiest foliage. But despite these nuances, “there’s still been this coarse distinction between grass and other plants,” says Kartzinel, “as if you partition those two resources finely enough, and suddenly there’s enough space in the savannah for dozens of herbivores.”

This picture is too simple. By using DNA to actually identify the plants that these animals eat—something no one had done before—Kartzinel has shown that their preferences go much deeper than just grass versus browse.

For example, the Grevy’s zebra and plains zebra—two species that live in the same places and consume almost nothing but grass—eat varying amounts of different species of grass. To them, a grassland isn’t just one uniform banquet. It’s a patchwork landscape full of different foods, with some bits that appeal to one species and others that delight another. “The appropriate question is not, ‘Does it eat grass?’ but rather ‘Which grasses does it eat?’,” says Kartzinel.

“When I talk to non-ecologists, they are stunned to learn that we have never really had a clear picture of what all of these charismatic large mammals actually eat in nature,” he adds. There are good reasons for that. These animals move over long distances, and they are hard (and dangerous) to observe up-close. They often eat small plants, in the middle of the night, under cover of thick bush. “Many of these plants are also exceedingly hard to identify to the species level, even for an expert botanical taxonomist with specimen in hand — meaning that it’s literally impossible to do while looking through binoculars at an animal feeding.”

Dik-dik. By Henry Palm. CC BY 2.0
Dik-dik. By Henry Palm. CC BY 2.0

To solve these problems, he and his team, led by Princeton’s Rob Pringle, turned to poo. Driving around Kenya, they tracked seven plant-eaters: elephants, plains and Grevy’s zebra, domestic cows, buffalo, and Guenther’s dik-diks. They waited for the animals to defecate, before rushing over to (carefully) collect their dung. Back in the lab, they extracted DNA from the samples, sequenced it, and used those sequences to identify the specific plants that the beasts had eaten.

This approach, called DNA metabarcoding, confirmed the traditional divide between grazers and browsers, but also revealed that species which eat exactly the same amounts of either category still have very different diets. Cows and buffalo are closely related grazers, but they graze on different food. Even the zebras ate different amounts of 15 plant species, 14 of which are grasses. The Grevy’s also supplements its diet with small legumes that its plains cousin ignores. “That was the big surprise,” says Kartzinel. “We can finally see these very cryptic differences that these animals have.”

He compares the herbivores to a family at a buffet: “You might all choose the same main course, but when it comes to side dishes and condiments, you have hundreds of options. It’s unlikely that you’ll all end up with the same meal.”

This discovery helps to explain how the savannah supports so many plant-eaters. It offers them a buffet of riches, and each species eats only part of the full menu. The reasons for these preferences are unclear. Maybe the plains zebra just likes the taste of a particular plant. Perhaps the Grevy’s craves nutrients that only some species can provide. Perhaps dik-diks have unique gut microbes that can detoxify the poisons in plants that its competitors can’t touch. The only way of working out which of these possibilities is true is to work out exactly what these animals are eating—which is where DNA metabarcoding comes in.

The team also hopes that the technique will help to reduce conflicts between farmers and Africa’s wild herds. “If people think that livestock and wildlife compete fiercely for food, they will eliminate wildlife from rangelands,” says Kartzinel. If they can show that such competition doesn’t actually exist, that pressure might abate.

Reference: Kartzinel, Chen, Coverdale, Erickson, Kress, Kuzmina, Rubsenstein, Wang & Pringle. 2015. DNA metabarcoding illuminates dietary niche partitioning by African large herbivores. PNAS http://dx.doi.org/10.1073/pnas.1503283112

The Echoes of Toothed Birds

Whenever I spot a grebe, I try to imagine the bird with teeth. This is another symptom of a chronically fossiliferous mind. You see, these snake-necked swimming birds have traditionally been taken as a proxy for a specific sort of ancient avian called hesperornithiforms. Best known by, as you might guess, Hesperornis – these toothed birds pioneered the diving lifestyle between 113 and 66 million years ago. Today’s grebes and loons look like edentulous echos of these lost Cretaceous days, or, as beautifully expressed by ornithologist William Beebe:

When in the depth of the winter, a full hundred miles from the nearest land, one sees a loon in the path of the steamer, listens to its weird, maniacal laughter, and sees it slowly sink downward through the green waters, it truly seems a hint of the bird-life of long-past ages.

No surprise, then, that paleontologists past sometimes considered loons and grebes to be the descendants of Hesperornis. Their bones carry the same superficial similarity. But this is an evolutionary ruse known as convergence. Loons and grebes are copycats that independently took up the same lifestyle as the toothed birds that dove after fish in warm Cretaceous seas and sometimes wound up in the stomachs of monstrous marine reptiles.

It takes an encyclopedic knowledge of anatomy to spot the differences, but the bones don’t lie. For example, as pointed out by Natural History Museum of Los Angeles paleontologists Alyssa Bell and Luis Chiappe in their new paper on Hesperornis and kin, loons, grebes, and the toothed birds all evolved different skeletal scaffolds for increasing their swimming power. Grebes have an expansion of the tibia for strong propulsive muscles, while loons split the space between a flange on their tibia and a kneecap. In the extinct toothed birds, however, the muscles mainly appear to have attached to a large, robust kneecap. Different anatomical solutions to the same mechanical problem.

The family tree of hesperornithiform birds created by Bell and Chiappe, 2015.
The family tree of hesperornithiform birds created by Bell and Chiappe, 2015.

From differences such as these, paleontologists have been able to discern that the hesperornithiformes are perched just outside the “modern” bird group – Neornithes to specialists – on the avian family tree. So far, so good. But as Bell and Chiappe point out in their paper, very little work has been done on sorting out the relationships of the various diving birds that snatched fish with snaggly jaws among the Northern Hemishphere’s Cretaceous waterways. With that in mind, the researchers cataloged 207 skeletal characteristics from 272 hesperornithiform specimens representing 18 different taxa to see who was related to whom.

After the various lineages grew or were pruned, Bell and Chiappe found that all the hesperornithiform birds created one group, and under this canopy there were several major branches. This is what allowed Bell and Chiappe to see how these birds became better and better adapted to lives spent at sea. Over time, the researchers point out, the birds show increasing specializations for better diving – such as a close connection of bone in the lower leg that allowed Hesperornis and other skilled swimmers to hold their toes close together during the recovery phase of a swim stroke, reducing drag and allowing them to get their feet in position for the next sweep faster.

Not that the story is one of straight-line progress from little flappy birds to flightless divers. Looking across the lineages, Bell and Chiappe found that these toothed birds evolved large body size at least three different times – in species of Brodavis and Pasquiaornis, as well as Hesperornis and its closest relatives. This might be a sign that each of these lineages were independently becoming adapted to being better divers. Bigger body size in diving animals, Bell and Chiappe point out, is related to larger lung capacity and the ability to better oxygenate the blood while paddling down deep. That means that even these toothy birds were copying each other before loons and grebes could continue the trend. In evolution, as with fashion and film, what’s old can be made new again.


Bell, A., Chiappe, L. 2015. A species-level phylogeny of the Cretaceous Hesperornithiformes (Aves: Ornithuromorpha): implications for body size evolution amongst the earliest diving birds. Journal of Systematic Paleontology. doi: 10.1080/14772019.2015.1036141