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How This Fish Survives in a Sea Cucumber’s Bum

Picture of a leopard sea cucumber excreting cuvierian organs, which look like white streamers, for defense
A leopard sea cucumber excretes its organs for defense. Photograph by WaterFrame, Alamy
Photograph by WaterFrame, Alamy

In 1975, Victor Benno Meyer-Rochow was diving off the Banda Islands in Indonesia, when he collected a leopard sea cucumber—a cylindrical relative of starfish and sea urchins. It was a large and stubby specimen, 40 centimetres long (16 inches) and 14 centimetres wide. He dropped it in a bucket of water, which he placed in a refrigerated room.

Sometime later, a slender, eel-like fish swam out of the sea cucumber’s anus.

It was a star pearlfish, and it wasn’t alone. Another wriggled out. And another. After ten hours, 14 pearlfish had evacuated the animal’s bum, each between 10 and 16 centimetres long. Another one stayed inside.

There are many species of pearlfish. Some live independently, but several make their homes in the bodies of shellfish, starfish, and other marine animals. Indeed, they got their name after one individual was found inside an oyster, dead and embedded within mother-of-pearl.

But sea cucumbers are their most infamous hosts. Having found one by following its smell, a pearlfish will dive into the anus headfirst, “propelling itself by violent strokes of the tail,” according to Eric Parmentier. If the sea cucumber objects and closes down its anus… well, it still has to breathe.

Oh yeah, sea cucumbers breathe through their anuses. By rhythmically expanding and contracting their bodies, they drive water through the anal opening and into a branching, lung-like structure called the respiratory tree. This process creates gentle currents that a pearlfish can use to find its hosts. It also creates a vulnerability, because a sea cucumber that’s clenching its butt is also holding its breath. When it exhales, as it eventually must, it dilates its anus, allowing the pearlfish to thread itself in. This time, it goes tail-first, bit by bit, breath by breath.

Some species just use the sea cucumbers as shelters. But the Encheliophis pearlfishes are full-blown parasites that devour their host’s gonads from within.

Pearlfish are typically found alone, and adults have been known to kill rivals that try to infiltrate the same host. Still, as Meyer-Rochow found, the fish can sometimes be more sociable—or at the very least, tolerant. No one knows why. It’s possible that when sea cucumbers are rare, the fish are forced to share a host. Alternatively, they could have gathered to breed. “If indeed the 15 fish entered for sexual reasons, one cannot help but think of the orgy that must have taken place inside the sea cucumber,” Meyer-Rochow says.

These anal abodes aren’t easy places to live.

These anal abodes shelter pearlfish from predators, but they aren’t easy places in which to live. Sea cucumbers produce bitter toxins called saponins that punch small holes in the membranes of cells. These chemicals ought to be especially destructive towards fish gills, whose cells come in thin, sensitive layers with a large surface area.

Pearlfish should be especially vulnerable, since they are literally swimming inside the saponin-producing structures. And yet, when Igor Eeckhaut exposed various fishes to sea cucumber saponins, the pearlfish survived 45 times longer than other species. How do they cope?

Sea cucumbers resist their own poisons because their cell membranes comprise special chemicals that interact less strongly with saponins. But Lola Brasseur from Eeckhaut’s team found that pearlfishes don’t use such fancy chemistry. Nor do they have any tricks for detoxifying the saponins.

Instead, they rely on mucus, which they secrete onto their skins. The mucus helps to lubricate them on their way into their hosts, but it also acts as a physical barrier against the toxic saponins. It’s especially effective because the pearlfishes make so much of it—six to ten times more than other fishes that have no interest in sea cucumber bums.

Of course, none of this explains why the sea cucumbers don’t use their most effective defence. When threatened, they can expel their respiratory trees at their attackers, relying on their regenerative powers to re-grow the lost organ.

Why, then, do they never evict their pearlfish lodgers in this way? No one knows.

Did Sabercats Have Spotted and Striped Coats?

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

As far as fossil cats are concerned, there is no greater artist than Mauricio Antón. He has a knack for capturing the essence of fossil felids – be it a Homotherium pinning its prey or Dinofelis taking a cat nap – and I love that so many of Antón‘s illustrations feature spots and stripes. The sabercats I saw in books and stop-motion documentaries were never so colorful. They always seemed to wrapped in a relatively plain, dun-colored coat, making Smilodon look like a lion with abnormally-long canines.

Unfortunately, short of finding a frozen sabercat comparable to the steppe lion kittens announced earlier this year, we’ll  probably never know the precise span of sabercat shades. But maybe we can narrow the field a little. Today’s cats, both big and small, might be able to help us predict the presence of spots and stripes in their toothy, extinct relatives.

Today’s cats wear a beautiful array of coat patterns, from plain to dense constellations of spots and stripes. These different color options are largely dictated by two genes – Taqpep and Edn3 – the first of which lays down the general pattern of spots and stripes while the second controls local color differences, like hair banding. But these patterns don’t follow family lines. Just have a look at Panthera, the genus that includes most of the classic big cat species. There are lions (spots giving way to “plain” coloration), jaguars (large, filled-in spots), leopards (large open spots), snow leopards (large open spots), and tigers (vertical stripes) all within the same genus. Something else is more important than felid family ties in determining coat colors, and, in a 2010 study, ethologist William Allen and colleagues suggested that the answer is “ecology.”

After pulling images of 35 wild cat species from the web – because what else is the Internet good for other than cat pictures? – Allen and coauthors analyzed how coat patterns related to different species’ habitat preferences and activity patterns. Cat coats, they realized, “function as a background matching camouflage.” Cats in open, well-lit environments are more likely to have relatively plain coats while those living in forested habitats or active at primarily at night typically have complex patterns of spots and horizontal stripes.

Cats in open environments are more likely to have "plain" coats. Photo by K. Fink.
Cats in open environments, like mountain lions, are more likely to have “plain” coats. Photo by K. Fink.

There are some exceptions to this rule. Cheetahs, servals, and black-footed cats have spotted coats despite living in the same type grasslands as lions, while the elusive bay cat has a mostly-uniform coat despite prowling forests. Maybe these discrepancies have something to do with “microhabitats” or some sort of behavior not parsed out in the study, Allen and colleagues wrote, but for the most part a cat’s coat is more influenced by its ecology than who its related to.

The same probably held true for the sabercats. So while the forest-dwelling Dinofelis would be more likely to bear spots and stripes, Homotherium and other open-country cats may have lost their spots to be less conspicuous out in the grasslands.

So what about Smilodon? The cat is the ambassador for its long-fanged relatives as well as the Ice Age in general. While we may never know for sure, places like La Brea – where the sabercat is found in abundance – suggest that the iconic sabercat frequented shrubby chaparral. If the ecological connection held, therefore, Smilodon may have worn more subdued hues like the modern mountain lions that live in southern California today, or perhaps it was decked in solid spots much like the cheetah, serval, black-footed cat trio in Africa.

Despite its common nickname “saber-toothed tiger”, though, we can be pretty sure Smilodon didn’t have vertical stripes. Not only are sabercats and tigers distant relatives, but, as Allen and colleagues found, tigers are the only cats to have vertical stripes on their flanks. Perhaps the best we can hope for is that some Pleistocene artisan somewhere was inspired enough by the fossil cats to record their pelage palette for us to envision as Ice Age world that we just missed.


Allen, W., Cuthill, I., Scott-Samuel, N., Baddeley, R. 2011. Why the leopard got its spots: relating pattern development to ecology in felids. Proceedings of the Royal Society B. doi: 10.1098/rspb.2010.1734

Kaelin, C., Xu, X., Hong, L., David, V., McGowan, K., Schmidt-Küntzel, Roelke, M., Pino, J., Pontius, J., Cooper, G., Manuel, H., Swanson, W., Marker, L., Harper, C., van dyk, A., Yue, B., Mullikin, J., Warren, W., Eizirik, E., Kos, L., O’Brien, S., Barsh, G., Menotti-Raymon, M. 2012. Specifying and sustaining pigmentation patterns in domestic and wild cats. Science. doi: 10.1126/science.1220893

Ortolani, A. 1999. Spots, stripes, tail tips and dark eyes: Predicting the function of carnivore colour patterns using the comparative method. Biological Journal of the Linnean Society. 67: 433-476

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.


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

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

Fossil Whale Found Surrounded by Prehistoric Puke

Messapicetus feeding on a school of prehistoric sardines. Art by A. Gennari.
Messapicetus feeding on a school of prehistoric sardines. Art by A. Gennari.

Spread along the southwestern coast of Peru, the 9.9 to 8.9 million year old rock of the Pisco Formation has yielded some stunning fossils. Paleontologists working there have found the bones of enormous predatory whales, delicately-preserved shark jaws, and sea turtles, just to name a few highlights. But even those finds pale in comparison to a real rarity that was announced just last month: prehistoric whale vomit.

The unusual fossil, described by paleontologist Olivier Lambert and colleagues, is encased in a chunk of exceptionally-hard dolomite. The stone is so resilient, in fact, that preparing the rock away from the bones with tools and acid proved impossible. Nevertheless, the lower jaws of the early beaked whale Messapicetus gregarius can clearly be seen jutting from the rock, and surrounding those jaws are dozens of ancient sardines.

No one has found a fossil like this before. Fossil whale gut contents are extremely rare, and the sardines scattered across the fossil block had previously only been known from scales and other tattered remnants picked out of the Pisco Formation. And while it’s true that association doesn’t always equate with interaction when it comes to fossils, Lambert and coauthors make a solid case that the fossil wasn’t an accidental burial of a whale that came to rest on a bed of fish. A search in the same narrow layer around the whale failed to turn up any more fish, and, if they were anything like their modern counterparts, the ancient sardines were filter feeders that wouldn’t have been scavenging on the whale carcass.

The remains of Messapicetus and prehistoric sardines. From Lambert et al., 2015.
The remains of Messapicetus and prehistoric sardines. From Lambert et al., 2015.

The strongest scenario, Lambert and colleagues argue, is that this Messapicetus gorged itself on sardines just hours before its death. The fish fossils are preserved along the whale’s chest, throat, and mouth, showing little to no sign of digestion. Not that all of them got buried as gut contents. A large number of the 40-60 fish are scattered around the whale’s mouth. The cetacean heaved them up in death. This might be a clue as to what happened to the unfortunate Messapicetus.

The fact that Messapicetus ate filter-feeding fish doesn’t only end up being a useful indicator for the timing of whale evolution – Messapicetus patrolled coastal surface waters and was not a deep diver like its modern beaked whale relatives – but it also provides a pathway by which the cetacean could have been poisoned. There were toxic algal blooms during prehistory just as there are today, and the sardines could have fed on crustaceans that had in turn eaten the algae, eventually passing the toxins up through the food web to the Messapicetus.

Unfortunately, though, no sign of toxic algae has shown up in the same rock layer as the whale and the fish. A suspect fitting the profile has yet to appear. But the idea itself gives paleontologists something else to look for. Multiple other Messapicetus have been found nearby, not to mention the various other marine creatures, and toxic algal blooms have been blamed for other aggregations of prehistoric whales. The fatally-queasy whale could be the initial sign of ancient killers almost too small to see.


Lambert, O., Collareta, A., Landini, W., Post, K., Ramassamy, B., Di Celma, C., Urbina, M., Bianucci, G. 2015. No deep diving: evidence of predation on epipelagic fish for a stem beaked whale from the Late Miocene of Peru. Proceedings of the Royal Society B. doi: 10.1098/rspb.2015.1530

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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.

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People Sometimes Like Stinky Things—Here’s Why

Updated September 30, 2015

A corpse flower smells like a heady mix of rotten fish, sewage, and dead bodies. It’s a stench meant to draw flies, but just as surely, it draws tourists. Braving a blustery Chicago night, thousands of people lined up Tuesday for a whiff of a corpse flower named Alice at the Chicago Botanic Garden.

This woman shows a classic "disgusted" face in a video about the 2013 blooming of a corpse flower (see video, top).
This woman shows a classic “disgusted” face in a video about the 2013 blooming of a corpse flower (see video, top).

In fact, the demand to see and smell a corpse flower is so great that botanical gardens now vie to own one. Gardeners lavish them with care, hoping to force more stinky blooms from a plant whose scent is so rare (up to a decade between flowerings) and so fleeting (eight to 12 hours) that visitors are often disappointed to miss peak stench.

But why do people want to smell the thing? The reaction is usually the same: the anticipation, the tentative sniff, then the classic scrunched-up face of disgust. And yet everyone seems happy to be there.

It turns out there’s a name for this: benign masochism.

Psychologist Paul Rozin described the effect in 2013 in a paper titled “Glad to be sad, and other examples of benign masochism.” His team found 29 examples of activities that some people enjoyed even though, by all logic, they shouldn’t. Many were common pleasures: the fear of a scary movie, the burn of chili pepper, the pain of a firm massage. And some were disgusting, like popping pimples or looking at a gross medical exhibit.

The key is for the experience to be a “safe threat.”

“A roller coaster is the best example,” Rozin told me. “You are in fact fine and you know it, but your body doesn’t, and that’s the pleasure.” Smelling a corpse flower is exactly the same kind of thrill, he says.

It’s a bit like kids playing war games, says disgust researcher Valerie Curtis of the London School of Hygiene and Tropical Medicine. “The ‘play’ motive leads humans (and most mammals, especially young ones) to try out experiences in relative safety, so as to be better equipped to deal with them when they meet them for real,” she says.

People around the world make the same face when disgusted, with a downturned mouth and sometimes a protruding tongue.
People around the world make the same face when disgusted, with a downturned mouth and sometimes a protruding tongue.

So by smelling a corpse flower, she says, we’re taking our emotions for a test ride. “We are motivated to find out what a corpse smells like and see how we’d react if we met one.”

Our sense of disgust, after all, serves a purpose. According Curtis’ theory of disgust, outlined in her insightful book “Don’t Look, Don’t Touch, Don’t Eat,” the things most universally found disgusting are those that can make us sick. You know, things like a rotting corpse.

Yet our sense of disgust can be particular. People, it seems, are basically fine with the smell of their own farts (but not someone else’s). Disgust tends to protect us from the threat of others, while we feel fine about our own grossness.

Then there are variations in how we perceive odors. Some smells are good only in small doses, as perfumers know. Musk, for instance, is the base note of many perfumes but is considered foul in high concentrations. Likewise for indole, a molecule that adds lovely floral notes to perfumes but is described as “somewhat fecal and repulsive to people at higher concentrations.”

University of California Botanical Garden
University of California Botanical Garden

No one has yet, to my knowledge, tried out a low dose of corpse flower in a perfume (though you can try on an indole brew in “Charogne,” which translates to “Carrion,” by Etat Libre d’Orange). But someone could. There’s an entire field of perfumery—called headspace technology, it was pioneered by fragrance chemist Roman Kaiser in the 1970s—that’s dedicated to capturing a flower’s fragrance in a glass vial and then re-creating the molecular mix chemically. I would love to see someone give eau de corpse flower a whirl, if only they can find a headspace vial large enough.

The stench of a corpse flower, after all, is a mix of compounds, including indole and sweet-smelling benzyl alcohol in addition to nasties like trimethylamine, found in rotting fish. So I’d be very curious to know if a small amount of corpse flower would be a smell we would hate, or maybe love to hate.

I’ll leave you with my favorite example of a “love to hate” smell, from my childhood in the 1980s. At a time when I loved Strawberry Shortcake dolls and scratch-and-sniff stickers, the boys in my class were playing with He-Man dolls. Excuse me, action figures. And among the coolest, and grossest, of them was Stinkor. He was black and white like a skunk, and his sole superpower was to reek so badly that his enemies would flee, gagging.

To give Stinkor his signature stink, Mattel added patchouli oil to the plastic he was molded from. (This confirms the feelings of patchouli-haters everywhere.) It meant that you couldn’t wash Stinkor’s smell away, and it wouldn’t fade like my Strawberry Shortcakes did. The smell was one with Stinkor. And of course, children loved him.

Writer Liz Upton describes the Stinkor figure that she and her brother adored (their mother did not). The kids would pull Stinkor out and scratch at his chest, smelling him again and again. “Something odd was going on here,” Upton writes. “Stinkor smelled dreadful, but his musky tang was strangely addictive.”

If you’re the kind of benign masochist who wants to smell Stinkor for yourself, you can pay $125 or more for a re-released collector’s edition Stinkor—or you can just find an old one on eBay. The amazing thing: 30 years later, the original Stinkor dolls still stink. And people still buy them.

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This Is What Happens When You Use Rat Poison: Flymageddon

I killed the rats in my basement ceiling. At the time, they were my biggest problem.

Then I found myself in my car one night with the headlights aimed at my back door, hoping to lure a swarm of carrion flies out of the house. Carrion flies, if you’re not familiar, are the kind that lay their eggs on dead things. So then that was my biggest problem.

It all started with a gnawing sound in my basement, in the ceiling above the family room. The steady crunch-crunch of rat teeth on rafters didn’t bother me much at first; I just turned up the volume on the TV. But then the entire basement began to smell of rat urine, which turns out to smell a lot like people urine. Eventually, it didn’t matter how much Febreze I sprayed; we had hit, as I called it, RATCON 5.

My next step was to push little green blocks of rat poison into the ceiling space behind the recessed lights. This turned out to be a mistake. Not only is rat poison bad for the environment and wildlife, but this tactic also left the sated rats free to scurry into some far corner of the ceiling space to die. An exterminator poked around up there, and shrugged. “Can’t find ’em.” Soon, my basement took on a new odor: eau de dead rat.

For the next week, I slept with my windows wide open for fresh air, and the flimsy lock on my bedroom door set against possible intruders.

But the gnawing stopped. And I celebrated my hard-won victory. I had toughed out the stink, and the worst was past. I thought.

Two weeks later,  I came home from a trip and opened the door to Flymageddon.

The house was filled with giant flies.  I realized instantly that the dead rats had become a breeding ground for blowflies. Blowflies are described by Wikipedia as medium to large flies, but I would describe them more as flying bookends.

Dozens buzzed around the kitchen, thunking into me as I made my way in. I needed a weapon, and I needed one fast. Years ago, Uncle Rocky and Aunt Martha, who live in Abilene, gave me a gag gift in the form of a giant three-foot, turquoise Texas-Size Fly Swatter. Turns out, it was the best gift ever.

So there I was. I gripped the Texas Fly Swatter like a baseball bat and slowly opened the basement door.  I could hear the hum. My pulse was pounding.

Bluebottle fly. Ripanvc
Kinda pretty, actually. The bluebottle fly.

I flipped on the light and saw thousands of big dark flies, each the size of a dime, peppering the walls and window shades. Flies filled the air, and bumped against the ceiling with little buzzing thuds. Suddenly a squadron broke ranks and rushed straight up the basement stairs at me.

Or at least it seemed like they were flying toward me. I was watching a black wave of flies boil out of a light fixture in the ceiling, so I was a little distracted. But I’m pretty sure I made a noise like a creaky hinge, and slammed the door shut.

Now what? No way was I opening that door again without chemical weapons.

So armed with a can of Raid, I cracked open the basement door, stuck my arm in and sprayed a long satisfying ssssssssssssss. Yessssssssssss, I thought as I sprayed.

Now normally, I’m the live-and-let-live, shoo-em-out the door kind of person. So I also tried opening the kitchen door and stirred up a cluster of flies to usher them out. In return, they promptly flew straight for my head. All bets were off.

I needed a plan—and a partner. I was home alone, but that didn’t stop me from dragging my husband Jay into the scene from 500 miles away. I called him on speakerphone blubbering about flies.

The great thing about being married is that you can take turns being brave, and when one of you is freaking out and ready to burn your house down, the other one can spring into action. And even from 500 miles away, Jay sprung. “Go downstairs and open all the windows to let them out,” he instructed. I politely declined. As in, “What?! NO NO NO NO! Not until some of them are dead. Or most of them.”

Jay thought.

“OK,” he said, “Turn off all the lights in the house, and go turn on the car’s headlights. In fact, put the brights on. Then, open the basement door.” Flies, of course, are drawn to light. It’s not entirely clear why some insects fly toward light, but it’s probably why you’ll find flies clustered on windows. (At least at my house you will.)

Erika Engelhaupt
One of the fallen in my battle with the flies. Erika Engelhaupt
One of the fallen in my battle with the flies.

It sounded like a plan that might work. So I carefully unlocked the basement door from outside; a couple dozen flies hovered between the glass and the window shade. I pushed the door open and ran for the safety of the car.

“Don’t fall and hurt yourself running from flies!” Jay yelled, still on speakerphone. “They can’t hurt you.” At this point, he’s picturing me laid up with a broken leg, a victim of my own horror of animals that don’t even have mouths that can bite.

“I know that, logically,” I said. But when it comes to a swarm, it’s not about logic. Since I write a blog called Gory Details, you might think it should be hard to turn my stomach, but it’s not. There’s a psychology test for how easily disgusted a person is, and I turn out to be entirely average.

So this is how I found myself in my car at 10:30 p.m., watching flies meander out the door and trying to decide how long I could run the brights before the battery died.

On cue, my mother called. Hoping to help, she looked up flies in the encyclopedia and reported that the pupal stage lasts two weeks. (My mother does not use the Internet much.) Her book didn’t say how long the adults live. “Hm, well, anyway, they’ll die eventually,” she said, “if you wait long enough.”

And I waited. The flies have kept coming. Every morning now, I vacuum up the night’s casualties, and every evening I come home to more. The other day, I arrived at work and dropped my purse on my desk, and a fly flew out. To cope, the Texas Fly Swatter and I have created a no-fly zone in my bedroom.

In the meantime, I have learned a few things about my opponents. I have three kinds; one is big with a shiny blue backside and another small and the prettiest green up close. The big blue ones might be the bluebottle fly Calliphora vomitoriaappropriately named—or  Calliphora vicina, the urban bluebottle fly. The little green guys are probably a species of Lucilia, the nice entomologists at bugguide.net told me after I posted photos.

As those petered out, the biggest flies emerged—flesh flies of the genus Sarcophaga. Like sarcophagus. They’re enormous, and they buzz when they fly, and they are still in my house.

My little Lucilia.  Erika Engelhaupt
My little Lucilia.
Erika Engelhaupt

All three have their charms. Lucilia maggots have an amazing ability to eat dead flesh and ignore the living, so they’re used in maggot therapy to eat away dead, infected tissue. This works fantastically, but of course assumes that you can talk someone with, say, an oozing foot ulcer into letting a mass of maggots eat away at their foot—I suppose you say to the person that they’re only going to eat your dead foot.

I thought talking to a forensic entomologist might help me appreciate my new housemates. Sibyl Bucheli studies insects at Sam Houston State University (home to a great criminal justice program) in Huntsville, Texas (home to the busiest execution chamber in the United States). I knew I’d like her when her email arrived with a photo of her wearing a Wonder Woman tiara. (You should also check out her entomology lab’s Harlem Shake video.)

Bucheli told me about the first recorded case of forensic entomology in the 1300s. It involved carrion flies—maybe one of the species zipping around my head as I talked to her. The Chinese lawyer Sung Tzu was investigating a stabbing in a rice field and had all the workers lay out their sickles. Blowflies immediately landed on just one, even though it had been wiped clean, and Sung Tzu knew that the sickle bore traces of blood.

One of Bucheli’s students tested this method, she tells me—and found that blowflies can indeed find a bloodied and wiped-clean surface within minutes, or even seconds.

As for my flies, Bucheli says I’m probably on the second generation by now, at least. The flies have been multiplying, babies growing up and having babies of their own. I suppose it would be sweet, if the family home being handed down wasn’t a dead rat.

What’s more, she gives me bad news about the yellow-orange spots all over my windows. “That’s fly poop,” she says. “Sorry. They’re pooping on your curtains.”

Still, she made me feel a little better about them. For one thing, she’s totally brave about flies, and it made me want to be just like her. Bucheli has been at actual crime scenes, with dead bodies covered in flies. Even then, they don’t bother her. “I feel calm if I’m in a place with a million flies,” she said. “But if I’m in a city with a million people around me, that freaks me out… I understand the flies.”

They’re just being flies—eating, mating, pooping, laying eggs. They aren’t out to get me, or anyone else. “The whole six-legs, four-wings thing is beauty to me,” Bucheli said.

I’m trying to get there. In fact, I only used the Texas Fly Swatter once this morning.

But last night, after I cleared the sofa of dead flies and settled in for an episode of Bones, I heard it. The crunch-crunch of rat teeth on rafters.

This time, it’s war.

[to be continued]


(Note: I have updated the link to a test for how easily disgusted a person is. It now takes you to the appendix of Valerie Curtis‘ excellent book “Don’t Look, Don’t Touch: The Science Behind Revulsion.”)

Giant Fossil Rodent Had an Awesome Bite

New York City rats are beasts of legendary size and ferocity. That reputation probably has more to do with East Coast attitude more than anything else. Even the largest of the city’s rats look puny in comparison to South America’s capybara – at sizes over 130 pounds, the largest rodent in the world. But even the capybara is a lightweight next to the largest rodent of all time. At an estimated weight of over a ton, Josephoartigasia monesi was truly a rodent of unusual size.

First described by paleontologists

Rather than preying upon adventurers, though, these real ROUS’ munched plants in prehistoric forests and deltas. They were more guinea pig than rapacious rat. But what exactly did they eat?

There are a few ways to detect the diet of a prehistoric creature. Gut contents certainly help, as well as cololites and coprolites (feces preserved inside and outside the body, respectively). For Josephoartigasia, however, paleontologists only have a cranium. Clues about what was on the rodent’s menu have to be drawn from the skull.

One method is to look at the damage to a prehistoric creature’s teeth. Worn edges, pits, scratches, and other jots and tittles can reflect an animal’s diet close to the time of its death. This is often paired with geochemical analyses that can match carbon isotopes to certain plant types. And then there’s Finite Element Analysis. Borrowing some techniques from engineering, paleontologists can estimate bite forces and see how skulls coped with the stresses of feeding. This latter method is what University of York anatomist Philip Cox, Rinderknecht, and Blanco chose to see what Josephoartigasia could have fed on.

The reconstructed Josephoartigasia skull used in the study by Cox et al., 2015.
The reconstructed Josephoartigasia skull used in the study by Cox et al., 2015.

The first step was completing the skull. After all, a bite requires both upper and lower jaws. As a stand-in, Cox and colleagues picked the mandible of the closest-living relative to Josephoartigasiathe plains viscacha. With a 3D scan of the living rodent’s jaw to complement that of its extinct cousin, the researchers simulated how Josephoartigasia bit at different positions along the jaw.

Josephoartigasia had an especially powerful bite. At the incisors, the rodent could chomp with a force of over 300 pounds. A bite at the molars was an even more powerful 936 pounds. While the researchers stress that these are maximum values and don’t represent a typical bite, they forces are still comparable to those of carnivores like bone-cracking dogs and large crocodylians. Josephoartigasia wasn’t restricted to soft foods, but could bite through some really tough stuff.

But what makes Josephoartigasia strange is that its incisor teeth were incredibly strong. These chisel-like teeth, Cox and colleagues write, “could resist much greater forces than could ever be generated by the masticatory muscles.” The question is why.

While stress-resistant choppers don’t have to be a direct adaptation and could have more to do with large body size, Cox and colleagues suggest that such strong incisors could have been useful for digging through the ground for roots or even defense. If this was the case, the researchers speculate, Josephoartigasia was “behaving in an elephant-like manner, using its incisors like tusks, and processing tough vegetation with large bite forces at the cheek teeth.” If so, this would only add to the evidence that was one mammoth rodent.


Cox, P., Rinderknecht, A., Blanco, R. 2015. Predicting bite force and cranial biomechanics in the largest fossil rodent using finite element analysis. Journal of Anatomy. doi:  10.1111/joa.12282

Rinderknecht, A., Blanco, R. 2008. The largest fossil rodent. Proceedings of the Royal Society B. 275: 923-928  doi:

New Frog Species Reproduces Like No Other

There’s not really a good time to bring up amphibian mating habits at the dinner table. I figured that I was probably safe given that I was surrounded by scientists, but, all the same, I tried to make sure that no one was raising a fork to their mouths when I blurted out “You guys! There are frogs that have sex!”

The inspiration for my outburst came from a PLOS One paper published just before I headed out the door for New Year’s Eve dinner. In it, biologists Djoko Iskandar, Ben Evans, and Jimmy McGuire describe a frog that reproduces unlike any other known species.

Most frogs and toads look like they’re having sex when they’re mating, but this is a superficial illusion. It’s a behavior called amplexus in which the male amphibian clasps the female around the torso, shoulders, or head and releases his sperm as she lays her eggs.

The new frog species – named Limnonectes larvaepartus – is one of the rare exceptions. Like a handful of other frogs and toads, this newly-described amphibian from Sulawesi Island is capable of internal fertilization. The way the frogs accomplish this is a mystery – the Limnonectes larvaepartus males appear to lack what science has politely called an “intromittent organ” – but what happens next is a sure sign that the fanged frogs don’t spawn like other species.

All other frogs and toad species that have sex deliver their young in one of two ways. The females either lay their internally-fertilized eggs in typical amphibian fashion or the mothers give birth to well-developed froglets. Limnonectes larvaepartus splits the difference. Females of the new species, Iskandar and colleagues report, gives live birth to tadpoles.

The researchers first discovered this unusual ability while prepping collected frogs. When they dissected some of the females, “the abdominal wall was observed to quiver, and incision resulted in living tadpoles emerging from the opening.” Live frogs later gave birth to squiggly tadpoles at the time of collection and while being held for study.

An adult Limnonectes larvaepartus with tadpoles in a pool (yellow circle) and a close-up of the tadpoles. From Iskandar et al., 2014.
An adult Limnonectes larvaepartus with tadpoles in a pool (yellow circle) and a close-up of the tadpoles. From Iskandar et al., 2014.

While there’s a possibility that the fanged frogs may have been capable of retaining those tadpoles until they fully metamorphosed into froglets, Iskandar and coauthors consider this unlikely. All 19 pregnant females collected for the study had tadpoles inside, not froglets, and the researchers also found free-living tadpoles in streamside pools. Once released into the outside world, the developing frogs live off what little yolk they have left before starting to feed for themselves. And given that this news was received positively as dinner concluded, I can heartily recommend that you share the tale of this remarkable frog the next time you meet friends for a meal. I’m sure they’ll find it ribbiting.


Iskandar, D., Evans, B., McGuire, J. 2014. A novel reproductive mode in frogs: A new species of fanged frog with internal fertilization and birth of tadpoles. PLOS One. 9 (12): e115884. doi:10.1371/journal.pone.0115884

How Dinosaurs Talk With Their Feathers

What did Tyrannosaurus sound like? The movies tell us that the dinosaur shrieked and roared, befitting its status as one of the largest carnivores of all time, but the truth is that we don’t really know. The soft tissues needed to reconstruct the dinosaur’s sounds have never been found, rendering the ancient bones mute. The same is true for almost every other species of non-avian dinosaur yet discovered. The only exceptions are the crested hadrosaurs, whose circuitous nasal passages have allowed paleontologists reconstruct their tuba-like calls.

Without preserved soft tissues, the nuances of the dinosaur vocal range remain out of earshot. But it’d be a mistake to simply lament the silence of the fossil record and move on. Dinosaurs would have been able to make noise in other ways. As paleontologist Phil Senter pointed out in a review of prehistoric animal sounds, non-avian dinosaurs may have communicated with each other by “hissing, clapping jaws together, grinding mandibles against upper jaws, rubbing scales together, or use of environmental materials (e.g. splashing against water).” Even without dinosaurian roars, the Mesozoic wouldn’t have been entirely quiet.

And there’s another possibility. Enfluffled dinosaurs may have been able to talk with their plumage.

Each year dinosaurs keep getting fuzzier and fuzzier. Feathers, protofeathers, and strange bristles are turning up on an increasing number of non-avian dinosaurs, indicating that such secondary body coverings either evolved multiple times in the dinosaur family tree or were inherited from the last common ancestor of all dinosaurs. And while such dinosaurian fluff and fuzz is often considered in the context of visual displays, it’s also relevant to sound.

Modern, avian dinosaurs may be our window into the past here. When male club-winged manakins try to impress females of their species, they make a “Tick-Tick-Ting” sound. They do this with their feathers. Thanks to some specialized feather anatomy, ornithologists Kimberly Bostwick and Richard Prum found, the male manakins are able to rub their feathers together to make sexy sounds that are just as loud as a typical bird song. And birds are hardly the only vertebrates to use structure for sound. Little mammals called streaked tenrecs can make clicking noises with specialized quills they rub against each other thanks to a unique patch of soft tissue called a “quill vibrator disc.”

Perhaps non-avian dinosaurs could have sounded with stridulating feathers and bristles, too. Maybe bird-like species such as Anchiornis or even Velociraptor could rub their exquisite feathers together to tick or buzz, and I can’t help but imagine Psittacosaurus shaking its tail to rustle its quill-like bristles.

Whether any extinct dinosaurs actually behaved this way, however, relies on first discovering intact sound-specialized structures along with the bones. Such a find seems like a long shot. But if paleontologists someday find a dinosaur fossil with acoustic feathers, they might be able to do something long thought to be impossible.

Just as paleontologists have been able to reconstruct dinosaur colors on the basis of feather microanatomy, structure may allow researchers to replay dinosaur sounds. In fact, paleontologists have already achieved such a feat with a very different animal. Working from a delicately-preserved fossil, paleontologist Jun-Jie Gu and colleagues were able to reconstruct the sound of a Jurassic katydid that had acoustic “files” on its wings which created a chirping noise when rubbed the right way. If paleontologists someday find a dinosaur with similarly musical plumage, we will be able to hear them sing again for the first time in over 66 million years.

[Thanks to Phil Torres for telling me about the club-winged manakins and inspiring this foray into speculative paleontology. Top art by the most-excellent John Conway.]


Bostwick, K., Prum, R. 2005. Courting bird sings with stridulating wing feathers. Science. 309: 736

Endo, H., Koyabu, D., Kimura, J., Rakotondraparany, F., Matsui, A., Yonezawa, T., Shinohara, A., Hasegawa, M. 2010. A quill vibrating mechanism for a sounding apparatus in the streaked tenrec (Hemicentetes semispinosus). Zoological Science. 27 (5): 427-432

Gu, J., Montealegre-Zapata, F., Robert, D., Engel, M., Qiao, G., Ren, D. 2012. Wing stridulation in a Jurassic katydid (Insecta, Orthoptera) produced low-pitched musical calls to attracts females. PNAS. 109 (10): 3868-3873

Senter, P. 2008. Voices of the past: a review of Paleozoic and Mesozoic animal sounds. Historical Biology. 20 (4): 225-287

Science Word of the Day: Kleptothermy

You could bask in the sun to remedy the cold. That’s a classic reptile way of working some warmth back beneath those scales. But there’s another option. You could steal your warmth. All you’d have to do is find some seabirds.

There’s a specific term for this warmth-sucking behavior – kleptothermy. The conditions, laid out by François Brischoux and colleagues, are really quite simple. There has to be a warm animal in a relatively cool environment and another animal that can use that body heat to raise their own body temperature. For example, a blue-banded sea krait that got nice and cozy in a wedge-tailed shearwater burrow.

When not in the underground nest, the researchers found, the sea krait had a body temperature of about 89ºF. Pretty warm for an ectotherm. But when the snake coiled up inside the seabird nest, out of the way of the owners, its body temperature was more stable and rose to about 99ºF. This was definitely because of the birds. When the accommodating avians weren’t at home, the lack of their body heat caused the nest temperature to dip to 82ºF.

The snake wasn’t the only reptile to borrow a little body heat. Other reptiles, from lizards to crocodiles, have been known to inhabit the burrows of warmer-bodied animals, as well as termite mounds where the activity of all the little insects keeps the colonies on the toasty side. And in a much broader study published this year, Ilse Corkery and colleagues found that tuataras are little kleptotherms, too.

Spare a little warmth? Henry the Tuatara. Photo by KeresH, CC BY 3.0
Spare a little warmth? Henry the Tuatara. Photo by KeresH, CC BY 3.0

Tuataras – which look like lizards but belong to a different group of reptiles called rhynchocephalians – face heating problems just like the sea snakes. In fact, scientists have found that the spiny reptiles are most comfortable with body temperatures between 67 and 73ºF. The trouble is that the temperature in the nighttime forest can dip below their preferred range, and basking back to a more tepid temperature the next day can take a while. So many tuataras seek out bird burrows to spend their nights.

After following the reptiles and taking temperature readings over three years, Corkery and coauthors found that many tuataras clambered into burrows made by fairy prions. Those that did so maintained higher body temperatures thanks to the bird-warmed air of the burrows. This probably let the reptiles start the day with a higher body temperature, reducing the time needed to bask in the sun the next morning and increasing the tuataras’ chances to spend much of the day foraging for insects and frogs.

Of course, mammals show similar behaviors. The difference is that mammals typically maintain high, constant body temperatures and share the warmth with each other. Although that knowledge is cold comfort when your significant other snuggles up to you with ice cold hands or feet. In such moments, you may be the victim of kleptothermy.


Brischoux, F., Bonnet, X., Shine, R. 2009. Kleptothermy: an additional category of thermoregulation, and a possible example in sea kraits (Laticauda laticaudata, Serpentes). Biology Letters. doi: 10.1098/rsbl.2009.0550

Corkery, I., Bell, B., Nelson, N. 2014. Investigating kleptothermy: A reptile-seabird association with thermal benefits. Physiological and Biochemical Zoology. 87 (2): doi: 10.1086/674566

Tail Whips and Face Bites

Yesterday I wrote about Andrew Farke’s new paper on dinosaur combat. There’s still much to study and discover, but, as Farke makes clear, there’s a decent smattering of evidence that at least some dinosaurs in the Ornithischia subgroup – from spiky stegosaurs to dome-headed pachycephalosaurs – beat up on each other. Ornithischians weren’t the only dinosaurs, though. Some of the most famous dinosaurs of all, including celebrities such as Apatosaurus and Tyrannosaurus,  belonged to a second dinosaur subgroup called the Saurischia. How did these dinosaurs fight?

Saurischian dinosaurs come in two flavors. There’s the sauropodomorphs – long-necked, hefty dinosaurs such as Brachiosaurus and their archaic predecessors – and the theropods, a group best known because of predators like Allosaurus but which also includes birds. As they diverged from their common ancestor, the sauropodomorphs and theropods evolved into strikingly different forms that necessitated very different fighting styles.

Among the oldest possible evidence for combat on the sauropodomorph side is a messy glob of 200 million year old bone. Described by Richard Butler and colleagues a year ago, the fossil testifies to what must have been an extremely painful event wherein an unlucky Massospondylus lost the end of its tail. Exactly what happened is a mystery. The dinosaur might have been attacked by a predator, trampled by a member of its own species, or had some sort of accident. Finding out what happened is beyond our reach, yet the traumatized tail is still a potential sign of a dinosaur scuffle.

Later relatives of that poor Massospondylus suffered tail injuries, too. Paleontologists have found multiple cases of healed, inflamed vertebrae near the end of some sauropod tails, often in Late Jurassic dinosaurs such as Apatosaurus and Diplodocus. Researchers previously attributed these injuries to sneaky carnivores nibbling at the tips of sauropod tails or the painful price of trying to mate, but the whip-like anatomy of these tails tips brings up another possibility. Perhaps sauropods with these long, delicate strings of tail bones – belonging to a group appropriately-named the Flagellicaudata – really did swing their tails like whips, occasionally breaking their own bones in the process.

Sadly, we can’t watch sauropods in action to see whether or not they really used their tails this way. Modeling what sauropods could have done may be the closest we can get. A 1997 biomechanics study by Nathan Myhrvold and paleontologist Philip Currie suggested that Apatosaurus and other sauropods really could crack their tails like whips. But rather than being a weapon to strike with, the authors proposed, the tail whips would have been better for making loud cracking sounds. Still, this would be just one sort of weapon in the sauropod arsenal. Other sauropods, such as Shunosaurus, had tail clubs that they could have come in handy for predator defense, fights with each other, or as a flag for species recognition.

If sauropods used their tails for self-defense, they probably swung them at the carnivorous theropods that nipped at their flanks. Not all theropods were dedicated carnivores – many appear to have evolved omniovorous or even herbivorous lifestyles – but the best evidence for combat comes from the dagger-toothed members of the group. These predators often fought with their mouths.

Lesions and healed wounds on Mesozoic skulls show that allosaurs, tyrannosaurs, and other theropods shared a common mode of attack. They bit each other on the face. Paleontologists Darren Tanke and Philip Currie noted at least four tyrannosaurs and one specimen of the allosaur Sinraptor with such injuries on their skulls, and the juvenile Tyrannosaurus “Jane” was recently found to have pathologies on her snout that match the bite of a similar-sized rival.

There may even be evidence of a fatal tyrannosaur duel. In 2010 Phil Bell and Philip Currie described a piece of tyrannosaur jaw bone with part of another tyrannosaur’s tooth lodged in the bone. The jaw shows no sign of healing, meaning it happened around the time of death or afterward. This could have been a case of scavenging, or, as Bell and Currie point out, it might be a rare example of a fatal fight between two tyrannosaurs.

Deinonychus at the Yale Peabody Museum of Natural History. Photo by Brian Switek.
Deinonychus at the Yale Peabody Museum of Natural History. Photo by Brian Switek.

Potential signs of theropod fights aren’t restricted to the big bruisers alone, though. The quarry that inspired Jurassic Park‘s pack-hunting raptors may instead be a sign of deadly aggression among the human-sized, switchblade-clawed Deinonychus.

The number of shed teeth and partial Deinonychus skeletons found in a single Montana quarry led paleontologist John Ostrom to speculate that these dinosaurs might have been hunting their prey – a dinosaur named Tenontosaurus found in the same place – as a group. But a 2007 reassessment of the site by researchers Brian Roach and Daniel Brinkman forwarded an alternative scenario. Instead of working together, perhaps Deinonychus fought each other as they competed for access to meat. With a skeptical eye towards proposals of cooperative theropods, Roach and Brinkman hypothesized that “nonavian theropod behavior was more agonistic, cannibalistic, and diapsid-like than has been widely believed.”

The case of the Deinonychus boneyard isn’t closed just yet, nor are many of the other possibilities I’ve mentioned in this post. As Farke pointed out in his paper on ornithischian tussles, there’s only so far the available evidence can take us. Comparisons with modern animals, biomechanical studies, and pathologies are useful guideposts for following dinosaur behavior, but each method of approach has limitations. Still, the fact that we have such records to scrutinize at all is a fortuitous turn in nature, and paleontologists will continue to test old ideas and propose new ones as they try to understand the lives that fossil bones represent.

Reconstructing Dinosaur Duels

Of all dinosaurian visions ever committed to canvas, few are as famous as Charles R. Knight’s depiction of a duel between Tyrannosaurus and Triceratops. In the mural, hanging on the wall of Chicago’s Field Museum, the titans stand poised to lash out at each other in a flurry of horns and teeth. And this is often how we think of dinosaur combat – ambushes and stand-downs between predator and prey. Often overlooked are the fights dinosaurs had among their own species.

In the ever-growing ranks of known dinosaurs, members of a major group called the Ornithischia are often cast as relatively peaceful herbivores. These are the tusk-toothed heterodontosaurids, spike-thumbed iguanodonts, shovel-beaked hadrosaurs, spike-tailed stegosaurs, heavily-armored ankylosaurs, dome-headed pachycephalosaurs, and multi-horned ceratopsids. But, contrary to their timid image, such dinosaurs frequently fought members of their own species. Raymond M. Alf Museum of Paleontology scientist Andrew Farke reviews the evidence in a new Journal of Zoology paper.

Farke lays out three lines of inference that clue paleontologists in to dinosaur combat. First, and most flimsy, is analogy to modern animals. Since antelope and other bovids sometimes lock horns in tussles, Farke points out, paleontologists thought that ceratopsid dinosaurs such as Triceratops did the same. That’s a fair hypothesis in broad strokes, but it quickly breaks down in the finer fossil points.

Bovids have sinuses in their skulls. Researchers thought that the spaces acted as shock absorbers for cranial clashes, and therefore similar structures in dinosaur skulls were believed to perform the same function. As Farke found out through some of his own research, however, the sinuses of bovids have little to do with combat, and so dinosaur sinuses probably were not shock-absorbers, either. Not to mention that dinosaur horns and bovid horns are different in shape, size, orientation, and number. A Styracosaurus is not a sable antelope.

A reconstruction of Triceratops at the Carnegie Museum of Natural History. Photo by Brian Switek.
A reconstruction of Triceratops at the Carnegie Museum of Natural History. Photo by Brian Switek.

Biomechanical studies get a little closer to what was actually possible for dinosaur fights. By simulating head-butting, spike-swinging, and other combat behaviors, paleontologists can estimate whether the animals were actually capable of inflicting, and surviving, the trauma seen in movies and richly-illustrated books. As Farke is quick to note, though, such analyses “are not proof that the behavior actually happened.” There may be not better case of this distinction than the thick-skulled pachycephalosaurs.

The bipdeal pachycephalosaurs are immediately recognizable for their tonsure-style skulls – bald, often-rounded tops with a ring of spikes of varying sizes around the back. And despite the fact that the anatomy doesn’t match up that well, the late paleontologist Edwin Colbert thought that such skulls had evolved for ramming contests of the sort bighorn sheep engage in. Researchers have since tried to model how pachycephalosaurs such as Stegoceras and Pachycephalosaurus would have coped from head-on collisions, but without much agreement. Where some researchers have concluded that the reinforced skulls of these dinosaurs were well-suited to butting, other scientists have proposed that such cracks on the noggin would have been extremely traumatic, if not fatal.

For decades, there was no independent line of evidence for dome-smacking dinosaurs. The closest paleontologists could get was modeling the fights. Then, in 2012, paleontologists Joseph Peterson and Christopher Vittore published a study focused on lesions pocking a Pachycephalosaurus skull. Along with further instances Peterson published with other authors the following year, such injuries could have been caused by head-butting. And this is Farke’s third category of evidence – paleopathology.

A restoration of a gored Nedoceratops, although the opening on the dinosaur's skull is no longer considered to be evidence of combat. From Lull, 1905.
A restoration of a gored Nedoceratops, although the opening on the dinosaur’s skull is no longer considered to be evidence of combat. From Lull, 1905.

Was head-butting the cause of the skull damage? That’s still a matter of debate among experts. It’s hard enough to diagnose the cause of a modern injury or disease, much less what created a pathology in an animal that lived over 66 million years ago. And what was once perceived as an injury could turn out to be caused by something else. The odd holes in the frill of a horned dinosaur named Nedoceratopspossibly a Triceratops – were once thought to be damage caused by a rival, but are now interpreted as possible signs of an as-yet-unknown disease, a case of individual variation, or a sign of transformation through growth. No one knows for sure. Nevertheless, pathologies are signs of real events in dinosaurs lives. When successfully decoded, injuries are signs of behaviors from feeding to fights.

While the holes in the frill of Nedoceratops probably weren’t punctures created by the horns of a rival, for example, Farke’s research with Ewan Wolff and Darren Tanke has made a strong case that lesions along the frills of multiple Triceratops skulls are indicators that these dinosaurs locked horns in predictable patterns. Similar cases have been harder to find, but some densely-armored ankylosaurs are a good place to look. Through extensive research on ankylosaurid tail clubs, paleontologist Victoria Arbour has suggested that these mace-like weapons were better suited to fights between dinosaurs of the same species than defense against carnivores. Injuries to the hips and ribs of ankylosaurids could be signs of tail-whacking contests, although clear evidence of battering battles hasn’t been found just yet.

The spiky thagomizer of Stegosaurus looks scary, but how did the dinosaur actually use it? Photo by Brian Switek.
The spiky thagomizer of Stegosaurus looks scary, but how did the dinosaur actually use it? Photo by Brian Switek.

Cases for dinosaur combat are strongest when all three lines of evidence come together, Farke notes. And beyond continuing to scour the fossil record, Farke urges fellow researchers to gain a better understanding of modern animals. If researchers can identify adaptations for combat in modern animals, as well as patterns of pathology that result from fights, then paleontologists will gain a more focused frame of reference for what to look for among dinosaurs. And even though there’s on ongoing debate about the evolution and function of “bizarre structures” in dinosaurs, paleontologists can still approach how dinosaurs tussled and the range of possible behaviors for flashy pieces of anatomy.

We may never really know whether or not Iguanodon used those thumb spikes for defense or why about ten percent of Stegosaurus spikes were broken during their owner’s lifetime, but Farke’s paper boils down to a simple conclusion – dinosaurs fought, and we’re only just beginning to understand how they pummeled each other during prehistory.


Farke, A. 2014. Evaluating combat in ornithischian dinosaurs. Journal of Zoology. doi: 10.1111/jzo.12111

What Do Croc Tools Mean For Dinosaur Innovation?

Alligators, crocodiles, and gharials are exceptional ambush predators. Carrying on a tradition of wait-and-strike that has worked for them since the Mesozoic, living crocodylians can watch from the water’s surface with little more than their eyes and nostrils breaking the surface of the water. But even such effective camouflage isn’t always enough to sneak up on potential meals. Independent of each other, American alligators and mugger crocodiles appear to have learned to use lures to entice avian prey.

Psychologist Vladimir Dinets and coauthors described the sneaky behavior late last year in an Ethology Ecology & Evolution paper. Silly as it may sound, mugger crocodiles at India’s Madras Crocodile Bank and American alligators at the St. Augustine Alligator Farm Zoological Park balanced sticks on their snouts to invite nesting egrets to come within chomping range. The twigs do little to hide the tough-skinned archosaurs beneath, but birds in need of building materials will sometimes risk being ingested to grab a stick from the crocodylians’ snouts.

A mugger crocodile "stick-displaying." From Dinets et al., 2013.
A mugger crocodile “stick-displaying.” From Dinets et al., 2013.

This is a rare report of tool use in reptiles, although not everyone is sold on that conclusion. Given that reptiles have traditionally been thought to be slow, stupid, and generally boring, the bar is set high for confirming behaviors as complex as intentionally using lures to snaffle up prey. But let’s say that Dinets and colleagues are right and crocodylians truly are capable of selecting and using tools. According to the study authors, this opens up the possibility that some of the late, great non-avian dinosaurs could have been tool-users, too.

An American alligator and the cattle egret in its stomach form an extant phylogenetic bracket. Birds are dinosaurs and crocodylians are the closest living relatives to the dinosaur group as a whole, and so characteristics shared by both lineages may have been present in the last common ancestor of both groups as well as extinct descendants of that common ancestor. Non-avian dinosaurs, from Triceratops to Tyrannosaurus, fall within this bracket, leading Dinets and coauthors to leave their paper with the coy line “Phylogenetic bracketing by birds and crocodilians suggests that the behavior of non-avian dinosaurs was most likely very complex as well.”

But that’s too simple an argument. The way mugger crocodiles use sticks as traps is quite different from the way birds such as the stunningly smart New Caledonian crows use tools to tackle a variety of tasks. Extant phylogenetic bracketing can work for anatomical features or biochemical characteristics than can be shown to be the same in two distantly-related animals, but behavior is much more malleable and prone to independent evolution of similar habits. Evolutionary bracketing alone can’t draw us to visions of Allosaurus draping ferns over its snout to lure unwary little Diplodocus or feathery little Troodon using sticks to dig insects out of their underground hiding places.

While they had very small brains, even large dinosaurs - such as this Diplodocus - may not have been as dumb as often thought. Photo by Brian Switek.
While they had very small brains, even large dinosaurs – such as this Diplodocus – may not have been as dumb as often thought. Photo by Brian Switek.

Nevertheless, clever crocodylians have opened the possibility of tool-using non-avian dinosaurs in a different way. By dint of their ecotothermic metabolism and relatively smaller brain size, reptiles have often thought to be dumb animals. A surge of interest has shown that this old understanding is wrong. Reptiles are more socially complex and smarter than expected, and the possible discovery of tool-use in crocodylians indicates that even non-avian dinosaurs, oft-ridiculed as small-brained, may have had the mental capabilities to use tools.

We can’t observe non-avian dinosaurs directly. We’re 66 million years too late for that. As far as intelligence goes, all we have left are the internal molds and in-filled casts of their brains. Matched with estimates of body mass, what remains of dinosaur brains have been used to derive an encephalization quotient that in turn acts as a rough proxy for behavioral complexity and intelligence. A 50 foot long sauropod with the brain the size of a walnut probably wasn’t as bright as a roughly human-sized troodontid with a brain as large as an ostrich’s.

Still, such studies have shown that non-avian dinosaurs were not as painfully small-brained as early paleontologists thought. Many non-avian dinosaurs had a relationship between brain and body size similar to living reptiles, including crocodylians, and some of the brainier dinosaurs were more similar to birds. If non-avian dinosaurs were generally on par with living reptiles, and living reptiles are smarter than expected, then it’s not unreasonable to wonder about tool-using dinosaurs.

But how would we know? If non-avian dinosaurs used tools, they would have made use of the materials around them – sticks, leaves, stones. We wouldn’t know a dinosaur tool even if we found one. Perhaps trace fossils could be of assistance – little insects pierced with a particular sort of twig, or scratches in the ground made by sticks rather than claws – but researchers would have to recognize them and find enough of a sample to support the weight of an exceptional hypothesis. We may never know whether any non-avian dinosaurs were innovative animals. I hope the fossil record proves me wrong.


Buchholtz, E. “Dinosaur paleoneurology,” in The Complete Dinosaur, 2nd ed., eds. Brett-Surman, M., Holtz, T., and Farlow, J. Bloomington: Indiana University Press. pp. 191-208

Dinets, V., Brueggen, J., Brueggen, J. 2013. Crocodilians use tools for hunting. Ethology Ecology & Evolution. DOI: 10.1080/03949370.2013.858276

Jerison, H. 1969. Brain evolution and dinosaur brains. The American Naturalist. 103, 934: 575-588