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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.

Looking Nature in the Mouth

Spotted hyenas seem to be the perfect archetypes of dirty scavengers. They’re smelly, not quite so charismatic as the big cats they compete with, and, most importantly, have bone-crunching jaws capable of dismantling most any carcass left to rot among the African grasslands. In the impression of savanna dominance that persists in many of our imaginations, lions are regal predators while hyenas are a dedicated clean-up crew, assisting the economy of nature by horfing down pungent gore. This is not at all true.

While these carnivores feed on carrion when they can, long-term studies of spotted hyena populations have shown that they hardly rely on kills made by other carnivores. Scavenging accounted for about 33% of the diet of the Serengeti’s spotted hyenas in classic observations made by Hans Kruuk, while a 1999 paper by Susan Cooper and colleagues reported that the “Talek clan” of spotted hyenas in Kenya’s Masai Mara got all but 5% of their meat from hunting, making them among the most predatory hyenas ever seen. And after reviewing the scientific reports of hyena feeding behavior, Matt Hayward found that hyenas are generalist hunters. They usually don’t bother with some of Africa’s largest herbivores – buffalo, giraffe, and plains zebra – but otherwise they literally take what they can get.

Spotted hyenas are not loathsome carrion chasers. They remain among Africa’s apex carnivores through their ability to hunt, either alone or in packs. Not all their kills remains theirs, however. Lions are their chief competition, and, based on observations by Kruuk, spotted hyenas lose anywhere from 5 to 20% of their kills to kleptoparasite lions. The “king of the beasts” has no honor when it comes to meals, and they have been tussling with hyenas over kills since the last Ice Age, at least.

None of this will surprise zoologists. Experts on Africa’s fauna have known about the predatory prowess of spotted hyenas since the 1960s. Yet the myth hangs on. The way we think about and categorize nature obscures variation and flexibility for simplified, distilled factoids. Animals are labeled as herbivore, carnivore, or omnivore, or, as with the spotted hyena, categorized as a hunter or scavenger, as if these titles lock the actual animals into patterns of behavior they cannot violate.

Tyrannosaurus rex stands over a kill at the Carnegie Museum of Natural History. Photo by Brian Switek.
Tyrannosaurus rex stands over a kill at the Carnegie Museum of Natural History. Photo by Brian Switek.

The same problem extends to the fossil record. For years, news pieces and documentaries have breathlessly forwarded the question of whether the great Tyrannosaurus rex was a consummate hunter or a grubby scavenger. Setting up such a dichotomy, where the carnivorous tyrant must have done only one or the other, was nonsense. T. rex certainly chased down prey and scoffed rotting flesh, a conclusion backed up by tooth-scored bones and injuries on the tails of at least two hadrosaurs. More than that, dinosaurs taken as the ultimate in predatory hypercarnivores likely scavenged when they had the chance. The turkey-sized, sickle-clawed Velociraptor was certainly well-equipped for tearing into prey, but, as bitten and ingested bones suggest, this wouldn’t have stopped the dinosaur from taking easy meals left out in the open.

Then there are the animals whose dietary exploration takes us entirely by surprise. Whether a spotted hyena or a tyrannosaur is hunting or scavenging, they’re still eating meat. But there are animals that we think of as dedicated carnivores that scarf plants now and then. Alligators and crocodiles, for example, eat fruit often enough that they might actually help disperse seeds. And primarily herbivorous animals vary their meals, too. As Darren Naish has pointed out, “‘pure herbivory’ is apparently much rarer than we used to think” – deer and cows will often eat small birds and other animals if they can. Would a cow eat you and everyone you care about? If you’re a little bird, maybe.

Hippos go one step further. The tubby, tusked mammals are imposing enough that they sometimes try to snatch kills from predators. In an incident reported by Joseph Dudley, a hippo in Zimbabwe’s Hwange National Park killed an impala that had the bright idea of trying to escape a wild dog by swimming across a small pool. The hippo presumably killed the herbivore for straying into the wrong territory, but that didn’t stop another hippo from inspecting and consuming some of the impala. And while this was going on, Dudley wrote, wild dogs took down another impala near the water’s edge. A group of hippos ran the dogs off from the kill for some unknown motive, and once the dogs were gone the hippos scooped up whatever loose bits of meat were left on the ground.

Deer and hippos are primarily herbivores, but it isn’t aberrant when they go carnivore. We simply weren’t looking when they did so, or didn’t acknowledge the behavior. There are likely plenty of other examples of such dietary flexibility that pay no mind to our preconceptions about what certain animals eat. Nature is far stranger and more varied than we could expect. To see apparent rapacity or docility is one matter. To truly look nature in the mouth is another.


Cooper, S., Holekamp, K., Smale, L. 1999. A seasonal feast: long-term analysis of feeding behavior in the spotted hyaena (Crocuta crocuta). African Journal of Ecology. 37, 2: 149-160

Dudley, J. 1998. Reports of carnivory by the common hippo Hippopotamus amphibius. South African Journal of Wildlife Research. 98, 28: 58-59

Hayward, M. 2006. Prey preferences of the spotted hyaena (Crocuta crocuta) and degree of dietary overlap with the lion (Panthera leo). Journal of Zoology. 270, 4: 606-614

Holtz, T.R. 2008. “A critical reappraisal of the obligate scavenging hypothesis for Tyrannosaurus rex and other tyrant sinosaurs.” in Larson, P. and Carpenter, K. (eds) Tyrannosaurus rex: The Tyrant King. Bloomington: Indiana University Press.

Hone, D., Choiniere, J., Sullivan, C., Xu, X., Pittman, M., & Tan, Q. 2010. New evidence for a trophic relationship between the dinosaurs Velociraptor and Protoceratops. Palaeogeography, Palaeoclimatology, Palaeoecology. 291, 3-4: 488-492

Hone, D., Tsuihiji, T., Watabe, M., Tsogtbaatr, K. 2012. Pterosaurs as a food source for small dromaeosaurs. Palaeogeography, Palaeoclimatology, Palaeoecology. 331-332: 27-30

Margalida, A., Campión, D., Donázar, J. 2011. Scavenger turned predator: European vultures’ altered behavior. Nature. 480: 457

Trinkel, M. 2010. Prey selection and prey preferences of spotted hyenas Crocuta crocuta in the Etosha National Park, Namibia. Ecological Research. 25, 2: 413-417


A Long-Lost Bone

I’m missing a bone. You are, too, although which bone that is depends on your anatomical sex. For me and male readers of this post, it’s the baculum – the enigmatic “penis bone” found in the members of many mammals and not us. There is nothing bony about a human boner. But, through the winding path of evolution, female readers are lacking their own genital ossification that’s just as mysterious and has been rarely discussed – the os clitoridis.

The os penis and os clitoridis are osteological correlates of each other. They are the same bone, but in different form in each sex. And while the os clitoridis – sometimes called by the more elegant-sounding name “baubellum” – isn’t a feature of all mammal lineages, the bone has been found in a variety of species among distantly-related beasts. In a 1954 paper in which he lamented that the peculiar bone has “been only sporadically studied”, zoologist James Layne documented that the os clitoridis has been found in a variety of rodents, carnivorans, and primates – marmots, seals, cats, bats, bears, galagos, gibbons, and more had some sort of bone beneath the clitoris.

For his part, Layne focused on the curious genital structures of squirrels. The bones were quite small, often between one and three millimeters long, but many were just as oddly ornamented as the penis bones of males. Figured in a gallery of equivalent bones from other species in Layne’s paper, the os clitoridis of the Tropical ground squirrel (Notocitellus adocetus) is a flared, spurred spoon. The same bone in other squirrel species twist, taper, and flare in their own distinctive ways, and, often, closely resemble the os penis in male conspecifics. Experiments in the lab, and not just anatomy, have underscored that baubellem and baculum are different versions of the same bone.

Rats and mice, those icons of laboratory studies, are our guides here. Female mice have a clitoral bone, and female rats of some study strains have a small bone that corresponds to the tip of the baculum in male rats. Few seemed to pay much attention to this fact until, in their efforts to understand how different hormones affected tumor formation in the genital tracts of rats during the late 1960s, researchers Alfred Glucksmann and Cora Cherry found that injections of testosterone caused the female rats to form new genital bone. Following that thread, Glucksman and Cherry discovered that testosterone injections during the early days of life caused the female rats to grow a larger os clitoridis which closeled resembles the male counterpart. Working with other researchers, Glucksmann later found the same to be true for mice. “With prolonged androgen treatment”, osteologist Brian Hall has written about this find in scientific deadpan, “growth of these induced bones can be promoted and the distal element extended.”

Yet the connection between hormone and baubellem isn’t always so clear. For one thing, testosterone and other androgens seem to have nothing to do with why female fossa have disappearing clitoral bones. Fossa (Cryptoprocta ferox), made famous by the exceptionally annoying kid’s film Madagascar, are lithe, tawny carnivores closely related to civets and genets. And, apparently, they are the first recognized case of what zoologist Clare Hawkins and colleagues term “transient masculinization.”

A fossa at the Bronx Zoo. Photo by Brian Switek.
A fossa at the Bronx Zoo. Photo by Brian Switek.

So far as zoologists have documented, about nine mammal species have females that take on male characteristics during the course of their lives. The most famous example is the spotted hyena. Females of Crocuta crocuta are masculinized to the point where they develop a prominent pseudo-penis that, in one of the most startling examples of evolutionary jury-rigging, hyena mothers give birth through.

Young female fossa don’t have to cope with changes quite so extreme, but, as Hawkins and colleagues noted in a 2002 study, they produce a “a mildly pungent orange secretion” also found in mature males and have “an enlarged, spinescent clitoris supported by an os clitoridis” similar to the corresponding genital equipment of the opposite sex. Unlike the female hyenas, though, female fossa don’t retain these traits. They’re only masculinized for a short part of their lives, starting around seven months of age until the fossa’s second or third year, before the traits start to fade. Only a smaller form of the clitoral bone is left in adult female fossa. Why?

Sex hormones don’t appear to be the answer. From anatomical, genetic, and hormonal examinations of wild and captive fossa, Hawkins and coauthors couldn’t find any difference in androgen levels between juvenile and adult females. Nor was there any connection between androgen levels and the masculine traits – such as “os clitoridis length” and “secretion score” – of young female fossa. It could be that young female fossa have “target tissues” where the relatively low levels of androgens have more influence over anatomy, but, Hawkins and colleagues noted, no one knows whether this is the case.

Exactly how the temporary change transpires is unknown. Despite the black box of the carnivoran’s transient masculinization, though, Hawkins and collaborators offered two hypotheses as to why secreting orangish fluid and having a spiny clitoris supported by bone might be advantageous to young female fossa.

The male traits start to become prominent about the time female fossa are aggressively run off by their mothers and, even though they are not yet mature enough to breed, they may encounter the unwanted attention of a wandering male seeking mates during the very brief mating season. Such an encounter can be dire. A male could maul or even kill a young female fossa, so, Hawkins and coauthors propose, looking like a male during the vulnerable period in their lives “could allow them to escape detection or could signal to males that they are not a potential mate.” Then again, territorial adult females can be just as much as a threat as roving males, so perhaps young female fossa have a better chance of finding their own patch of forest if they disperse from home in disguise.

Female fossa changes could be attributable to both scenarios. The immature civets face dangers from males and females alike. But, beyond the enigmatic mechanics of the anatomical change, we still don’t know why young female fossa evolved such mimicry. Nor is this the only mystery the os clitoridis embodies. Why some of our primate relatives have genital bones, while we lack them, is an evolutionary conundrum just as vexing.

For my part, I’m glad I don’t have a baculum. I can’t imagine that I would have been keen on playing soccer or sparring in Taekwondo classes if there was a possibility that I’d be carted off to the emergency room with a shattered penis bone. (Although, speaking of such injury, there are pathological cases of penis bones forming in humans, including after trauma such a kick or gunshot wound to the area. Perhaps I should have reconsidered my childhood activities, after all.) But I still want to know why the genital bone – in both female and male humans – disappeared without a trace.

We’re not unique among primates in lacking osteological genital curiosities. In a review of human reproduction from a primatological perspective, anthropologist Robert Martin noted that tarsiers don’t have penis or clitoris bones, nor do several genera of New World monkeys. And even in primates that have them, such as our close ape relatives, the genital bones have shrunk to a negligible, almost unnoticeable size. While os penis and os clitoridis bones are prominent in ring-tailed lemurs, for example, they’ve almost entirely disappeared in gibbons and chimpanzees.

In primates, at least, a baculum is hypothesized to help support the penis during long bouts of sex between individuals that rarely encounter each other during the mating season. Males that are often around their mates, the following argument goes, can copulate more frequently for shorter amounts of time and therefore don’t require osteological assistance for their erections. Perhaps. There are other hypotheses out there, not all of which are mutually exclusive. But what, then, are we to make of the baubellem? The baculum and baubellum are old bones that have been retained in some forms of placental mammal and lost in others over millions and millions of years. And while a great deal of ink has been spilled over the function of the baculum and our lack, I haven’t been able to find so much as even a minor degree of interest into why the baubellum evolved and exists in many mammal species.

Even in reduced form, a clitoral bone is present in an array of female primates. And when we look beyond our primate kin – among Layne’s squirrels, for one – female mammals have os clitoridis of prominent size and intricately complex morphology. So much so that zoologists have occasionally pondered using the bones to tell species apart. But beyond such utility, the clitoral bone is often ignored.

There’s an assumption that the clitoral bone is functionally unimportant and just a case of females developing a masculine trait – a reverse of males having nipples. But I believe the bone is more unstudied than insignificant. The importance of the clitoral bone in the life of female fossa, for one, is a clue that there is more to the curious bone than researchers have appreciated. Given how little we know about this varied skeletal feature, we’d be terribly foolish to relegate the os clitoridis as a masculine leftover of only passing interest. All the same, the os clitoridis, so inscrutable, is a totem of our shared history with our therian relatives. Tracing back what we’re missing, we walk along the pathway of our deep history – a mysterious absence guides us back through evolutionary enigmas barely considered.

[Top image by Flickr user Nathan Rupert.]


Glucksmann, A., Cherry, C. 1972. The hormonal induction of an os clitoridis in the neonatal and adult rat. Journal of Anatomy. 112, 2: 223-231

Glucksmann, A., Ooka-Souda, S., Miura-Yasugi, E., Mizuno, T. 1976. The effect of neonatal treatment of male mice with antiandrogens and of females with androgens on the development of the os penis and os clitoridis. Journal of Anatomy. 121, 2: 363-370

Hall, B. 2005. Bones and Cartilage: Developmental and Evolutionary Skeletal Biology. San Diego: Elsevier Academic Press. p. 344

Hawkins, C., Dallas, J., Fowler, P. Woodroffe, R., Racey, P. 2002. Transient masculinization in the fossa, Cryptoprocta ferox (Carnivora, Viverridae). Biology of Reproduction. 66: 610-615

Layne, J. 1954. The os clitoridis of some North American Sciuridae. Journal of Mammalogy. 35, 3: 357-366

Martin, R. 2007. The evolution of human reproduction: A primatological perspective. Yearbook of Physical Anthropology. 50: 59-84

Murakami, R., Mizuno, T. 1984. Histogenesis of the os penis and os clitoridis in rats. Development, Growth, and Differentiation. 26, 5: 419-426

Stockley, P. 2012. The baculum. Current Biology. 22, 24: R1032

The Puzzle of the Frugivorous Crocs

Crocodylians have a carnivorous grin. Their conical teeth and crushing jaws leave little doubt of their predatory inclinations, and this impression is only reinforced by staple documentary scenes of Nile crocodiles launching themselves from the water with the aim of snagging an unwary zebra or wildebeest. Yet the fearsome Crocodylus niloticus – as well as twelve other species of crocodylian found around the world – occasionally snaffle up less meaty fare. A variety of crocodylians put their intimidating jaws to work on fruit and other vegetation; so much so that they may actually be significant players in helping plants disperse their seeds.

Wildlife Conservation Society herpetologist Steven Platt and colleagues have collated a list of fruit and seed-eating crocodylians in a new Journal of Zoology review. The evidence the zoologists compiled comes in two types. There are direct observations of crocodylians scoffing fruit and seeds, but a great deal of information – particularly for American alligators – has been extracted from dissected stomachs and feces. The trick is determining how those fruits and seeds got there.

Just because an alligator or crocodile had seeds in its stomach doesn’t mean that the animal intentionally ate fruits or nuts. An alligator might accidentally consume vegetation while trying to catch small insects or gastropods, or when swallowing stomach stones. Hard seeds might even act as gastroliths themselves, helping grind up food in the stomach. Fruits and seeds could also come from the gut contents of swallowed prey, particularly small birds and mammals.

Despite these caveats, though, there are accounts of several crocodylian species intentionally eating fruit. Captive broad-snouted caimans have been seen eating Philodendron fruit, and captive American alligators have been observed foraging on wild grape, elderberry, and various citrus fruits. (Not to mention the occasional watermelon during enrichment.) The question is whether this happens in the wild.

In the case of the frugivorous broad-snouted caimans, researchers initially speculated that the crocodylians learned or copied the strange behavior from fruit-eating reptiles kept in the same enclosure. But the review by Platt and coauthors notes that there are scattered reports of wild crocodylians consuming fruit and seeds, and through Central and South America there are even fruits nicknamed “alligator pear” and “alligator apple” because different species of caiman regularly eat them. And sometimes wild crocodylians are inadvertently fed by humans – American alligators have been captured on motion-sensitive cameras eating corn left out by automatic wildlife feeders.

Why crocodylians are eating fruits and seeds, as well as how they’re detecting the plants, is unclear. With the exception of a fruit hitting the water and the crocodylian snapping in reflex, the attraction of fruits and seeds to the carnivores is a mystery. But, contrary what was traditionally assumed about their digestive systems, crocodylians are capable of breaking down the carbohydrates, proteins, and fats in vegetable matter, so the fruit-eating by these archosaurs could be a nutritional supplement and not just a mistake or unusual behavior.

Regardless of why crocodylians are eating fruit and seeds, the digestive system of the consumers seems to treat the hard objects just like snail shell and other indigestible items. Even though crocodylian gastric fluids are highly acidic – a pH of 1.2 to 2.0, the review notes – seeds are often found intact in the stomach contents or feces of alligators and their kin. No one knows how seeds fare after being eaten away by an alligator’s gastric fluids and beaten by gastroliths, but that’s primarily because no one has thought to investigate the question. And, as the authors point out, “the defecation habits of wild crocodiles are poorly documented,” thus hampering our ability to understand whether the seeds are being deposited in spots amenable to later germination.

Assuming that at least some seeds survive the rough treatment, though, Platt and colleagues propose that crocodylians could act as toothy, armored seed dispersers. Depending on size, life stage, and species, different sorts of crocodylians have been seen to move long distances in short intervals – several American alligators traveled at least 13.4 kilometers in a single day, while a saltwater crocodile once traveled a distance of 23.3 kilometers in a day. Given the long stretches of waterways they travel, alligators, crocodiles, caimans, and gharials could transport seeds far along river systems, distributing seeds wherever they stopped to ditch their stomach contents or otherwise relieve themselves.

More is unknown than known about crocodylians and fruit. But as Platt and coauthors argue, intentional fruit-eating seems to be a widespread behavior among these knobbly, pointy-toothed archosaurs. Crocodylians can be considered “occasional frugivores.” And while they don’t seem to have discriminating tastes about the fruit and seeds they eat, crocodylians nonetheless have the ability to transport those plant parts far and wide. Beyond those facts, though, researchers need better data. “Basic information on the defecation habits of crocod[y]lians would go far toward understanding the likelihood of post-digestive seedling survival,” Platt and collaborators write, and vegetable matter found in the guts and feces of crocodylians should be studied carefully rather than being assumed to be non-food items.  The case that crocodylians are significant seed dispersers is tantalizing, but there’s a great deal of dirty work left to do.


Platt, S., Elsey, R., Liu, H., Rainwater, T., Nifong, J., Rosenblatt, A., Heithaus, M., Mazzotti, F. 2013. Frugivory and seed dispersal by crocodilians: an overlooked form of saurochory? Journal of Zoology. doi:10.1111/jzo.12052

The Turtle That Wasn’t There

Last month I attended a TEDx symposium on the controversial prospect of “de-extinction.” All day long, I heard researchers of various stripes give their expert opinions on whether we can – and should – reinvent extinct species to add a new dimension to conservation. But there is another way to de-extinctify a species. Researchers Heiko Stuckas, Richard Gemel, and Uwe Fritz have just removed a turtle from the ever-growing list of extinct species by demonstrating that the reptile never existed in the first place.

Sometime between 1901 and 1906, the Natural History Museum in Vienna, Austria acquired a trio of turtle specimens from the Zoological Museum Hamburg. According to the labels, the reptiles had been collected by the German naturalist August Brauer a decade before, when Brauer sampled critters from the island of Mahé – part of the Seychelles island chain, situated nearly halfway between India and Madagascar. Strangely, though, the turtles closely resembled a species found hundreds of miles away on mainland Africa.

A map showing the range of Pelusios castaneus (blue) and the supposed island species P. seychellensis (red). From Stuckas et al., 2013.
A map showing the range of Pelusios castaneus (blue) and the supposed island species P. seychellensis (red). From Stuckas et al., 2013.

When the Viennese zoologist Friedrich Siebenrock had a look at the preserved reptiles in 1906, he was struck by how closely Brauer’s turtles resembled a turtle now known as Pelusios castaneus – a turtle found over a wide swath of western Africa. If the distance between the mainland and island turtles were not so great, Siebenrock commented in his description of the Mahé turtles, he’d be tempted to call them the same species. But there was no way the little turtles could have crawled all the way across Africa, nor somehow dispersed from habitat to habitat around the edge of the continent. The distance deemed that the two had to be different species.

Not everyone agreed with Siebenrock’s conclusion. For years afterward, different researchers often lumped Brauer’s turtles into the west African species or another island species on the basis of anatomy. That is, until 1983 when herpetologist R. Bour proposed that Brauer’s old specimens truly did represent a distinct species. Bour called the turtles Pelusios seychellensis, and it seemed that Brauer had collected some of the last ones. Several searches after 1983 tried, and failed, to find the turtles. In the span of a century, it seemed, Pelusios seychellensis had gone extinct – perhaps the only time on record that humans totally exterminated a species of freshwater turtle.

But Siebenrock’s hunch about the connection between the island and mainland turtles was more right than he knew. When Stuckas, Gemel, and Fritz sampled mitochondrial DNA from the museum specimen that bears the name Pelusios seychellensis and compared those genetic clues to those of other turtles, they found that the museum specimens fell within the range of variation for west African Pelusios castaneus individuals. The unique island species never actually existed. Somehow, researchers had misidentified Brauer’s specimens. But how could west African turtles have found their way to Mahé? According to Stuckas and colleagues, they didn’t.

There’s no evidence that Brauer’s turtles hauled themselves clear across Africa. Nor is there any indication that humans brought them there at some point in the past. All this confusion might simply be the result of poor labeling and miscommunication.

Brauer took the trip during which he was supposed to have collected the turtles between May 1895 to January 1896. But he didn’t immediately give his finds to a museum. Specimens from his private collection didn’t get transferred to the Zoological Museum Hamburg until five years after the Seychelles trip, and those turtles soon went on to Vienna’s Natural History Museum. Somewhere in all that shuffling, the west African turtles might have been lumped in with the Seychelles reptiles or otherwise confused. Whatever happened, though, a prominent clue indicates that the turtles were not collected from the wild. One, and possibly two, of the turtles have a perforation through their shells identical to the sort that turtle purveyors have traditionally used to tie turtles together until they are sold for food. Wherever Brauer got the turtles from, he seems to have purchased them.

This isn’t the first time bad bookkeeping has led zoologists to erroneously erect new species. Stuckas and coauthors point out two other instances – a mislabeled American snapping turtle was confused for what was thought to be a new species from New Guinea’s Fly River, and a supposed new tortoise found in Vietnam turned out to be “an escaped pet tortoise from Madagascar.” This is why well-kept locality data and responsible curation practices are essential. We need to know when, where, and how a specimen was collected to understand what we’re studying. (Paleontologists also know this well.) And that context is not only essential for exploring the diversity of life, but also conservation. In our efforts to assist imperiled species, we need to know whether or not we’re looking at something unique and critically endangered, a wayward member of a more common species, or whatever other alternative may be the case. Understanding even such a basic facet of ecology as the identity of a species requires a great deal of attention and care.


Stuckas, H., Gemel, R., Fritz, U. 2013 One extinct turtle species less: Pelusios seychellensis is not extinct, it never existed. PLoS ONE 8, 4: e57116. doi:10.1371/journal.pone.0057116