Just got the APP new issue alert and there are three papers that I think readers of this blog will find particularly interesting:

That’s all for now, just popping in to let people know about these things.

ostrich peeing

cormorant peeing

alligator peeing

Stand by . . . grumpy old man routine compiling . . . 

So, someone at Sony decided that an Angry Birds movie would be a good idea, about three years after the Angry Birds “having a moment” moment was over. There’s a trailer for it now, and at the end of the trailer, a bird pees for like 17 seconds (which is about 1/7 of my personal record, but whatever).

And now I see these Poindexters all over the internet pushing their glasses up their noses and typing, “But everyone knows that birds don’t pee! They make uric acid instead! That’s the white stuff in ‘bird poop’. Dur-hur-hur-hurrr!” I am reasonably sure these are the same people who harped on the “inaccuracy” of the peeing Postosuchus in Walking With Dinosaurs two decades ago. (Honestly, how I didn’t get this written and posted in our first year of blogging is quite beyond my capacity.)

Congratulations, IFLScientists, on knowing One Fact about nature. Tragically for you, nature knows countless facts, and among them are that birds and crocodilians can pee. And since extant dinosaurs can and do pee, extinct ones probably could as well.

So, you know . . . try to show a little respect.

So, you know . . . try to show a little respect.

Now, it is true that crocs (mostly) and birds (always?) release more of their nitrogenous waste as uric acid than as urea. But their bodies produce both compounds. So does yours. We mammals are just shifted waaaay more heavily toward urea than uric acid, and extant archosaurs – and many (but not all) other reptiles to boot – are shifted waaaay more heavily toward uric acid than urea. Alligators also make a crapload of ammonia, but that’s a story for another time.

BUT, crucially, birds and crocs almost always release some clear, watery, urea-containing fluid when they dump the whitish uric acid, as shown in this helpful diagram that I stole from International Cockatiel Resource:

International Cockatiel Resource bird pee guide

If you’ve never seen this, you’re just not getting to the bird poop fast enough – the urine is drying up before you notice it. Pick up the pace!

Sometimes birds and crocs save up a large quantity of fluid, and then flush everything out of their cloacas and lower intestines in one shot, as shown in the photos dribbled through this post. Which has led to some erroneous reports that ostriches have urinary bladders. They don’t, they just back up lots of urine into their colons. Many birds recapture some water and minerals that way, and thereby concentrate their wastes and save water – basically using the colon as a sort of second-stage kidney (Skadhauge 1976).

Rhea peeing by Markus Buhler

Many thanks to Markus Bühler for permission to post his well-timed u-rhea photo.

[UPDATE the next day: To be perfectly clear, all that’s going on here is that the birds and crocs keep their cloacal sphincters closed. The kidneys keep on producing urine and uric acid, and with no way out (closed sphincter) and nowhere else to go (no bladder – although urinary bladders have evolved repeatedly in lizards), the pee backs up into the colon. So if you’re wondering if extinct dinosaurs needed some kind of special adaptation to be able to pee, the answer is no. Peeing is an inherent possibility, and in fact the default setting, for any reptile that can keep its cloaca shut.]

Aaaanyway, all those white urate solids tend to make bird pee more whitish than yellow, as shown in the photos. I have seen a photo of an ostrich making a good solid stream from cloaca to ground that was yellow, but that was years ago and frustratingly I haven’t been able to relocate it. Crocodilians seem to have no problem making a clear, yellowish pee-stream, as you can see in many hilarious YouTube videos of gators peeing on herpetologists and reporters, which I am putting at the bottom of this post so as not to break up the flow of the rant.

ostrich excreting

You can explore this “secret history” of archosaur pee by entering the appropriate search terms into Google Scholar, where you’ll find papers with titles like:

  • “Technique for the collection of clear urine from the Nile crocodile (Crocodylus niloticus)” (Myburgh et al. 2012)
  • “Movement of urine in the lower colon and cloaca of ostriches” (Duke et al. 1995)
  • “Plasma homeostasis and cloacal urine composition in Crocodylus porosus caught along a salinity gradient” (Grigg 1981)
  • “Cloacal absorption of urine in birds” (Skadhauge 1976)
  • “The cloacal storage of urine in the rooster” (Skadhauge 1968)

I’ve helpfully highlighted the operative term, to reinforce the main point of the post. Many of these papers are freely available – get the links from the References section below. A few are paywalled – really, Elsevier? $31.50 for a half-century-old paper on chicken pee? – but I’m saving them up, and I’ll be happy to lend a hand to other scholars who want to follow this stream of inquiry. If you’re really into the physiology of birds pooling pee in their poopers, the work of Erik Skadhauge will be a gold mine.

Now, to be fair, I seriously doubt that any bird has ever peed for 17 seconds. But the misinformation abroad on the net seems to be more about whether birds and other archosaurs can pee at all, rather than whether a normal amount of bird pee was exaggerated for comedic effect in the Angry Birds trailer.

ostrich excreting 3

In conclusion, birds and crocs can pee. Go tell the world.

And now, those gator peeing videos I promised:


Jan. 30, 2016: I just became aware that I had missed one of the best previous discussions of this topic, with one of the best videos, and the most relevant citations! The post is this one, by Brian Switek, which went up almost two years ago, the video is this excellent shot of an ostrich urinating and then defecating immediately after:

…and the citations are McCarville and Bishop (2002) – an SVP poster about a possible sauropod pee-scour, which is knew about but didn’t mention yet because I was saving it for a post of its own – and Fernandes et al. (2004) on some very convincing trace fossils of dinosaurs peeing on sand, from the Lower Cretaceous of Brazil. In addition to being cogent and well-illustrated, the Fernandes et al. paper has the lovely attribute of being freely available, here.

So, sorry, Brian, that I’d missed your post!

And for everyone else, stand by for another dinosaur pee post soon. And here’s one more video of an ostrich urinating (not pooping as the video title implies). The main event starts about 45 seconds in.


Crocodiles vs. elephants

November 18, 2014

I’ve been reading The Guinness Book of Animal Facts and Feats (Wood 1982) again. Here’s what he says on pages 98-99 about the strength of crocodiles, and what happens when they bite off more than they can chew.

The strength of the crocodile is quite appalling. Deraniyalga (1939) mentions a crocodile in N. Australia which seized and dragged into the river a magnificent 1 tonne Suffolk stallion which had recently been imported from England, despite the fact that this breed of horse can exert a pull of more than 2 tonnes, and there is at least one record of a full-grown black rhinoceros losing a tug-of-war with a big crocodile. Sometimes, however, even crocodiles over-estimate their strength. One day in the 1860s a hunter named Lesley was a witness when a saurian seized the hind-leg of a large bull African elephant while it was bathing in a river in Natal. The crocodile was promptly dragged up the bank by the enraged tusker and then squashed flat by one of its companions who had hurried to the rescue. The victorious elephant then picked up the bloody carcase with its trunk and lodged it in the fork of a nearby tree (Stokes, 1953). Oswell (1894) says he twice found the skeletons of crocodiles 15 ft 4.6 m up in trees by the river’s bank where they had been thrown by angry elephants. On another occasion a surprised crocodile suddenly found itself dangling 15 ft 4.6 m in mid-air when it foolishly seized a drinking giraffe by the head.

The idea of elephants lodging crocodile corpses up in trees seems too bizarre to be true, but seeing it independently attested by two witnesses makes me more ready to accept it. There’s plenty of Internet chatter about this happening, but I’ve not been able to find photos — or better yet, video — proving that it happens.


  • Deraniyalga, P. 1939. The tetrapod reptiles of Ceylon, vol. 1: Testudinates and crocodilians. Colombo Nat. Mus., Ceylon.
  • Oswell, W. Cotton. 1894. South Africa fifty years ago. Badminton Library of Sports and Pastimes (Big Game Shooting), London.
  • Stokes, C. W. 1953. Sanctuary. Cape Town.
  • Wood, Gerald L. 1982. The Guinness Book of Animals Facts & Feats (3rd edition). Guinness Superlatives Ltd., Enfield, Middlesex. 252 pp.
Schachner et al 2013 fig-13-full

Schachner et al. (2013: Figure 13): Diagrammatic representations of the crocodilian (A) and avian (B) lungs in left lateral view with colors identifying proposed homologous characters within the bronchial tree and air sac system of both groups. The image of the bird is modified from Duncker (1971). Abbreviations: AAS, abdominal air sac; CAS, cervical air sac; CRTS, cranial thoracic air sac; CSS, caudal sac-like structure; CTS, caudal thoracic air sac; d, dorsobronchi; GL, gas-exchanging lung; HS, horizontal septum; IAS, interclavicular air sac; L, laterobronchi; NGL, non-gas-exchanging lung; ObS, oblique septum; P, parabronchi; Pb, primary bronchus; Tr, trachea; v, ventrobronchi.

Gah! No time, no time. I am overdue on some things, so this is a short pointer post, not the thorough breakdown this paper deserves. The short, short version: Schachner et al. (2013) is out in PeerJ, describing airflow in the lungs of Nile crocs, and showing how surprisingly birdlike croc lungs actually are. If you’re reading this, you’re probably aware of the papers by Colleen Farmer and Kent Sanders a couple of years ago describing unidirectional airflow in alligator lungs. Hang on to your hat, because this new work is even more surprising.

I care about this not only because dinosaurian respiration is near and dear to my heart but also because I was a reviewer on this paper, and I am extremely happy to say that Schachner et al. elected to publish the review history alongside the finished paper. I am also pleasantly surprised, because as you’ll see when you read the reviews and responses, the process was a little…tense. But it all worked out well in the end, with a beautiful, solid paper by Schachner et al., and a totally transparent review process available for the world to see. Kudos to Emma, John, and Colleen on a fantastic, important paper, and for opting for maximal transparency in publishing!

UPDATE the next morning: Today’s PeerJ Blog post is an interview with lead author Emma Schachner, where it emerges that open review was one of the major selling points of PeerJ for her:

Once I was made aware of the transparent peer review process, along with the fact that the journal is both open access and very inexpensive to publish in, I was completely sold. […] The review process was fantastic. It was transparent and fast. The open review system allowed for direct communication between the authors and reviewers, generating a more refined final manuscript. I think that having open reviews is a great first step towards fixing the peer review system.

That post also links to this one, so now the link cycle is complete.


Schachner, E.R., Hutchinson, J.R., and Farmer, C.G. 2013. Pulmonary anatomy in the Nile crocodile and the evolution of unidirectional airflow in Archosauria. PeerJ 1:e60 http://dx.doi.org/10.7717/peerj.60

Hemisected gator

Okay, before some wag makes this point, the gator is missing a good chunk of its tail, so this is more like the left half of the anterior two-thirds of a gator. But that would make a lousy title.

We might have more to say about this in the future, but for now, I’m going to let this 1000-word-equivalent speak for itself.

Many thanks to Elizabeth Rega for the use of the gator.

Let’s look at some animals!

February 20, 2012

An important new paper is out:

R. Kent Sanders and Colleen G. Farmer.  2012.  The pulmonary anatomy of Alligator mississippiensis and Its similarity to the avian respiratory system. The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology (advance online publication). doi:10.1002/ar.22427

(It’s paywalled, naturally, but let’s just assume that everyone who reads this blog is affiliated with a big university and has access.)

First of all, congratulations to the authors on doing this properly: publishing a proper paper (sixteen pages) to follow up their big-splash Science paper of just over a year ago.  As Mickey Mortimer has shown, follow-through rates when people publish in Science and Nature are generally not at all good, and it’s always encouraging to see an exception.

Here’s the abstract:

Using gross dissections and computed tomography we studied the lungs of juvenile American alligators (Alligator mississippiensis). Our findings indicate that both the external and internal morphology of the lungs is strikingly similar to the embryonic avian respiratory system (lungs + air sacs). We identified bronchi that we propose are homologous to the avian ventrobronchi (entobronchi), laterobronchi, dorsobronchi (ectobronchi), as well as regions of the lung hypothesized to be homologous to the cervical, interclavicular, anterior thoracic, posterior thoracic, and abdominal air sacs. Furthermore, we suggest that many of the features that alligators and birds share are homologous and that some of these features are important to the aerodynamic valve mechanism and are likely plesiomorphic for Archosauria.

The main reason I want to post this (apart from the fact that it’s an important finding) is because someone had to blog David Marjanovic’s classic response on the Dinosaur Mailing List (quoted with permission, since David doesn’t have his own blog):

See, this is the kind of thing where I’m totally baffled that it wasn’t figured out a hundred years ago, or 120 or 130.

I suppose the logic that has prevented people from dissecting crocodilian lungs for so long went like this:

1) Crocodilians are reptiles.
2) So, crocodilians have reptile lungs, not mammal lungs or bird lungs.
3) What are reptile lungs like? Let’s dissect the nearest reptile and find out!
4) We’re in Europe, so let’s just take the nearest lacertid, perhaps the nearest “colubrid” and maybe the nearest viperid and cut them open.
5) <snip> <snip>
6) Hooray! We’ve figured out what reptile lungs are like!
7) Textbook describes and illustrates generic non-varanid squamate lung as “reptile lung”.
8) Everyone believes it is known what reptile lungs are like.
9) Everyone believes it is known what crocodilian lungs are like, because crocodilians are reptiles.

Ceterum censeo Reptilia esse nomen delendum.

If you must keep the name, follow Joseph Collins and restrict it to Squamata or Lepidosauria. Otherwise, destroy it. Kill it with fire.

So true.

We could draw a whole lot of conclusions from this analysis, but let’s just concentrate on one: look at animals.  See how they behave.  Then cut them open and see what’s inside.  Don’t assume.  Don’t guess.  Find out.  To quote the splendid motto of the Kirkcaldy Engineering Works, “FACTS, NOT OPINIONS”.

Seriously.  Who’d have though there was a Science paper and an Anatomical Record paper just in cutting open an alligator and having a poke around in there?  Sometimes, science doesn’t progress by paradigm shifts; sometimes it progresses just by looking at things.

Vanessa Graff and I spent yesterday working in the herpetology and ornithology collections at the Natural History Museum of Los Angeles County (LACM). The herpetology collections manager, Neftali Comacho, pointed us to this skull of Alligator mississippiensis. It’s not world’s biggest gator–about which more in a second–but it’s the biggest I’ve seen in person. Normally it lives in a big rubbermaid tub in the collections area, but this Sunday it will be out on display for Reptile and Amphibian Appreciation Day (RAAD) at the LACM. RAAD will include guest talks, tours of the collections, and live animal demonstrations. If you’re in SoCal and you’re into herps–or have kids, grandkids, nephews or nieces that are into herps–it will be well worth checking out. While you’re there, don’t neglect the newly renovated Age of Dinosaurs and Age of Mammals halls, which are frankly phenomenal: spacious, well-lit, loads of actual material on display, skeletons you can walk all the way around, informative but unobtrusive signage, tasteful integration with existing architecture…I could go on. Better if you just go and see for yourself.

About that gator. First the bad news.  It came to the LACM from another collection, and has no data–no locality, no date collected, nothing. The skull is also missing all of its teeth, the left retroarticular process, the back end of the braincase and the occipital condyle. I think the latter losses were probably caused by a foramen of Winchester.*

Now, the awesome news. The length from the snout tip to the end of the articulars was 680mm and from the snout to the end of the quadrates was 590mm. Irritatingly I did not get a dorsal head length, which is the gold standard for comparative croc skull measurements, because I only reread Darren’s giant croc skull post after I got home last night. Going from the photos, I think the dorsal head length was right around 50 cm (beware, the yardstick in the photos is marked off in inches).

Darren’s post led me to this one, which has some very useful measurements (yay!) of giant croc skulls. The table at the end of that post lists alligator skulls with dorsal head lengths of 58, 60, and 64 cm, so the big LACM gator is nowhere near being the world’s largest. In fact, the 64 cm skull would be a quarter again as large, which is a truly horrifying thought. Still, it’s a big damn skull from a big damn gator.

You might get the impression that here in the Wedel lab we are shamelessly obsessed with giant saurians. And that is in fact true. But we also look at tiny ones, too. Here I’m playing with the skull of a little Tomistoma, the false gharial. Tomistoma is notable because another individual of the genus produced the longest skull of any known extant crocodilian–a whopping 84 cm dorsal head length (photos of this monster are in both of the giant croc skull posts linked above).

The moral of the story? If the sign says don’t go swimming, don’t go swimming. Go to RAAD instead, and see the giant alligator skull, and a ton of other cool stuff besides. And if you’re into gator skulls or just like geeking out on awesome anatomy, check out the 3D Alligator Skull site, a joint project of the Holliday lab and Witmer lab. Have fun!

* bullet hole