Interspecific prey theft in extant theropod dinosaurs – Ardea vs. Spheniscus

Golly, what a science journal-worthy title! An unnecessarily complicated and grandiloquent Ersatz for a simple “Heron steals penguins’ fish!”

The Tierpark Friedrichsfelde in Berlin has started announcing feeding times a while ago, and the penguin feeding (Humboldt penguins, Spheniscus humboldti) is a huge favorite with many people. And with local Grey herons (Ardea cinerea), obviously, as they stand a not-too-shabby chance at nabbing a few fishes, too. The penguin keepers aren’t stupid, and feed the penguins individually, instead of just tossing the fish into the enclosure. But some penguins love dragging their fishes to their nesting holes and deposit them next to the entrance. And that’s when the herons see their chances.

Here’s the line-up and starting formation:

heron

A penguin couple has stashed two fish at the entrance of their den, and the heron stands a few feet away, trying to figure out how to get at the fish without getting nipped by the powerful penguin beaks.

heron
A quick stab – but the penguins are alert! Although the heron managed to grab a tiny bit of the fish skin, the defenders moved too fast to allow it to get a good grip, and the steal failed.

So, wait some more….

heron
STRIKE!
This time the heron didn’t just uncoil its neck in the heron-typical fish-grabbing motion they use when fishing, but also made full use of its wings to counterbalance the extremely rapid stab for the fish. And succeeded:

heron

But not every attempt is successful, and a determined defense combined with a strategically less inept fish storage location can work miracles. Keeping the fish not that far out and really going after the heron allowed these two penguins to keep their share for a relaxed dinner later on.

heron

heron

Some other birds are also on the scrounge. Not quite as daring in their approach, but then a heron is much bigger than a Humboldt penguin, whereas a Hooded crow is quite a bit less hefty. Still, some fish end up lying around……. and what proper crow would pass such a free meal by?

heron

heron

In the end, all those who were in the enclosure were well fed. Can’t say the same about some of the less daringly minded herons, though – each tree around the penguin pen had quite a few of them perched on top, and many of them stayed hungry. I’ll toss in a few gratuitous pics of them.

heron

I especially like this one:

heron

To wrap this up, below there is an animated gif I made of all the shots of the successful fish-grab. Sorry for the borders; I simply moved the camera so much that I can’t crop any better.

heron

Posted in "fish", Aves, Dinosauria, lower vertebrates, Maniraptora, Theropoda, Tierpark Berlin, Zoos | 2 Comments

My awesome digiS project: mass digitizing sauropod bones

Last year I applied for a grant from the Senatskanzlei Berlin for the 2015 digiS funding programme. digiS is a state-wide (i.e. Berlin-wide) programme intended to coordinate and support digitizing efforts.They have an about page on their website that is in English, all the rest is in German (sorry!).

I had heard that there were a lot of applications in 2014, and that it would be difficult to get an application funded. However, the rules for applications were fairly straightforward, and they didn’t ask for a lot – just a clear description of the intended project with some background, a short discussion of why it is important, and who will benefit from the results. Along with that a short financial plan – a really simple one. And that was all that they asked for! In sum, I decided that the programme was worth a shot, as the cost of writing an application was not out of proportional to the potential gain.

I decided to go for a 3D digitizing project that has showcase character, with scientific gain, methods development, and room for outreach: 3D digitizing the long bones and girdle bones of Tendaguru sauropods stored in the Museum für Naturkunde’s Bone Cellar. These bones:

BoneCellar_06

bone cellar OLYMPUS DIGITAL CAMERA

The digiS programme limits individual projects to 100,000 € and a maximum run-time of one year (i.e., starting at the earliest on January 1, 2015 and ending at the latest on December 31, 2015 in this case), but I was unofficially informed that successful projects in the past had never received more than 50,000 €. Given the overall limits, digiS obviously wants to fund not just one or two projects a year, but a wide diversity. After all, digitization has many forms, and the cultural heritage institutions in Berlin have diverse needs. Therefore, I decided to design a program plan that stayed below 40,000 €, but still offered plenty of data for the public in the end.

The largest item in such a plan would then have to be personnel, and not tools. A nice hand-held laser scanner easily costs over 10,000 €, and squandering more than 25% of my total budget on one just wasn’t on. As usually the case, I therefore had to plan the digitizing via photogrammetry. Given the confined space available in the Bone Cellar, photogrammetry also seemed a good idea. After all, I didn’t want to have to carry the bones elsewhere, especially as there currently is no lift due to construction work at the museum.

In the end, I sent in a proposal that promised to digitize 360 long bones and girdle elements of the Tendaguru sauropods and Kentrosaurus, bones that are difficult to handle and should see more study than they do. Additionally, I will also clean up scans of the old dig diaries’ excavation sketches in which these bones are mentioned. All the data goes online via a special web interface, so that people all over the world can easily find the data, check out the 3D files, and request high-resolution versions for their research.

And lo and behold! – my project was granted in full! I got a call a few days in advance of the official decision, and was told that it was the first 3D digitizing project digiS would fund, because for the first time they saw a real use for the 3D files, and that although the project was very ambitious, the digiS team felt that if anyone could do it, I could. They had looked at my publications and at my blog, and basically wanted to see if I was all talk or if I would do the job :) Well, here goes!

disigmethod01

One thing I really needed to find was a very quick method to digitize all the bone in the confines of the Bone Cellar. And by now I have perfected my first rough idea, by trial and error, into something that works quite smoothly! I’ve already posted about the photography method, including a video, in the last post. Here, let me quickly explain how I create my models from the photos.

As you can see above, the images from all photography sets (two sets, in the example above) all go into one chunk in Agisoft Photoscan Pro. Because the background has been completely changed in between the sets, the resulting alignment and sparse point cloud has two floors:
disigmethod01

I put a styrofoam support under the bone for both sets. Obviously, that’s visible in the sparse point cloud as well. However, it is important to do this, as you will see in a second.

The really cool thing here is that the only points that both sets of photographs have in common are those that are on the bone! This means that all photos can only be aligned based on the camera position relative to the bone, not to the background. Which means a near-perfect alignment in one chunk – which mans practically no work effort for me :)

Next, I optimized the sparse point cloud and re-optimized camera positions. More on how to do that in a later post. Then, I calculated the dense point cloud:

disigmethod01

Well, that’s quite a bunch of floating nonsense data there, but as you can (I hope) see in this screenshot, the floating stuff does not touch the bone! That’s because the bone projects beyond its support all around, instead of lying flat on the ground. And it means that cutting away the excess points is quick and easy.

So there you are: a quick and reliable method for taking photos that results in very little manual editing later on :) I am quite confident that I can digitize a huge number of bones for the digiS project :D

 

Posted in Berlin, Dicraeosaurus, digiS, Digitizing, Dinosauria, Giraffatitan, Kentrosaurus, Ornithischa, photogrammetry, Sauropoda, Sauropodomorpha, Stegosauria | 10 Comments

Photogrammetry tutorial 10: an improved method for mid-sized objects

Last December I was granted a sack full of money by the Senatskanzlei Berlin for the 2015 digiS programme. I’ll soon post more about that; what matters for this post is that I promised to mass digitize the rather unwieldy sauropod longbones and girdle bones that reside in the Naturkundemuseum’s Bone Cellar.

BoneCellar_06

Overall, there’s ca. 360 such bones, ranging in size from half a meter to nearly 2.5 meters. As a collection they are, therefore, too heavy to transport around. You can lug one or two or even five up the stairs and into a spacious lab, but not hundreds. Therefore, digitizing has to happen in place, in the confines of the stuffed-full Bone Cellar. And that pretty much excludes the vast majority of scanning methods.

Room to set up a large and sturdy turntable with a background that doesn’t offer any features? Forget it!
Room for a laser scanner? Forget it!
Control over lights? Forget it!
Time to set up each bone in the middle of a lot of free space? Forget it!
Space to wave a held-held scanner around? Maybe, but those that offer a high resolution are quite expensive. Forget it!
Time, space and personnel to take the bones elsewhere? Don’t get me started…….

What was needed was a protocol that allowed quick, high-resolution digitizing in place. And with “quick” I mean quick. My aim is to spend not more than 6 minutes per bone for the entire process, including set-up and all.

Photogrammetry to the rescue!

So here’s how, after some trial& error, I decided to go about it. In general terms, you can copy this process for practically any Big Bone room and similar collection rooms worldwide, and for all kinds of large, heavy objects – provided you are allowed to handle them. Some, like statues and busts, you will not be allowed to stand on their heads. But then, there normally is no need to digitize the underside of a statue ;)

Setting up

The Berlin Bone Cellar has long rows of wooden shelves, and aisles between them that I consider just wide enough to digitize a large bone in them. Therefore, I get help from a preparator to pull out one bone per shelf segment each and  put it on a large piece of Styrofoam in the centre of the aisle. Around each bone I place three scale bars. My colleague Matteo Belvedere has created sets of scale bars of various lengths (10 cm to 50 cm) using coded targets, printed on lightweight but stable foam board.

Coded target: a picture that Photoscan recognizes and can automatically place a marker in the middle of. Basically, an automatically recognizable bull’s eye. If you have two of them on a piece of material that doesn’t bend, and if you know the exact distance between them, you can use that as a scale bar that the software automatically recognizes the ends of. Saves quite some time when you scale your model.

I also prepare a large number of trash bags by cutting their bottoms so they are flat when folded open. I could additionally slit them open lengthwise, but I am too lazy to do that. The last item on the list of auxiliary implements are lots of big, stiff cardboards.

Also, I obviously need a camera. With a fairly wide-angle lens – in my case it’s a Canon 70D with a 10-18 mm lens. And, because the lighting is rather suboptimal in the Bone Cellar, a LED ring light. I bought mine cheap: with a set of high-capacity rechargeable batteries it cost me ~70 € only. I could use a proper Canon ring flash, too (Matteo has one, we ran a test and that worked just fine), but the LED ring light works quite well.

Shooting the image sets

Now is the time to start photographing each bone. Then, they must be flipped over and photographed again – with a twist: I change the background completely for the second set, so that the photogrammetry software cannot find features on the background that link the two sets. This way, I avoid a lot of cumbersome masking even though the background of each photoset is not featureless.

To shoot a photo set, I start by snapping a picture of the specimen tag. Then, I walk around the the first bone, snapping pictures with the camera held low, trying to aim it squarely at the bone at a nearly horizontal angle. Then I do another round, slightly higher up, and finally some overview pics. Or I start with the overview shots and do the near-horizontal round later – doesn’t matter. What counts is making sure I take them all.

I end the round with a shot of the ceiling or the tag again, or whatever – simply something that looks very much different from the bone. That makes sorting photos easier, as the different image will stand out the among the Windows explorer previews.

Flip them bones!

Once all bones have been photographed this way, I put the camera aside (making sure to turn off the LED light, to conserve battery), and start flipping over the bones. Now, it is really important to have help with this process, as I also need to alter the background by placing the trash bags all around and under the bone. The stiff cardboards go against the shelves, so that this part of the background is also altered.

The scale bars must be removed at this step, otherwise features on them will lead to wrong alignment of photos! It doesn’t matter that the next set of photos will be without scales, because it is enough to have scales on a handful of images.

I now take the next set of photos as described above, and for most bones that’s enough. Some, like sauropod tibiae and ulna, tend not to rest stably in two positions roughly 180° apart, but rather in three positions roughly 120° apart. These I need to shoot a third set of. And sometimes I shoot even more sets…..

And then it is time to clear away all the bones and paraphernalia. DONE!

Now I just toss all photos of one bone into one chunk each in Photoscan, and align….. and get models like this one:

3D model

May I introduce MB.R.2636, a left Giraffatitan brancai femur?

Got it?

Well, have you understood what I do? Can you do it yourself?

Thought so….. it is not easy to image how I do this based on the above description alone. Thus, you can find a video on youtube showing me doing this process for one bone (and Matteo helping). Run time is slightly over 5 minutes, so overall I achieved my 6-minute-aim. I didn’t have the stiff cardboards when I did this, so they are missing. As a consequence, I had to mask the second set of photographs. But other than that the video shows exactly how I do things.

Posted in 3D modeling, Digitizing, Dinosauria, Giraffatitan, How to, MfN Berlin, photogrammetry, Sauropoda, Sauropodomorpha | 2 Comments

The BBC’s awesome ‘Planet Dinosaur’ now in 3D on Blu-ray

A few years ago I had the pleasure to work with people from Jellyfish Pictures on what was to become known as the BBC’s Planet Dinosaur series (wikipedia). And as opposed to the all-too-normal process, where the producers have basically formed a complete mental picture of how the film is to be made, where the artists have already build rigged 3D models and have animated them, where the storyline is completely finished BEFORE experts are brought in (a process that invariably leads to frustration all around)  Jellyfish contacted dinosaur experts worldwide in advance, when only rough drafts had been made. Someone among the large number of people they contacted suggested they should also talk to me. They did, and it was a fun process that (I hope) improved the final result a bit.

clapper

The really great thing was that they would send me videos they wanted my comments on, then we had a phone conference with the artists (! – they got my feedback unfiltered) while running Cinesync, a program that lets several people at different computer see and interact with the same video. I could stop and advance or reverse the video as I pleased and draw and type on the screen, as could everyone else – very helpful! The videos showed early drafts of 3D models in simple walking or running cycles, and we talked through any issues very thoroughly. A great bunch of people, who didn’t let their egos get tied to positions, so that I was free to simply say “that’s wrong, you need to fix this, because……” instead of having to pussyfoot around issues. They clearly valued the time I put in, and wanted to make the most of it.

One of the things I noted early on was pronated hands on all theropods, i.e. they had their palms facing down, not in. That’s a common error, and it was only over the last decade that some colleagues and I, especially Matt Bonnan and Phil Senter with a seminal paper, managed to raise awareness for the non-pronated state of most dinosaur hands. Dave Hone wrote a wonderful post on his blog in 2009, clarifying that theropods were clappers, not slappers. In any case, I told the assembled artists that a slapper-handed theropod reminded me of a little old lady carrying her large bag by gripping it with both hands from above. Laughter all around and the hands got altered – see above!

clapper

A fun thing was that Jellyfish contacted me about theropods and ornithischians initially. When I told them I was more of a sauropod person, being employed in the sauropod research unit FOR 533, they also started showing me sauropod material and asked me on their planned storyline, despite having sauropod people on board already. A smart decision, as they got more info, and for free.

A specific topic I remember well was baby sauropods. They had this nice idea of them hatching and running around being cute, which they implemented very well – see above. However, I also suggested that baby sauropods were, essentially, meals on stilts for large theropods. And, to their great credit, although a segment showing huge ugly beasts chugging down cute tiny babies wasn’t really something that sells very well to a general audience, they did put it in! Hooray!!!!!!!

clapper

gobble, gobble,……

clapper

yummy!!!!!

I must say I was very much surprised that they actually went and put a scene in that clearly was not going to be a viewers’ favourite, just because it was science’s best reconstruction of the actual life history of dinosaurs!

In the end, I greatly enjoyed working with the Jellyfish and BBC people, and I liked their final product even more! Below is another shot from it that shows off the wonderful work they did – which you can now finally buy in the 3D version on Blu-ray. Yes, that’s what this post really is about, although I relished the chance to laud the great team and the great result again: you can buy Planet Dinosaur 3D now. Go do it – it is totally worth it! I haven’t seen it yet, but I have seen a few out-takes using these weird red-green glasses, and it does make the entire thing look quite a bit more alive – even more alive I should say. Here’s the link to the shop (US).  It’s only ~25 bucks, for a really great dino documentary.

clapper

Posted in 3D modeling, Dinosaur models, Dinosauria | 7 Comments

Australia!

Yesterday, after a rather excruciatingly long flight, I arrived in Armidale. I’m spending two weeks here with the FEAR Lab, doing some modelling work. I’ll obviously report on that, but for now I just want to dump a bunch of photos on you.

Sydney

This is a shot from my stopover in Sydney, where I went through immigration and – surprise! had to stand in line again for customs. Well, quarantine….. which makes a lot of sense, seeing how Australia has a flora and fauna totally separated from much of the rest of the world. Therefore, they do a quick check of what people and luggage they want to check in detail at the customs check, and that caused a line to form. This little incident made being on a totally different continent quite real for me.

Oh, and as you can see, all of Sydney easily fits under an A-380 wing ;)

Sydney

Unsurprisingly, a totally different fauna also means totally different birds. So far, I’ve only seen one species of bird that I’ve seen before outside zoos – unsurprisingly the European starling. Other than that Armidale is full of Australian magpies (Cracticus tibicen), above on the antenna of my hotel, who make their ubiquitous presence very well heard all over town. Being used to corvids making “koww” of “cawh” sounds, it is weird to hear a bird that looks just like one imitating a flute, from which they got their German name of Flötenvogel (flute bird).

Sydney

I also saw several kookaburras, Dacelo novaeguineae. This one flew in and sat on the playground equipment in a park while I stood a few meters away.

Sydney

A red wattlebird (Anthochaera carunculata) – I heard a lot of them, and saw several.

and lots more – for two hours of walking around town(!) I photographed a surprisingly large number of taxa.

Posted in Aves, Maniraptora, Theropoda | 2 Comments

Theropod Thursday 53: Snow White

Last Monday, work took me to the Weltvogelpark Walsrode (wikipedia). It is really weird that I haven’t been there before, and I was determined to make the most of this visit, despite a so-so weather forecast. The Weltvogelpark is a huge one, the largest bird park in the world both in number of species and land area (claims wikipedia), and it has only birds (no, not even guinea pigs somewhere), as opposed to many other bird parks. You’ll get Theropod Thursday-ed to death here with photos I took there, but today I want to focus on a handful of birds I saw that that have one thing in common: they are white.

Let me warm you up with a bird that is mostly white – in the photo below I managed to “hide” the dark head in an underexposed background ;)

Madagascar sacred ibis

This is Threskiornis bernieri, the Madagascar or Malagasy sacred ibis. Looks a bit ruffled, which is not surprising. Monday was a stormy and rainy day, with some hail thrown in for fun, too. The next bird doesn’t look ruffled, and doesn’t have any non-white feathers.

white

Can you guess the species? Or at least the genus?

OK, more info may help you……

white

recognize it now? It good old Corvus corone, the Carrion crow! An albino one, to by sure, as the red eyes show. Real albinism, a total lack of the pigment melanin, is much rarer than just a reduced amount of melanin, a condition called leucism. Leucistic animals (including humans) typically have enough pigment in the iris to make it not totally translucent, and so we do not see the blood vessel rich retina.

white

Yep, an albino! And if this bird doesn’t deserve the name Snow White, maybe this one does:

white

white

white

As you can see, this peacock (Pavo cristatus, I guess from the head shape and the other animals running free in Walsrode) is leucistic, but not an albino. The eyes are black.

So that’s two really rare things here: an albino crow and a leucistic peacock – in one place. But Walsrode has much more to offer than just freaks (as I threatened above). Today, I’ll wrap up the post on white birds with one that is completely white except for its beak and the tips of a handful of feathers: the coscoroba swan (Coscoroba coscoroba). Walsrode has a pair, and while one of the was sitting on the nest, the other was quite a show-off. Clearly, the intent was to keep us sufficiently impressed so that we would stay away from the nest. The coscoroba isn’t the biggest of swans, but its ego is certainly not too small.

white

white

white

white

 

 

 

Posted in Aves, Dinopics, Dinosauria, Theropoda, Weltvogelpark Walsrode, Zoos | 1 Comment

Theropod Thursday 52: pulling a leg! Erhm….rather: pulling a tail!

hiding_02

Hungry I am. An aardwolf (Proteles cristata), too. A hungry aardwolf. Yep, that’s it. A hungry aardwolf. Now get me my food. Now!

This is the elusive critter that David Hone, my esteemed colleague with plenty of zoo experience, and I totally missed seeing during our legendary winter visit. Legendary for me, as it made me aware of how much cooler a zoo the Tierpark is than I was previously taking note of. Dave kept repeating “I’ve never seen this animal before!” The aardwolf was the one animal that we really wanted to see but didn’t. And on my many other visits to the Tierpark – I place I practically live at during summer weekends – the aardwolf stayed elusive. I did see it, but generally just as a furry blur popping out of one hole in the ground and into another one.

So imagine my delight when the Tierpark, under the new director Dr. Knieriem, started announcing the feeding times of some of the animals, and included not only the echidna but also the aardwolf on this list! Obviously, I dragged my children there at the appointed time, 2:15 p.m. And lo and behold, the elusive aardwolf put in an appearance! He came out of his hiding place when fodder was presented and greedily gobbled it up.

hiding_02

hiding_01

But, waitamoment!” you say. “What’s this to do with Theropod Thursday?

Well, here goes:

hiding_02

A hooded crow (Corvus cornix) is paying a visit. And not a polite one, as we will quickly see.

Aardwolves feed mostly on termites, so the Tierpark feeds them a pretty yucky looking protein-rich slurry. And believe me, crows love anything protein-rich. And crows being crovids, some of the most inventive birds, they come up with ways to make you, me, and aardwolves involuntarily share that yummy protein cocktail.

hiding_02

grab……..

hiding_02

and pull!

Hm, ain’t nothing happening. Well, let’s do this again.

hiding_02

Ouch!

Now, corvids have a pathological obsession with tail pulling. They just can’t help themselves! See here. If it’s got a tail, that tail’s gotta be pulled!

Still no effect? Here we go again!

aardwolf

harder!

aarwolf

Oh wow, finally there’s a reaction!

aardwolf

aardwolf

and so, finally, the poor crow that risked life and wing got the deserved go at the trough!

To be honest, I don’t believe the aardwolf minded the tail pulling very much. He simply had had his fill, and thus would have wandered off anyways.
To end this on a more theropodish than mammalian way, here’s a Hooded crow proudly strutting around.

aardwolf

Posted in Aves, Dinosauria, Mammal pic, Mammalia, Maniraptora, Theropoda, Zoos | 1 Comment