Did Velociraptor Hunt In Packs?

Ever since the movie Jurassic Park came out in 1993, people from all over the world added the name Velociraptor to their often-short list of dinosaurs they had heard of, joining more famous dinosaurs such as Tyrannosaurus, Stegosaurus, and Triceratops. While the dinosaurs portrayed in the movie have often been hailed as “ahead of the times,” Steven Spielberg of course had to make some assumptions about dinosaur behavior.

Michael Crichton, the author of the original Jurassic Park book, did too, which can be clearly seen when reading both of his Jurassic Park books. In the first one, a theory was circulating that Tyrannosaurus had eyes like a frog, that would be unable to see something so long as it didn’t move. This is reflected in the way Dr. Alan Grant, one of the protagonists in the novel (as well as the subsequent movie) tells his comrades to react when they are spotted by a Tyrannosaurus: just don’t move. (Don’t blink. Don’t even blink. Blink and you’re dead.)  

However, this theory was debunked by the time that it came for Crichton to write his next dinosaur-themed book, The Lost World, a sequel to Jurassic Park.  In the sequel, Ian Malcolm, who was also a protagonist in the first novel, moves to the forefront. He explains that the Tyrannosaurus from the first novel was probably just not hungry enough to attack them, and that it was just toying with them. A clever way of seamlessly working that scientific transition into the books without disrupting the canon of the story!*

Spielberg also played a lot of things up throughout the movies to make it more cinematic and exciting: and, to be honest, I can’t really blame him, at least not as critically as some paleontologists do. (That, however, is a story for another time). Today, however, we are going to be talking about one cinematic Spielbergian leap, and the resounding effect it has had on paleo-enthusiasts the world over: the idea of raptors hunting in packs.

In the books and movie, the Jurassic Park raptors are portrayed as clever, cool, and calculating killing machines with the intelligence of a dolphin or an ape. Scientists know, however, that while animals such as Velociraptor and Troödon may have been smarter than their mammalian counterparts of the time, their intelligence nowhere near reaches that of some modern day cetaceans and primates. Most people don’t want to accept that, though: they want their dinos really smart!

Here’s my stab at psychology for the day. In my semester long psychology course that I took last year, we discussed something in a relationship and everyday life called a fiction. Essentially, when human beings have feelings for someone, they develop what we call “fictions” in their mind. Fictions  about physical appearance, fictions about intelligence, and fictions about other redeeming qualities as well. If two people are projecting these fictions onto each other, then a relationship can develop. On the other hand, sometimes these people are confronted with these fictions, and they realize that they are not all that they are cracked up to be. When these people fall short of their fictions, some emotional turmoil can result. In my opinion, the reality of the Velociraptor, as well as the reality of the rest of the dromaeosaurs, falls short of people’s expectations. I think a similar thing is occurring right now with dinosaurs and feathers: people want their T-rex scaly, not feathery! That might be why many people seem so opposed to the idea.

“All right,” people say. “So Velociraptor wasn’t a genius. It still hunted in packs, though, right?” It seems like a fairly obvious answer: “Of course they did! ….Right? I mean….if you think about it….” It’s when you start to really think about the evidence that this idea really falls apart. First, let’s look at a related animal called Deinonychus. Deinonychus is a mid-sized dromaeosaur, about thirteen feet long, and weighing about as much as a wolf. Living during the Early Cretaceous Period, between about 118 – 110 MYA, remains of Deinonychus have been found in the western United States. Deinonychus remains aren’t always found solo, however: in some cases, it looks like Deinonychus might have dined and died! At several different sites, Deinonychus remains have been found buried in close proximity to a large herbivorous ornithopod called Tenontosaurus.  Shed teeth from multiple animals seems to indicate that these animals might have been feeding together. Some paleontologists take this a step further, and propose that, not only did these animals feed together, but they lived and hunted together, too!

In this post, I am going to be using several modern-day analogues to point out flaws in some theories. (We’ve already done it with the deer!)  This time, we’re flying over to Indonesia to visit the Komodo dragon. The Komodo dragon is a very interesting animal that, like many other animals, will resort to cannibalism. The young Komodos take to the trees, hiding up in branches to light to support the weight of the adults.  The Komodos lead a generally solitary existence: that is, until it comes time to feed. At feeding time, the dragons will swarm all over the carcass, each fighting for a stake of the meal. To an outsider, unaware of how the animal had been killed, it might be interpreted that perhaps this was a family group that worked together to bring down a much larger prey.

Another comparison I like to make is a theoretical one. Imagine that a pride of lions has subdued a zebra on the plains of Africa. After they have eaten their fill, they move off into the shade to sleep off their recently acquired weight. Immediately afterwards, the vultures swoop in on the kill. Suddenly, somehow a flash flood overtakes the carcass and the vultures, leaving them buried in mud, sand, and silt. Over the next few thousand years, their remains fossilize. One million years later, paleontologists come across this find. To their eyes, it would appear, for all intents and purposes, like the vultures ganged up in a pack to subdue this one-toed creature. Maybe not the best comparison, but one that I always like to think about.

So does the evidence seem to allow us the conclusion that multiple Deinonychus fed together? I would say yes, the evidence does support that conclusion. Does the evidence support the conclusion that multiple Deinonychus lived together, and worked together to bring down the Tenontosaurus? In my opinion, I don’t think that that is enough evidence. Other paleontologists disagree, however, leaving the matter open for debate. Right now, what we need is a good fossil trackway.

Pyg learns about several baby Apatosaurus tracks at the Morrison Natural History Museum.  Together, these tracks create a trackway, which has revealed some very interesting behavior about these young sauropods!  To learn more, make sure to check out the museum's Facebook page HERE!

We’ve talked about trackways on the blog before. Fossil trackways are also often good evidence for group moving. We have many trackways that show groups of dinosaurs, such as sauropods, moving together in multi-age herds. We’ve talked before about the exciting conclusions that paleontologists are drawing by studying blocks of fossil footprints at the Morrison Natural History Museum. While fossil footprints aren’t always necessarily the final say, they are simply one more piece of the puzzle. And when it comes to dromaeosaur footprints, footprints that many different paleontologists agree belong to a dromaeosaur, we have none. Zilch. Zero. Nada. No dromaeosaur footprints. Not yet, anyways. So there’s one possible line of evidence down the drain.

Pyg compares her foot to the smallest baby Stegosaurus footprints in the world, also at the Morrison Natural History Museum!  These footprints us gain insights into social behavior, animal size, and locomotion.

Thus far, it doesn't seem like we have any evidence in FAVOR of Velociraptor hunting in packs. But evidence can work both ways: what about evidence AGAINST Velociraptor as a pack hunter? As a matter of fact, there is one main line of evidence that I find to be, if not conclusive, highly indicative of the truth being the pack hunting. This line of evidence comes from the environment that Velociraptor would have lived in. Velociraptor inhabited what is now the Gobi Desert of Mongolia between around 70 and 75 million years ago, during the Late Cretaceous. Back then, the Gobi looked a lot like it does today: deserty. Now, this is very important. Think about desert animals today, specifically the carnivores, but the herbivores as well. Although the desert is certainly not a lifeless place, it is by no means a party like the African Serengeti, or the great plains of North America (before the railroads came through and people killed almost all of the bison). There simply isn't enough food for large animals to get by, especially not large groups of them.

Now think about a standard predator/prey ratio seen in environments today. Let's talk about my home-state of Colorado. There are lots of places to hike in Colorado, and in almost any part of the state you can see some sort of deer, be it mule deer, white-tailed deer, elk, or moose: you name it, you can probably see at least one of these cervids at almost any place in Colorado. Now, consider this: how often do you see bears in Colorado? Or mountain lions? Not terribly often, and especially not very often when you consider how often one sees deer. That's because of the predator/prey ratio. Essentially, if the balance between predator and prey is not kept in check, then populations will crash. Therefore, it is imperative that the prey species outnumber the predator species by what is usually a significant margin, otherwise the predators will overhunt, and they will starve to death. (For a more complete discussion of the predator/prey ration, this time in the context of the lynx/hare cycle of Canada, click HERE).

Some predators can get away with hunting in groups or packs because the prey species are relatively abundant. For example, the African Serengeti. The prey density is just so incredibly high that many different types of predators, such as lions, hyenas, and African wild dogs, can all hunt in packs. It works for them, because there are just so many prey species there!

Now let us bring our attentions back to the deserts. You can walk for miles, you can drive for even more, and see hardly a sign of any vertebrate life. Most likely, all you will see is a vulture or a hawk soaring the thermals high above you, watching for its next meal. If you're lucky, you might see a deer, or possibly even a javelina (a pig-like creature native to the south western United States, as well as Central and South America). You aren't going to see a lot of them, though. And if the prey isn't plentiful, then the predators sure aren't going to be, either!

Although dinosaurian-dominated ecosystems were undoubtedly different in some aspects from the mammalian-dominated ones of today, the fundamentals of the predator/prey ration would still stand true. There just wouldn't have been enough food to go around for these animals to have been pack hunters!

So, the final question: did Velociraptor hunt in packs? Or didn't it? If I had to hazard an answer, I would say no, no they did not. Due to the extreme lack of evidence in favor of this social behavior, as well as some evidence that seems to indicate that they wouldn't have, I would say that they did not hunt in packs. Obviously, with future discoveries, my ideas may change, which is one of the great things about science: we are always learning new things! And who knows: maybe one day, it will be one of YOU who discovers that crucial bit of evidence that shows that Velociraptor did, indeed hunt in packs!

OK, that was WAY too cheesy to leave like that. I felt uncomfortable even writing it. Let's end on a joke, instead. Why couldn't T-rex clap its hands? Huh? Give up? Because he was dead. Thank you ladies and gentlemen, I will be here all week.

A special thanks to Matthew Mossbrucker and Robert Bakker for their helpful information in making this post!

*To be honest, the whole concept of the theory doesn’t make a lot of sense: think about modern-day deer as an analogue for extinct prey species. If they see a predator, they are going to freeze, as it is much more difficult to pick out a still animal from the surrounding landscape than it would be a moving animal.  So predators would have to be able to pick out the prey, otherwise it would never capture one.  This freezing behavior on the part of deer when they are startled also explains why deer often freeze in front of car headlights: deer in the headlights!

What is a Pterosaur?

Most of you have probably heard about the so-called "pterodactyls," the flying creatures that lived during the time of the dinosaurs. Like most of us, you might not know exactly what a pterodactyl, more properly known as a pterosaur, is. Is it a bird? A bat? A dinosaur? Possibly even an insect? Or a distinct group of archosaurs that are thought to be fairly closely related to both dinosaurs and crocodilians, but scientists still aren't 100% positive how they fit into the reptilian family tree? Well, if you were thinking the last option, then lo and behold: you're right! Although the pterodactyls would have soared through the skies much like birds, bats, and even some insects of today, they would have been a distinct group altogether. They are also not quite dinosaurs: as the last option says, no one knows quite yet how exactly they fit in!

Pyg perches next to the skeleton of one of the most famous pterosaurs, Pteranodon, at the Morrison Natural History Museum in Colorado!  

Another misconception you might be suffering under is what these extinct flying reptiles are actually called. Although most people call them pterodactyls, that isn't quite the correct term for them. Scientifically, these creatures are known as the pterosaurs. The name pterodactyls actually originates from a small pterosaur that is commonly found in the fine-grained Solnhofen fossil beds in Germany. Known as Pterodactylus, several hundred of these little reptiles have been discovered!

Pyg checks out a cast of one of the more famous Pterodactylus specimens from Solnhofen!

The Solnhofen quarries are world renknowed for their excellent fossils. Not only have a large number of Pterodactylus specimens been uncovered there, but it was from these quarries that the very first Archaeopteryx was uncovered in 1861.  This primitive bird is one of the missing links between birds and dinosaurs, as it shares many features in common with both groups (such as feathers with birds and hand claws and teeth with dinosaurs). Other famous and important animals to come out of the Solnhofen Quarries include numerous crustaceans, insects, and even a small crocodile called Alligatorellus!

Pyg learns more about both the Pterodactylus specimen from above (left), but also about Archaeopteryx (right)!  This cast is of the best specimen of this primitive bird, and was discovered in 1877!  (The original specimen was, not the cast).

Part of the reason why the Solnhofen Quarry is so darn special is the extremely fine-detail preserved in the fossils. As I just mentioned in the previous paragraph, feathers have been discovered with Archaeopteryx specimens. Feathers, much like skin, hair, and other soft-tissues, rarely fossilize. As the science of paleontology slowly evolves, just like the animals it studies, paleontologists become better and better equipped to deal with, not to mention find, these soft-tissue elements of these extinct animals. More and more dinosaurs are being discovered with not only skin, but oftentimes feathers, such as Microraptor, an animal fairly closely related to Velociraptor of Jurassic Park fame; Dilong, an ancient ancestor of Tyrannosaurus rex; and the bizarre therizinosaurs; amongst many others.

And it's not just feathers that fossilize, either. Wing membranes, composed of a flap of skin, are being discovered more and more frequently when it comes to pterosaurs. When it comes to Pterodactylus, scientists have such a large sample size that they are able to reconstruct much of the soft-tissue anatomy of this particular pterosaur! Scientists also have a very thorough growth series for this particular pterosaur, with individuals ranging from hatchlings, just a few days to a few weeks old, all the way to very old individuals with wingspans of around five feet, which, for a Pterodactylus, is very hefty indeed!

Although we've talked a lot about Pterodactylus, there are many other fascinating pterosaurs! I've taken a recent interest in pterosaurs, but before we dive on in to a wide variety of posts, I wanted to provide a brief introduction! Remember, this is a VERY brief introduction. For a more thorough introduction to pterosaurs, consult a book or something, or check back in the future as we learn more about pterosaurs! Don't hold me to it, but I feel like sometime in the near future, I will be talking about Dimorphodon and the anurognathids! Check back soon!

Treuchtlingen on Dwellable

Harris Hawk at the Dinosaur Hotel!

A few times now, I have mentioned the fantastic dinosaur-themed renovation that the folks over at the Best Western Denver Southwest.  Complete with life-sized models, museum quality casts lining the hallways, and a pool in the shape of the Western Interior Cretaceous Seaway, this is a hotel that paleo-fans of all ages won't want to miss!  Another awesome thing they do is a weekly raptor show on Saturday's at 5:00 PM.  I don't mean raptor like Velociraptor (which would be both amazing and terrifying at the same time), I mean bird of prey raptors.  But don't be too disappointed: they are still really super cool!  I went for the first time last Saturday, and was blown away by both the birds and the knowledge and passion of the presenter, Anne Price.  I plan on sharing many of these birds with you, and today I am going to share one of my favorites from last week, the Harris hawk!

In this picture, you can see the Harris hawk is not too happy about the great-horned owl being held by another volunteer about ten or fifteen feet in front of it!

There are three different subspecies of the Harris hawk, and this one was native to the Sonoran desert, in the American southwest.  Although sometimes the other sub-species will live in more forested areas, this particular type of Harris hawk prefers a desert life.  

Due to the fact that much of what lives in the desert is spiny, the Harris hawk learns from a very young age how to pick spikes and thorns out of its feet, especially the spines of the saguaro cactus.  This particular cactus is SO huge and so integral to the surrounding ecosystem that it is illegal in Arizona to either harm or destroy a saguaro cactus!

When abbreviated, the scientific name of the Harris hawk, Parabuteo unicintus, spells "P. u."

Unlike many raptors, the Harris hawk is a very social bird, hunting cooperatively in packs often numbering four or five individuals.  These packs, or family groups, will often have one or two of the birds fly down low to flush out prey, and once the prey is on the move, the rest of the pack will swoop in for the kill.

 

Since it is so darn hot in the Sonora Desert,  the adult Harris hawks are forced to shield their nests, with their offspring inside, with their outstretched wings to keep them from cooking alive.  If the "shield-bird" has to move, for whatever reason, an aunt or an uncle or just another member of the pack will instinctively swoop in to take up the shielding duties!  

I feel like since the Harris hawk lives in groups, it would be more tolerant of other birds.  Since they kept the Harris hawk out almost the entire time, even while the other three birds were out, this would make sense.

You can see in the picture above and the picture below that, while the Harris hawk wasn't too bent out of shape because of the presence of the great-horned owl, it wasn't necessarily super excited about it.  I mean, let's face it: if you or I were a hawk in the presence of this incredible owl, I might be a little nervous, too!

Like in most other birds, the Harris hawk is pretty much full-sized when it leaves the nest, since it has to be able to fly, feed, and take care of itself.  When their entire volume is taken into account, the young apparently are often bigger than the adults!  I don't remember exactly why that would be, but most likely due to the fact that the young have just been sittin' around on their heinies, and their parents have been working their heinies off to feed and care for them.

As you can sort of see in the picture below, the innermost toe claw of the Harris hawk, and most (if not all) hawks, is much larger than the other two forward-facing toe claws.  As you can probably see in the picture above, the hallux, or backwards-facing claw, is also much larger than those other two forward-facing claws.  I don't recall if this is a feature seen in other raptors, I'll make sure to ask this Saturday!

I also have a short video that I took there of the Harris hawk.  You can see how it looks, get a good size comparison, and listen to a little bit of the information that Anne has to say about it!

Here is a second video where the Harris hawk is featured, however briefly.  Although it features the red-tailed hawk, at one point the hawk poops on the floor, which unfortunately happens off camera!

Finally, here is another video in which the Harris hawk makes an appearance.  You can see when the camera pans over to the Harris hawk (the cinematography, by the way, is reminiscent of Star Wars or Planet Earth or something like that) that the Harris hawk, like we talked about before, is not terribly happy about the great-horned owls presence so close to it, but it is tolerating it nonetheless.  Despite the fact that it doesn't feature the Harris hawk all that much, it's still a really cool video, and will give you a hint for what's in store for later posts!

Make sure you check out the website for the Raptor Education Foundation by clicking HERE, and checking out the Facebook page for the Best Western Denver Southwest by clicking HERE!  

Top 10 Favorite Dinosaurs by Zack Neher (Part 2)

Part two of my Top Ten Favorite Dinosaurs list.  Enjoy!

6. Pachycephalosaurus

The largest of the pachycephalosaurs, the name Pachycephalosaurus translates to "thick-headed lizard."  A large orbital socket indicates good vision, and, according to my "Prehistoric Life" book, the small teeth in its mouth indicates either herbivory or omnivory.  I have never heard anyone ever say anything about the pachycephalosaurs being omnivorous, so I have doubts about the authenticity of the statement.  Jack Horner suggested that Pachycephalosaurus and the other two pachycephalosaurs that lived in North America at the same time, Dracorex and Stygimoloch, were actually the same dinosaur and just represented different ontogenetic stages in their growth development, but that hypothesis has been almost completely refuted.  Due to the extremely tough-looking and thick skull, many paleontologists also have suggested that the pachycephalosaurs would clash heads much like the extant bighorn sheep, but studies of the necks of these animals indicate that these animals were likely not able to do this without breaking their necks.  Needless to say, this behavior was probably not something that they would attempt to do more than once.  Remains of Pachycephalosaurus have been found in the United States in the states of Wyoming, South Dakota, and Montana.

5. Amargasaurus

A fairly small sauropod, Amargasaurus is certainly quite unusual, as you can see in the pictures below!  On each of its twelve neck, or cervical vertebrae, a pair of spikes project out.  The functions of these spikes are unknown, but many theories have been put forth, from defense, to a sail being attached between each of the spikes to make the animal look bigger, even for heat control.  If a sail was not attached to the spikes, it is likely that they were covered in a layer of horn.  Whatever was on those spikes, it doesn't look like Amargasaurus had a very wide range of vertical mobility in its neck, so it seems likely that the small sauropod would have been mostly a ground-level feeder.  Amargasaurus has been found in Argentina in South America.

4. Utahraptor

While making Jurassic Park, Steven Spielberg decided that the real-life Velociraptor wasn't scary enough for his movie.  Not only was Velociraptor actually pretty small (see the size comparison chart below), it was feathered!  But while they were making the movie, remains of the creature that would one day be known as Utahraptor were uncovered, and Spielberg had his monster.  (If you want to read more about this interesting happenstance, check out the introduction to Robert T. Bakker's FANTASTIC novel, Raptor Red, one of my top five favorite books of all time).  Utahraptor remains have been discovered in (can you guess?  I hope you can!) Utah. 

TO BE CONCLUDED IN PART 2

The Biggest Carnivorous Dinosaur Part 3: Spinosaurus, The World's Largest Penguin

Spinosaurus quickly smashed its way to the top (literally!) following the success of Jurassic Park III.  At up to 56 feet (17 meters) in length, Spinosaurus (found in Egypt and Morocco) is unquestionably the longest carnivorous dinosaur that has ever been discovered, and by a significant margin, too.  But how could Spinosaurus be so successful when another carnivorous monstrosity, Carcharodontosaurus, lived in such close proximity?  The answer lies in what it ate; in fact, Spinosaurus appears not to have been as carnivorous as we once thought, and seems to in fact have been more piscivorous.  Essentially, it is thought that Spinosaurus might have survived on a diet consisting a great deal upon fish.

There is a great wealth of information that indicates the staple diet of Spinosaurus was fish.  Here we will take a more in-depth look at this evidence.

A picture of Spinosaurus drawn by the talented young artist Sam Lippincott.

1.  POSITION OF THE NOSTRILS:  Spinosaurus, unlike most other theropod (meat-eating) dinosaurs had nostrils situated very high up on its skull.  By contrast, most other theropods, like Tyrannosaurus, had nostrils very close to the front of the skull.  The nostril placement in Spinosaurus would have allowed it to stick its nose into the water quite deep, enabling it to hunt fish more effectively.

2.  SENSORY ORGANS ON THE TIP OF THE SNOUT:  Along with the high placement of the nostrils, Spinosaurus also had a number of small sensory organs at the front of the snout, revealed by CT scans.  These greatly resemble those of the crocodile, who uses them to sense where prey is by "seeing" tiny movements in the water.  Thus, a crocodile can attack its prey without ever seeing them with their eyes.  Spinosaurus appears to have been able to do much the same thing, making its hunting method of choice quite obviously effective, given its immense size.

3.  ISOTOPIC EVIDENCE:  A study of the isotopes in the skull of a Spinosaurus specimen revealed something quite interesting.  Spinosaurus shares a great deal of isotopic overlap with crocodiles, fairly aquatic animals.  By contrast, other carnivorous dinosaurs like Tyrannosaurus have very different isotopic readings, indicating a terrestrial lifestyle.  Given the great deal of overlap possessed by Spinosaurus and crocodiles, it appears that Spinosaurus spent much of its life like a crocodile; semi-submerged in rivers and streams.

4.  THE TEETH TELL THE TALE:  Spinosaurus, unlike most other carnivorous dinosaurs like Tyrannosaurus, Allosaurus, or the famous Velociraptor, possess conical, round teeth.  These other carnivores possess thin, blade-like teeth, made for slicing, crushing or tearing into other animals.  Spinosaurus has teeth much like a crocodile; round and conical.  These teeth are made for gripping and making sure that an animal does not escape. 

5.  THE TEETH TELL THE TALE....AGAIN:  Yet again, we come to the issue of teeth, and this is one of the most damning pieces of evidence of all.  During the time that Spinosaurus lived in North Africa, another inhabitant of these streams and rivers was a saw-toothed fish called Onchopristis.  Two fossils involving Onchopristis have been discovered in conjunction with the remains of Spinosaurus.  One was the skull of a Spinosaurus; imbedded in one of the tooth sockets was a vertebrae from an Onchopristis.  The other discovery was the barb of an Onchopristis embedded in the jaw of the Spinosaurus.

6.  PLUS:  We only ever seem to find Spinosaurus in shallow aquatic environments, where fishy prey would be abundant.

All in all, it seems like an inevitable conclusion to draw that Spinosaurus was, in fact, a piscivore, at least much of the time.  A fascinating example of the crazy turns evolution can take.