Raptors – Group Hunters or Cannibals?

The question to answer is did dino-raptors live and hunt and feed in packs, like wolves?

I’m biased. I worked on the movie “Jurassic Park,” consulting with the special effects artists. And the book “Jurassic Park” has references to my research.

And…my first dig was excavating raptors near Bridger, Montana, in 1964. I was a freshman. Grant Meyer was the Field Boss – a fine fellow with delicacy of touch that was surprising in such a hulking physique.

Grant is the guy who really started “Jurassic Park.”

It was Grant Meyer who found the raptor Deinonychus, four of them, their bones intermingled in a thin layer of dark gray clay-stone. He directed us kids in extracting the bones. Back at Yale, another undergrad, Peter Parks, cleaned the rock off the bones. Professor John Ostrom named the beast “Terrible Claw” – Deinonychus.

I prepared the first restoration and the temporary exhibit.

Model of a Dromaeosaurus raptor claw

Raptor Kick-Boxer of the Cretaceous
Deinonychus became a dino celebrity.  It was fast, smart, maneuverable – we imagined it as a Kick-boxer of the Cretaceous. It would leap up and slash its victims with the huge, curved hind-claw, shaped like a box-cutter.

We wondered whether the four Deinonychus were a social unit in real life. Maybe the hunted together. Since Deinonychus was close kin to Velociraptor, dug in the 1920’s in Mongolia, we started calling all the similar critters “raptors.”

Michael Crichton read about the Yale raptors and he got thinking: “hmmmmm…wouldn’t it be cool to use genetic engineering to bring back to life…a pack of Dino-Raptors…”  His best-seller “Jurassic Park” was the result. In his book, he called Deinoncyhus a species of Velociraptor (they are close).

CSI of Multiple Victims.
But how can we be sure that the four raptors lived and hunted together? Perhaps these four raptors lived separately, died separately, and then their bodies got washed in together. How can we be certain that the way fossils are buried truthfully preserves the way they lived?

We can’t.

Here’s a Fundamental Rule of paleontology: all species tend to leave their dead bodies in clumps. Whether or not they hunted together, extinct animals get buried together.

Example of Non-Pack Mass Burial

Dimetrodon
Creative Commons License photo credit: kaurjmeb

We’re digging in north Texas now, excavating the first specialized top predator that ever evolved – the Finback Dimetrodon. It’s 170 million years before Deinonychus. Dimetrodons had very small brains, slow legs, and certainly were not  nearly as quick witted or quick legged as a Komodo Dragon Lizard of today.

Lizards don’t make wolf-packs. We wouldn’t expect Dimetrodon to make well organized social units.

But we find them buried in clumps. In one quarry there are fossils from at least 500 Dimetrodons. Maybe 5000…we find hundreds of bones from scores of Dimetrodons all mixed together at dozens of spots within the quarry that is about 200 yards long.

There are babies, adolescents, young adults, and old Dimetrodons all piled on top of each other – in fifteen separate layers.

And…..DIMETRODONS WERE CANNIBALS!!!!!!

Here’s the proof:

What we look for is ballistic evidence. First, we search for clues that victims were dismembered and gnawed – we want to find marks on bones left by carnivore teeth.

Second, we want fossil bullets. Bullets are the tooth crowns shed by meat-eaters as they fed. Like crocs and sharks today, dinosaurs and primitive reptiles like  Dimetrodon shed old tooth crowns as they fed. New crowns would grow in to replace the old. So…when we find many shed teeth mixed with chewed bones that’s excellent CSI evidence about who ate whom.

Do our Dimetrodon bones have tooth marks? Yes!  And do we find shed teeth from  the perpetrators? Yes again.  Who’s the perp? 98% of the shed teeth at our big Dimetrodon quarry are from……

….Dimetrodon!!

Dimetrodon cannibalism surprised us at first, but it shouldn’t have. It’s Standard Operating Procedure today. Meat is hard to come by and most carnivore species won’t turn up their noses at a meal of their own kind.  Lions eat lions. Wolves eat wolves. Hyenas will eat everybody.

Our mega-Dimetrodon quarry was different from the Four Raptor Site. The Dimetrodons included babies, adolescents and adults. And a dozen other species were buried with the Dimetrodons, including big and small herbivores, insect-eaters, fresh-water sharks, and bottom-living aquatic amphibians shaped like salamanders.

We don’t know yet what killed our Dimetrodons. We don’t know why so many carnivores came to one spot – maybe they were attracted to amphibians who were trapped in a pond that was drying up. But it’s perfectly natural that the Dimetrodon survivors would gobble up the Dimetrodon victims. Cannibalism is just common sense.

Back to the Four Raptors……
Did dinosaur predators feed together?

X-ray of an allosaur upper jaw showing the
new tooth crowns growing inside
the tooth sockets

I’ve dug several Jurassic spots with shed teeth from carnivorous allosaurs. These Jurassic sites show that the allosaurs were cannibals but still may have been good parents. We dug a spot with heaps of giant, multi-ton prey.  Herbivore bones were tooth-marked and chewed. There were shed teeth only from one species – an allosaur. Both baby shed teeth and adult shed teeth were mixed with the giant bones.

So here it looked like parents and babies did eat together – and the parents may have brought food to the young.

Five of the victims chewed by adult and baby allosaurs were….adult allosaurs. Perfectly natural – cannibalism is nature’s way.

Did Deinonychus eat its own dead?
They’d be foolish if they didn’t. At the Four Raptor Site there are some tooth marks on some bones and a few shed teeth. We just dug another Montana site where someone had chewed on a Deinonychus hip and left some shed teeth. The chewer was…..another Deinonychus.

Ok – no surprise to find chewed & clumped raptors. Cannibalism is Ubiquitous.  But we’re not through with our Dino-CSI.  We need to analyze why the four raptors died and were buried so close together.

The Three D’s of Death:
There are three big mass killers in Nature, the three big D’s:

Disease. Drought. Drowning.
A long-lasting drought can kill thousands, both herbivores and carnivores. A sudden flood can drown thousands of all species. Epidemics wipe out multitudes of plant-eaters and meat-eaters.

The D’s work together: A drought can kill and dry up many victims. Then, a flood can wash the desiccated carcasses into a sandbar. After disease kills many, the bodies may dry up, then get washed in together.

Did a flood drown the raptors and wash them into one spot?
No evidence for that. The water that carried in the mud was moving very slowly – it wasn’t a killer flood.

And…this is important…there weren’t other victims bunched up with the raptors. A major flood would wash in turtles and crocs, fish and dino-herbivores. The four raptors were alone in their burial – no other species.

There are flood sites with dinosaurs – huge river sand bar deposits with hundreds of skeletons. Usually there are many species – plant-eaters and meat-eaters. Bone Cabin Quarryin Wyoming was such a sandbar and had stegosaurs, apatosaurs, Diplodocus, camarasaurs, camptosaurs – all herbivores, adults and youngsters. And there were allosaurs and Ornitholestes, both predators.

The Four-Deinonychus quarry wasn’t like that.

Did Drought Kill the Four Raptors?
No evidence here either – the habitat seemed peaceful and normal. Drought should concentrate water-loving critters – we should see crocs and turtles huddled together in the last ponds and lakes. That’s not our Four Raptor site.

What Could Clump Raptors in Life?
The four raptors were all adults, one a bit older than the others. No babies. In many Jurassic and Cretaceous digs, we get adolescent predators – one of my Como digs had a half dozen young allosaurs. But not at the Deinonychus site dug by Grant Meyer.

What would concentrate four adults of one raptor species and no one else? Why didn’t the young die and get buried?

Did Disease Kill the Raptors?
Disease today hits social predators hard. Since they live together, all the predators in a pack can come down with a virus or bacterial ailment together.

Age Segregation and Adult-Only Death

Model of a Dromaeosaurus
from the same family as the Deinonychus

Plus – social predators do separate the young from the adults during hunting. Group hunting is common among mammals, birds and some advanced reptiles. Crocs are the most social reptiles alive today. Nile Crocodiles do some adult-group hunting when wildebeest herds cross rivers. Several big crocs (probably brothers) gang up on the wildebeest.

Hunting groups - wolves, hyenas, lions, crocs - usually contain only adults, babies and adolescents are well advised to stay away so they won’t get hurt. Therefore, social hunting is one way adults clump together and may die together.

Working Hypothesis:

Therefore….at this stage in our investigation…when we look at all the clues from the mud, current velocity, lack of babies, lack of other species…

…group hunting by adult Deinonychus Raptors is a viable hypothesis.

It’s not the ONLY hypothesis but still, I think, the strongest one.


Connecting the Dots

Connecting the dots….. This blog could have many headers. I settled on “connecting the dots” because there are many interconnected topics I would like to address here. The starting point for all of us is a brief mention of our museum in a recent CNN blog. In a story about the US government returning cultural treasures to Iraq, one can read about one particular item being returned:

Roman denarius featuring the head of Apollo

A roman coin (not the one featured in the article)
Creative Commons License photo credit: Smabs Sputzer

“A Roman coin from A.D. 248-250, when the Romans occupied the region. The coin had been left at the Houston Museum of Natural Science by a man who said he was a contractor in Iraq. The museum’s curator of anthropology alerted federal authorities.”

In late February 2005, a visitor to the museum left a coin. This individual, who said that he had been working as a civilian truck driver in Iraq, had acquired other antiquities as well, including a clay statue. Excavations were going on all over the place, he said. They are indeed, except, in my world these excavations would be called looting. Here are the first two dots I want to connect: the coin, and the Parthians.

The coin was well preserved, with a legible Greek legend. With the help of the American numismatics society’s website it was possible to identify the coin as dating back to the reign of Emperor Philip (244 – 249 AD). Also known as Philippus Arabs, this Emperor lived during a period of major upheavals besetting the Roman Empire. Born in the Roman province of Arabia around 204 AD, he held several important positions before becoming Emperor in 244 AD. He succeeded Gordian III who had suffered an ignominious defeat against the Sassanid Empire. Gordian ended up being killed by his own soldiers. Sassanid artists commemorated the death of Gordian and the subsequent suing for peace by Philip in a large rock carving at Bishapur in modern Iran. After this rather rocky start to his own reign as emperor, in 248 AD Philip presided over the festivities celebrating the 1,000 anniversary of the founding of Rome, a celebration commemorated on many Roman coins. Things turned sour pretty quickly after that however. One year later, he was killed by his own soldiers after a defeat against rebellious forces near Verona.

I can imagine people thinking “A Roman coin in what is now Iraq? Surely that must have gotten there by accident?” Not really. Here are dots number two and three: the Parthians and their successors, the Sassanid Empire.

Statue of Alexander in the
Istanbul Archaeology
Museum

Emerging from the upheaval caused by Alexander the Great and his successors, during the third century BC, the Parthians established themselves as a major political, military and economic force in what is now Iraq, Iran and Afghanistan.

As Rome slowly grew and started asserting itself in the eastern Mediterranean, clashes occurred between the two empires. These encounters did not always end well for the Romans. In 53 B.C. Crassus and over 40,000 Roman troops were annihilated by the Parthian forces of Orodes II in the battle of Carrhae, a clash that continues to inspire modern historians.

The western border between Rome’s dominions and Parthia gradually stabilized on the banks of the Euphrates, but war was always a threat. Over the next two hundred years, Romans and Parthians would fight many wars. By 232 AD, the Parthians themselves were overtaken by the Sassanid Empire, which brings us back to dot number one: the coin left at the museum. The coin residing ever so briefly at the museum is a silent witness to those final years of Roman involvement in that part of the world. This brings up dot number four: looting and repatriation.

Looting is a scourge that besets archaeologists all over the world. Archaeological sites are being destroyed on a wholesale basis, with materials ending up in private hands, and sometimes in museum collections. International treaties attempt to curb these activities but are not always very successful in doing so. International treaties aimed at stopping this wanton destruction of our past are good, but… there is also a need for people to know why this is necessary. Failure to communicate this need usually makes people think “Sure, it is only the archaeologists who want to be able to dig. Why shouldn’t I be allowed to do the same?”

Here is why you cannot or should not be digging randomly looking for “treasure.”

Pottery Shards
Context is important in Archaeology -
Knowing where the pottery comes from is
just as important as having the shards
Creative Commons License photo credit: Todd Huffman

Any object retrieved from the soil has a context. There is a story that can be told based on how the object got there. The coin that was brought in, the pot that was found, all got to the place they were found because someone dropped it, or placed it in a tomb, etc. Archaeologists are trained to retrieve materials and take note of the surroundings in which they found these items. Context makes the story much more complete. It represents the difference between retrieving half a book versus a whole book, half a story versus a complete story. In specific terms, context will help us to decide which of the following headlines makes sense: “A Roman ship landed in Mexico!” Or: “Something cool collected from the crew of a Spanish ship or an early Spanish colonist got traded to the residents of the town of Toluca.”

The coin in question dates to the end game of large-scale Roman involvement in Mesopotamia. I am not sure if a lot of these coins have been found in what is now Iraq. Without an accurate accounting of what is found and where it was found, we will never know. Conceivably, the coin’s context could have told us something about those final years of Roman presence. Perhaps it came from a small military encampment. Perhaps it was found with a lot of other coins – a hoard as it is sometimes known – which would indicate that the owners buried it for safekeeping. We will never know.

Saying no to looting is not the end of the story. Archaeologists have their work cut out for them too. We need to collect the context information, look for patterns to make sense out of it all and then share our findings with the public. The latter is very important. The more people know about what we do, the greater the understanding will be as to why it is a bad thing to acquire looted items or to go out and dig holes yourself. You are not doing history any service, and you might be breaking the law as well.

And so it is that we come full circle, connecting dots from coins to Romans and Parthians and international treaties regarding the protection of cultural property. It is all interconnected. I am sure that colleagues at other museums have had similar experiences. This is proof that working at a museum is so interesting, or “QED” as the ancient Romans would say.