This is the third post in a series called “Cretaceous Cold Cases” in which the science of taphonomy, or prehistoric forensics, is explained by fascinating cases from the files of Terry “Bucky” Gates, a research scientist with a joint appointment at NC State and theNorth Carolina Museum of Natural Sciences.
Thanks to awesome shows like “Matlock” (does anyone remember this show?), “Law and Order”, and “CSI” we all know the routine that police investigators follow when examining a crime scene. Find the victims, gain personal/demographic information, carefully sweep the crime scene for clues left by the perp, run evidence through fancy glowing machines in dimly lit club-esque police laboratories, then nab that killer. Easy enough, huh?
Honestly, investigating wildlife scenes is almost exactly like that…we don’t actually catch the animal that killed the other animal.
Our purpose investigating skeletons in the Okavango Delta was to determine what happened to animals from the time that they died until we arrived at that scene. And every skeleton we find, we will revisit on every trip to see how the bones may have changed over time.
First, after the death, what happens? There have been great studies where scientists watch a dead animal bloat as their insides fill with the gas of the bacteria that are decomposing the body from the inside out. If left unharmed by scavengers, the body will eventually rupture (no, I will not show a picture), and trust me, you don’t want to be near a body that does…it really stinks!!
Most often scavengers find the carcass and begin pulling meat away. Different scavengers feed differently, and most all of the skeletons that we find are scattered over large areas, hundreds of square meters. Smaller animals are consumed in one sitting by a single animal or one group so remains may not be as spread.
The bite marks left on the bones tell us who was eating what parts of the skeleton. Lions, hyenas, and vultures all leave very specific breaks and scratches on the bones because of feeding styles and the tools they have in their mouths.
So we have a body, we have the weapons of destruction, what next?
Time of death…
this can be trickier to determine. With a fresh carcass it is not that difficult, but the further away from the time of death the larger our error becomes. The easiest carcass we found was a leopard tortoise that died the previous night. We know this because one day the shell was not there on our drive, the next day it was. Yet, as years go by more and more evidence is destroyed, but that destruction can be a great clue. See, bones crack when exposed to the sun, and the pattern of cracking estimates the time of exposure. So we can determine if a skeleton was laid down up to 15 years prior!!
The killer. Sometimes we know what killed an animal because our guides saw it happen and can tell us. Or there are clues such the placement and size of carcasses that tell us leopards versus lions were the culprit. But a lot of times we can’t be sure. Once multiple animals begin feeding on a carcass bones get scattered and bites overlay one another. Still we try our best to determine patterns of predator behavior. Changes to the way predators feed can be wonderful indicators of ecosystem health.
Finally, game trails, or animal highways, can be a terrible disrupter to bone sites. As animals walk through a bone site they kick bones around, break them into pieces, or push them into mud. All around causing us grief. It was interesting though to see so many carcasses along game trails. Predator killing behavior? We need more data.
Lots of other information can be obtained from bone sites to help us understand the lives of the animals, including DNA sequences, stable isotopes revealing diet and travel of the animal, and amino acid decay to help time death. We hope to pursue many of these in the future on our quest to breath new life into old bones.
The Utah team is in an area of the state called Mussentuchit Flats looking for dinosaurs about 98 million years old. There is nothing at all out there except lots of rock with dinosaurs!! Cell phones are useless, which is one of the great things about paleontology field work every now and then…to go somewhere no one can reach you. Communing with prehistory and yourself actually is healthy. But the lack of showers gets old after about 10 days.
So while we all wait for the next field update I wanted to fill in a little more information about our trip to Botswana.
Conversations about my research trip to Botswana usually went something like this:
“Oh, you are heading to Africa!? That’s exciting. What kind of dinosaurs are you looking for?”
“None, then why are you going?”
“I am looking for dead animals.”
At this point their face would crinkle into a funny contortion of disgust at the thought of a dead animal, and smoke would arise from their ears as they tried really really hard to figure out why in the world anybody would actually want to find a dead animal, let alone as many as humanly possible.
The answer is really quite simple. That is…because everything in the fossil record is dead.
Well DUH!! But really think about that. If everything that we are studying as fossils are dead, all of the experiences and history that each of those animals led is barely transferred to their fossilized remains.
So the best way to tease out every ounce of information about ancient life is to understand exactly what types of information can be preserved by studying modern dead animals.
The main purpose of this trip was to first find, map, and detect any patterns in what bone sites looked like. We did not have armed guards with us on this trip, and the one short walk that was taken through a savannah felt like a literal death march because our guide spotted tracks from a pride of lions that passed through only a few hours earlier. Therefore, most of our carcass prospecting was from the vehicle. Nonetheless, we found over 30 carcasses, some over 10 years old.
And our preliminary findings are positive. It seems that giraffe carcasses are found where the giraffes live, as well as the water buffalo (these animals don’t live in the same habitat). Elephants are just everywhere.
Our next goal is to walk miles across the Okavango Delta to find even more carcasses. Ultimately, our data can be used to assess conservation efforts, changes in populations, and predator behaviors through time.
Tomorrow, I will talk about the forensics of a carcass site…
I figured we’d be driving around on safari gazing through our binoculars at spectacular wildlife and documenting the incredible interplay of species struggling for survival in the African wetlands with our keen “super-scientist” powers of observation.
Then I remembered… we study dead things.
“What exactly are we going to be doing?” I asked, not really sure that I wanted to know the answer.
“Walking around looking for animal carcasses…” came the unfortunate reply.
“Of course,” I grumbled.
Now to be fair as a vertebrate paleontologist, I am used to studying skeletons… it’s just that, well, the animals have usually been dead for tens or hundreds of millions of years, so the “gross” factor isn’t really an issue. Even when I taught gross anatomy to med students, the cadavers were (thankfully) embalmed. To put it mildly, Botswana was a bit different.
Our first stop? An dumping ground with one dozen, I repeat, one dozen, fresh elephant carcasses baking in the hot African sun. (Thanks Bucky). Now you might ask, what might one dozen fresh elephant carcasses be doing in one spot? And that would be a fair question. I certainly wanted to know. Turns out that the government allots the local community here a certain number of permits for the hunting of elephants. In the Sankuyo Community this year that number was around two dozen. And this? This is where they compile the aftermath.
As a scientist, I generally take a matter of fact approach to data collection and I’m no neophyte when it comes to flesh and bone. So I was surprised to find myself suddenly surveying the morbid scene splayed out in front of me with a heavy heart. Having only seen elephants in the wild a few times in my life, they still held a certain majesty to me—an almost ethereal beauty—and it was hard to imagine a good reason for this loss of life. Later, in taking to the wildlife officer we learned that after the hunters flew home with their trophies (nearly all Americans and Europeans on the record books), the Community Trust distributes the elephant meat to feed the families within their care. (We’ll post more about this controversial and difficult topic later).
Sometimes the hardest part about being a scientist, is sticking to the data… but stick to the data we did.
After collecting our data on decomposition, predation and bite marks by hyenas, area of scatter, and so on, we paid reverence to the fallen elephants and headed off to find carcasses of animals that had died in the wild. Just as we were packing up to head out we witnessed a fleeting moment of beauty on one of the elephants, a Foxy Charaxes butterfly. We snapped a few photos for a colleague at NC State University who studies butterflies and went on our way.
As I climbed into the vehicle, my science-self was grateful for the reminder: in the natural world, death begets life.
In Africa, such reminders are not in short supply.