In this unit we'll be talking about dinosaur behaviors. To start off, we're going to focus on behaviors that pertain to catching prey and fending off predators. Now, behaviors don't fossilize, so we need to be creative in finding ways to test for possible actions and reactions in dinosaurs. Even though as paleontologists, we work on extinct animals, we use living animals as guides to what behaviors dinosaurs might have had. So, in this module we'll be spending a lot of time looking at behaviors and adaptations in modern animals. We'll also examine specimens from our zoology museum here at the University of Alberta. First, we're going to talk about interactions between members of different species. How do predators acquire prey, and how does prey avoid being eaten. Later, we'll talk about some of the ways animals interact with members of their own species. It's hard to be near the bottom of the food chain. Here a list of adaptations and behaviors. Check the items that would allow an animal to avoid being eaten by predators. A) Make yourself look bigger. B) Make yourself smell or taste bad. C) Live in a large group. D) Have a good sense of sight, smell, or hearing. E) Be good at hiding. F) Have defensive armor or horns. Or G) By being quick. In fact, all of these are great answers. There are many ways to avoid predators, and certain strategies work better in certain situations. Let's look at each of these various defensive strategies in turn. Some animals use armor to avoid being eaten. Hard shells make it difficult for predators to weaken or cripple something like a turtle. Armadillos, crocodiles, and some lizards have bones in their skin called osteoderms, just like some dinosaurs had. And pangolins, which are mammals, have modified hair that looks like scales. Avoiding detection with camouflage is one of the best ways to avoid being eaten. Small animals like lizards, birds, and small mammals often blend seamlessly into the background and are tough for predators to spot. Given the inherent limitations of studying fossils, which of the following adaptations for avoiding predation do you think we can correctly identify in dinosaurs? Multiple answers may be correct, so check each answer you think is right. A) Warning displays. B) Fighting with weapons like horns or spikes. C) Herding. D) Keen eyesight or hearing. E) Camouflage. F) Armor. G) Chemicals or bad odors. Or H) speed. In general, skeletal adaptations such as horns, orbit or ear size, armor or leg length can be detected in the fossil record. Some things can potentially be preserved like her behavior when we find a lot of skeletons or footprints together. Things that are only behaviors like warning displays, or that wouldn't be part of the skeletal structure like camouflage or chemical odors cannot be identified. Therefore answers, B, C, D, F and H are correct. Some things like armor are easy adaptations to see in the fossil record. Even things like eyesight and hearing can be determined by looking at the size of the orbit, or the structure of the inner ear. Likewise, we can estimate the speed of an animal by looking at the shape of its limbs and then comparing them to modern animals. Although behaviors don't fossilize, the structures necessary for some behaviors do. For example, although we can't observe a dinosaur using its horns for defense, we can see that it has horns. And we can potentially find evidence of combat in scars left on bones of other creatures. Finally, we can make educated guesses about hurting behavior when we find large accumulations of dinosaur skeletons, or find track ways from many individual dinosaurs of the same species in the same place. However, it is important to note that because we cannot directly observe how fast dinosaurs move, or if they heard, we can only develop good theories about these activities. Some behaviors are impossible to find in the fossil record. Things like warning displays, chemicals, or camouflage patterns don't fossilize. However, since there are so many extinct dinosaurs, and numerous defensive behaviors are so common in modern animals, it is very likely that at some point, dinosaurs had these adaptations as well. But to be honest, we may never know for sure. Let's take a look at one group of dinosaurs now. The Ankylosaurs. Here's an image of the Ankylosaur Edmontonia. What do you think its main method of predator defense was? A) Speed. B) Armor. Or C) Acute eyesight. Ankylosaurs probably used armor as their main mode of defense. Their limbs were relatively short, so they couldn't run very fast. And their eyes were not overly large. It's even likely that their line of sight was possibly blocked by some of their armor plating. Answer B is correct. Now, we're going to go to Paleontology grad student and published Ankylosaur expert, Victoria Arbour, who's going to tell us about another potential defensive adaptation in a type of Ankylosaur known as Euoplocephalus. And that adaptation is the tail club. >> Ankylosaurs had bony plates in their skin called osteoderms which would've made them really spiky looking and probably worked really well as a defense against being eaten because it would've made them really crunchy. Some ankylosaurs like Anodontosaurus, Euoplocephalus and Dilophosaurus, which were all from Alberta, had modified tail vertebrate called a tail club. And I have an example in front of me here. The vertebrae and the back half of the tail interlock and would of been really rigid. At the end of the tail, were huge which basically formed a ball of bone around the end of the tail. Because the tail of ankylosaur is different from the tail of many other dinosaurs, maybe it had a unique function. Did ankylosaurus use their tail as a defensive weapon? Maybe they used it to strike at predators to avoid being eaten. Paleontology is a science, and like all sciences, our experiments start with observations and then questions. So our observation for ankylosaurus is that the tail is really weird and different. And the question we can ask is, what did Ankylosaurus use their tail for? Did they use them as a weapon for defending themselves? How can we figure this out? >> What sort of information do you think we might need to figure out if Euoplacephalus clubbed its attackers? Multiple answers might be correct, so check every answer you think is right. Is it A) what color the tail was. B) How far the tail could swing from side to side. C) How hard the tail could hit things. D) Could the tail break if it hit something too hard. Or E) How smart euoplocephalus was. Well, knowing the color of the tail and how smart euoplocephalus was wouldn't hurt. First, we need to figure out if euoplocephalus could swing its tail at all. If it could move its tail from side to side, then we need to know if it could swing its tail hard enough to cause any pain or damage to an attacker. Finally, we need to know if the fail would break if it hit something hard. If euplocephalus swings its tail at a tyrannosaur like gorgosaurus, but the tail snaps in half, then that would cause a lot of trouble for euplocephalus. So the correct answers are B, C, and D. >> Ankylosaurs use their tail clubs with something that I was really interested in, and so part of my research here at the University of Alberta has been to investigate tail club function. I looked at how bones of the tail fit together to see how far an Anchilosaur could swing it's tail from side to side. The tail club itself is fused and rigid, but the front half of the tail is flexible just like in any other dinosaur. I estimated the size and strength of the tail-swinging muscles, and how heavy the tail club itself was. Using that information, I could then calculate how fast the tail club could swing from side to side,. And from there, we can figure out the impact for stirring a tail club strike. I found that large ankylosaur tail clubs impacted with somewhere between 35,000 and 70,000 newtons of force. It's a lot, it's not as bad as getting hit by a car, but it would be a lot like getting hit by a baseball bat by a professional baseball player. It would hurt a lot. And you definitely would not want to get hit by an ankylosaur tail club. So we know that the tail could impact with a lot of force that would cause pain. And that suggests that it would work pretty well as a defensive weapon against predators. But if the impact forces are that high, would the ankylosaur tail club break during an impact? If so, that would be really bad news for the ankylosaur. Was the club strong enough to withstand the impact forces that I calculated? To figure out if the tail club would break during impact, I used a computer simulation called Finite Element Analysis or FEA. This is a technique that's used by engineers to figure out stress and strain within manmade objects, and it's increasingly used by paleontologists to solve biomechanical problems. The first step was to CT scan a bunch of different tail clubs including this one here. And from there, I made digital models of those CT scans. I told the computer to apply properties of bone like brittleness or flexibility, and then I applied the force that we calculated before at the place that we think the tail club would have impacted something. The end result is a colorful picture like this that shows where stress is located, and how much stress there was. If there was too much stress, bone will break. I found that the maximum stress in a medium sized tail club was not enough to break the tail club itself which is really good news for the Ankylosaur. Its own tail wouldn't break if it used it for swinging. But I had to estimate many things in order to get this result. Things like muscle size and strength. Tail flexibility, how fast the tail could swing, and even the force that was applied on impact. All of those required estimates. And all of these assumptions were reasonable, but each one of them introduces potential sources of error into the final result. What if the tail muscles were a lot larger or smaller than we thought? Or what if the tail wasn't really as flexible, or if the tail club mass was estimated a little bit too high or a little bit too low? Although we may have some idea of how strong the force from clubbing was, we can't really say with exact certainty what the force would have been and what the results were. >> And here's another question about Euoplocephalus's potential defensive adaptation. Through our data gathering, modeling and experimentation, did we prove that euoplocephalus used its tail club to defend itself against predators? The answer is no. We were able to say that euoplocephalus could swing its tail with plenty of force, and would not break its own tail while doing so. But we cannot say for certain that euoplocephalus did swing its tail, or that it used it to defend itself against predators. Maybe predators didn't try to eat euoplocephalus, because it was simply well armored. As scientists, we always have to be careful about drawing conclusions from our experimental data. >> We could say that ankylosaurs probably did not use their tail clubs for clubbing attackers if the tail couldn't be swung very hard, or if the tail would have broken during an impact. It's easier to say a dinosaur didn't do something than that it did do something. Or, in other words, it's much easier to reject than prove a hypothesis. In science, it's actually much more accurate to say that you reject or do not reject a hypothesis than to say that you've proved something. So in this example, we did not reject the hypothesis that ankylosaurs could use their tails for making forceful impacts
