Social Behaviour in Dinosaurs - with David Hone

thank you very much indeed it is honestly a genuine and real pleasure to be here as we said today social behavior in the dinosaurs evidence from Mongolia for the last few years I've been doing a variety of different research projects my research is actually quite general I tend to cover lots of different areas and while I try and focus on behavior and ecology within the dinosaurs it also means I get to play around with some other things so I've done little bits on things like flight specimen preservation I've been lucky enough to name several new species in my time and in particular recently I've been working on this guy this is one of the largest is the largest member of a group called the ornithischian dinosaurs from China and this is a wonderful specimen from a bone bed with we estimate about 70 to 80 individuals each of which is probably in the range of about 15 to 20 tonnes so this is a colossal assemblage of really big animals and body sizes we'll see actually features to a certain degree um I spent three years as a researcher in China and this meant I got to do quite a bit of field work in the Gobi Desert in what is called naming also Chinese Inner Mongolia this is myself with a couple of colleagues digging out a large block of bones over three or four dinosaurs within that and indeed the whole place is replete with bones both of dinosaurs and also the local goats and sheep it is unfortunate because we will see from the next slide it's very hard to tell him apart at first glance I quite often find yourself trekking up a hill as you can see this enormous desert landscape I only discover that what you thought you'd found was very interesting turned out unfortunately to be sheep and goat but it is absolutely full of dinosaur bones it is one of the most productive areas on earth for dinosaurs particularly from the Late Cretaceous so this is about 70 million years ago as you can see here on the right this is actually a small nest of eggs there's one very obviously front-and-center but there's also a couple more to the side and actually some pieces of bone along so I and on the left here's actually a partial skeleton very incomplete and more importantly it's actually very badly eroded we weren't actually able to collect this but you can see a number of ribs on the side part of a limb and then a jaw with a series of teeth and they are absolutely everywhere in an area the size of this room you would find a few pieces of dinosaur bone perhaps not anything more than a partial tooth or a bit of rib but you would find something it is that replete with material and occasionally of obviously you find lots of bits but occasionally you find things like this so this is a skeleton discovered by a friend of mine he found just the tip of a cloth sticking out of the rock face we dug in and that's what we pulled out it turned out to be a new species he found another new species the same day so some people have all the luck but on the upside I know it will never get any better for him so that is my one consolation when it comes to behavioral ecology in the fossil record it's obviously something difficult if we want to look at the behavior of living species we can go out and observe them in the world we can bring them into the lab and observe them we simply can't do this for extinct species so it has to be inferred rather than observed but it doesn't mean that it was just guessing which a lot of people kind of assume we can draw together multiple lines of evidence if we're careful and bring up a fairly clear picture of what's going on at least in some cases so we can look for obvious things like anatomical specializations and analogous structures pretty much all animals that are carnivorous have some form of sharp teeth and usually some form of sharp claw therefore it is not a big surprise when we see things like Tyrannosaurus Rex that it was a carnivore we can tell that fairly immediately we can look towards acknowledge e acknowledge E is the study of traces of fossils so this is anything that was not the body of an animal so that can mean things like footprints nests sets of eggs bite marks on bones and other kind of sources of data like this and then finally we can compare them to living tax of my ancestry what living species that are close relatives of extinct ones have similar kinds of behaviors so for example among the living animals the nearest thing to dinosaurs we have are the crocodiles and birds birds are literally living dinosaurs the dinosaurs did not go extinct birds are still with us they are literally dinosaurs so in fact when I talk about dinosaurs for this entire lecture I mean the extinct ones but almost all of those animals all modern crocodiles or modern modern crocodilians and almost all modern birds exhibit post hatching parental care in other words they look after the eggs and when the eggs have hatched they also look after the babies for at least a short period and often a long period of time it's reasonable to infer them that dinosaurs probably did the same and actually we have supporting evidence for that as well but we can at least begin to draw that in and ideally we should pull our evidence from multiple sources so this for example is Baryonyx this is a British carnivorous dinosaur that you can actually go and see it's on display at the Natural History Museum and there's good reason to think that Baryonyx was for at least part of its life or a main part of its diet feeding on fish and we can draw this again from numerous areas so first of all analysis of the mechanics of the skull showed that actually it's very similar to modern crocodilians and modern crocodiles and how they feed if we examine the shape and structure of the teeth we find they're actually similar to very other so it's very similar to other animals that often eat fish so things like crocodiles and actually various extinct marine reptiles which must have been eating fish we can look at the isotopic signatures within the bones and teeth themselves animals that spend the majority of their time in water actually have unusual and unique chemical signatures to the bones and this stays and is preserved in the fossil record and if we look at Baryonyx and its near relatives we find they're actually closer to things like crocodiles hippos and Terrapins than they are other terrestrial dinosaurs implying they're spending a large amount of their time in water and then finally this is actually a fish scale that was found within the chest cavity of the baryonic specimen and has acid etching from the stomach on it that on its own is a bit of a killer argument but if you put the entire picture together it's clear they must have been spending a fair amount of their time eating fish but not exclusively the bones of another baby dinosaur were also found inside Baryonyx so don't get don't fall into the trap of they just ate fish but clearly it was a major part of their diet but that's all relatively simple what things ate what about something that probably doesn't leave any obvious trace like social behavior and social interactions well that excites to get a little harder but first of all we need to kind of define our terms a little bit often the term sociality or social behavior is considered to mean some kind of living together in groups humans we would probably agree our generally social creatures and it also tends to imply some kind of social interaction or level of hierarchy if we think of things like dogs we think of classically you know the alpha male alpha female beta males and females there is a structure there and regularly large numbers of social interactions and this does collectively have important implications for dinosaur behavior and it Dean actually even bird origins how these animals interacted with one another what were the evolutionary drivers that are affecting behavior as well as anatomy and what was actually changing them as they lived and as they grew and as they evolved and can we really begin to get this from the fossil record well we can start to piece it together on the left for example this is part of the quarry in China which feature that giant dinosaur I mentioned at the start this photo doesn't really do it justice that quarry is about 300 meters long by about 30 meters wide this is one of the largest dinosaur quarries on earth it's produced several thousand bones about four and a half thousand bones were found within that quarry so far and they're still digging all but five of those bones come from that single species there's a bit of crocodile there's a bit of Tyrannosaur there's a tooth and that's about it other than that it's all of one species it looks like a big group that died together similarly here we have a trackway and it shows multiple individuals traveling in the same direction probably presumably therefore at the same time that suggests these animals were living together but we can't go much further than that in fact we can't even necessarily say they were living together perhaps this was a migration that would force them all in the same direction at the same time doesn't meant they live together the rest of the year or that there were strong social interactions so we need to be careful now at this point I want to step back a little and just do an introduction to dinosaurs themselves I appreciate them probably a few dinosaur experts here so it's always nice to cover the basics dinosaurs were the dominant terrestrial clade of the Mesozoic period so between about two hundred and sixty-five million years ago if there was a large animal on land it was probably a dinosaur and it's a fair statement to make as I said they're close relatives of modern crocodiles and birds are the literal living descendants of the theropod carnivorous group of dinosaurs they were remarkably diverse there's around 1,500 valid species described from out 30 major clade something roughly equivalent to a family you're probably familiar with dog family cat family those terms are changing a little these days but it's a approximate equivalent and we're naming dinosaurs currently the rate of about one a week and we have been for about the last four or five years so that number is not just high it's actually growing quite rapidly and they had a worldwide distribution we're very kind of familiar with the idea of dinosaurs living in rainforests and tropical swamps and lush environments but they lived in the High Arctic they were living in mountain areas they were living on the coast they were living in deserts they got absolutely everywhere both in a geographic sense but also in terms of environments and ecosystems and in terms of size this is always a very difficult area obviously lots of specimens incomplete and estimating mass or weight in particular is very difficult but certainly there were adult dinosaurs as small as around 50 centimeters in total lengths including the tail and probably around 30 meters or even more when it came to the real Giants so there is a huge range of dinosaurs there in particular today I'm going to be talking about a group called the ceratopsians also known as the horned dinosaurs these were herbivorous animals from a group called the oneth Asians and they lived exclusively as far as we can tell within the northern hemisphere particularly in Asia and North America early forms are actually bipeds but as they got larger over time and diversified they all became quadrupedal and again quite a big range in sizes the smallest about a meter getting up to eight meters or so and we're most notable for the arrangement of horns and frills and spikes and bosses that covered the head this is Triceratops which I'm sure is familiar with it's three horns and the large front the back it's probably the one dinosaur one of the few dinosaurs that most people could name and probably recognize but it really doesn't do justice to the arrange of horns and frills and spikes and bosses and absolutely everything else that he's out there with in the ceratopsians you can see here this enormous diversity of shape structure and patterning here of course is inferred but it quite probably things like that as well unfortunately we're looking at Protoceratops which doesn't really have any horns at all so we have to scale down to a much smaller animal this is about two meters in length and lived in the Late Cretaceous of East Asia indeed it is from Mongolia both the modern Chinese Inner Mongolia and also Mongolia the country and it's known from very large numbers of fossils in excess of 100 specimens are in museum collections there are far more out there often we don't collect very incomplete or damaged specimens and indeed in more recent times because we have such a huge collection it's less of a collection priority we could probably get quite a few more if we want and the specimens actually represent in particular a range of different sizes from very young juveniles right the way through to adults now actually if you look into the scientific literature there are two different reports of numerous adult Protoceratops found together one from China and one from Mongolia in both cases the individuals were of similar size and therefore probably of similar age they shared a similar orientation so they were all facing the same way now that's important because if these were buried in something like a flood or a drought we could easily expect they'd be turned over faced multiple different directions all facing to the last remaining waterhole or something like this no they're all facing the same way and would appear to have been overwhelmed from a natural disaster one lovely thing about deserts is that animals are often buried under and that sound is often transported by wind and we can actually tell that from the geological record now wind could mean it was windblown from a sandstorm or something like a sand dune collapse but again it's a fairly instantaneous thing not associated with water and couldn't happen over a long period of time it's it's probably a one-off single event so this suggests actually that in both cases they were naturally aggregated at the time of death they were together for whatever reason and then keeled over or at least were buried we also know of this specimen these are a very young animals there's a total of 15 of them preserved together so here for example is one head here is another you can see the eyes in each case there's the body limbs and tail 15 of them again all roughly in the same orientation all about the same size presumably therefore all about the same age and these are very young only around this size 15 20 centimeters or so in total lengths and a number of features about them suggests that they are very young animals more recently we have a sub-adult pair so we can divide dinosaur ages up into a number of kind of different groups and a sub-adult pair is roughly analogous to a human teenager clearly closer to adult than perhaps anything else but not quite fully mature in any true sense of the world they had bird sorry they have a bit of growing still to do and in the case of these animals they're about a metre or so long so still half the size of what we consider true adults but much closer along that spectrum in terms of their development than these younger specimens and these again from Mongolia the first individual is rather obvious and easy to make out the second one sadly is rather badly eroded so there's little more than a nose and a leg but again similar size similar orientation probably similar age and found together in isolation of anything else wonderfully however a new specimen has turned up I say new it was actually found in 1991 I only found this out at the last minute this is based on a paper of mine that I recently published with a number of and it was literally only in the last couple of days where I said you know she should really put in when you found this specimen I saw it in 2011 and then my colleague emailed and said oh yeah we dug it up in 1991 they'd been sat on it for nearly 20 years before anything happened with it which I simply hadn't realized this was found once more in southern Mongolia and here we have for juvenile specimens larger than those tiny ones we showed but about half the size of that sub-adult pair and they've been excavated and more importantly prepared as a single piece to prepare something you actually have to physically get the bones out of the rock and in doing so of course you want to preserve their original positions there is information in the bones yes but there's also information in how they are structured within the block and therefore actually extracting that kind of information without destroying it is extremely skilled operation and the job done here is absolutely magnificent the topmost specimen has actually suffered some erosion that's how it was found on the surface but the others are actually quite superb some of the best I've ever seen so here is our top specimen as soon as the head or as was the head you can see the whole back all the ribs and legs and ribs and limbs sorry here's our second specimen to the right with its legs pointing out here is the third one with the head up so it's got an open mouth as the eye the pelvis and the tail runs around and the fourth one down here the third one is actually literally physically standing on the head of the fourth here it is from an other orientation so this is just flipping the block around and again number one number two number three and number four again the preparation work to do this is absolutely phenomenal this is years of work and extremely delicate because that sand just crumbles literally when you breathe on it even just touching the piece a couple of times bit started to fall off it really is that delicate so here are the two best skulls number two on the left and number three on the right again it shows this fantastic detail the preservation from these localities are absolutely amazing indeed it's one of the main reasons they're so important for us now interestingly as I said they're kind of intermediate in a between the ones we just looked at em if we take this very young juvenile to the left we see it has an absolutely enormous eye most young animals have giant eyes and they kind of grow into them as they get older its frill up the back barely exists and if we compare that to a sub-adult or close to an adult animal has a much smaller eye and a much larger frill and again if we flip over to our specimen number three we see it fits almost perfectly as an intermediate its eye is quite large but not huge its frill is clearly developing but not that big it's also almost exactly intermediate in size and one thing that's worth fighting at this point is of course these animals change shape quite dramatic dramatically as they grow they can be quite drastic in their alterations so how can we be confident we're actually examining the same species and we haven't mixed them up well very fortunately for us Protoceratops and indeed one species of Protoceratops Protoceratops andrew's eye has a unique feature that we don't actually see in any other dinosaur or at least any other on efficient and it's this it has a tooth in this part of the jaw no other animal actually has this and we see it in the tiny juveniles in these the sub adults and the adults so it can be really quite confident that it's actually a single species so if we put that all together we now have aggregations of Protoceratops as very young animals as these kind of intermediate sized young animals as sábados and adults well the exact circumstances of any of these are open to interpretation you don't want to try and over interpret every single specimen it does appear reasonable to say that groups of Protoceratops were forming and they were spending at least some part of their lives together in groups everything from kind of hatchling size right the way through to late stage adults it was very common for them to form groups and wonderfully for us these are all from the same time geologically and almost all exactly the same place as well these are about as close to each other as we're ever going to get in terms of a true population when it comes to the fossil record often we're picking data from specimens that are found thousands of miles apart and possibly tens of hundreds of thousands of years apart whereas here they're actually very close together in time in place and there as I say is the four different size categories that we have now and it really does fit this really quite nice pattern of tiny animals right the way through two large adults so we've got some new aggregations and that's lovely and indeed dinosaurs are actually known in groups of all adult animals as we've just seen of all juvenile animals as we've just seen and mixtures of juveniles and adults together if we look across all dinosaurs we can find all these different kind of groups now interestingly juveniles actually only make up about 5% of the fossil record for dinosaurs if you go out and take out 20 new skeletons on average only about one of them will actually be of a juvenile animal so younger than sub-adult but all juvenile groups in other words cheek groups that consist entirely of juvenile animals make about half the total number of aggregations 9 so even though juvenile dinosaurs are one animal in 20 if you go and find a group about half of them on average will probably be of all juveniles so where are the rest of the juveniles and why this discrepancy between solitary specimens and groups of specimens well there's some interesting aspects to the biology here groups of adults will come together for a number of reasons they'll come together for things like breeding and raising offspring that's clearly not affecting juveniles we might expect juveniles and adults to be driven together by something like a drought or a famine or something like a migration pattern everything will need to go from where it is now to somewhere else we might expect then to find a group of juveniles and adults together but that's a mixed group that doesn't produce juvenile only so it suggests that there's an alternate explanation for why juveniles hang around together when adults don't and therefore why we keep finding them as groups and the most obvious reason for this is actually predation we know from looking at living animals that predators actively target juveniles juveniles are by far and away the most fed upon or targeted offspring it's virtually one of the first lines of reasoning of Darwin's Origin of Species more offspring are born than can possibly survive where do they all go well the vast majority of them go down the gullet of carnivores and is no reason to think that dinosaurs were doing anything differently so juveniles will cluster together as a defense against carnivore because vigilance is one of the big things juveniles have to spend loads of time looking for food they're often naive about it they're looking for food in bad places they're eating low-quality food and of course they are very vulnerable to predators and the biggest way of getting over that quickly and effectively is being in a group at least someone's probably keeping an eye out now actually if you look at depictions of dinosaurs any kind of artwork and almost any kind of reconstruction or documentary what you will typically see is Tyrannosaurus trying to eat something like an adult Triceratops in other words an animal just as heavy as it is with horns about this long this is not an ideal target this is not what carnivores do generally what they do is go after the little ones which are stupid foraging in the wrong areas and don't have any horns to defend themselves this is what you should be doing and actually if we look at the fossil record for carnivore it's what we see there are numerous incidences of theropods the carnivorous dinosaurs either having actively consumed juveniles like Baryonyx with the juvenile inside it or having attempted to do so there are several records of young dinosaurs with the teeth of carnivores broken off inside their bones and the bone having then healed over the top so they survived a predation attempt and clearly they were still juveniles after they'd survived that so it must have occurred at an even younger age we also see this from healed bite marks we see it from stomach contents and we even see it from coprolites does anyone want to volunteer what a coprolite is several people know is his fossilized waist but we see the bones of baby dinosaurs macerated and passed out through these animals they were eating and in contrast few and very few examples of feeding on adult dinosaurs which we think happened pre-mortem there's definite scavenging and feeding on adults but things that were actively killed or targeted basically don't exist now the discrepancy the absence of juveniles in the fossil record has been suggested to simply be a result of them being missing a few years ago over 10 or 20 years ago there's a paper saying well maybe juvenile dinosaurs were just really rare and that's why we never find them that's when we're certainly not the reason there are biases against finding juvenile dinosaurs their bone structure is such that they probably don't fossilize as well and also importantly they're small smaller things are harder to find than big ones it's a real bias that affects how we find specimens but it probably doesn't account for their extreme rarity for a start and dinosaurs are notably fecund lots of them are laying lots of eggs when we go and find necessary dinosaurs there are often tens of eggs present and they might have been laying 2 or 3 times a year and yet again dinosaurs are being only found or juveniles are only representing about 5% of the fossil record so clearly they're going somewhere so if we actually start to piece all of that information together we actually start to get something for coherent pattern here despite the limits of the fossil record these observations actually fit something that we know well about living species most predators targeted juvenile dinosaurs that makes sense most modern predators target juveniles most groups are of juvenile dinosaurs and they're the group that are most at risk to predation and in modern species groups tend to form as a defense against predation we see groups forming when predators move into an area or we see groups getting larger when predator numbers increase or start to appear so we know that vigilance is a major defense against them so it's likely then that many of the groups we find of juvenile dinosaurs where is response to a predict predation threat so this fits all of the available data and therefore this may explain why we keep finding aggregations of juveniles when we don't find aggregations of adults or when we find mixed aggregations but does any of this make them social and here we come into a definitional problem there's a big difference between sociality and the formation of an aggregation in other words simply a group of animals of the same species being together at the same time and in the same place and we really need to understand this difference if we're going to unravel the biology and ecology and behavior of these extinct animals sociality real direct interactions hierarchies in all of that is very different to gregariousness simply a tendency to form groups and we need to be careful that we don't conflate the two over here we have meerkats they live in social groups females will look after the juveniles of both themselves and other females their social hierarchies there's division of labor there's everything going on grizzly bears are not social typically if you put two Grizzlies together they're going to fight but under some circumstances we can have groups of Grizzlies in the same time and same place with no antagonism between them but there is no way that this makes them either gregarious or social and yet if a flash-flood came down and buried the lot I can guarantee there's at least a few paleontologists who'd go all but is were social no they weren't you happen to have found a group of bears and the two are not the same thing if we look at social groups in modern animals terrestrial mammals despite the fact that they are evolutionarily quite different to dinosaurs in some ways make quite a good model they actually differ quite a lot between age groups as well and again this fits what we've just seen with the difference between juvenile and adult dinosaurs and also groups can be all male or female equal numbers of males and females or a harem you know primarily females with perhaps one or even two males there and it can be very dangerous therefore to make statements about even simple aggregations in the fossil record again that aggregation we had of that giant hadrosaur there's perhaps 7080 individuals there but if we real expect to find 50% male and 50% female I think some people would probably think that quite a natural expectation if you've got a big enough sample and males and females are generally at a 50/50 split then you've probably got at least 30 and maybe 40 males there well these are Red Deer and here we have a group of all males a group of all females a group of males and females and a harem of females with one male these are all from the UK as well and that's one species or even arguably one single population we can produce all of these different effects so again just because we've sampled a hundred animals from one time doesn't necessarily mean we've got equal split there and that has important implications for how we understand these species lots of dinosaurs have big crests it's very interesting to try and work out quite what they may or may not be doing and whether or not they're sexually dimorphic in other words did males look different to females well of course if they all have a crest the obvious implication is well males and females both had a crest isn't that interesting how would you know they're not all males how do you know they're not all females there are actually some ways of telling male from female in the fossil record including for dinosaurs but again until we do those kinds of tests we can't make a statement about it finally I just want to come back to sociality and say that actually what I've mostly said this afternoon is we can't say that a lot of things were social and we need to be very careful about the terms in which we use but that's not to say that dinosaurs were not we do have good evidence for aggregations forming we have good Agri evidence for lots of aggregations of lots of different species and I am personally sure uncertain that lots of dinosaurs aggregated Lots from gregarious and lots were social the difficulty is pinning them down and saying this is a social species this wasn't from the available data if we just look at big cats for example both lions and cheetahs switch enormous Lea between being social and a social at various times of their lives depending whether or not they're males or females and yet the nearest relative to lions are Tigers who are just fundamentally solitary occasioning they'll get into groups of two or three particularly during the breeding season but they're basically solitary animals leopards are almost entirely solitary another very close relative so you do have very big mixes and plasticity both within species and between closely related species so again big statements like all ceratopsian dinosaurs were social because we keep finding groups I think is a very dangerous statement so we need to strike that balance between evidence for sociality and dinosaurs generally and this is a social species and at the moment I think we're going to struggle to do that in conclusion then the specimen presented here that new group of intermediate sized juveniles I think collectively with the available data provides some good evidence for aggregations of Protoceratops from the young age through to adult and this is actually the first time we've been able to do this for a single dinosaur species show evidence of aggregations forming throughout life juvenile dinosaurs likely aggregated at least in part as a response to predation and we also need to be very careful about how we distinguish between aggregations gregariousness sociality in all of these terms from the fossil record despite the fact that if we're careful with that data we can probably start to build up some big important coherent pictures about how these animals lived and evolved as a result and very finally I must thank a number of my collaborators on this and a number of other projects which all comes together colleagues in Japan China the US and Germany and funding support in particular the Chinese Academy of Sciences there's lots more information on this and some of my other research at my website so I'll leave you there thank you very much for your attention thank you you you

Channel: The Royal Institution

Views: 243,810

Rating: 4.9046264 out of 5

Keywords: Dinosaurs, behaviour, ecology, fossils, Dinosaur (Character Species), Social Behavior (Literature Subject), palaeontology, david hone, jurassic, T-rex, did dinosaurs live in groups

Id: 7kxRaVTVNjk

Length: 33min 11sec (1991 seconds)

Published: Wed Apr 15 2015