Dinosaurs dominated the land for around 180 million years. Yet we have little idea what life was like for these prehistoric icons as interpreting fossils that are at least 65 million years old is fiendishly difficult. Finding out more had long seemed impossible. No longer.
In the past few decades, new technologies and new specimens have provided previously unimaginable windows into their behaviour and ecology. This, along with insights from living animals, is finally allowing palaeontologists to build a picture of dinosaur life ranging from parental care, migration and hunting styles to communication, sociality and combat.
Advertisement
David Hone is one of those working to glean more about life in the age of dinosaurs. A palaeontologist at Queen Mary University of London, he has collated the latest findings into a forthcoming book, : What they did and how we know. He gave 快猫短视频 a taste of what has been discovered, from migrating herbivores and semi-aquatic predators to why ostriches are a problem for understanding which dinosaurs doted on their young.
Colin Barras: Some of the largest dinosaurs 鈥� sauropods such as Diplodocus or Brachiosaurus, for example 鈥� were nothing like any living animal. How do you even begin to work out how they behaved?
: One of the most important things we can do as palaeontologists is use our understanding of modern animal ecology and behaviour in a much better way. Mouth shape is a good example. If you鈥檝e got a small mouth, you are usually targeting individual buds or leaves 鈥� high-nutrition foods. If you have a very broad mouth, you are usually bulk feeding. That鈥檚 a simple observation we can apply to sauropods. But I think we have the real potential to go much beyond that.
Could you provide an example?
Well, we have moved away from simply saying 鈥渢his sauropod was very big, so it probably moved slowly鈥�. We are now beginning to realise that some of these slow animals were actually relatively energy efficient, meaning they could travel long distances 鈥� even if it took them a long time. That opens up new questions. Why might a sauropod travel a long way? An obvious reason might be that it鈥檚 in search of food. Can we test that? Well, yes: we can study the chemical isotopes in sauropod teeth and see a recurring signature reflecting their diet that tells us an animal was shifting between two spots every six months. That鈥檚 an annual migration. Then we can begin asking how that ties in with our reconstructions of the local ecology at the time to understand the drivers of migration. Or we can begin asking how this migration might have affected the behaviour of the predators in the region. We鈥檝e gone from 鈥渂ig sauropods moved slowly鈥� to something far more sophisticated.
Can we infer from this that all or most of these gigantic sauropods were migrating animals?
You have to be careful: we know from today鈥檚 animals that behaviour is astonishingly flexible. Wildebeest are a great example. To many of us, almost the defining feature of these animals is the mass migration they make across the Serengeti and Masai Mara. But go to South Africa and the wildebeest there don鈥檛 really migrate. It鈥檚 the same species behaving in a completely different way. That tells you the mass migration behaviour seen in the Serengeti isn鈥檛 tied to the biology of these animals, it鈥檚 entirely environmentally driven. The same must have been true for at least some dinosaurs.
That鈥檚 important to know because there are implications for other aspects of behaviour 鈥� behaviours like parental care. If you鈥檙e constantly moving, it鈥檚 more of a challenge for offspring to keep up. But if you are relatively stationary, it鈥檚 possible to protect young offspring. Today, lots of people are very happy with the idea that many of these dinosaurs showed extended parental care. We actually have very good data for that.
You mean , where fossilised nests appear to show hatchlings were fed on vegetation brought back by their parents?
Yes, that nest study was really fundamental research 鈥� although, of course, it only tells us about the behaviour of one dinosaur species at just a handful of sites that have fossilised. It鈥檚 not a model for all members of that group, let alone all dinosaurs.
Another surprising idea is that . What do you make of research suggesting that the giant theropod Spinosaurus was a crocodile-like predator?
Those ideas don鈥檛 always stand up to scrutiny once you look at all the available information and think through all the implications. For example, it was argued that Spinosaurus could sit in the water like a crocodile with just the eyes and nostrils above the water, but the , not the top, and the eyes aren鈥檛 any more raised up in these dinosaurs than others. In fact, they鈥檙e rather lower than in many, so it really doesn鈥檛 match the available data.
These days we know that birds are living dinosaurs. Does that mean we can enhance our understanding of prehistoric dinosaur behaviour by studying birds?
People are doing this now, but it鈥檚 really important to be sure you understand modern bird species before you begin making inferences. For example, in birds, there is a complex interchange between the number of eggs laid, how big the eggs are and how much care the parents give the hatchlings. But then you have ostriches. Now, ostriches are very, very annoying in this context, because a successful male will court a number of females and they will each come and lay a few eggs in his nest. Was that true of some dinosaurs? If so, then if you find a dead dinosaur on a nest of 50 eggs, you don鈥檛 know whether that reflects the output of one female or 10. So, ostriches tell us it鈥檚 not enough to simply say: I have this many eggs in the nest that were laid by one animal, which cared for the offspring.
How are new tools and technologies transforming our understanding of dinosaur behaviour?
With new techniques we can get at information we didn鈥檛 even realise was preserved in dinosaur fossils. But it doesn鈥檛 necessarily lead to easy conclusions. A great example is using CT scans to look at dinosaur embryos. We can see growth rings on the teeth of these tiny animals that were deposited daily. That鈥檚 astonishing to begin with, but you can then use those growth rings to work out how long the embryos remained in the egg. When people did this for two plant-eating dinosaurs, , it turned out they had an extraordinarily long incubation time. We鈥檙e talking up to six months, when you might have expected this to be more like weeks or a couple of months.
That blows some of our assumptions out of the water. What were the parents doing? All of the options look weird. Alligators will guard a nest for a couple of months, but I honestly can鈥檛 easily imagine a dinosaur hanging around for six months to guard its nest, which would be difficult without food being available. But completely abandoning the nest is not necessarily something I would expect them to do either. Then there鈥檚 the possibility that they abandon the nest for a time and then come back to it to look after the babies when the eggs hatch 鈥� but that鈥檚 almost unprecedented among today鈥檚 animals.
So, basically, none of the options are clear. But, of course, you鈥檇 rather know about that problem. The alternative is being mistakenly confident in assumptions that are actually wrong.
Are there other instances where we have to be careful not to make assumptions when using new technology on specimens?
Colour is a perfect example. With new imaging techniques we can spot pigment-containing melanosomes that are in fossil feathers and work out their colour.
This technique has been applied to feathered dinosaurs like the small Chinese predator Anchiornis. It told us that one individual had . But this is just one animal when it died.
Modern birds tell us that there might have been more going on. Look at the grouse: babies look different to adults, males in the breeding season look different to females, and in winter both males and females living at higher altitudes or latitudes turn white for camouflage in the snow. So, yes, it鈥檚 wonderful we鈥檝e worked out what one Anchiornis looked like at the time it died. Now we have to do it again with 50 or 100 Anchiornis.
I guess that study isn鈥檛 possible because we just don鈥檛 have that many fossils?
But we do. I鈥檝e been to a collection in eastern China that had the thick end of 1000 specimens of Anchiornis, and about one-third of them had feathers. Most of those are probably going to have melanosomes. Analyse 300 of them and you will learn so much more about the ecology and behaviour of this dinosaur 鈥� especially if you combine that with information from other techniques, such as analysing stable isotopes to find out which specimens died in winter and which died in summer, and examining bone microstructure to see if you can work out which were male and which were female. For example, if males show bright colours and females don鈥檛, this would likely tell you something about their courtship and also rearing behaviours: unornamented male birds usually help raise chicks. And if they are both showing camouflage patterns year-round then they might well have been very vulnerable to predators.
People love to hear about new or unexpected discoveries about dinosaur behaviour, but is it a problem that today鈥檚 super-realistic dinosaur nature documentaries often feature the more speculative ideas?
Well, if those documentaries just showed the things we definitively knew that dinosaurs did, then they would be very short. From my perspective, as long as some good information is communicated and people start to understand things, then I鈥檓 comfortable. I think there is a general accumulation of good information. For instance, it鈥檚 now normal not just to show feathered dinosaurs, but to show feathered dinosaurs with the right kind of feathers in the right places and being used in ways that we think they were used. That鈥檚 something that has happened in big-ticket documentaries only within the past 10 years, and the idea of dinosaurs with feathers is probably now beginning to stick in the public鈥檚 mind. So, I do think the documentaries are moving in the right direction.
