Baby Deinonychus Could Fly

[Balaur]

http://blogs.scientificamerican.com/tetrapod-zoology/climbing-flying-babies-of-deinonychus/

Another cool article.

[Rathalosaurus]

WHAAAAAAAAAAAAAAAAAAT?

[triceratops83]

For some reason this reminds me of baby Komodo Dragons climbing up trees and living a different niche from the adults.

[suspsy]

It makes a lot of sense to me. Very cool.

[Shadowknight1]

Welp.  I'm glad we don't live in a time where we have to worry about little dromaeosaurs dropping on our heads out of the trees.

[Pachyrhinosaurus]

What implications does this have on the lifestyle of deinonychus? It looks to me as though the adults wouldn't have taken care of their offspring, since they were likely in the trees, while the adults would have stayed on the ground.

[Balaur]

I'm thinking that Deinonychus likely had a breeding style similar to megapodes. They make a huge mound, lay a bunch of eggs in it, cover it, and then walk away. When the young hatch, they go right into the trees, as I would imagine that adult Deinonychus would be cannibalistic. The young may have fed on small vertebrates, some insects, maybe even some plant matter. I believe they would rarely fly, maybe flapping over to another branch, and sometimes flying to another tree. They probably weren't good fliers. Then, as they grew, they became terrestrial animals, and lost their ability to fly. At least that's my theory.

[Halichoeres]

I'm not sure how much we can infer about parental care from the abilities of youngsters. After all, young gorillas are excellent climbers but as they get older they grow too large to clamber much. Nevertheless, they get extensive parental care. Granted, Deinonychus is much more closely related to a megapode than to a gorilla, but the last common ancestor of megapode+Deinonychus is still probably 150 million years ago. Not sure the niche differentiation can be reliably optimized in a phylogenetic context given that distance.

[stargatedalek]

I'm wondering how this relates to their living amongst tenontosaurus. That given the evidence for cannibalism amongst deinonychus leads me to assume that the young probably didn't live with the adults.

[Halichoeres]

I'm wondering how this relates to their living amongst tenontosaurus. That given the evidence for cannibalism amongst deinonychus leads me to assume that the young probably didn't live with the adults.

I didn't know there was evidence for cannibalism, although Balaur made an offhand allusion a few posts up. That's pretty interesting and would definitely alter the probability; however, cannibalism and parental care aren't necessarily mutually exclusive! Hamsters, pigs, rabbits, lions, and a variety of birds all eat their own or each others' babies from time to time.

[Gwangi]

Fresh from the eggs I doubt Deinonychus chicks had full fledged feathers, more likely a down covering like modern game birds. Perhaps during this part of their life the parents took care of them and once the down was replaced with proper feathers they went off on their own into the trees?

[Tyto_Theropod]

Fresh from the eggs I doubt Deinonychus chicks had full fledged feathers, more likely a down covering like modern game birds. Perhaps during this part of their life the parents took care of them and once the down was replaced with proper feathers they went off on their own into the trees?

That does indeed make sense Gwangi. I must admit that the idea of 'flying' Deinonychus was a bit of a culture shock to me, which it shouldn't have been considering relatives like Microraptor. It makes their social life, or lack thereof, even more of an enigma, given that we have the famous mass burial of Deinonychus (which could either be a group or a mobbing event), the trackways of more than one very similar animal walking together (points towards at least some tolerance and social behaviour), and now this (which when you compare it to animals like komodo dragons would indicate solitary behaviour). Given that I'm currently reading up (and speculating about) Velociraptor for a project I have in the works, this is definitely something that's going to keep me thinking! It's worth noting, though, that even closely related species can behave in completely different ways.

[Takama]

Well there goes my idea of a baby deinonychus riding it's parent.      I guess I just make it acurate and sweet.

[stargatedalek]

I didn't know there was evidence for cannibalism, although Balaur made an offhand allusion a few posts up. That's pretty interesting and would definitely alter the probability; however, cannibalism and parental care aren't necessarily mutually exclusive! Hamsters, pigs, rabbits, lions, and a variety of birds all eat their own or each others' babies from time to time.

https://en.wikipedia.org/wiki/Deinonychus
I couldn't find any particular citation of cannibalism, but I could have sworn there had been intraspecies bite marks on some of those bones from the Yale quarry. If five animals are dying in some form of organized attack, than something was definitely not right with those animals. One could say perhaps it was a freak event that a pack got that desperate, but if that was the case why are they nearly always found alongside tenontosaurus? I think its pretty easy to say they were not hunting in organized packs, the most likely scenario seems to be a feeding frenzy. One of their larger companions dies or falls ill and they converge, wounding or attacking each other in the chaos. Regardless of how they hunted it seems clear that they lived alongside tenontosaurus, so I feel that the young wouldn't have been able to stay with their parents for more than a few days at most before the parents would need to move on. This is all conjecture of course

[DinoLord]

Interesting that Mr. Naish has only just written this blog post, as I recall reading the published paper a couple of months ago. It was written on a specimen found in Montana. Most of the paper was spent justifying that the specimen was indeed a juvenile Deinonychus instead of another type of maniraptoran. The latter portions of the discussion were spent on establishing the biomechanical feasibility of flight capability in a juvenile Deinonychus of that size, providing mass estimates and considering the range of motion in the forearm and shoulder joints to determine if a flapping motion could be executed and eventually concluding that brief bursts of powered flight were technically possible.

[Balaur]

Fresh from the eggs I doubt Deinonychus chicks had full fledged feathers, more likely a down covering like modern game birds. Perhaps during this part of their life the parents took care of them and once the down was replaced with proper feathers they went off on their own into the trees?

I don't know. Megapodes can run and fly the same day they are hatched.

[HD-man]

http://blogs.scientificamerican.com/tetrapod-zoology/climbing-flying-babies-of-deinonychus/

Another cool article.

No offense, but it's mind-boggling how many ppl here have just assumed that Parsons/Parsons' hypothesis is correct & gone w/it. I know there have been annoyingly-popular dino hypotheses b-4 ( http://dinotoyblog.com/forum/index.php?topic=1712.0 ), but still. Besides the lack of actual evidence, it's been panned several times throughout the comment section of the article linked above (E.g. "Look I like Bill, and I am glad this paper is getting some play, but I think that any talk of ontogenetic shifts is premature at best, fan fiction at worst"; "Yeah, I mostly wrote this because I want this to get some critique, the mention of ontogenetic shift is ashamedly speculative"). I'm also surprised no one has mentioned Willoughby's "The Noble Savage" (which is based on said hypothesis: http://ewilloughby.deviantart.com/art/The-Noble-Savage-480298007 ). I talked to her about said hypothesis on the 1st page. The following quotes are the main parts of that conversation & sum up pretty much everything that needs to be said in this thread.

You probably already know this, but just to be safe, I'm sorry if it sounded like I was baiting you or anyone else. I only just realized that my previous comment could potentially come off that way. I probably wouldn't have cared so much about Parsons/Parsons' hypothesis, given the lack of attention from other experts (which is probably b/c of the lack of actual evidence), had it not been for a certain bad source
(you probably know which 1: jd-man.deviantart.com/journal/... ) trying to use it to prove that theropods in general & dromaeosaurids in particular were basically megapodes. Anyway, I have 2 major problems with said hypothesis (besides the lack of actual evidence): 1) It seemingly ignores the other, more likely possibilities (E.g. See the Sampson quote; In the case of both Deinonychus & Allosaurus, the final possibility is most likely); 2) It seemingly ignores the fact that most young theropods (including dromaeosaurids) have miniature replicas of the adult teeth & thus probably ate the same things as the adults. In other words, most young theropods were probably shown/brought food by the adults (How else could they have eaten prey so much larger than themselves?). Based on what I've read (E.g. See the Bakker quote), that's how it works w/living predators.

Quoting Sampson ( www.amazon.com/Dinosaur-Odysse... ): "Studies by Mark Loewen...and others indicate that juvenile allosaurs likely possessed greater speed and agility than adults. Perhaps young allosaurs consumed a diet based on smaller, nimble prey such as lizards, amphibians, and mammals. Conversely, greater foot speed may have been necessary for juveniles to keep pace with adults. Still another (to my mind, unlikely) alternative is that allosaurs engaged in cooperative hunting, with the faster juveniles responsible for herding prey animals toward lurking adults. Finally, it's possible that the greater speed and agility of juveniles was not an adaptation at all but merely an evolutionary holdover. In other words, theropods ancestral to Allosaurus may have been smaller and more agile even as adults, and the loss of these qualities in adult allosaurs simply reflects an evolutionary shift toward bigger bodies."

Quoting Bakker ( www.amazon.com/Dinofest-Intern... ): "A striking difference exists in modern communities between cold-blooded predators and hot-blooded predators. Most bird and mammal species feed their young until the youngsters are almost full size; then and only then do the young set out to hunt on their own. Consequently, the very young mammals and birds do not chose food items independently of the parents. Young lions and eagles feed on parts of carcasses from relatively large prey killed by the parents. Most snakes, lizards, and turtles do not feed the young after birth, and the new-born reptiles must find prey suitably diminutive to fit the size of the baby reptilian jaws and teeth. A single individual lizard during its lifetime usually feeds over a much wider size range of prey than a single individual weasel or hawk, because the lizard begins its life hunting independently.
Therefore, a predatory guild of three lizard species with adult weights 10g, 100g and 1000g would require a much wider range of prey size than a guild of three mammal predator species with the same adult weights. If allosaurs had a lizard-like parental behavior, then each individual allosaur would require a wide size range in prey as it grew up. The evidence of the Como lair sites strongly suggests that the dinosaur predatory guild was constructed more like that of hot-blooded carnivores than that of lizards or snakes.
This theory receives support from the shape of the baby allosaur teeth. In many cold-blooded reptilian predators today, the crown shape in the very young is quite different from the adult crown shape. For example, hatchling alligators have the same number of tooth sockets in each jaw as do the adults, but the hatchling crowns are very much sharper and more delicate. In the hatchling all the teeth are nearly the same shape, and the young gators have less differentiation of crown size and shape along the tooth row; the hatchlings lack the massive, projecting canine teeth and the very broad, acorn-shaped posterior crowns of the adults. Young gators feed extensively on water insects, and the sharp crowns are designed for such insectivorous habits. Adult gator species use their canine teeth for killing large prey, such as deer, and employ the acorn crowns to crush large water snails and turtles (Chabreck, 1971; Delaney and Abercrombie, 1986; McNease and Joanen, 1977; Web et al, 1987).
If allosaur hatchlings fed independent of adults, I would not expect the hatchling tooth crowns to be the same over-all shape as that of the adult. However, the over-all tooth crown shape in the tiniest allosaur IS identical to that of the adult (figs. 3,4). Thus it appears that hatchlings were feeding on prey tissue of the same general texture and consistency as that fed upon by adults."

Thanks for your well-reasoned and thoughtful comments.

I don't think that these Sampson and Bakker quotes are mutually exclusive to an arboreal hypothesis for immature Deinonychus. Remember, this isn't a discussion about how very young, hatchling, or fledgling Deinonychus behaved—surely very young animals were more likely to have been fed by their parents than anything else (I agree the megapode idea is pretty unlikely). Rather, this is an idea about how these animals behaved when they've reached adult size—and for the most part, adult morphology—and are no longer being cared for by the parents, but still haven't reached sexual maturity.

Birds of prey are the best analogue here. Bald eagle nestlings, for example, will stay in the nest for 10-12 weeks while their parents bring them food. During this time, the young eagles are growing rapidly to adult size. After fledging, they'll hang around the nest site for another month or two, relying on their parents for lessons in prey capture and flight skill. After this period of around half a year, they usually disperse to find new territories and start hunting entirely on their own (often quite unsuccessfully for some time). However, it takes a bald eagle several years to reach full sexual maturity, which is judged primarily by its plumage. An immature eagle that has left the nest is streaky brown, and doesn't get the solid white head and tail until at least 5 years. This is the analogous period of time where I'm suggesting the idea of arboreal behavior in dromaeosaurs. The young Deinonychus has grown to adult size, it has left the nest and does not rely on parental care any longer, but is still in a prolonged period of sexual immaturity where it may be more vulnerable to both attack by larger predators (due to lack of experience) and aggressive territorial competition from its own kind (Andrea Cau suggested at Facebook that this would be consistent with evidence of cannibalistic predation on young Deinonychus by adults).

If during this time the immature Deinonychus are subsisting on different kinds of prey, it wouldn't be nearly as different as insects are from large vertebrate flesh. In eagles, for instance, the immature bird's rhamphotheca and talons do not differ in shape from the adults, but the young will often spend several years subsisting mostly on "easier" prey (especially that which is stolen by other predators, as well as carrion) before tackling larger, more dangerous stuff. Of course, a different menu is only one of many reasons why an immature Deinonychus might take refuge in the trees.

Thanks as well for the information about young gators and their different feeding styles—I was not aware of that, though in this context I think birds are a better analogue for the hypothesis in question.

Though I've pointed this out several times in different contexts, it's worth reiterating that I don't mean my interpretation of this idea to be any more than speculation. I agree that actual evidence for this idea is lacking (though as I point out here, the idea is at least partially testable with the right kinds of evidence). The unique immature features (longer arms, more recurved claws) certainly could be nothing more than an evolutionary holdover, and would be consistent with the idea of Deinonychus descending from a more arboreal ancestor.

[alexeratops]

Welp.  I'm glad we don't live in a time where we have to worry about little dromaeosaurs dropping on our heads out of the trees.

New accurate dinosaur movie idea! "Accurate Mesozoic Park!"

[Dinoguy2]

HD-Man wrote: "given the lack of attention from other experts"

I agree that nobody should just accept a newly published hypothesis as The Truth until we are able to build up more evidence for it. But it is silly to expect attention from other experts to be published in less than a month after the initial paper! Even if 100 experts have somehow had time to write and edit a response and submit it to a journal, it would be at least half a year, bare minimum, before any of them start seeing print. Unless you mean attention in the form of online comments, which many experts would not consider an appropriate venue for a detailed support or takedown commentary.

[HD-man]

HD-Man wrote: "given the lack of attention from other experts"

I agree that nobody should just accept a newly published hypothesis as The Truth until we are able to build up more evidence for it. But it is silly to expect attention from other experts to be published in less than a month after the initial paper! Even if 100 experts have somehow had time to write and edit a response and submit it to a journal, it would be at least half a year, bare minimum, before any of them start seeing print. Unless you mean attention in the form of online comments, which many experts would not consider an appropriate venue for a detailed support or takedown commentary.

Sorry for the confusion. I'll re-explain myself: 1st, Parsons/Parsons published their hypothesis in 2009 ("Morphology and size of an adult specimen of Deinonychus antirrhopus, (Saurischia, Theropoda)"); Then, Willoughby made "The Noble Savage" based on said hypothesis & I talked to her about it in 2014. In other words, same hypothesis, different paper.