Deinonychus may not have hunted in packs

[suspsy]

https://www.sciencedirect.com/science/article/abs/pii/S003101822030225X

Different diets between young and old individuals appear to suggest that they were lone hunters.

[stargatedalek]

Adult diet varying from young hardly proves they were asocial animals, rather it shows only exactly what it says on the tin, that the young and adults eat different kinds of food.

They use Komodo dragons and a crocodylian as references, citing similar dietary transitions as evidence inherent that Deinonychus similarly were not social animals. As a counter example; you'd get similar results for most small bird species. With the young eating entirely insects and the adults being omnivores with preference for vegetation and seeds.

Tenontosaurus was a large animal, and if Deinonychus really was hunting them or similar animals with some frequency it makes sense they might keep the young animals separate from this. Perhaps even parents with chicks would temporarily switch to eating smaller prey to avoid injury while caring for them.

And if they were social animals that lived in colonies and/or hunted in groups but not explicitly amicable cooperative hunters like Harris hawks or corvids are, they may have temporarily left the colony to have their young in a safer environment. We see this in a lot of highly competitive bird species that otherwise live in social groups, even in many herbivores.

[Gwangi]

I've always been in the camp that Deinonychus and dromaeosaurs did not live in social groups like those promoted through pop culture. Analogous more to crocodilians, Komodo dragons to an extent, and for the sake of bringing birds into this... vultures or gamebirds. All of them are still social of course. Crocodilians and gamebirds provide care for their young but the young also largely feed themselves, and I would not be surprised if Deinonychus was similar in this way. This study seems to support that notion. Fossil sites where Deinonychus and Tenontosaurus are associated is not guaranteed proof of pack hunting. Crocodilians, Komodo dragons, vultures, eagles, they will all congregate together to "share" a meal that one animal may have killed, or died from other means.

Yes, I realize the potential can of worms I'm opening up. It's only a matter of time until HD-man catches wind of this thread and takes me to task. 

[stargatedalek]

I certainly don't think Deinonychus were likely to have been coordinated pack hunters like Harris hawks or crows, but I find it difficult to discount the multiple examples of adult Deinonychus dying together in groups, especially around prey. I think there was something at least more deliberate going on than Komodo dragons all detecting the same prey and closing in together one by one, or crocodilians living together but hunting alone.

I would suggest something of a middle ground, both living and moving together in groups, but competing as individuals. With pairs temporarily leaving the large groups during nesting and the young joining a group once sufficiently sized. Kind of like giant starlings.

[Gwangi]

I certainly don't think Deinonychus were likely to have been coordinated pack hunters like Harris hawks or crows, but I find it difficult to discount the multiple examples of adult Deinonychus dying together in groups, especially around prey. I think there was something at least more deliberate going on than Komodo dragons all detecting the same prey and closing in together one by one, or crocodilians living together but hunting alone.

I would suggest something of a middle ground, both living and moving together in groups, but competing as individuals. With pairs temporarily leaving the large groups during nesting and the young joining a group once sufficiently sized. Kind of like giant starlings.

Modern game birds come to mind again with this analogy. Or gulls and vultures. Living socially while also competing with one another. I imagine dromaeosaurs as essentially being ground dwelling birds of prey. Living in pairs or alone, mostly hunting small or similarly sized game, coming together when there's a plentiful food source, like bald eagles do. That's just what makes most sense when I evaluate the evidence.

[Libraraptor]

In this discussion I see myself in the middle ground as well. No matter what is yet to be found out about Deinonychus via the fossil record, I am sure it will strengthen my fascination for one of my favourite dinosaur species.

[Concavenator]

I saw a video not long ago that explained why dromaeosaurids like Deinonychus were not suited for attacking bigger animals than them. The video explained what the actual function of their sickle claw is, that is, subduing smaller animals (like small mammals, lizards...). And because of that, it's been suggested they didn't live in packs (and also didn't prey on bigger animals like Tenontosaurus).

https://youtu.be/vNinGTKzsL0

Here's the video. It's in Spanish, but the video also includes some bibliography on the description.

but I find it difficult to discount the multiple examples of adult Deinonychus dying together in groups, especially around prey.

Perhaps they saw a Tenontosaurus corpse and they were heading that direction and didn't notice quicksand around there and got trapped, something similar to what happened in La Brea Tar Pits.

[suspsy]

Here's the PDF if anyone wants to read it:

https://drive.google.com/file/d/18-dpj__D1KlMLW71XIvAjgXmDRNYDTsm/view

[HD-man]

https://www.sciencedirect.com/science/article/abs/pii/S003101822030225X

Different diets between young and old individuals appear to suggest that they were lone hunters.

I wouldn't take it too seriously. As Albertonykus & others pointed out at SVP 2018, it's very flawed. IIRC, 1 of the main problems is that it ignores the fact that raptorial birds feed their young smaller prey than what they'd normally catch for themselves:

https://nmbu.brage.unit.no/nmbu-xmlui/bitstream/handle/11250/187123/skouen2012.pdf

https://www.tandfonline.com/doi/pdf/10.1080/00063657.2014.940838

Since eudromaeosaurs were basically "terrestrial hawks" in terms of ecology/behavior ( https://qilong.wordpress.com/2011/12/19/dromaeosaurs-are-terrestrial-hawks/ ), it makes sense that the same would've gone for them. This reminds me of how much I miss "ASK A VELOCIRAPTOR" (which summed up what we knew or could infer about real Velociraptor in a silly/fun way): https://askvelociraptor.tumblr.com/post/23590224406/while-currently-lacking-any-females-andor

[Duna]

I saw a video not long ago that explained why dromaeosaurids like Deinonychus were not suited for attacking bigger animals than them. The video explained what the actual function of their sickle claw is, that is, subduing smaller animals (like small mammals, lizards...). And because of that, it's been suggested they didn't live in packs (and also didn't prey on bigger animals like Tenontosaurus).

https://youtu.be/vNinGTKzsL0

Here's the video. It's in Spanish, but the video also includes some bibliography on the description.

but I find it difficult to discount the multiple examples of adult Deinonychus dying together in groups, especially around prey.

Perhaps they saw a Tenontosaurus corpse and they were heading that direction and didn't notice quicksand around there and got trapped, something similar to what happened in La Brea Tar Pits.

Thank you for the video. It's really interesting. I was wrong about the size of the preys.

[stargatedalek]

With most dromaeosaurs I would agree that single or pair hunting of small animals is the most likely behaviour, but Deinonychus appears to be an exception.

We have multiple fossil sites of dead Tenontosaurus with multiple dead Deinonychus that don't appear to have been killed by other Deinonychus. I vaguely recall some showed evidence of having been crushed, but perhaps I'm remembering a less trustworthy documentary there (I think we all can guess which one).

If these were unusual events, such as a group of Deinonychus being killed by external forces as they attempted to scavenge, a Tenontosaurus wandering into a nesting area and being attacked by many Deinonychus, or a group of Deinonychus attacking prey they couldn't handle only for another group to appear and finish the prey off in the same location, I wouldn't expect to see multiple fossil sites with the exact same herbivore and in different locations. It just isn't statistically parsimonious for this rare scenario to be preserved multiple times and to be the only preserved hunting sites of Deinonychus.

The key part is that there were multiple dead Deinonychus and still enough left to finish off and eat the Tenontosaurus without instead fleeing. This behaviour is strange for cooperative pack hunters, but even stranger still for animals that usually would only hunt small prey alone or in pairs that just happened to converge on an apparent easy target.

[Gwangi]

I will first admit that I have not researched any of this in awhile so I've gone off to Wikipedia to brush up, judge me if you want. Anyway, I'm only seeing two cited examples of Deinonychus remains (aside from teeth) being found associated with Tenontosaurus. The Yale quarry contains four adults and a juvenile. The other is in the Antlers formation and contains the remains of 6 Tenontosaurus, Deinonychus teeth, and one partial Deinonychus skeleton. These don't suggest pack hunting to me. It looks more like an abundant predatory species taking advantage of a situation where they can easily feed upon an abundant herbivore when the chance arises. Tenontosaurus dies, Deinonychus shows up. Like bears converging on a dead whale. This especially seems evident in the case of the Antlers formation site where there are 6 individual Tenontosaurus that I highly doubt were all killed by Deinonychus. The Yale quarry has a suspicious number of dead Deinonychus. It could represent a hunt gone terribly wrong but perhaps, instead, the Tenontosaurus was in distress and the Deinonychus that were killed made a fatal miscalculation in taking on what appeared to be an easy meal? This brings to mind Komodo dragons converging on dying water buffalo. Or maybe they were killed by other Deinonychus, we don't have soft tissue to indicate one way or the other. The Wikipedia article claims that parts are missing from the dead Deinonychus that could indicate cannibalism.

Everything about these animals seem to point away from pack hunting large prey. The way we now know their claws were used, their bird-like body plan, etc. Gregarious ground hawks seems more likely than pack hunting wolf-birds to me. But that's just how I'm interpreting the evidence. Ultimately it makes no difference to me, wolf-birds certainly sounds cooler I guess.

[stargatedalek]

I didn't mean to suggest cooperative hunting like wolves. Rather that whatever they were doing it was distinct from other dromaeosaurids.

I wouldn't buy for a moment that Velociraptor would converge in groups on large prey, even if it was injured. Their anatomy is just so unsuited for that. That Deinonychus even did that much suggests their behaviour was distinct and we can't rely on assumptions about other better known species.

[Gwangi]

I didn't mean to suggest cooperative hunting like wolves. Rather that whatever they were doing it was distinct from other dromaeosaurids.

I wouldn't buy for a moment that Velociraptor would converge in groups on large prey, even if it was injured. Their anatomy is just so unsuited for that. That Deinonychus even did that much suggests their behaviour was distinct and we can't rely on assumptions about other better known species.

I get what you're saying. There are always species that break the mold for their family as a whole. Big cats are a good example what with lions being unusually social. Or Harris hawks and their unique hunting strategy. Speaking of Velociraptor and large prey, what do you make of the "fighting dinosaurs"? I recently watch the YDAW about Velociraptor and found it to be highly informative.

[stargatedalek]

I didn't mean to suggest cooperative hunting like wolves. Rather that whatever they were doing it was distinct from other dromaeosaurids.

I wouldn't buy for a moment that Velociraptor would converge in groups on large prey, even if it was injured. Their anatomy is just so unsuited for that. That Deinonychus even did that much suggests their behaviour was distinct and we can't rely on assumptions about other better known species.

I get what you're saying. There are always species that break the mold for their family as a whole. Big cats are a good example what with lions being unusually social. Or Harris hawks and their unique hunting strategy. Speaking of Velociraptor and large prey, what do you make of the "fighting dinosaurs"? I recently watch the YDAW about Velociraptor and found it to be highly informative.

I find the fighting dinosaurs fossil unconvincing evidence for predation. Velociraptor is just so focus built for hunting small animals, with its narrow jaws and long thin toes. I think it's more likely it would have been stealing eggs or young, or Protoceratops may just have been prone to attacking them.

[Gwangi]

I didn't mean to suggest cooperative hunting like wolves. Rather that whatever they were doing it was distinct from other dromaeosaurids.

I wouldn't buy for a moment that Velociraptor would converge in groups on large prey, even if it was injured. Their anatomy is just so unsuited for that. That Deinonychus even did that much suggests their behaviour was distinct and we can't rely on assumptions about other better known species.

I get what you're saying. There are always species that break the mold for their family as a whole. Big cats are a good example what with lions being unusually social. Or Harris hawks and their unique hunting strategy. Speaking of Velociraptor and large prey, what do you make of the "fighting dinosaurs"? I recently watch the YDAW about Velociraptor and found it to be highly informative.

I find the fighting dinosaurs fossil unconvincing evidence for predation. Velociraptor is just so focus built for hunting small animals, with its narrow jaws and long thin toes. I think it's more likely it would have been stealing eggs or young, or Protoceratops may just have been prone to attacking them.

Agreed. I think if it does represent an act of predation than it's out of desperation on the part of the Velociraptor.

[Neosodon]

Maybe most comparable to a coyote. They hunt smaller prey but will sometimes do so in packs.

[HD-man]

I wouldn't take it too seriously. As Albertonykus & others pointed out at SVP 2018, it's very flawed. IIRC, 1 of the main problems is that it ignores the fact that raptorial birds feed their young smaller prey than what they'd normally catch for themselves:

https://nmbu.brage.unit.no/nmbu-xmlui/bitstream/handle/11250/187123/skouen2012.pdf

https://www.tandfonline.com/doi/pdf/10.1080/00063657.2014.940838

Since eudromaeosaurs were basically "terrestrial hawks" in terms of ecology/behavior ( https://qilong.wordpress.com/2011/12/19/dromaeosaurs-are-terrestrial-hawks/ ), it makes sense that the same would've gone for them. This reminds me of how much I miss "ASK A VELOCIRAPTOR" (which summed up what we knew or could infer about real Velociraptor in a silly/fun way): https://askvelociraptor.tumblr.com/post/23590224406/while-currently-lacking-any-females-andor

Having since read Frederickson et al. 2020 in its entirety, I can confirm that it has the same main problem now that the original presentation did at SVP 2018. It's also worth mentioning that it cites Fowler et al. 2011 & Ellis et al. 1993 (which doesn't come up enough in related topics), yet ignores the aspects of those papers that contradict it. More specifically, it ignores the facts that 1) in terms of ecology/behavior, "Dromaeosaurs Are Terrestrial Hawks" ( https://qilong.wordpress.com/2011/12/19/dromaeosaurs-are-terrestrial-hawks/ ), & 2) "highly developed cooperative hunting may be important for many raptorial birds" ( https://www.researchgate.net/publication/247843773_Social_Foraging_Classes_in_Raptorial_Birds ). This is especially apparent when it uses Varricchio et al. 2008 to argue that Deinonychus had Rhea-like paternal care despite that facts that 1) that paper doesn't cover any dromaeosaurids, let alone eudromaeoaurs, & 2) unlike the more crane-like omnivores that paper does cover, eudromaeosaurs were raptorial hypercarnivores (See the 1st Bakker quote AWA the highlighted paragraph in this link: https://books.google.com/books?id=hTTUBAAAQBAJ&pg=PA6&dq=%22stork-like+than+raptorial%22&hl=en&sa=X&ved=0ahUKEwiz4LzOtbDWAhUGOiYKHSyHD5MQ6AEIKDAA#v=onepage&q=%22stork-like%20than%20raptorial%22&f=false ). This is also especially apparent when a paper that focuses on teeth ignores the fact that "juvenile teeth display the same features as those of adults, but on a smaller scale" ( https://www.academia.edu/1974330/SWEETMAN_S._C._2004._The_first_record_of_velociraptorine_dinosaurs_Saurischia_Theropoda_from_the_Wealden_Early_Cretaceous_Barremian_of_southern_England._Cretaceous_Research_25_353-364 ), which means "that hatchlings were feeding on prey tissue of the same general texture and consistency as that fed upon by adults" (See the 2nd Bakker quote).

Quoting Bakker (See Raptor Red):

Female dominance is a powerful piece of evidence that permits us to reconstruct the private lives of Cretaceous predatory dinosaurs. A family structure built around a large female is rare in meat-eating reptiles and mammals today, but it's the rule for one category of predatory species...carnivorous birds. Owls, hawks, and eagles have societies organized around female dominance, and we can think of tyrannosaurs and raptors as giant, ground-running eagles.

Quoting Bakker (See Wolberg's Dinofest International: Proceedings of a Symposium Sponsored By Arizona State University, page 62):

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.

[Kapitaenosavrvs]

Interesting. I thought this is not "new" news. I saw a couple of Videos taking about this. I think the Velociraptor Video vom YDAW was one of them. One of the best "easy to consume" Dinosaur Content on Youtube. At least it feels like that.

[HD-man]

@Kapitaenosavrvs

Interesting. I thought this is not "new" news. I saw a couple of Videos taking about this. I think the Velociraptor Video vom YDAW was one of them. One of the best "easy to consume" Dinosaur Content on Youtube. At least it feels like that.

This video?: https://www.youtube.com/watch?v=y-3bImbSJCM