Deinonychus may not have hunted in packs

[Gothmog the Baryonyx]

Whilst I don't find this evidence remotely conclusive, I have ways preferred the idea that droameosaurs were solitary animals that favoured mostly prey smaller than themselves, with Deinonychus as a possible exception to the last part. Though I still think Tenontosaurus was mostly killed by Acrocanthosaurus and scavenged by Deinonychus.

[HD-man]

@Gwangi

I'm only seeing two cited examples of Deinonychus remains (aside from teeth) being found associated with Tenontosaurus.

I'm glad you mentioned that. It reminds me of the best evidence for pack-hunting in Deinonychus (I.e. Shed teeth in general & MOR 682 in particular; See the Maxwell quote), which Frederickson et al. 2020 ignores despite having cited Maxwell & Ostrom 1995 ( https://sci-hub.tw/https://www.jstor.org/stable/4523664?seq=1 ). As you can see, the evidence suggests that individuals/packs preferred to attack juveniles/subadults, respectively (as opposed to fully-grown adults). Just to clarify, I'm not saying that all dromaeosaurids were definitely pack hunters, just that some eudromaeosaurs were probably pack hunters. I also concede that pair hunting was probably much more common than 3+ member hunting as it is w/pack-hunting raptorial birds. In other words, eudromaeosaur pack-hunting probably looked something like this:

Quoting Maxwell ( http://www.naturalhistorymag.com/htmlsite/master.html?http://www.naturalhistorymag.com/htmlsite/1299/1299_feature.html ):

Nobody knows for certain what took place at the Shrine site. We do know, however, that whether hunted down and killed by a pack or simply scavenged after death, Tenontosaurus was the preferred food of Deinonychus. Approximately eighty occurrences of Tenontosaurus remains have been discovered in the Cloverly formation to date, and thirty-five include Deinonychus teeth. While Deinonychus fossils are rarely found with other possible prey animals, three or four Deinonychus teeth typically turn up wherever there are Tenontosaurus remains. And at a site discovered in the Cloverly formation in 1992, there were even more.

Laid out in its death pose at this new site was a beautifully preserved, near-complete specimen of a young Tenontosaurus. Four Deinonychus teeth were found alongside the bones; later, in the laboratory, seven more teeth were uncovered. It's possible that a few more teeth were missed in the field or unwittingly discarded during preparation because they were concealed within small lumps of rock. So we have a subadult Tenontosaurus no more than fourteen feet long (compared with a length of about twenty feet for the adult at the Shrine site), preserved with at least eleven Deinonychus teeth.

But how can we distinguish between the remains of a victim hunted down and devoured by a pack and an animal that simply died and was scavenged by a few passing Deinonychus? As is the case at the Shrine site, this Tenontosaurus was preserved where it died. After death, the desiccation of the abundant supporting tendons that line the vertebrae of the neck and tail cause these parts to coil. The tail of Tenontosaurus, which accounts for about one-third of the animal's total length, is particularly heavy with supporting tendons. In this specimen, the pronounced curvature of the tail and the neck toward each other effectively counters any claim that the bones were carried to the site by water currents. The Deinonychus teeth were found in the region of the abdomen and pelvis, suggesting that the predators lost their teeth while feeding on the viscera. Most modern carnivores begin with the areas around the anus and abdomen when they feast on freshly killed prey, and it's likely that carnivorous dinosaurs did the same.

The number of teeth indicate that more than one Deinonychus was involved with the carcass. Like all other theropod dinosaurs, Deinonychus shed and replaced teeth throughout its life. The teeth would fall out upon the animal's reaching maturity but also could be wrenched out earlier by the stress associated with the biting and tearing of flesh. Because of this, theropod teeth are very common in sediments containing dinosaur fossils. The teeth from this site vary from recently erupted to fully mature ones. Given that Deinonychus had only sixty teeth in its jaws at any one time, it's unlikely that all eleven were wrenched from the mouth of just one feeding animal. This would leave the Deinonychus toothless after five similar meals. The possibility that Deinonychus was replacing shed teeth in a few weeks or months, and therefore had the ability to sustain such dramatic tooth loss, was quashed by Greg Erickson, who, as a master's degree student at the Museum of the Rockies, worked on replacement rates of teeth in various dinosaurs and living reptiles. After CT-scanning portions of the lower jaw of Deinonychus and studying individual teeth, he came up with an estimate of 300 days for the time it took Deinonychus to replace a shed tooth with a mature one.

We know that this Tenontosaurus was not yet an adult, so it didn't die of old age. Of course, this doesn't rule out death from disease or injury and doesn't confirm that it was cut down by a pack, but it's a start. Next, we have a concentration of teeth around the abdomen and pelvis. This may indicate that the pack fed on the abdominal contents while they were still warm and moist. If, after the viscera had been consumed, the remainder of the carcass was scavenged over time by many individuals, we would expect a much more disturbed carcass and a wider scattering of teeth. Similarly, if the Tenontosaurus had been killed by a larger predator-such as the unknown owner of the three-inch-long serrated teeth that occasionally crop up in the Cloverly formation—then whatever remained of the carcass would have been strewn around the area.

[Kapitaenosavrvs]

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

First off yes, i ment this Video.

But i am not shure if he talked about Packhunting in this Video. I Remember one thing i read a couple of times and that was about the Brain. The Idea, that They've been intelligent, but Coordinated Packhunting required a bit more. Moreover the Size of a Brain does not show how "intelligent" a being is. In the End it can be discussed, which i always find interesting. I am no Scientist in this field or a Scientist in genreal, so it sometimes happens that i and other people make conclusions that we think are plausible. We often forget, that theres more in detail most of the time.

In my personal opinion, it could be Packhunting or Hunting alone or they sometimes grouped up, to hunt young and weak Animal from a Group. Lets see, what the Future brings.
Since the Animals have been quite large during this time, Raptors do not seem to be a dominant group. Compared to our Time and our size, they appear to be quite large and dangerous Animals and maybe we still have the classic raptorbehavior in our subconscious and it takes time to change that completely. Keep on writing, i like to read all the Ideas here. Thank you for this discussion.


EDIT: H @HD-man oops, yes. Thank you. I forgot to check before. I just replied to the Videoquestion in this Post, because it was posted by you. I thought that should be fine. I'll edit that aswell. Since your bigger Post is directly above me, i spared the Big Quote to have it more tidy here.

[HD-man]

@Kapitaenosavrvs

1stly, looks you replied to the wrong post. The 1 w/the video is on page 1 of this thread.

2ndly, looks like you accidentally put your reply inside the quote. You might wanna edit that so others can see what you wrote more easily.

EDIT: Anytime. Glad I could help.

[HD-man]

UPDATE: I've collated all my thoughts on Frederickson et al. 2020 (See "New #1 Contender"): http://dinotoyblog.com/forum/index.php?topic=1712.msg257654#msg257654

[ITdactyl]

Found a video that sums up my thoughts:

https://youtu.be/0hWexI1W6WQ

2 adult and 1 immature bald eagles hunting (what seems to be) a merganser as a group, but not cooperatively.

Maybe we should think/compare less in terms of mammalian packs, and more in terms of crocodilian or corvid mobs.

[HD-man]

2 adult and 1 immature bald eagles hunting (what seems to be) a merganser as a group, but not cooperatively.

Maybe we should think/compare less in terms of mammalian packs, and more in terms of crocodilian or corvid mobs.

In reference to the 1st part, I'm no expert, so I can't comment on whatever's going on in the video.

In reference to the 2nd part, you say that as if bald eagles haven't already been observed pack hunting: https://sora.unm.edu/sites/default/files/FFN_20-4p110-112Folk%5B1%5D.pdf

[ITdactyl]

In reference to the 2nd part, you say that as if bald eagles haven't already been observed pack hunting: https://sora.unm.edu/sites/default/files/FFN_20-4p110-112Folk%5B1%5D.pdf

Err, nope. I just used the video as an example of mobbing, not as a general statement that bald eagles do not hunt cooperatively.

On that note, are we using pack hunting as an umbrella term? As far as I know, mammal packs are family groups. Mobs are just whichever disassociated individuals who are conveniently present when a chase starts.

Or maybe I'm just not too familiar with the terminology. Maybe deinonychus really are the harris hawks of the dromie family.

[HD-man]

On that note, are we using pack hunting as an umbrella term? As far as I know, mammal packs are family groups. Mobs are just whichever disassociated individuals who are conveniently present when a chase starts.

Or maybe I'm just not too familiar with the terminology. Maybe deinonychus really are the harris hawks of the dromie family.

In reference to terminology, pages 271-272 of Orellana & Rojas 2005 ( https://www.academia.edu/3513923/Possible_social_foraging_behavior_in_the_Red-backed_Hawk_Buteo_polyosoma_ ) sum it up. There's non-cooperative hunting (E.g. Mobbing), cooperative searching, pseudo-cooperative hunting, & true cooperative hunting (I.e. Pack hunting).

In reference to pack hunting, it "is executed by pairs, family groups, or sibling groups, and is generally related to cooperative breeding (Bednarz 1988a, 1988b)" (See page 272). AFAIK, the same goes for both birds & mammals:
-"Packs can be as small as a pair or number as many as 30 including adult and yearlings": http://www.painteddogconservation.iinet.net.au/aboutdogs.html
-"Female cheetahs are solitary, but male cheetahs live in coalitions usually made up of brothers": https://nationalzoo.si.edu/center-for-species-survival/news/different-kind-cheetah-coalition

[ITdactyl]

Those PDFs were awesome reads, thanks H @HD-man .

After reading that, apparently the video I shared isn't an example of mobbing - but it is in fact an example of avian cooperative hunting (i.e. sequential/relay stooping). Nice to learn something new.

Hammers in the point though, as a lay person with not much reference (prior to being shown those papers), my only reference to pack hunting is the big 3 of wolf/lion/orca (since you are fed this information as a child).  I was already an adult when I learned Chimps actually hunt in packs.

So when you have articles that claim "Deinonychus may not have hunted in packs", a layperson's brain would probably go "oh, no alpha led group attacks on bigger dinosaurs? Bummer." - when in fact, that study about their diet doesn't actually rule out all cooperative hunting styles.

[HD-man]

Those PDFs were awesome reads, thanks H @HD-man .

Anytime. Glad I could help.