Strong evidence of instraspecific combat in ceratopsians?

[andrewsaurus rex]

it's been much speculated that there was intraspecific rivalry, probably among males, of various ceratopsian species, but how strong is the evidence supporting this?

The combat would probably take the form of locking horns and wrestling, pushing etc.  For short horned species, there may be little evidence possible of these fights.  But for longer horned animals, such as Triceratops, Pentaceratops and Torosaurus, you would think it would not be uncommon to find damage to the skull and frill, from the horns of an opponent.

Does such evidence exist and if so is there much of it?

[stargatedalek]

There is strong evidence against the idea that ceratopsian horns were used for intraspecific combat.

For one, all members of a given species, in every single known ceratopsian species, have identical horns. They are not gender specific. If they were used for intraspecific combat, it was decidedly not mating related, as if it was we'd see these structures start to vary within a species but they never do.

For two, only in a few species are their horns even combat functional. Many are fragile, or bend in weird directions or shapes. These were ultimately display structures, perhaps for species recognition or perhaps aposematic, or a mix of both. Those that were useful in combat like Triceratops likely evolved their shape coincidentally, and the animals behaviour changed to make use of them.

[andrewsaurus rex]

Interesting.  So, in the genera where the horns were useful for combat (eg Triceratops, Pentaceratops and Torosaurus) are you suggesting that they WOULD have been used or just could have been used for intraspecific combat, as there is no evidence to support it?

And by saying the horns may have aposematic purpose, you are saying that the horns were there to look scary and deter predators, without really being dangerous to them?  Would not most predators quickly learn that the horns were not very harmful to them?  Aposematic features are usually there to warn predators and others. that the animal IS dangerous not just looks dangerous.

I have long felt that ceratopsians are very similar to today's antelopes.  They have a variety of horn types, some of which are useful against predators, some of which are not, often males and females have similar horns, they travel in herds etc.  So, regardless of why the horns evolved, eg species recognition, defense, or intraspecific rivalry, the animals quickly learn other uses for them (eg defense).  The horns on Sable and Roan antelopes don't look very useful for defense but are. The animals have learned to swing their heads sideways and backwards at predators attacking from those directions...with potentially fatal results to the predator if they are slashed by them.   So, could not the unusually positioned horns of some ceratopsian species, similarly be dangerous once the animal learns to use them properly?

[stargatedalek]

It's unlikely even Triceratops used them for intraspecific combat, rather in defense against predators. But there are also cases of intraspecific combat that are not mating related, so it could have used them in that way, but that's purely speculation, no evidence in favour of it that I'm aware of. For example, if herds were not inherently matriarchal or patriarchal, they may have still been used in combat against one another.

More likely these big fancy structures were brightly coloured and patterned. The ceratopsians who were the healthiest would have brighter and healthier looking horns.

The horns themselves don't need to be the dangerous part of the animal for them to be functioning aposematic displays. Ceratopsians were bulky creatures with large powerful beaks. Add to that big intimidating structures that are easy to see and recognize for other species, and that makes it much easier to deter predators without having to risk injury.

I have trouble picturing something like Einiosaurus using its horn for combat, no matter what sort of angle it attacks with. The beak is just a far better weapon if the predator is already that close anyway. Plus all of the fragile horns or horns placed high up on the frills of many species, hitting those into a predator or each other would likely do serious damage.

[HD-man]

A @andrewsaurus @stargatedalek Sorry to be the "actually" guy, but there IS "Evidence of Combat in Triceratops": https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0004252

[andrewsaurus rex]

I actually came across that study last night, after my postings.  It's interesting and certainly decent evidence, not sure I would call it 'strong' evidence as the sample sizes are small and the lesions can be explained in other ways.  For those who want to believe in intraspecific combat, like me, it is certainly supportive.  I found the conclusion that centrosaurs may have attacked their opponent's body interesting; backed up by increased evidence of broken ribs in centrosaurs. vs. chasmosaurs, again with small sample sizes.

I would like there to be a similar study for Pentaceratops.....with about a dozen skulls found, that would give a reasonable sample size.  You'd think at least 3 or 4 of the skulls should show credible horn damage (ie half the skulls are female, who didn't fight (perhaps) and the other half are male who did fight but some didn't bother to fight or didn't get injured while fighting).

One problem is that we (I) may be attributing mammal like behaviours to non-mammalian animals.   Big males fighting over sex or territory is very much a mammal thing, but was it a dinosaur thing?  Perhaps dinosaurs learned to get along in other ways eg. there's not much evidence of intraspecific combat in tyrannosaurs, despite the large number of skulls found.  And the evidence for ceratopsians is debatable at best.  There is a bit of evidence for ankylosaurs but with very small sample sizes.

[stargatedalek]

A @andrewsaurus @stargatedalek Sorry to be the "actually" guy, but there IS "Evidence of Combat in Triceratops": https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0004252

I happily stand corrected! And it makes sense that at least the species whose horns were already combat ready may have been fighting.

Though I stand by my assertions that it doesn't make sense for this to have been mating related, given all Triceratops of a species have the same horns.

[Bowhead Whale]

A @andrewsaurus @stargatedalek Sorry to be the "actually" guy, but there IS "Evidence of Combat in Triceratops": https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0004252

I happily stand corrected! And it makes sense that at least the species whose horns were already combat ready may have been fighting.

Though I stand by my assertions that it doesn't make sense for this to have been mating related, given all Triceratops of a species have the same horns.

I know a lot of modern species where males and females both have horns or antlers, even if the female's look different to the males': musk oxen, reindeers, african buffalos, european and american bisons, gnus... in those cases, females use the horns to defend their youngs against the predators... or to sometimes intimidate males who want to mate despite the presence of a calf. Think of Musk oxen for example. To protect their youngs against wolves, all the adults, males and females, form a circle with their horns pointed outside. The wolves then face a series of horns when wanting to attack them. In Africa (I saw it in a documentary), a mother cheetah tried to kill a baby buffalo. The mother came to her and dodged the cheetah who fell on the ground. As for reindeers and caribous, females keep their antlers all winter, which give them the advantage when fighting for food while bearing their youngs.

Couldn't it be the same with ceratopsians? Couldn't the horns, especially the one on the nose, be used as defense in similar occasions? It seems to me that nature does not make horns just for display. All organs have a purpose. Horns also. And a horn looks too much like a weapon not to be a weapon. No?

As for the beak also being a weapon, well, it does not mean that beak was the ONLY weapon ceratopsians had. Many modern animals have more than one weapon. Rhinoceroses don't just dodge, they also stomp on adversaries. Horses don't just kick, they also bite fiercely. Crocodiles don't just bite, they also swipe their tail when the opponent is behind them. Couldn't ceratopsians have also more than just one weapon? The nose horn PLUS the beak?

[andrewsaurus rex]

i tend to agree about ceratopsian horns being more than just display features.  If it looks like a weapon, then it will probably be used as a weapon, even if that is not why it originally evolved.

And while many ceratopsian brow horns may not initially look useful as weapons, most are, in my view.  They don't have to be used for stabbing; in fact stabbing may not be the best way to use them, as they could become stuck in your victim and difficult to pull out again.  During WWI trench fighting bayonets were not a great weapon.  One reason for this is that it would get stuck in the person you stabbed with it and while you are trying to get it out, you are vulnerable.  Same could be true for stabbing with brow horns (and for that matter stegosaur tails spikes)...if they get stuck in your victim, while you are trying to get them back out you could get seriously injured as the victim writhes and struggles.

I think slashing is a far better use for brow horns.  Instead of stabbing with them, a sideways slash would cause long painful cuts that would result in serious injury or death to the victim, with no chance of the horns getting stuck in them.  And most all ceratopsian brow horns are well configured and long enough for a sideways slash, especially the ones that bend outward.

[Gothmog the Baryonyx]

I don't think it would be possible for an Einiosaurus to slash anything with its horn but its own tongue (if the tongues were mobile). And nothing at all if they weren't.

[andrewsaurus rex]

perhaps, but that is one example out of dozens of ceratopsian species that are horned and have horn shapes that would be useful for defense.

[Bowhead Whale]

I don't think it would be possible for an Einiosaurus to slash anything with its horn but its own tongue (if the tongues were mobile). And nothing at all if they weren't.

Andrewsaurus is right, although you may have a point. Many modern animals have tusks or horns that grow so long that, when the animal is old, it cannot even use them as weapons anymore. I am thinking of babyrussas, hippopotamuses, rams, bulls... In some cases, the horns or the tusks grow and grow until they pierce the skin at an impossible place. Maybe that is what happened with the Einiosaurus you mentionned. What do you think?