What was the apex predtor in late Cretaceous Europe?

[andrewsaurus rex]

North America had T-rex, Asia had Tarbosaurus, what was Europe's apex predator around that time?  There were lots of Titanosaurss to feast on, what was doing the feasting?

[stargatedalek]

Nothing was eating (healthy adult) Titanosaurs. Large sauropods in general don't offer a noteworthy food source to a large predator except as juveniles (which we see in the Morrison for example).

Arcovenator was no slouch, but not exactly rivalling large Tyrannosaurs or Spinosaurs. I beleive it might be a tossup between it and Hatzegopteryx as the largest terrestrial predator.

[Dynomikegojira]

I'm gonna say the only correct answer with Mosasaurus.lol

[andrewsaurus rex]

packs of wolves take down healthy adult Bison and Moose.  I've seen videos of it.  Why couldn't a pack of decent sized theropods take down an adult titanosaur?  I'm sure juveniles would be preferred but that's not always possible.  Something had to be keeping the titanosaur population in check, otherwise they would have overrun their environment.  There must have been a keystone predator keeping their numbers down.

[stargatedalek]

packs of wolves take down healthy adult Bison and Moose.  I've seen videos of it.  Why couldn't a pack of decent sized theropods take down an adult titanosaur?  I'm sure juveniles would be preferred but that's not always possible.  Something had to be keeping the titanosaur population in check, otherwise they would have overrun their environment.  There must have been a keystone predator keeping their numbers down.

A) A wolf is still ~1/4 the size (not weight) of a large moose or bison.
B) Large =/= healthy adult.
C) Animals become less mobile the larger they get, no predator 1/4 the size of a large sauropod is going to be able to maintain the mobility required to outmanoeuvre it even in a pack.
D) There is/was no (non-desperate) natural predator regularly targeting adult; elephants, the larger rorquals, Galapagos tortoises, orcas, emus, cassowary, elephant birds, dodos... there are plenty of other ways an animals population can be stable than just control by predators. Some reproduce(d) slowly like whales and dodos. While others age(d) slowly despite reproducing quickly, such as tortoises and, yes, sauropods.

[Gwangi]

I imagine that very few sauropods made it to adulthood and predation on young animals probably kept the population in check.

[thedeadlymoose]

I imagine that very few sauropods made it to adulthood and predation on young animals probably kept the population in check.

Read this post recently: https://tetzoo.com/blog/2020/5/1/stop-saying-that-there-are-too-many-sauropod-dinosaurs-part-5

What this means is that sauropod populations were skewed towards juveniles; that the population of a given species was formed – mostly – of small animals, and that adults, especially giant adults, were rare. Taphonomic biases mean that the bones and footprints of juveniles are less preservable than those of adults. But even so, juveniles of Morrison sauropods are relatively well represented, in cases being present at nearly 90% of relevant sites (Foster 2005). And trackways indicate that about 70% of sauropods in some areas (meaning worldwide, not in the Morrison biota specifically) were small juveniles (Lockley 1994).

Fascinating and counterintuitive if you grew up with classic dinosaur conceptualizations.

The whole series on sauropods has a lot of cool detail like this. (Hopefully not outdated, as it's from 2020.)

[andrewsaurus rex]

That's very interesting and makes sense.  However, given the significant number of huge  sauropod remains that have been found, even if only small portions of a skeleton, and the rarity of fossilization, to me this suggests more than just a few sauropods made it to adulthood.

[Gwangi]

That's very interesting and makes sense.  However, given the significant number of huge  sauropod remains that have been found, even if only small portions of a skeleton, and the rarity of fossilization, to me this suggests more than just a few sauropods made it to adulthood.

When I say "a few" I mean a few per clutch, or what have you. A modern example would be sea turtles where something like 1 in 1,000 survives to adulthood. It's pitifully low but still enough to sustain the species.

[stargatedalek]

That's very interesting and makes sense.  However, given the significant number of huge  sauropod remains that have been found, even if only small portions of a skeleton, and the rarity of fossilization, to me this suggests more than just a few sauropods made it to adulthood.

Even if 100% of them reached adulthood, that doesn't inherently mean they had a predator that targeted them as adults.

[andrewsaurus rex]

well, if 100% of them reached adulthood, that would mean they don't have a predator targeting them at any age,  not when young or as an adult.  Given that it is known sauriopds laid large amounts of eggs, there would eventually be sauropods in every square inch of the prehistoric world. 

But I can see the points everyone is making.  It's just a little difficult to initially wrap my head around, with no real analogue in the modern world.  Sea turtles aren't quite the same, nor are elephants.   It's sort of a blend of the two I guess; large numbers of offspring, decimated by predation (like sea turtles) and adults that are essentially immune from predation (like elephants).

[Lynx]

A bit off-topic, but it may fit into this thread.

Do we have any actual proof Sauropods abandoned their young? I recall this just being an idea popularized by WWD, with little actual evidence behind such behavior. I see more dinosaur media nowadays portraying Sauropods as caring parents instead.

[dinofelid]

A bit off-topic, but it may fit into this thread.

Do we have any actual proof Sauropods abandoned their young? I recall this just being an idea popularized by WWD, with little actual evidence behind such behavior. I see more dinosaur media nowadays portraying Sauropods as caring parents instead.

I don't think there's anything definitive, but this article has some evidence for the idea that they abandoned their young:

https://www.washingtonpost.com/news/speaking-of-science/wp/2016/04/22/rare-baby-dinosaur-fossil-suggests-a-harsh-lonely-childhood/

By the time the baby krausei died — around 39 to 77 days later — it had packed on about 80 additional pounds. That's some impressive growth, but it's nothing compared with the thousands of pounds an adult probably weighed.

But despite its tiny size, the baby dino's bones were proportioned similar to an adult's. That's something usually seen in animals that set out on their own not long after birth. While some sorts of animals — cats, dogs, humans and even some dinosaurs, for example — have big-headed, helpless babies, other species are born with the bodies they need to fight, flee and feed without the help of a parent.

The word for this immediate independence, by the way, is "precocial," which comes from the same root as "precocious," which I personally find delightful.

Brian Switek at National Geographic reports that the baby appeared to have been very active during its short life and that it was "ridiculously overengineered" with a body built to carry the massive weight it never lived to put on.

They also note that the baby seems to have died of starvation, I'd think that would also favor the idea it was foraging on its own.

[Halichoeres]

This paper interprets skeleton and trackway assemblages as indicating that while sometimes mixed-age herds formed, others were juvenile-only. None of this is consistent with parental care.
https://www.sciencedirect.com/science/article/pii/S003101820900011X

But I can see the points everyone is making.  It's just a little difficult to initially wrap my head around, with no real analogue in the modern world.  Sea turtles aren't quite the same, nor are elephants.   It's sort of a blend of the two I guess; large numbers of offspring, decimated by predation (like sea turtles) and adults that are essentially immune from predation (like elephants).

Yeah, we're used do seeing our big animals as "K selected," but some of that is just because our large animals have to (or are able to, to reframe it) invest a huge amount of energy and time into each offspring. The geometric constraints of egg laying mean you can't gestate a nearly-invincible fetus for 20 months, so you have to play a numbers game, as sea turtles do. (If "K selected" doesn't ring a bell here's a good summary: https://en.wikipedia.org/wiki/R/K_selection_theory)