Sunday, September 8, 2013

Paleo Myth Number 1: The Past Was More Awesome Than the Present



Now I might get some slack for saying this, maybe some paleo-nerd rage directed my way, but I don't think Megalodon is worthy of all the bad-azzery attributed to it. Why would I say this? Well first of all, the morphology and physique given to Megalodon is basically a scaled up great white, a conjecture we have no proof of save the similar tooth design. Instead of the homocercal tail that great whites utilize for rapid cruising and sustained acceleration augmented by endothermy, how do we not know that Megalodon had a heterocercal tail for slow cruising and ocassional short bursts of speed? What if Megalodon was not, like the great white, endothermic at all? * But I am going to venture that the greatest weakness of all for Megalodon is in fact the accolade most generously heaped upon it- it's size.


Now it does not really matter where you end up on the spectrum between the grey and red one, you still have a very large fish- probably among the largest fish that ever existed. But this brings up an interesting pattern, why do all the largest fish cluster around this 40-60 foot range? The largest predatory sharks, the largest filter feeding sharks, Leedsichthys and it's ilk of Mesozoic filter feeders- they all seem to cluster around this size but fish never truly reach blue whale size despite having a much longer tenure in the ocean to do so.

Martill. 1986. Leedsichthys and Liopleurodon
The answer, as succinctly as I can put it, is that as size increases in an organism the volume increases disproportionately faster. And this holds true if you are a single cell organism trying to diffuse wastes across a permeable membrane or if you are 30 tonne shark trying to supply oxygen throughout your body with a limited surface area (gills) for gas exchange. As Megaladon, and other giant fish, got larger and larger they start running into problems. Their volume is increasing exponentially while their surface area is increasing linearly. And the amount of area they have for gas exchange, their gills, is a function of their surface area and therefore not increasing at the same rate as the volume. What you have therefore is a whale shark, or a Leedsichthys, or a Megalodon that is approaching a size of diminishing returns and eventually a glass ceiling for gill-breathing animals. These mega-fish, I would argue, are not  sustained aerobic fast cruisers, had minimal endurance, probably slow metabolisms and essentially became dead in the water if pushed too hard. If you want to picture how Megalodon swam around, the video below of a whale shark going after a bait ball offers more insight, I believe, than modern hunting 1 tonne great whites do breaching after agile pinnipeds.


Megalodon succeeded because it lived at a time when their was just enough slow swimming marine mammals, abundant carcasses, and lack of competition from derived predatory pack hunting toothed whales to exist. It was limited to probably warm temperate seas and was basically good for one or two quick lunges at prey, but not extended chases like modern great whites engage in. When derived, social, and intelligent toothed whales came on the scene it was in trouble. Unable to out-swim or out-manoeuvre a couple of well placed strikes at the gills by these marine mammals and a tip into tonic immobility spelled doom for the last Megalodon just as it does today for many sharks at the hands (flippers) of killer whales. The feasts of liver ripped from Megalodon must have been a sight!!

Killer Whale w/Mako Shark. Visser/Barcroft (c)
Ok I will stop savaging the myth of Megalodon, the supposed marine bad-ass of all time. Admittedly I am playing devil's advocate a bit here- of course I would love to see a Megalodon, it probably is near the top of my all time list of extinct critters I would love to see alive. It must have been an amazing spectacle. But what I am trying to illustrate here, what I am getting at, is that we often fetishize the past at the expense, or ignorance, of the present. We build up these monsters of the past into fantastical, mythical god-creatures- when in reality they were just animals, with strengths and weaknesses all of their own. I could have easily started by debunking pseudo-mythical velociraptors, tyrannosaurs, Sarchosuchus, or Spinosaurus. What you must keep in mind when comparing past organisms to present  ones, is that we tend to look at the whole pantheon of awesome extinct animals- and cherry pick the most outrageous ones- and then compare them to the small finite sample available in this little slice of geologic time. And although our land fauna is very impoverished compared to the Mesozoic or even 10,000 years ago- our marine megafauna, especially whales, dominate all other epochs in terms of size, growth, and amazing feeding styles- lunge feeding baleen whales, super intelligent pack hunters, sonar aided hunting.

I'm sure everyone remembers the hoopla surrounding that god-awful faux-documentary about a live Megalodon and all the blowback discovery channel got for it? You know when shark week, umm, jumped the shark (sorry)? Well at about the same time everyone was ranting and raving about that horrible show on Megalodon during shark week, for a critter I argue has been hyped up beyond recognition, real science about a real arch-predator of the ocean was being published that did not garner 1/100th the attention the Megalodon debacle did. And this was the revelation that a whole new species of killer whale, the type D genotype, is alive and well and swimming around the southern oceans as we speak. A whole new species of killer whale!!! No discovery channel special!! No nat-geo special!! No media hoopla!!! Hardly any fanfare to speak of for a whole new species of multi-tonne marine arch-predator!!

Type D killer whale. Jean Pierre-Sylvestre. Nat Geo (c)
And here is where I want to crystallize my argument. And this is the case that not only are orcas super awesome marine predators, they are the baddest of the bad when it comes to marine arch-predators of all time. A cultured, highly intelligent, pack hunting, echo-locating, tool using, matrilineal, fast, strong, and persistent cosmopolitan family able to launch attacks on everything from schooling fish to herds of sperm whales and even the largest animal ever, the blue whale. Adult males are as large as t-rex and at least as intelligent as the average Wal-mart shopper. I put them over Megalodon, over Pliosaurs, over giant extinct raptorial sperm whales, over great whites which they casually snack upon, over mosasaurs. I believe they would find a way to kill each and every marine arch-predaor that lived before them. And they live with us right here right now. Yet we stuff them into unnatural concrete enclosures and wonder why they go insane and kill us. And when a whole new species is discovered we hardly take notice and pay respect to the all time maritime king.

Shame on us.




* Amendment 9/9/13. It has come to my attention that there is a paper Dermal scales of Carcharocles megalodon from the Miocene Mizunami Group, Central Japan! Author Hiroyuki Nishimoto et al 1992. Bulletin of the Mizunami Fossil Museum that purportedly shows evidence of placoid scales suggestive of high speed, fast growth and perhaps endothermy. I have not seen/or read the paper but it does exist. I don't claim to be a specialist in shark evolution, merely a fan. However I don't think this invalidates one of the premises of my article concerning gill surfaces area versus volume increase and the possible eco-physio-behavioral constraints imposed upon such large fish.


Support me on Patreon.
Like antediluvian salad on facebook.
Watch me on Deviantart @NashD1.Subscribe to my youtube channel Duane Nash.










19 comments:

Winona said...

Last night I dreamt I was scuba diving with grey whales and orcas. It was not a sweet dream: "Get me the hell out of this water! I'm gonna die!!!!"

Duane Nash said...

Anything bigger than 20 lbs and you are in the water with it - can be darn scary!! Or even small stuff like jellies can really put on the hurt. I guess grey whales were once referred to as devil fish for the ferocious fights they would give whalers.

ted said...

It needed 29 orcas to severly injure a 18 m immature blue whale. The battle lasted more than 5 hours. At the end, the orcas gave up and the whale escaped alive, perhaps dead later.

I think you definitely overrate orcas predation capabilities. They are very capable but they are just as mythified than others.

They rarely attack large adult whales, and whhen they do it, it takes a while, at great number, and not always with success.

And there is NO documented case of orcas engaging an adult male sperm whale.

If they avoid to engage the squid sucking odontocete, don't expect them to engage the 50-60 tonnes otodontid which effectively preyed on large whales, alone.

ted said...

About tonic immobility.

How do you expect orcas to use tonic immobility on a 50 tonnes plus active-macropredator shark when when they need almost 30 individuals and 5 hours to injure a 18 m, immature probably no more than 30-40 tonnes blue whale ?

Because the female orca CA2 is known to have used tonic immobility on a...much smaller, immature great white shark ?

CA2 is 6.5 m, the shark was estimated at 3.5 m. CA2 is probably 5 times heavier than its prey.

There's really nothing spectacular to see an orca using tonic immobility on a much smaller shark. That's fascinating but not that badass.

And tonic immobility does not show the same aspec depending the shark, the context, the agressor.
Ever seen a pod of orcas using tonic immability on a whale shark ? No.

But once again, C. megalodon is typically estimated at 50 tonnes body mass. If this is valid, which is likely, there's simply no predator that could ever perform tonic immobility on it.

Duane Nash said...

Thanks for commenting ted.

"And there is NO documented case of orcas engaging an adult male sperm whale."

True, but predators tend to take easily subdued prey all things being equal. Attacks on herds of sperm whales is well documented.

http://newswatch.nationalgeographic.com/2013/04/30/astonishing-and-rare-orca-vs-sperm-whales-video-explained/

Killer Whale Predation on Sperm Whales: Observations and Implications
http://bec.ucla.edu/papers/MesnickPaper2.pdf

While I would tend to believe that the large aggressive and toothed adult males are left alone, maybe we just have not seen this predatory behavior? After all not all killer whales are marine mammal killers. And for those that are they generally have easier pickings available to them than adult bull sperms.

"If they avoid to engage the squid sucking odontocete, don't expect them to engage the 50-60 tonnes otodontid which effectively preyed on large whales, alone."

Well played. But extending this argument to include 50 tonne sharks is wrong as I explain below.

"How do you expect orcas to use tonic immobility on a 50 tonnes plus active-macropredator shark when when they need almost 30 individuals and 5 hours to injure a 18 m, immature probably no more than 30-40 tonnes blue whale ?"

Because blue whales, rorquals of all sorts actually, are very sleek, fast, and have stamina. Their endurance and speed causes problems for orcas and, before high powered whaling boats and harpoons, humans as well.

blue whale speed:
http://web.archive.org/web/20070711025158/http://www.acsonline.org/factpack/bluewhl.htm

So here I do not find blue whale predation a very useful comparison to large shark predation.

That we don't have proof of killer whales attacking adult male sperm whales is not the same as saying that killer whales avoid to engage them. And even if killer whales do not engage adult male sperm whales- using this observation to deduce that killer whales did not attack Megalodon is a false equivalence. As I addressed in the post Megalodon vulnerability would be due to its lack of stamina due to limitations on gill surface exchange for oxygen and those big gill slits on each side of its head. Having external gills is a lot like having your lungs on the outside of your body. For social, cultural, and intelligent killer whales the gills are an easy target. Adult sperm whales do not have external gills or really anything like that in terms of an easy kill spot. So it is false to compare large odontids to large sharks. In fact I would argue that because of their vulnerabilities large sharks are more vulnerable than large whales of any sorts.

Additionally because Megalodon would have been a direct competitor and predatory threat to orcas, unlike sperm whales which do not predate on orcas or compete for food, I would argue that the big shark would not have been tolerated.

Oh yeah about whale sharks and killer whales.

"There's really nothing spectacular to see an orca using tonic immobility on a much smaller shark. That's fascinating but not that badass."

"And tonic immobility does not show the same aspec depending the shark, the context, the agressor.
Ever seen a pod of orcas using tonic immability on a whale shark ? No."

Well you kind of set yourself up for this one.

O'Sullivan, J. B.; T., Mitchell (2000). "A fatal attack on a whale shark Rhincodon typus, by killer whales Orcinus orca off Bahia de Los Angeles, Baja California". American Elasmobranch Society 16th Annual Meeting, 14–20 June 2000. La Paz, B.C.S., México. Retrieved 2010-02-18.

Duane Nash said...

In addition here is an account of killer whales attacking and killing a minke whale. The chase lasted over 2 & 1/2 hours and 25 miles. And minke whales are smallish- about 5 tonnes.

http://doug-anderson.com/2010/02/valentines-day-massacre/

ted said...

You welcome, thanks for responding me.

"While I would tend to believe that the large aggressive and toothed adult males are left alone, maybe we just have not seen this predatory behavior? After all not all killer whales are marine mammal killers. And for those that are they generally have easier pickings available to them than adult bull sperms."

It is true that we lack the vast majority of the observations in the wild but even so, there is no documented case of adult bull Physeter wearing scars by orcas attacks, not even in old archives. Several papers hinted that orcas simply avoid an adult 40 tonnes plus bull Physeter.
Despite all their power and abilities, they still showed difficulties against a 18 m, immature B. musculus, at almost 30 members. Based on this, I'm not surprised that a bull sperm whale is potentially virtually immune to even transients orcas.

ted said...

"That we don't have proof of killer whales attacking adult male sperm whales is not the same as saying that killer whales avoid to engage them. And even if killer whales do not engage adult male sperm whales- using this observation to deduce that killer whales did not attack Megalodon is a false equivalence. As I addressed in the post Megalodon vulnerability would be due to its lack of stamina due to limitations on gill surface exchange for oxygen and those big gill slits on each side of its head. Having external gills is a lot like having your lungs on the outside of your body. For social, cultural, and intelligent killer whales the gills are an easy target. Adult sperm whales do not have external gills or really anything like that in terms of an easy kill spot. So it is false to compare large odontids to large sharks. In fact I would argue that because of their vulnerabilities large sharks are more vulnerable than large whales of any sorts."

You actually speculate that orcas would definitely target the gills but the truth is that in the rare observations where pods of dolphins attaced small reef sharks, they did not particularly targetted the gills, but also the belly.

There is no example of large sharks being primarily targetted in the gills by smaller, pack mammalian foes.

This is where I come from the mythification of orcas. There ability and predatory intelligence is legendary, so much that everything is assumed with them, even if not verifiable.

C. megalodon has survived during the Miocene and Pliocene to various generas of raptorial odontocete, a number as large and larger than orcas. It is well possible that some of these species may have been too pack hunters. While, I don't think raptorial physeteroids were as smart as modern delphinids, being pack predators even bigger than the average orca makes them foes potentially even more dangerous for C. megalodon.
Still, the shark got extinct about 2 millions years ago, when raptorial sperm whales were long gone.

You're right while hinting about the cardiovascular limitations of megalodon. This is more because of its internal system, very simplistic among sharks, than because of its gills.

I have access to a paper in preparation about this, by Brett Kent, where he talks about the potential limitations in maneuvrability a very large Carcharocles (+18 m) would have, and the enormous constraints it'd experience. Based on this, it is possible the largest, oldest Carcharocles were primarily uge scavengers scaring off any other carnivore in the sea from a kill.

But you have to keep in mind what 18 m + otodontid would represent in terms of endurance, power, durability. Sharks are basically very though animals. It took 39 hours, five harpoons and more than 100 bullets to subdue a 12 000-13 500 kg, 38-foot whale shark individual off Florida.

It takes 5 hours to 30 orcas to "only" seriously injure a air-breathing filter feeding 18 m, probably 30-40 tonnes baleen whale. According to the regression from Gottfried et al. a 18 m Carcharocles would reach potentially around 70 tonnes. I simply do not see a pod of orcas posing a great threat to a fish that massive able to simply going deeper in the worst case.

ted said...

"Additionally because Megalodon would have been a direct competitor and predatory threat to orcas, unlike sperm whales which do not predate on orcas or compete for food, I would argue that the big shark would not have been tolerated."

The various raptorial sperm whales, more diverse, more numerous and bigger than orcas, did not outclass Carcharocles.

Also, orcas and Carcharocles wouldn't directly compete. Carcharocles was at first specialized on large marine mammals. Orcas are far more generalists.

"Well you kind of set yourself up for this one.

O'Sullivan, J. B.; T., Mitchell (2000). "A fatal attack on a whale shark Rhincodon typus, by killer whales Orcinus orca off Bahia de Los Angeles, Baja California". American Elasmobranch Society 16th Annual Meeting, 14–20 June 2000. La Paz, B.C.S., México. Retrieved 2010-02-18."

I know that case, two bull orcas against an immature 8 m whale shark. No real comparison with the attack of an agressive, macro-predatory 50 tonnes behemoth.

"In addition here is an account of killer whales attacking and killing a minke whale. The chase lasted over 2 & 1/2 hours and 25 miles. And minke whales are smallish- about 5 tonnes.

http://doug-anderson.com/2010/02/valentines-day-massacre/"

I know that case too !

Again, it's at the same time impressive and unimpressive. That's a long battle for such a smaller bodied, surface breathing 5 tonnes almost defenseless prey.

That's not the same case with a foe 7-8 times heaver than T. rex able to stay infinitely underwater, at greater depths that any orca can reach.

ted said...

Sorry for the potential tiping, grammatical errors, english is not my mother tongue !

ted said...

Another indication in that gills are not so easy targets, weak points in large sharks :

http://www.gr8-white.com/1129/wounded-great-white-shark-surprises-divers/

Bk Jeong said...

I seriously doubt that extinct giant marine predators were that slow and stupid. Isn't that what we thought about dinosaurs?

Gabe said...

I agree on the gills limitation for the giant fishes (a paper is in prep about that).

But considering megalodon as only a dumb big shark is certainly a huge disservice to the species, a long-lived, cosmopolitan, apex predator that possibly prevented whales to grow to gigantic sizes until it vanished (see Pimiento 2014) and was already absolutely unique in size, no cartilaginous fish, let alone macropredator, has ever reached such a size by far, which implies some other unique adaptations that C. megalodon may have possessed. Size speaking, C. megalodon is perhaps the largest macropredator that ever lived (putting aside the teuthivorous sperm whale), it outsizes in length and presumably mass the largest known pliosaurs, mosasaurs and theropods. I've not mentionned the extremely robust dentition and the presumed propencity to target harder bony parts and the well-recorded ability to saw through large whale bones.

Yes there's always some overhype in extinct predators, including C. megalodon, and O. orca is indeed quite possibly the most complete and perfect apex arch-predator ever (though I'm not especially impressed by their individual predatory power) but in terms of sheer, primal brute raptorial strength, megalodon is quite possibly the most spectacular of all the recorded carnivores (on an individual basis).

Duane Nash said...

Thanks for commenting Gabe and nice points.

I'm sorry if I gave the impression that I consider megalodon " a dumb big shark" that wasn't my intent at all. And actually the total point of the post was to highlight the need for conservation of today's biota and how the animals of today are doing things as amazing as any time in this planet's past. And I have actually written a theorized hunting tactic in great white sharks that points to potential hyper-intelligence in this species used to catch absolutely faster tuna Scrummy for Scromboids: How Do Great White Sharks Catch Tuna Anyways? So I actually quite love sharks and respect them immensely.

So I will cop to using Megalodon as a bit of a foil to make my larger point. And, if i ever get that time travelling maching built Megalodon would certainly be a top five on my wish list. But we should not deify these animals. And I am glad you caught the point about gill surface area being a potential weakness in large fish. Orcas have their weaknesses too - those big mammal brains suck up a lot of toxins from the environment which might be their potential undoing... and if their "cultural" adaptations to target only certain foods this could well be a liability in increasingly stressed ocean ecosystems where opportunism would be advantageous.

Gabe said...

Thanks for responding Duane.

I fairly agree on your points, the past is not that more awesome than the present and we should not deify any of these extinct giant predators.

But I think there are some points to nuance. Definitely modern biota is amazing, wondeful and absoluly needs to be preserved.

Now we can't deny that staring at a herd of >60 tonnes titanosaurs or witnessing the hunt of 8 000 kg terrestrial predators, ten times bigger than our biggest ursids, would be something absolutely unparalleled today, in the same way that, as you remaked, orcas are probably unprecedented apex predators in history, or that no recorded fauna has ever been as huge as our modern baleen whales.

So let's be cautious to not exagerrate the opposite trend. I've actually read about people who truly deify orcas and think they can overpower anything or could dominate anything that has ever lived, while they have been observed in difficulty while stalking large whales and a number of times had to give up their hunt. Like most predators, they usually target the youngs, the sicks individuals and to my knowledge have never been seen engaging an adult sperm whale.
Regardless, I totally agree they can be regarded as the penultimate predators given their incredibly vast range of potential preys. Though this can be complicated given the high probabilities that there are several separate species of orcas with specific dietary preferences.

Regarding the gills and vulnerability in sharks, while I agree they're certainly not unvulnerable areas, I'm not sure they are that sensitive. I've seen pictures of healty sharks with gruesome, deep wounds on the gills. In the few records where dolphins have been seen killing a small reef sharks, they did not target specifically the gills. So while certainly weak points, I'm not sure that a single punch there can stop a charging Carcharodon or Galeocerdo. Overall, sharks have been observed as being particularly durable animals, I have in mind the case of a 11 m, 15 tons whale shark that took 39 hours, 5 harpoons and 151 bullets to be subdued... I think that a 50 tons Carcharocles would be somewhat harder to kill !

Also, I don't think there is direct evidences that our modern O. orca actually met C. megalodon. Modern research seems to indicate that Cacharocles was extinct one million years earlier than we thought, about 2.6 millions years ago. Pimiento 2014 suggests that the evolution of gigantic mysticetes occured right after that date and I suspect it is the same for the evolution of large Orcinus. The only Orcinus we have evidence for being a contemporary of Carcharocles is the 4, smaller toothed Orcinus citonniensis from the Pliocene of Italy, 4 million years ago. Not exactly a match for Carcharocles which was already. I think we're more in the case of an ecological void left to the big delphinids by the big shark rather than a progressive replacement of one apex pradator by another (like what occured between Cretoyrhina and the large Late Cretaceous mosasaurines and tylosaurines). I think more investigation about this is planned.

Duane Nash said...

Good points Gabe I definitely seem to have oversold my case, now that I reread it!! Well it is a post from a couple of years ago so live and learn you know. And it is most likely true that environmental changes (cooling ocean/shifting whale migration patterns) and not outright competition caused the extinction of Megalodon. Sorry for not showing respect Mr Megalodon!!

Speaking of mosasaurs and shark replacement - I have heard that suggestion before but is there anything to substantiate it? I am more partial to the notion that established top oceanic predators are never really usurped by other predators making inroads on their niche but dying off due to more mundane ecological/environmental reasons. Followed by other predators filling that void.

Gabe said...

Sorry Duane, I had forgotten to respond.

Regarding the replacement of sharks by mosasaurs and the oceanic ecological battles between the different type of apex predators, these lecture talks by Mike Siverson should be of interest :

https://www.youtube.com/watch?v=e4p9EWuVxYQ
https://www.youtube.com/watch?v=fEg_YwFwHPs

Bk Jeong said...

Can this post be edited now? Leaving the gill issue in but in such a way that it isn't C. megalodon-bashing and orca overglorification?

Bk Jeong said...

Especially the bit about orcas killing C. megalodon since it neither coexisted with orcas nor suffered from raptorial sperm whales (yes it had competition from raptorial cetaceans. Livyatan for one, though that too is unfortunately overhyped.)

And C. megalodon's intellect needs to be emphasized more-sharks are not animals than can be outsmarted easily, and modern great whties are as versatile (even more so possibly since orcas are restrained by their pod's culture while a shark does whatever it wants) at hunting as orcas

Related Posts Plugin for WordPress, Blogger...