What Did Megalodon Eat? – The Bristol Dinosaur Venture

Visitor Creator: Jack Cooper, MSc
UoB Graduate / PhD Pupil, College of Swansea

As we’ve seen up to now, there have been adjustments and updates to the scientific consensus of Megalodon’s taxonomic task and most physique measurement. Nevertheless, its favorite snack is one thing that’s universally agreed upon within the scientific neighborhood. In one other rarity, it’s one thing that’s often portrayed with fairly good accuracy in fiction. Enable me to introduce a shark that ate whales – precise whales!

A lot of right this moment’s massive macropredatory sharks are recognized for consuming marine mammals, particularly our previous pal the nice white shark. A few of the most iconic pictures of this shark embrace it hurling itself out of the water with its newest sufferer between its jaws (Fig. 1). Nevertheless, juvenile white sharks don’t eat seals proper from the get-go. As an alternative, they begin off consuming fish and smaller sharks [1]. If we glance once more on the Gatun formation in Panama, we discover loads of fossil sharks, rays and otoliths (buildings from the internal ears of fish), as properly a plethora of invertebrates like molluscs [2,3].

One thing we don’t discover, nevertheless, is fossil marine mammals. This appears to point that Megalodon younger had been additionally consuming fish and smaller sharks reasonably than instantly going after marine mammals. That is one thing referred to as an ontogenetic shift in weight loss plan, that means that the shark adjustments its most popular meals supply because it grows. By consuming bigger meals, and doubtless a lot of it, because it reached its grownup measurement, Megalodon would’ve been capable of keep the metabolic calls for of being so massive. It might’ve performed this by consuming not solely whales, however absolutely anything it got here throughout.

Given how a lot meals Megalodon would’ve wanted to eat to justify its huge measurement, it was virtually definitely an opportunistic feeder. The fossil document is our greatest information right here. That is because of the presence of hint fossils, that are geological data of organic exercise. This will vary from dinosaur footprints to scratches on bones indicating that one thing bit the animal that bone belonged to. And Megalodon left a couple of of those hint fossils behind, offering key proof of its kills.

A number of fossils have been discovered belonging to quite a lot of cetaceans with notable chunk marks on them. One well-cited instance comes from the Yorktown formation in Maryland, the place a number of whale bones had chunk marks that had clearly been made by massive serrated enamel [4]. In truth, Megalodon enamel are generally discovered straight related to these bones [5].

Sharks lose and exchange enamel 1000’s of instances all through their lives, and thus sharks ceaselessly lose enamel when making a violent kill. This can be a key motive why shark enamel are such widespread fossils. The presence of the shark’s enamel proper by a scratched whale bone does point out that feeding was happening. However, one thing that palaeontologists ought to at all times take into account when these fossils are discovered is: was this really predation? Or was it maybe scavenging?

Scavenging is a standard feeding behaviour in fashionable macropredatory sharks resembling nice whites (Fig. 2) and tiger sharks [6,7]. When these sharks encounter useless whales floating on the floor, it’s an all-you-can-eat buffet. Critically, scavenging requires no power expenditure, one thing that may be wasted on a failed predation try. Provided that Megalodon wanted to have the ability to keep its huge measurement, it wouldn’t make a lot sense to go on a free meal if it encountered a useless whale. Thus, by proxy of how massive fashionable sharks feed, most of us could be prepared to wager that Megalodon in all probability did scavenge when given an opportunity.

This mentioned, there’s one notably outstanding fossil that implicates Megalodon in a predation try. And, crucially, we all know this primarily as a result of its try failed. A paper revealed in 2010 [8] described a partial rib Pliocene fossil belonging to a cetacean from the Yorktown formation in North Carolina (yep, two Yorktown formations). This fossil additionally confirmed harm resembling chunk marks, however notably there seemed to be a woven bone masking over these marks. The authors interpreted this as an indication of an an infection that had occurred whereas the animal had been recovering from bone trauma brought on by these chunk marks. These marks matched up properly with a serrated chunk, suggesting that the attacker had serrated enamel – identical to Megalodon. The examine due to this fact instructed {that a} Megalodon, or one other massive shark, had attacked the animal the fossil had come from, however the sufferer had survived the try solely to die of an an infection from its harm six weeks later [8].

Much more not too long ago, the primary ever fossil chunk marks discovered within the southern hemisphere attributed to Megalodon had been present in Peru’s Pisco formation [9]. Maybe it was meant to be, as this is similar website the place Gordon Hubbell discovered his distinctive Carcharodon fossil (mentioned in Q1). The bitten materials discovered right here included cranium and rib stays, suggesting that the shark had bitten its goal from the aspect. Most importantly, the stays had been recognized to a person species for the primary time – that species being Piscobalaena nana, a small baleen whale. Like within the different hint fossils, the chunk marks matched up properly to massive serrated enamel – an excellent case for accusing Megalodon of the assault (Fig. 3). It due to this fact appeared that Megalodon was additionally able to focusing on smaller whales (be it predation or scavenging), very a lot consistent with options that it seemingly additionally focused dolphins, sea turtles and different smaller prey [9].

Whereas predation methods are arduous to interpret from fossils, fashionable sharks could give us an concept of how Megalodon hunted. Its chunk power would’ve been exceptionally highly effective for damaging whale bones. A pc mannequin of a white shark cranium has proposed that it has a chunk power exceeding c. 1.8 tonnes, giving it one of many strongest chunk forces of any dwelling animal [10]. By extension, this examine suggests Megalodon’s chunk power was even bigger, estimating at a rare 108,514-182,201 N.

Scientists have additionally made makes an attempt at calculating Megalodon’s swimming velocity, which can assist give us a sign of the way it hunted. Sharks can have a burst velocity, which is a fast jolt of quick swimming, usually used for grabbing prey. However their typical velocity for his or her informal swims are what we name sustained swimming speeds. This varies between species, however one examine led by David Jacoby [11] mixed information on 26 species from 64 prior research to develop a mannequin that might predict a scaling relationship between sustained swim velocity and the shark’s metabolism and physique mass. Their mannequin incorporating metabolism revealed a scaling exponent of 0.173, summarised as the next equation:

Swim Pace (ms ¯¹) ∝ Mass (kg)^0.173

After they corrected the information for phylogeny, nevertheless, they discovered that minimal swim speeds scaled with physique mass on the barely decrease exponent of 0.15. The above equation moreover assumes a continuing of 1 to match the proportions however the information revealed that this fixed was really 0.266. They due to this fact constructed the facility equation:

Swim Pace (ms ¯¹) = 0.266 Mass (kg) ^0.15

From this, they can calculate the sustained swimming velocity of Megalodon relying on its mass. For instance, the ~48,000 kg Megalodon calculated because the mass of a 15.9 m shark in Gottfried’s work [12] would reveal a shark swimming constantly at 1.34 m/s – roughly 4.8 km/hr [11,13]. Making use of this to a 52,000 kg Megalodon reveals a sustained swim velocity of 1.36 m/s or 4.9 km/hr whereas if we went actually excessive and simulated a 100,000 kg shark, this mannequin would end in a swim velocity of 1.50 m/s or 5.4 km/hr. This mannequin has confirmed very efficient not simply in calculating Megalodon swim velocity, but additionally in offering a mannequin for a number of shark species (Fig. 4) [11].

Nevertheless, it’s the burst velocity that sharks use to shortly snatch their prey. White sharks utilise this for his or her “breaching behaviour” during which they propel themselves out of the water by speeding prey from beneath to catch them abruptly (Fig. 1) [14]. They will do that as a result of they’re properly camouflaged attributable to countershading. So, as a result of Megalodon was seemingly countershaded as properly, and had related ecology and physique construction to white sharks [15], this begs the query: was Megalodon able to breaching too?

Possibly. White shark burst velocity is powered by a physiological adaptation referred to as mesothermy [14]. That is one thing Megalodon has not too long ago been instructed to have had as properly (to be mentioned intimately in Q5). Mesothermic fishes typically have quicker sustained and burst swimming speeds than ectothermic fishes [16], and this has been used to counsel that Megalodon could have had a burst velocity of as much as 37.15 km/hr [17].

That extremely fast velocity for such a big shark might be sufficient to have the ability to breach. Past this, the basking shark (Cetorhinus maximus), right this moment’s second largest shark, has additionally been noticed breaching [18]. Maybe the enormous Megalodon was certainly able to leaping out of the water because it grabbed its newest meal. We simply don’t know but, however my private and (considerably) skilled opinion is that it could properly have been doable.

With such a broad menu to select from, Megalodon was an apex predator, with no recognized predators of its personal. This implies two vital issues. Firstly, it seemingly had stiff competitors for its prey, one thing which will have finally contributed to its extinction. Secondly, as an apex predator, Megalodon would’ve been of utmost significance to its ecosystem as it might’ve stored its prey populations in test and thus preserved a wholesome ecosystem.

Because of this sharks of right this moment are so vital to marine environments. The lack of an apex predatory shark produces irreversible cascading results that change the neighborhood it leaves behind [19]. As such, our marine ecosystems are the way in which they’re partially as a result of Megalodon is now not part of it. And the big whales of contemporary oceans can relaxation simple because of this.

References

1. Estrada JA, Rice AN, Natanson LJ & Skomal GB 2006. Use of isotopic evaluation of vertebrae in reconstructing ontogenetic feeding ecology in white sharks. Ecology 87, 829-834.
2. Pimiento C, Ehret DJ, MacFadden BJ & Hubbell G 2010. Historical nursery space for the extinct large shark Megalodon from the Miocene of Panama. PLoS One 5, e10552.
3. Pimiento C, González-Barba G, Ehret DJ, Hendy AJ, MacFadden BJ & Jaramillo C 2013. Sharks and rays (Chondrichthyes, Elasmobranchii) from the late Miocene Gatun formation of Panama. J. Paleontol. 87, 755-774.
4. Purdy RW 1996. Paleoecology of fossil white sharks. In: Nice White Sharks: the biology of Carcharodon carcharias (eds. Klimley AP & Ainley DG), 67-78, Educational Press, San Diego.
5. Aguilera OA, García L & Cozzuol MA 2008. Big-toothed white sharks and cetacean trophic interplay from the Pliocene Caribbean Paraguaná Formation. Paläontol. Z. 82, 204-208.
6. Fallows C, Gallagher A. & Hammerschlag N 2013. White sharks (Carcharodon carcharias) scavenging on whales and its potential function in additional shaping the ecology of an apex predator. PLoS One, 8, e60797.
7. Dudley SFJ, Anderson-Reade MD, Thompson GS & McMullen PB 2000. Concurrent scavenging of a whale carcass by nice white sharks, Carcharodon carcharias, and tiger sharks, Galeocerdo cuvier. Fish. Bull. 98, 646-649.
8. Kallal RJ, Godfrey SJ & Ortner DJ 2010. Bone reactions on a Pliocene cetacean rib point out short-term survival of predation occasion. Int. J. Osteoarchaeol. 22, 253–260.
9. Collareta A, Lambert O, Landini W, Di Celma C, Malinverno E, Varas-Malca R, Urbina M & Bianucci G 2017. Did the enormous extinct shark Carcharocles megalodon goal small prey? Chew marks on marine mammal stays from the late Miocene of Peru. Palaeogeogr. Palaeoclimatol. Palaeoecol. 469, 84-91.
10. Wroe S, Huber DR, Lowry M, McHenry C, Moreno Ok, Clausen P, Ferrara TL, Cunningham E, Dean MN & Summers AP 2008. Three‐dimensional laptop evaluation of white shark jaw mechanics: how arduous can an incredible white chunk? J. Zool. 276, 336-342.
11. Jacoby DM, Siriwat P, Freeman R & Carbone C 2015. Is the scaling of swim velocity in sharks pushed by metabolism? Biol. Lett. 11, 20150781.
12. Gottfried MD, Compagno LJV & Bowman SC 1996. Measurement and skeletal anatomy of the enormous “megatooth” shark Carcharodon megalodon. In: Nice White Sharks: the biology of Carcharodon carcharias (eds. Klimley AP & Ainley DG), 55–66, Educational Press, San Diego.
13. Jacoby DM, Siriwat P, Freeman R & Carbone C 2016. Correction to ‘Is the scaling of swim velocity in sharks pushed by metabolism?’ Biol. Lett. 12, 20160775.
14. Watanabe YY, Payne NL, Semmens JM, Fox A & Huveneers C 2019. Swimming methods and energetics of endothermic white sharks throughout foraging. J. Exp. Biol. 222, jeb185603.
15. Cooper JA, Pimiento C, Ferrón HG & Benton MJ (in press). Physique dimensions of the extinct large shark Otodus megalodon: A 2D reconstruction. Sci. Rep.
16. Watanabe YY, Goldman KJ, Caselle JE, Chapman DD & Papastamatiou YP 2015. Comparative analyses of animal-tracking information reveal ecological significance of endothermy in fishes. Proc. Nat. Acad. Sci. 112, 6104-6109.
17. Ferrón HG 2017. Regional endothermy as a set off for gigantism in some extinct macropredatory sharks. PLoS One, 12, e0185185.
18. Johnston EM, Halsey LG, Payne NL, Kock AA, Iosilevskii G, Whelan B & Houghton JD 2018. Latent energy of basking sharks revealed by distinctive breaching occasions. Biol. Lett. 14, 20180537.
19. Myers RA, Baum JK, Shepherd TD, Powers SP & Peterson CH 2007. Cascading results of the lack of apex predatory sharks from a coastal ocean. Science, 315, 1846-1850.

Edited by Rhys Charles