Paddington’s dangerous cousin

Arctodus simus by Sergiodlarosa via Wikimedia Commons

Arctodus simus by Sergiodlarosa via Wikimedia Commons

North and South America were the last continents to be conquered by humans. We have been in Africa since we first evolved, Europe and Asia for over a million years, in Australia for about 60,000 years, but in the Americas for only about 15,000. Considering that reaching Australia required a treacherous ocean voyage but you could walk to Alaska without getting your feet wet via the flat, treeless, mammoth steppe of Beringia (with plenty of game to hunt en-route), why did it take people so long to reach the promised land? Some researchers have suggested that perhaps people did reach Beringia much earlier, but what they met there prevented them from penetrating any further. Along with the mammoths, cave lions, bison, and horses, Beringia had something else. Something that would have been completely unfamiliar to the humans who encountered it. Something seemingly crafted from our deepest, darkest nightmares. Arctodus simus: the giant short-faced bear may have been the most terrifying land carnivore our species ever encountered.

Today, the polar bear (Ursus maritimus) is the largest land carnivore but 12,000 years ago that title went to a member of the subfamily of bears known as the Tremarctinae. We still have one member of this unique subfamily left; the spectacled bear (Tremarctos ornatus). The only bear found in South America (including deepest, darkest Peru), this predominantly vegetarian teddy is technically the largest carnivore left on that continent, despite being a relatively puny 100-200kg. A sister species, the Florida cave bear (Tremarctos floridanus), also roamed Pleistocene North America. However, their close relative, the giant short-faced bears (genera Arctodus and Arctotherium/ Pararctotherium) were absolutely colossal beasts. Arctotherium/Pararctotherium (opinion is divided on how valid these generic distinctions are) has been found all over South America, even down into southern Patagonia. Arctodus simus has been found at sites all over North America, from Alaska and the Yukon Territory down to Florida and Texas. Whilst we have a mitochondrial genome from Arctodus and know it diverged from the spectacled bear during the late Miocene/early Pliocene, it is not known exactly how closely related Arctodus and Arctotherium/Pararctotherium are to each other. Ancient DNA work is happening right now that should give a handle on the complicated phylogenetics of these bears.

The relatively cuddly spectacled bear (Tremarctos ornatus)

The relatively cuddly spectacled bear (Tremarctos ornatus)

Arctodus simus was an 800kg monster. To give some impression of its size: while on all fours this bear could gaze directly into my eyes (I’m 6’2”). Standing on its hind legs an average bear could reach 12-feet (in fact, the site of Riverbluff cave in Missouri has claw marks 15 feet up on some side walls that were probably produced by a large Arctodus). Another site with Arctodus is Big Bear cave in the Ozark mountains. The articulated skeleton found there is impressive for the amount of information it left about short-faced bear biology. The animal, like many other cave finds, was a small female, which cumulatively suggest that Arctodus females denned (perhaps surprisingly, only one fossil Arctodus baculum has ever been recovered). The Ozark skeleton is also unique in the preservation of fossilised hair at the site.

What natural forces could possibly have conspired to produce a carnivore of such enormous dimensions? Most researchers think that the specialisations present in Arctodus (i.e. long legs, large size, short jaws), are adaptations to a life of extreme hypercarnivory. Long legs allow for efficient movement over a wide home range, necessary to locate carcasses, large size can act as an effective deterrent to other carnivores to scare them off a kill site (kleptoparasitism), and short jaws give extra bone crushing power. It seems that this hypothesis is backed up by good data. Stable isotope analysis of Arctodus remains show elevated ∂15 Nitrogen values- this indicates that Arctodus was consuming a very meaty diet, perhaps with a large component of caribou (Rangifer tarandus). However, as with most things in science, different researchers think that the opposite is true and have concluded that the morphology of short-faced bears indicate a life of herbivory with some omnivory. My money is still on Arctodus simus being one of the biggest and baddest animals ever to have lived.

How badass was it? Well, a very interesting pattern cropped up when palaeontologists were looking at late Pleistocene radiocarbon dates from eastern Beringia. They found that during time periods when Arctodus simus was present (i.e. 20,000-45,000 14C years BP) there is a noticeable lack of other predators (lions, scimitar cats, brown bears). Either the environment was selectively excluding everything but short-faced bears during this time period, or perhaps more likely, Arctodus simus was such an efficient predator/scavenger that there was simply not enough prey biomass left for other carnivores to get a look in. If this was the case, it is perhaps no surprise that human presence in eastern Beringia is only known from after Arctodus’ extinction. Maybe one day we will find an Arctodus coprolite with some evidence of the pre-pre-Clovis pioneers!

Written by Ross Barnett (@DeepFriedDNA)

Further Reading:

Barnes, I., P. Matheus, B. Shapiro, D. Jensen, and A. Cooper. “Dynamics of Pleistocene Population Extinctions in Beringian Brown Bears.” Science 295, no. 5563 (Mar 22 2002): 2267-70. [Full Text]

Christiansen, P. “What Size Were Arctodus Simus and Ursus Spelaeus (Carnivora: Ursidae)?”. Ann. Zool. Fennici 36 (1999): 93-102.[Full Text]

Figueirido, B., J. A. Perez-Claros, V. Torregrosa, A. Martin-Serra, and P. Palmqvist. “Demythologizing Arctodus Simus, the ‘Short-Faced’ Long-Legged and Predaceous Bear That Never Was.” Journal of Vertebrate Paleontology 30, no. 1 (2010): 262-75.[Full Text]

Fox-Dobbs, K., J. A. Leonard, and P.L. Koch. “Pleistocene Megafauna from Eastern Beringia: Paleoecological and Paleoenvironmental Interpretations of Stable Carbon and Nitrogen Isotope and Radiocarbon Records.” Palaeogeography, Palaeoclimatology, Palaeoecology 261 (2008): 30-46.[Full Text]

Krause, J., T. Unger, A. Nocon, A. Malaspinas, S. Kolokotronis, M. Stiller, L. Soibelzon, et al. “Mitochondrial Genomes Reveal an Explosive Radiation of Extinct and Extant Bears near the Miocene-Pliocene Boundary.” BMC Evolutionary Biology 8 (2009): 220.[Full Text]

Matheus, P. “Diet and Co-Ecology of Pleistocene Short-Faced Bears and Brown Bears in Eastern Beringia.” Quaternary International 44 (1995): 447-53.[Abstract]

Prevosti, F. J., L. H. Soibelzon, A. Prieto, M. San Roman, and F. Morello. “The Southernmost Bear: Pararctotherium (Carnivora, Ursidae, Tremarctinae) in the Latest Pleistocene of Southern Patagonia, Chile.” [In English]. Journal of Vertebrate Paleontology 23, no. 3 (SEP 12 2003): 709-12.[Abstract]

Schubert, B. W., and J. E. Kaufmann. “A Partial Short-Faced Bear Skeleton from an Ozark Cave with Comments on the Paleobiology of the Species.” Journal of Cave and Karst Studies 65, no. 2 (2003): 101-10.[Full Text]

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102 Responses to Paddington’s dangerous cousin

  1. Don’t shoot me down for asking what probably appears obvious to you, but what do you think brought about the demise of Arctodus Simus?

  2. katherinejlegry says:

    With climate change and the ice melt, within the last decade and now more than ever, polar bears in Alaska are encountering brown bears… there is speculation that the brown bears will win the food fight as they are better acclimated to the warming temperatures. Polar bears are up next for extinction… 😦

  3. But Paddington looks so snuggly. Congrats on being Freshly Pressed.

  4. Pollock of Light says:

    Reblogged this on Pollock of Light.

  5. Anna says:

    This is such a wonderful article, and I’m chuffed for a science-related topic to have reached the front page. Also I am still reeling from the response to ‘How badass was it?’… that sounds like one badass Pudsey!

  6. cg says:

    Interesting. I lived in the Ozarks for several years

  7. cg says:

    Yet, the Polar Bears are not declining. Global Warming is a hoax. A Ponzi Scheme. Look up Lord Christopher Monckton about this.

  8. molvi0849 says:

    Animals are the beauty of our earth. They should be dealt mercifully.

  9. Quite an impressive beast. With their nutritional requirements and the relative scarcity of food in polar regions, they would have had to roam quite a range, which means small human populations should have been able to slip through. And even with its impressive physique, it wouldn’t be able to survive ten thrusts with flint tipped spears, which a group of four hunters could quickly deliver. There must have been other adverse conditions that kept humans at bay for so long.

  10. SouthernSunshine says:

    Kool article! “Badass” ❤️ it!

  11. SouthernSunshine says:

    Reblogged this on SimplySouthern.

  12. Willowwisp says:

    The title 😂

  13. iostwostep says:

    Interesting 2015-01-13 12:01:51 +0000

  14. Really fascinating and informative piece! Thank you for sharing it! 🙂

  15. Congratulations making freshly pressed not easy to do!

  16. thekikijones says:

    Very interesting!

  17. awax1217 says:

    I wonder if this is the creature mistaken for Big Foot. In the mist or the fog of the mind it could be thought to be.

  18. Gabriel Goonewardene says:

    Reblogged this on The Foolish Savant and commented:
    My love for nature and animals is no secret but to this day I find It insane as to how many different life forms there have been throughout history and how they’ve changed as whole species in order to adapt to the world.

    The fight for survival and change in environments triggers what is plausibly the greatest gift any creature on the planet has, the ability to evolve. I’m not talking about that instant (yet highly gratifying) evolution us gamers have experienced over years playing pokemon but the slow, purposeful and sometime mistaken process that is evolution.

    With all that being said, why is it that for such evolved beings, we humans have allowed ourselves to be stuck in the same tribal mentality of our ancient ancestors? Why is it that instead of truly evolving we’ve decided to stagnate into a species that allows it’s majority to suffer while it’s minority reap the benefits?

    Existential queries to the side. That is one big bear and it’s almost too bad that other animals of such size don’t exist anymore. Not that I’d want to be dodging the tree trunk legs of an apatasaur on my way to work in the mornings.

    Either way this is food for thaught. The effect of a species of carnivore has on the explorational impulses of the worlds most intelligent apes and why said apes continue to evolve in a way that leaves much by the wayside.

    Oh well, maybe in a few millenia we’ll have dragons and if that’s the case I might have to get me some of that cryogenic freezing.

  19. mustaphabarki2014 says:

    Reblogged this on Engineering WordPress 2015 and commented:
    Join on tsū, they are sharing social revenues with all o me f us #tsunation

  20. toddfisk says:

    Polar bears may soon be eaten by enraged starving walruses.

  21. thank you for the additional readings that you provided. big help

  22. Looks like you are an animal researcher. Very informative blog on animals, not sure I could understand everything though.

  23. DiyDaisy says:

    Youre freshly pressed!😃

  24. mindocr says:

    Reblogged this on Mindocr’s Weblog.

  25. Simon says:

    If these species was so successful that other predators including humans couldn’t get a piece of the meat pie I wonder what kept them from spreading towards east? I mean, there may easily have existed reasons why this didn’t happen, I just wonder if anybody who knows more about it than I do wonders too. 🙂

  26. Simon says:

    towards west, I mean, not east – into Asia and on to Europe, wherever

  27. kmarysmith says:

    Thank you for recreating lost worlds and their inhabitants. My imagination loves your posts!

  28. Pingback: Space, Poetry, the Pleistocene, and Food: Blogs I Like

  29. Therese Lu says:

    Great read! Thanks for sharing.

  30. nicktitmus says:

    Interesting! Any comparable e xamples of an efficient predator acting as a barrier to migration?

  31. Reblogged this on and commented:
    i love geo wild and this reminds me of it

  32. molvi0849 says:

    It’s a wonderful post.Thanks for sharing.

  33. mcbarlow5 says:

    Paddington on steroids!

  34. it is dangerous animal

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