Bearzilla’s Diet

WordPress has a feature that lets me see how many daily views my blog articles get.  For several years my article entitled “Bearzilla: the Biggest Bear Ever” is almost always the single highest viewed article of the day. https://markgelbart.wordpress.com/2012/12/10/bearzilla-the-biggest-bear-in-history/  The subject of that popular blog entry is Arctotherium angustidens, an extinct South American species of bear that reached estimated weights of 3500 pounds–the largest size of any bear known to science.  In that blog entry I also discuss the largest specimens of extant species of bears and include a photo I ripped off from google images of a 2100 pound polar bear.  I suspect that photo is what draws so many views.  I came across a fairly recent research paper in the Journal of Paleontology about A. angustidens with enough information for me to write an addendum to my original article.

Image result for Arctotherium angustidens

Illustration showing the early Pleistocene giant short-faced bear that lived in South America. It later evolved into a smaller more herbivorous species.

Scientists studied the pathology, morphology, chemical signatures, and biomechanics of A. angustidens bones to determine what this species ate.  Missing, broken, and worn teeth were common.  The evidence of these dental problems suggests the bears were damaging their teeth when they clumsily gnawed on bones.  Some bear teeth even had bone splinters lodged in them.  An individual young female bear had a tooth infection caused by a bone splinter in its tooth, and this was the probable cause of death.  These giant bears had large teeth cheek similar to the extant giant panda (Ailuropoda melanoleuca), but pandas don’t exhibit tooth damage on their diet of bamboo.  The frequent occurrence of tooth damage in Arctotherium can only be explained by a diet high in bone consumption.

An analysis of stable isotope ratios in Arctotherium bones does suggest this species included lots of meat in its diet, but it also ate plant material.  The scientists conclude Arctotherium was an omnivore.

When large bears first colonized South America they competed with just a few large carnivores such as saber-tooth cats.  There was an abundance of large slow-moving prey the bears could wrestle down.  Eventually, more species of predators colonized the continent, and some prey species evolved into faster runners.  Other prey species–the large ground sloths for example–may have evolved into stronger adversaries as well.  Bears that consumed more plant material had a better chance of surviving than those that competed with predators or failed to obtain prey.  This may be why Arctotherium’s descendants  evolved to eat more plants than meat.

Reference:

Soibelizon, Leopoldo; et. al.

“South American Giant Short-Faced Bear (Arctotherium angustidens) Diet: Evidence from Pathology, Morphology, Stable Isotopes, and Biomechanics”

Journal of Paleontology 88 (6) 2014

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One Response to “Bearzilla’s Diet”

  1. ina puustinen-westerholm Says:

    Well then..how about..breaking down the..remnant population..of humankind..who are drawn to, in this ugly era of being revolted by science-anything..and see what causes all those of us who find..a joy, a comfort..in lifting edges, prying apart..what we think we know, and how we..addin..new informations..and see how..we..in the aggregate..came to be..Drawn..to innovative..viewpoints? What..across this globe..caused us..to be..unafraid, or..underafraid? We needs..MORE such!

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