The history of prehistoric predators did not end with the extinction of the dinosaurs, where the Tyrannosaurus rex was one of the most formidable of these. The mass extinction which marked the end of the Cretaceous (145 million years to 66 million years BCE) certainly saw the disappearance of many giants, but others appeared much later.
During the Pleistocene or Ice Age (2.6 million years ago to approximately 11,000 years BC), a giant reigned supreme over the vast expanses of North America. The Short Faced Bear, Arctodus simus, the largest carnivore the continent has ever knowndominated with its colossal stature of 3.5 meters an ecosystem populated by predators, also very ferocious.
Anatomical supremacy in a world of titans
The Pleistocene constituted a theater of rare intensity for large predators, and for megafauna in general. In this natural arena where short-faced bears and ice age coyotes clashed (Canis latrans orcutti), American cheetahs (Miracinonyx), dire wolves (Canis dirus), saber-toothed tigers (Smilodon fatalis Or Smilodon populator) and American lions (Panthera atrox), daily survival was a precarious balance.
Arctodus simus anatomically surpassed all his contemporaries ; Standing majestically at 3.5 meters in height, this predator displayed phenomenal muscle mass, supported by a particularly robust frame. It was not uncommon for males to weigh more than a ton, making them the largest predator of the Pleistocene.
The anatomical comparison with contemporary ursids would almost make them look like teddy bears : its skull greatly exceeded the already impressive dimensions of that of the current grizzly bear (Ursus arctos horribilis), yet capable of crushing the strongest bones of its prey.
Its forelimbs, equipped with hypertrophied musculature, gave it a devastating strike force. Its teeth were a weapon in themselves, an alliance between grinding molars and piercing canines. The structure of its cervical vertebrae, particularly developed, suggests an ability to manipulate massive prey with surprising dexterity for an animal of this size.
This anatomical magnificence contrasts singularly with its only current descendant, the spectacled bear (Tremarctos ornatus). This modest heir of a once dominant lineage, confined to the South American forests, retains only a pale reminiscence of the attributes of his imposing ancestor.
A remarkable dietary adaptation
According to this research from 2017 published in Scientific Reportsthe short-faced bear didn’t just live as a predator. In the Pacific Northwest, the species exhibited pronounced hypercarnivory, while populations in southern California adopted an omnivorous diet similar to that of modern-day grizzly bears. This dietary variability can be seen in particular in the dental traces of specimens discovered in the Los Angeles basin, where the presence of cavities could be explained by a significant consumption of fruits and foods rich in starch.
How can these differences be explained? Arctodus simus actually occupied a very vast territory: fossils have been found in many American states, ranging from Alaska to Mexico. This considerable geographical distribution necessarily implied adaptation to local resources. Some specialists also put forward the hypothesis of scavenging behavior facilitated by a stature making it possible to oust other predators from the coveted carcasses.
The twilight of a dynasty
Of course, all these large mammals which included Arctodus simus have now disappeared. Emily L. Lindsey, assistant curator of the La Brea Tar Pits, a Pleistocene fossil bed in Los Angeles, points out the extent of this extinctioncalled the Quaternary extinction. “ The last thirteen millennia have seen the majority of the continent’s large mammals disappear, marking the most massive episode of extinction since the disappearance of the dinosaurs.“explains the scientist.
All Pleiostocene megafauna washed away : giant sloths, mammoths, mastodons, giant beavers, camels and giant armadillos disappeared over a long period, but intensified around 50,000 to 10,000 years ago. The Short-Faced Bear, for its part, disappeared around 11,000 years ago.
The causes of this mass extinction still remain subject to debate. The end of the Pleistocene coincides with significant climatic upheavals – melting ice and warming of the atmosphere – but also with the arrival of the first humans on the continent, around 15,000 years ago.
The Quaternary extinction is a complex and multifactorial phenomenon, where many variables could have intervened. Anthropogenic pressure through hunting, rapid and significant climate fluctuations, changes in ecosystems, potential role of diseases brought by the human species, etc. Only future research will allow us to better understand the mechanisms that led to this massive disappearance and to refine our prediction models for current extinctions. Arctodus simus will remain, in any case, one of the most colossal animals that our planet has ever carried.
- Arctodus simusa giant of the Pleistocene, dominated North America with its stature of 3.5 meters and its 1,000 kg.
- A versatile predator, it adapted its diet according to local resources.
- The Quaternary mass extinction, due to climatic and human factors, marked the end of this exceptional predator 11,000 years ago.
