Posts Tagged ‘Catalina Islands’

The Giant Short-Faced Bear (Arctodus simus) Ate Seals

September 21, 2020

Scientists excavated the foot bone of a giant short faced bear from Daisy Cave on San Miguel Island 30 years ago, but the most modern scientific techniques were not used to analyze the specimen until recently.  The giant short-faced bear was a large bruin, weighing up to 2000 pounds, that ranged across North America from Alaska to Florida until it went extinct about 11,000 years ago.  It was closely related to the extant spectacled bear (Tremarctos ornatus) and the extinct Florida spectacled bear (T. floridanus).  The latter species was apparently more common than the giant short-faced bear in southeastern North America, but specimens of Arctodus have been found in Florida, eastern Alabama, and Virginia.  New studies of Arctodus have dispelled long-held erroneous misconceptions about it.  It was not hyper-carnivorous and was more of an omnivore like most extant species of bears.  Its legs were not unusually long as wrongly depicted in most illustrations, and its face was not that short.

Typical erroneous illustration of Arctodus simus.  It was very large, but its legs were not unusually long nor was its face unusually short.

figure2

The foot bone discussed on this blog entry.  Image from the below reference.

San Miguel Island is 1 of the Catalina Islands located off the coast of California.  The Arctodus specimen found in Daisy Cave is unusual because not many species of extant and extinct mammals occurred on the Catalina Islands.  Scientists are aware of just 10 species, including the extinct pygmy mammoth (Mammuthus exilis).  Today, Daisy Cave is located adjacent to the ocean, but 17,000 years ago (the age of this specimen) it was located well inland because sea levels were much lower during the Ice Age.  Arctodus specimens are known from 9 sites in California, but this is the only 1 known from the Catalina Islands.  The authors of the below referenced study propose 4 possible scenarios explaining the presence of this specimen here: a) it came from an individual that belonged to a population of Arctodus that colonized the island, b) it was an individual straggler than swam to the island, c) the bone was carried to the island by people, or d) a bird of prey such as a terratorn, condor, or eagle carried the bone to a nest on the cave.  No other bones of Arctodus have ever been found on the island, while dozens of pygmy mammoth bones have, suggesting it probably didn’t come from a population of Arctodus that lived on the island.  The date of the specimen pre-dates the known occurrence of man in the region by about 4,000 years, though there’s ephemeral evidence of people in the region earlier.  The authors of the study favor scenario d, but I doubt a bird would carry an heavy foot bone of a bear that far from the mainland.  I favor scenario b. During the Ice Age San Miguel Island was just a 5 mile swim from the mainland–not too strenuous for a strong healthy bear.

Scientists identified the foot bone using morphology and genetics.  It compared favorably to known specimens of Arctodus foot bones.  Though grizzly bears (Ursus arctos) can have similar size dimensions in their foot bones, they are not known to have occurred in California prior to 5200 years ago (the date of the oldest known grizzly bear specimen from within the state.)  An analysis of the genetics determined the bone belonged to a bear more closely related to the spectacled bear than any bear in the Ursid genus.

Scientists also analyzed the bone chemistry of the specimen to determine its diet.  Based on the chemical ratios, they estimate seals made up 16%-22% of this individual’s diet, while bison and/or camel made up the balance.  (I’m skeptical of these studies.  See: https://markgelbart.wordpress.com/2016/06/24/trust-the-coprolites-not-the-stable-isotope-analysis/ )  The authors of this paper assume the bear scavenged dead seals, but I’m sure a 2000 pound bear is quite capable of subduing a live seal.  Arctodus likely ate whatever it came across and could catch.

Video of a polar bear killing a walrus.  I’m sure a giant short-faced bear could easily kill a seal and would not necessarily rely on scavenging to obtain seal meat.

Reference:

Mychajliw, A. et. al.

“Biogeographic Problem-Solving Reveals the Late Pleistocene Translocation of Short-Faced Bear to the California Channel Islands”

Scientific Reports 10 2020