The California Channel Islands are famend for his or her archaeological, organic, and paleontological significance and richness, containing a few of the most essential early human websites in North America. This significance is simply rising with new excavation, chemical, and biomolecular methods, increasing our imaginative and prescient of this dynamic ecosystem and its enduring significance to people and wildlife alike.
Right now, a group of researchers from the College of Oklahoma, the Smithsonian Nationwide Museum of Pure Historical past, the College of Oregon, and others report the primary prevalence of the extinct large short-faced bear, Arctodus simus, from the California Channel Islands. This fearsome beast — weighing by some estimates 2,000 lbs. — as soon as roamed various environments from Alaska to Mexico, however has by no means been present in such an remoted island context. Whereas this isn’t the primary unusual mammal to be discovered on the California Channel Islands, which was as soon as dwelling to a pygmy mammoth and a large mouse, it’s the first case of a probably native megafaunal carnivore, which might problem earlier fashions of colonization and evolution of the islands’s biodiversity.
This little bone, excavated in 1996, was lengthy assumed to be from a seal, however specialists recommended that it was from a bear — the primary and solely bear ever recorded for California’s Channel Islands.
“Present in a stratum dated to over 13,000 years in the past, the bone posed a big thriller,” stated Jon Erlandson, a College of Oregon professor who has directed investigations at Daisy Cave for the reason that 1990s. Was it from a big grizzly or black bear? The specimen rested safely in Erlandson’s lab for greater than 20 years.
In 2016, the toe bone arrived on the Laboratories of Molecular Anthropology & Microbiome Analysis on the College of Oklahoma.
“From the second I heard this might be a singular specimen, I dealt with it with further care. I bear in mind having a tough time slicing the bone piece out; it was such a inflexible, morphologically well-preserved pattern, because of the cave’s surroundings. Fortunately, its DNA was well-preserved, too,” stated Nihan Dagtas, who efficiently extracted amplifiable DNA on the world-class clear room facility of LMAMR.
In parallel, the specimen was analyzed for historic bone proteins (collagen) on the College of Manchester within the UK, producing chemical fingerprints that almost all carefully matched a reference of the spectacled bear from South America — the one residing relative of the short-faced bear. These two impartial molecular analyses, mixed with conventional morphological proof of the form and measurement of the toe, confirmed its identification as belonging, unexpectedly, to a large short-faced bear.
Torben Rick, who participated within the Daisy Cave excavations and is now on the Smithsonian’s Nationwide Museum of Pure Historical past, was excited to use a set of recent, minimally damaging applied sciences (aDNA, proteomics, and many others.) to assist resolve the questions surrounding this mysterious bone. “When the outcomes got here again that this was a short-faced bear dated to roughly 17,000 years in the past, we had been all actually intrigued in regards to the implications for island biogeography and ecology,” stated Rick.
Researchers had been puzzled at first — what was a large short-faced bear doing so distant from its identified vary on the California mainland? They developed a set of hypotheses to check whether or not it arrived on the island earlier than or after demise, and weighed the proof.
If the bear died on the island, it would indicate that a native inhabitants of short-faced bears swam to the islands and developed over hundreds of years alongside the pygmy mammoths. Or did a single particular person swim to the island searching for a snack? The researchers recommend that a “pre mortem” arrival of the toe was unlikely, as it’s the solely specimen from the species ever discovered on the islands, and bears that die in caves are often discovered intact.
Then, researchers turned to a “publish mortem” speculation: the toe was dropped at the island by one thing or somebody. “A human transport of the toe bone appears unlikely given its age and glorious preservation, however quite a few animals — condors, eagles, seagulls, and others — are identified to scavenge and transport bones and shells in coastal areas,” Erlandson stated.
The analysis group means that the almost definitely mode of transport was by wing. Chemical analyses generally known as secure isotopes point out that this bear was feeding opportunistically on marine mammal carcasses, maybe placing it on the proper time and proper place for its personal carcass to ultimately be scavenged by a hen, comparable to a California Condor or bald eagle.
“We had been in a position to combine interdisciplinary toolkits, together with morphology, historic DNA, collagen fingerprinting, radiocarbon courting and secure isotopes, to develop a strong speculation testing framework permitting us to discover the origins of this mysterious bone,” stated Courtney Hofman, assistant professor of anthropology on the College of Oklahoma, co-director of LMAMR, and senior writer of the research.
Regardless of as soon as being so widespread, there’s important debate over the ecology and habits of short-faced bears, and out there information are sparse. Earlier research counting on tooth form and cavities recommended that short-faced bears from Los Angeles’ famed La Brea Tar Pits ate massive quantities of carbohydrates, whereas different research utilizing secure isotopes recommended the species relied on animal protein in Alaska and Canada. Surprisingly, this toe was the primary specimen to check dietary hypotheses in the identical means in California.
“This little toe helped us lay the groundwork for addressing some large questions in paleontology,” notes Alexis Mychajliw, a postdoctoral analysis affiliate on the College of Oklahoma, analysis affiliate on the La Brea Tar Pits, and lead writer of the research. “Southern California was full of massive carnivores 17,000 years in the past, and it’s doable that the opportunistic use of marine sources helped short-faced bears survive some powerful competitors. That’s, till climates modified, and people arrived.”
Reference: “Biogeographic problem-solving reveals the Late Pleistocene translocation of a short-faced bear to the California Channel Islands” 16 September 2020, Scientific Reviews.