Present-day Japan may see its fair share of bears, but the islands’ big cat populations are long gone. Between 129,000 and 11,700 years ago, temporary land bridges allowed the ancient predators to migrate between mainland Asia and the islands. Paleobiologists have long believed tigers were the primary cats to make this trek, but recently analyzed evidence published in the Proceedings of the National Academy of Sciences suggests a different timeline.
“Our findings challenge the prevailing view that tigers once took refuge in Japan and that cave lion distribution was limited to the Russian Far East and northeast China,” explained the study’s authors. “These findings provide evidence that lions, rather than tigers, colonized the Japanese archipelago during the Late Pleistocene.”
The earliest big cats got their start in Africa around 6.4 million years ago, but it would take another 5.4 million years for the first lions to travel into northern Eurasia. While their tiger cousins largely migrated toward Eurasia’s southern regions, the predators still occasionally crossed paths in the “lion–tiger transition belt,” an area spanning portions of the Middle East through Central Asia into eastern Russia where the two intermingled.
Amid these Late Pleistocene migrations, Earth also experienced glacial periods that lowered sea levels and revealed land bridges linking Asia’s lion–tiger transition belt to the Japanese archipelago. Fossil records suggest that many tigers took advantage of these pathways, but they are not without some instances of mistaken identity. According to the study’s authors, researchers previously catalogued these big cat fossil discoveries based on morphological evidence instead of more reliable DNA data.
To double-check these past conclusions, the team reexamined a set of fossil specimens using genetic sequencing and radiocarbon dating. Although many examples are now in poor condition, five yielded enough information to facilitate lineage profiling. In each case, the “tiger” in question instead possessed molecular information aligning with a now extinct species of cave lion (Panthera spelaea). Even more striking, the team didn’t find any tiger evidence in Japan from the Late Pleistocene.
Radiocarbon analysis of one specimen indicates that it lived around 31,060 years ago, but researchers believe the first cave lions possibly arrived as far back as 72,700 years ago. It now appears the big cats also thrived on the islands for at least 20,000 years after their species went extinct in Eurasia. Researchers believe the reason for their prolonged survival is what brought them to the archipelago in the first place—the land bridges.
“This extended survival of cave lions may reflect Japan’s unique paleogeographic history,” they wrote, adding that “This finding extends the known range of cave lions in East Asia and refines our understanding of how far south the lion–tiger transition belt shifted during this period.”
