The Japanese sea lion, locally known as the Nihon ashika, disappeared sometime around 1974 at the latest. It was thought to simply be a subspecies of the California sea lion, but genetic mapping in 2003 led scientists to realize that we had lost another species completely. Just like the passenger pigeon, the ashika wasn't studied while it was alive. Find out what we do know about it in this episode.
If there are any papers that you would like to read but do not have access to, I highly recommend using sci-hub.tw as a way to view them. Science should be accessible, and the woman who runs that site is doing great work.
The Early History of the Fur Seals: The Beasts of the Sea by George William Steller in 1899
Yamamura 1998: https://www.jstor.org/stable/40316472?seq=1
Heath and Perrin 2009: https://sci-hub.tw/10.1016/B978-0-12-373553-9.00046-8
Blaricom et al 2013: https://sci-hub.tw/https://doi.org/10.1016/B978-0-12-384719-5.00187-8
Shoda et al 2017: http://eprints.whiterose.ac.uk/118721/1/Shoda_et_al_2017_PURE.pdf
The Sannai Maruyama Site:
Alaskan use of sea lions: http://www.adfg.alaska.gov/index.cfm?adfg=wildlifenews.view_article&articles_id=325
Cover photo via Wikimedia Commons/Naturalis Biodiversity Center