Discovering Yakushima; A Most Successful Pilot Study (Part I)
With much of the world still shut due to the ongoing COVID-19 pandemic, just being able to set foot on the island of Yakushima already felt like a triumph.
Yakushima is famous for it's moss rich forests, home to giant Yakusugi cedar trees and many rare and endemic species of plants.
This plant life is sustained through up to 8 meters of annual rainfall on parts of the island, which also creates the beautiful rivers, streams and waterfalls that criss-cross the mountainous terrain.
After making it safely to our field site we began to tick off the first research action on our to-do list: locating a tanuki latrine. That was our goal - just one. We weren't sure how easy it would be to find a latrine - a communal pile of poo, one of the signature behaviours of this species - on the Seiburindo forest floor which was littered with.. well, forest litter. So it was with delighted shock that we confirmed our first latrine find a mere 2.5 hours into our first transect on our first day on the island. Followed by unbridled joy at the discovery of our second latrine, less than half an hour later.
The endemic subspecies of macaque and Sika deer found on the island are often seen grazing together. They kept a careful watch of our activities while we combed through the forest for latrines.
Little did we know at that moment, we would find 6 more just that day.
There's no mistaking a tanuki latrine - no other mammal on the island shares this communal deficating behaviour.
And in the end, that turned out to be just a fraction of what we would find. At the conclusion of our three weeks on Yakushima, we had identified 26 latrines, and collected ~50 fresh fecal samples for analysis.
What does one do with poo? - you might find yourself wondering. For our purposes, fresh feces are as good as currency. The Tanuki Project currently hopes to address 3 major elements of the tanuki invasion on Yakushima, namely:
1) tanuki population dynamics on Yakushima,
2) competition of tanuki with native species through diet, and
3) competition of tanuki with native species through parasite and disease transmission.
Yakushima is home to many endemic and rare species, including endemic Geothalphusa species of freshwater crabs. It is possible these are predated by tanuki. We have not yet identified the species of crab in the photo above. It was found near to a tanuki latrine site.
DNA from tanuki poo can shed some light on all of these aspects of our research. Our next steps are to extract DNA from our samples and analyze them using species specific primers looking for specific animals tanuki have eaten, like rare or endemic species, or species which are also important prey items for the other small carnivore species on the island; the endemic subspecies of Japanese weasel. We're also analyzing the feces for specific parasites that tanuki may have. Looking for poo wasn't the only thing on our agenda in Yakushima, read on to part II of the adventure.
Part II has some updates about our drone work on the island.