Never before have a I felt more like Sherlock Holmes trying to solve a who-dunnit mystery than when I arrived on Inakahama Beach at the start of August, peering at the pawprints seemingly in every direction along the beach.
Was it cats? The size was about right for some feral felines, and Yakushima does have a population of stray cats on the island. But squinting into the sand at fresher prints yielded the faint impression of claws at the tops of the paw pads, indicating they are canine prints (cats retract their claws while they walk, leaving no trace of clawmarks in their prints).
Was it an invasion of terriers accompanying their owners on walks on the beach? Half of the beach had been sectioned off from human movement, and while it's possible domestic dogs could have wandered en-masse away from their owners to invade these carefully sectioned off areas, I found is suspicious how all of the prints were nearly of identical size. There's a certain feeling I get when I feel like the evidence is leading me somewhere more meaningful - the thrill of the chase. Trying to untangle the mass of prints on the beach and follow individuals to their preferred entry points, I felt like I was on to something here... I spent some long evenings sitting quietly on the beach, squinting into the dark, trying to catch a glimpse of movement on the beach which would confirm the species leaving behind the footprints on the beach - with no luck. Were they coming to the beach still?
After a few unsuccessful sleuthing attempts, a fellow researcher kindly suggested "the oldest trick in the book" - wipe the foot prints off from a heavily trafficked section of beach, and see if they reappear. Armed with a piece of bamboo, I set about clearing a section of beach heavy with little pawprints.
...Only to find them all reappear the next morning!
I had found a heavily trafficked entry point - and so I set up my camera traps, and waited...
... but not for long! The following days confirmed my suspicions, and the suspicions of the locals in Nagata. Inakahama beach has a tanuki problem.
And the impact of this problem is more significant than simply leaving prints on the sandy beach. One of the reasons tanuki may be attracted to this special beach could be its abundant food source - it is the largest remaining nesting ground for endangered loggerhead turtles (Caretta caretta) in the Northern Hemisphere. Endangered Green Sea Turtles (Chelonia mydas) also nest here. And while the main nesting area is roped off to prevent human interference, tanuki are able to access the area freely. Locals informed us that they frequently see tanuki on the beach, and footage allegedly taken on Inakahama beach shows tanuki eating emerging sea turtles. Nagata has a dedicated team of volunteers who monitor nests on the beach, and they have confirmed that they regularly see tanuki in the area. Members from the volunteer group even took me to see predated nests in the area - neatly dug up nests with 50, 60, 70 eggs completely consumed - and those same paw prints leading to and from the gaping holes left behind in the sand.
The number of turtles returning to the beach to nest in recent years has suffered a decline, likely due to pollutants in the water column, and accidental capture of adult turtles in fishing nets as bycatch. Protecting nesting sites of turtles to protect their population is imperative for their continued existence.
How many tanuki come to this beach to feed, and how many turtles they consume, is presently unknown, but is a question our team is hoping to begin to address in our effort to understand the impacts of tanuki on the island. Follow our project updates as we continue to seek evidence to better understand the invasive tanuki on the island and their effects on the island species through their population dynamics, predation, and parasites.