Amami Oshima is a Japanese island in the Ryukyu archipelago and lies roughly between Kyushu and Okinawa. It’s known for its endemic species, including the Amami rabbit. The Amami rabbit is one of the hardest rabbits to spot in the world. It’s nocturnal, dark-furred, and keen on dense forest growth for grazing, which makes it difficult to see, but it’s also rare, endemic to two islands, Amami-Oshima and Tokunoshima. Now research by Kenji Suetsugu and Hiromu Hashiwaki has found another interesting feature. Their paper in Ecology shows that they disperse vampire plants.

Plants that look like red bobbly fungi on the left. On the right, the caps are eaten showing a hollow interior.
Balanophora yuwanensis plants (left: intact individuals, right: individuals with feeding marks from the Amami rabbit). Each round mass looks like a single fruit, However, each cluster is composed of several thousand fruits, each measuring approximately 0.3 mm in size. Upon closer examination, the clusters can be seen to be composed of numerous red bumps These bumps are not the fruits, but modified leaves that that hide the actual fruits underneath. Photo by Yohei Tashiro

The plant is Balanophora yuwanensis, which may be a subspecies or sister species of Balanophora yakushimenis. It’s an odd-looking plant that looks a bit like a mushroom, and might be proof of the saying, ‘you are what you eat’. This is because Balanophora yuwanensis doesn’t make its own food through leaves. Instead, it taps into local fungi and deprives them of food, water and nutrients.

While fungi cater for most of its needs, Balanophora yuwanensis has a problem when it comes to dispersing its seeds. It produces lots and lots of tiny, one-seeded fruits in collections called infructescences. Typically, you’d expect small dry seeds to be carried away on the breeze, but you don’t get a lot of that in the undergrowth where Balanophora yuwanensis lives. What you do get are odd bite marks on the infructescences. And you get rabbits.

As far as anyone can tell, Pentalagus furnessi, the Amami rabbit, is an unusual rabbit. Not much is known about it, as it’s hard to find. It lives forages in the undergrowth of two islands in the Ryukyu archipelago, and it does this at night. To make it more difficult, they are all dark-furred. So ecologists are left looking for a few black rabbits, hiding in shadows at night.

What they do know is that they’re almost living fossils. Amami rabbits are the remains of a lineage of rabbits that have since died out on mainland Asia. They survived on islands like Amami Oshima as they were isolated from changes elsewhere.

Suetsugu and Hashiwaki set up camera traps in the undergrowth to see if they could catch a rabbit damaging the Balanophora yuwanensis infructescences. They found both birds and mammals feeding on the fruits, and also got this clip of one of the nocturnal visitors.