Japanese animal diversity

Even though the main focus of the QuakeRecNankai project is directed towards finding geological evidence of past earthquakes and tsunami, fieldwork showed us that there is much more to see! This short overview of some of our flying, swimming, crawling and creeping companions proves so.

When crossing the waters of Lake Hamana, cormorants (Phalacrocoracidae) greeted us more than once. Cormorants are fish-eaters, diving into the water from the surface. After fishing they often go ashore to dry their plumage by spreading and flapping their wings in the sun.

Japanese cormorants at Lake Hamana, sitting (left) and drying their feather pack (right) on poles that mark the main pathway for boats in the lake.

Not only cormorants, but herons (Ardeidae) as well crossed our path several times on and around Lake Hamana, providing some beautiful and sometimes even dramatic images.

Herons, motionless (left) and in full flight (right).

While taking samples from a marshy environment along the coast of Lake Hamana, a group of sandpipers (Scolopacidae) kept us company. These brown-grey shorebirds eat small invertebrates picked out of the mud or soil using their elongated beaks.

Group of sandpipers, feeding themselves on small invertebrates that are living in the coastal mud.

One of the most surprising encounters with Japanese fauna, was the one with the ‘jumping fish’ in Lake Hamana. The jumping ability of silver carps (Hypophthalmichthys molitrix) combined with their attribute of being scared easily by boat engines, causes them to leap high into the air. Moreover, observations and laboratory experiments in the past have shown that carps are extremely sensitive to impending earthquakes, picking up on minor temblors up to weeks before the main shock. For example, before the magnitude 7.6 earthquake struck Taiwan in 1999, carps were reported to batter themselves to death by repeatedly colliding their heads against the walls of their pond (Earthquake Precursors by Motoji Ikeya, http://www.eqsigns.net/aquatic_animals.html).

Jumping Asian carp, splendidly captured by Svenja... during one of many attempts (left). Shoal of carps in a park pond in Tsukuba, framed by autumnal coloured tree leaves (right).

In the category of insects, the praying mantis (Mantidae) and Japanese hornet (Vespidae) played a memorable role. Several hornets came to visit us in our office rather unexpectedly, causing some commotion among the Japanese collaborators, who were well aware of the wasps’ highly painful stings. 

Praying mantis, enjoying a walk on our survey vessel on Lake Sai (Fuji area).

Defeated (left) and still living (right) hornet in our office in the fisheries lab near Lake Hamana. A 50 yen coin serves as scale.

After being slightly alarmed by the ‘unfriendly’ appearance of the Nephila clavata or Jorō spider, we became used to its (omni)presence. Despite their large size as well as their bright colours (yellow stripes on their legs and red marks on their abdomen), these spiders are harmless and even used for commercial production of spider silk in Japan. 

Jorō spiders, guarding their webs made of, in the sun, gold-shining thread.

During a calm afternoon of coring in one of the many paddy fields surrounding Lake Hamana, a nutria or coypu (Myocastor coypus) came strolling by through one of the field-bordering channels. These ratlike mammals with their characteristic, orange teeth, are native to South America, but meanwhile colonised most of the world. They are one of the invasive species in Japan, often seen in wetland areas. 

Our friend, the nutria, splashing through the water of a drainage channel.

Despite the frequent warnings for pit vipers, hiding themselves in between grass and in puddles within rice fields, we ‘unfortunately’ never got to see one of them...