奄美群島

Biological situation of the Amami Group of the Loo Choo Islands is outstanding. As remarkable endemic murine-animals, Diplothrix legata and Tokudaia osimensis were recorded from the islands of Amami-oshima and Tokuno shima. Besides, there occur common house rats, Rattus rattus and Rattus norvegicus. As regards to ecology of these animals we have very little informations previously. Since old time the farmers of these districts have noticed the damages of these rodents, especially that were done on crops. Moreover they are frequently threatened by the attacks of venomous snake, so-called "Habu" Trimeresurus flavoviridis flavoviridis which is common in both islands. As Habu seems to inhabit near human dwellings and feed on murine-animals, we tried to make clear their ecological relationships, although the present surveys could not bring much light on this subject. The results obtained by the present surveys on murine-animals, reptiles and amphibians of these islands are as follows. Our collections and observations were fulfilled from July 3 to July 19, 1957. 1) We have obtained fairly large number of specimens of four species which represent Murinae of these districts. 2) Any murine-animal was collected neither in forested area of the mountain nor in bushes of plain-field. 3) Three individuals of Tokudaia osimensis were trapped in weedy place along a path half-way up Mt. Yuwan. The contents of their stomachs mainly consisted of insects and somethings like starches. 4) Both R. rattus and R. norvegicus were trapped in paddy-field ; the riceshoot at that paddy-field just attain on the milk-ripe stage. The problem about relative abundance of individuals of each species of house rats at that habitat will be interesting, although we could not touch this problem at present, since our available materials are too few. 5) In the house, R. rattus was exceedingly commoner than R. norvegicus. 6) In the Amami Islands, main farm cultivations such as rice-plants, sugar-canes and sweet potatoes are damaged by rodents. In the case of riceplant, the rodents devour them at two periods corresponding to the stage of ear formation and the milk-ripe stage respectively. 7) Yellow weasels, Mustela sibirica itatsi had been introduced to Kikaijima as a natural enemy of the rats, successively from 1945 to '46, and fairly good result was obtained. Thereafter, they have also been introduced to Okinoerabu- and Yoron-jima, later to Amami-Oshima. About introduced Indian mongoose, Herpestes edwardsii in Okinawa and other islands, there are controversies about the usefulness of this animal as regards to agronomy of these districts. 8) Two species of bats, Miniopterus schreibersii blepotis and Rhinolophus cornutus pumilus were collected at the foot of Mt. Yuwan. They seem to be new records to the fauna of this district. 9) We have dissected stomachs of six specimens of Habu captured in the field, and found that five were empty and one contained hairs of rat. More knowledges are necessary to discuss about the f ood-chain between Habu and rats. 10) Habu seems to inhabit more abundantly in the peripherals of village where the density of rat-population is rather high. 11) Fif teen species of land reptiles and nine species of amphibians which include Hemibungarus boettgeri, Gymnodactylus sp., Gehyra mutilata and Rana ishikawae are collected in both islands ; these rare species are rather recently found by Koba ('55, '56) in the Amami Group. 12) Hemibungarus japonicus frequently pushes its sharp tip of the tail against enemy as a threatening behaviour. But it was manifested by our experiments that it gives no practical poisonous effect on enemies.