The day when a fox disappeared from Sato-yama: 14C dating of a fox remains found from the space under the floor of the Jizo-temple in Kodenosawa, Toyota

Japanese Red foxes (Vulpes vulpes japonica) establish stable home ranges within particular areas or are itinerant with no fixed abode around human habitations. They are popular wild animals and feature prominently in the folklore of human culture. The population, however, was decreased until the beginning of the 1970's, and no fox has been seen since about 1975 in Kodenosawa, a small habitation about 17km NE from the urban area of Toyota City. A fox remains was found from the under floor of the Jizo-temple together with a ragged package of Nissin Chicken-Ramen which was used from 1971 to 1983. The fox's remains is c. 50 cm in body length. The left half of the remains exhibits soft tissues including skin and dried muscle, but the right half facing to the ground is completely decayed. To determine when the fox died, we measured 14C concentration in collagen extracted from a tooth and a rib of the remains. The δ13C (-18±1 ‰) normalized 14C concentrations are 129.2±0.4 pMC for the tooth and 129.0±0.4 pMC for the bone. Although the values intersect the calibration curve at 1962 and 1979, the 1979 age only agrees with the time span supported by the envelope of Chicken-Ramen. Drying of muscle tissue without rotting was likely to take place in cold winter. Thus, the fox's death is reasonably definable in the period from late November 1979 to early January 1980. The δ13C (-18±1‰) values suggest a diet containing a significant amounts of C4 food or protein with higher isotopic values. There is little C4 plants in Kodanosawa, but sizable amounts of cone were constantly brought from outside for cow's and chicken's food. A possible protein source is the herbivore and the omnivorous feeder within the area. An alternative may be marine fish and the derivatives including dog- and cat-food. To test whether the fox took food brought from outside or not, we analyzed the 87Sr/86Sr isotopic ratio of the remains. The 87Sr/86Sr isotopic ratios, 0.709439±0.000016 for the tooth and O.749464±0.000014 for the bone, are distinctly lower than those of wild boar's bone (0.709944±0.000016 and 0.709912±0.000012), river water (0.710079±0.000016) and the granite (0.710218±0.00016) that underlies the wide area of Toyota City. The initial 87Sr/86Sr ratio of 0.7096±0.0001 constrains the lowest isotopic ratio of water, plants and animals within the area. The distinctly lower 87Sr/86Sr values documents that the fox took sizable external food with higher δ13C values. After the disappearance of foxes from Kodenosawa around 1980, wild boars swelled in population. Voracious scavengers dug slope of hills side and paddy fields as they foraged for bulbs, yams, earthworms and grubs, and eventually ate voraciously paddy, sweet potatoes and beans in the field. This triggered the abandonment of cultivation of fields that face mountains. It is likely presumed that foxes were preventing wild boars from invading the human habitation through attacking Uribou, young wild boars.