As the result of rapid increase in Sika deer population, trampling and grazing have a great influence on natural vegetation. Although many deer tracks are found in mires of Hokkaido, northern Japan, there are a few reports on damages to mires.

We selected the Sarobetsu Mire and investigated deer impact on bog and fen vegetation through time-series analysis of deer traces based on geographic information system derived air photographs (taken in 2000, 2003, 2005 and 2009) and field survey.

The deer trail length in 2009 is about 20 times as much as that in 2000. Especially, in the air photographs, the density of deer trails was higher near the forest. Compared to field survey, trail length on air photographs was estimated shorter. These findings suggest the rapid increase in the population size of sika deer in Sarobetsu Mire in the past 9 years.