Seasonal and year-round use of the Kushiro Wetland, Hokkaido, Japan by sika deer (Cervus nippon yesoensis)

The sika deer (Cervus nippon yesoensis) population in the Ramsar-listed Kushiro Wetland has increased in recent years, and the Ministry of the Environment of Japan has decided to take measures to reduce the impact of deer on the ecosystem. However, seasonal movement patterns of the deer (i.e., when and where the deer inhabit the wetland) remain unclear. We examined the seasonal movement patterns of sika deer in the Kushiro Wetland from 2013 to 2015 by analyzing GPS location data for 28 hinds captured at three sites in the wetland. Seasonal movement patterns were quantitatively classified as seasonal migration, mixed, dispersal, nomadic, resident, or atypical, and the degree of wetland utilization for each individual was estimated. The area of overlap for each individual among intra-capture sites and inter-capture sites was calculated for the entire year and for each season. Our results showed that the movement patterns of these deer were classified not only as resident but also as seasonal migration, dispersal, and atypical. Approximately one-third of the individuals moved into and out of the wetland during the year as either seasonal migrants or individuals with atypical movement. Some of the individuals migrated to farmland areas outside the wetland (the farthest being 69.9 km away). Half of the individuals inhabited the wetland all or most of the year, i.e., 81–100% of their annual home range was within the wetland area. Even among individuals captured at the same site, different seasonal movement patterns were identified. The overlap areas of the home ranges of individuals from the same capture sites were larger than those for individuals from different capture sites (e.g., mean of annual home range overlap with intra-capture sites: 47.7% vs. inter-sites: 1.3%). To achieve more effective ecosystem management including deer management in the wetland, management plans should cover inside and outside of the wetland and separate the population into multiple management units to address the different movement patterns and wetland utilization of the population.

Seasonal and year-round use of the Ramsar-listed Kushiro Wetland by sika deer (Cervus nippon yesoensis)

The sika deer (Cervus nippon yesoensis) population in the Ramsar-listed Kushiro Wetland has increased in recent years, and the Ministry of the Environment of Japan has decided to take measures to reduce the impact these sika deer are having on the ecosystem. However, their seasonal movement patterns, i.e., when and how the deer inhabit the wetland, remain unclear. Thus, we examined seasonal movement patterns and the population structure of sika deer in the Kushiro Wetland from 2013 to 2015 by analyzing GPS location data for 28 hinds captured at three sites in the wetland. Seasonal movement patterns were quantitatively classified as seasonal migration, dispersal, nomadic, resident, or atypical, and the degree of wetland utilization for each individual was estimated. The overlap areas of population-level home ranges among capture sites were calculated for both the entire year and for individual seasons. Our results showed that approximately one-third of the individuals moved into and out of the wetland during the year as either seasonal migrants or individuals with atypical movement. Some of the individuals migrated to farmland areas outside the wetland (the farthest being 64 km away). Half of the individuals inhabited the wetland all or most of the year, i.e., 81–100% of their annual home range was within the wetland area. The movement patterns of these deer were classified not only as resident but also as seasonal migration, dispersal, nomadic, and atypical. Even among individuals captured at the same site, various seasonal movement patterns were identified. Annual population-level home ranges showed little to no overlap, and seasonal population-level home ranges were completely segregated among capture sites. Individual deer used the wetland either seasonally or year-round, and some populations inhabiting the wetland had sub-populations with different seasonal movement patterns, which need to be considered to achieve more effective ecosystem management including deer management in the wetland.