Impacts of sympatric mammals on reintroduced Chinese water deer (Hydropotes inermis) in a peri-urban fragmentation

Anthropogenic disturbances drive global biodiversity loss, necessitating continuous conservation efforts to protect threatened species through reintroductions. Post-reintroduction success depends critically on interspecific interactions between reintroduced populations and sympatric native or invasive species. We used camera-trapping data collected in the urban landscape of Shanghai to examine how native Chinese hare (Lepus sinensis) and free-ranging dogs (Canis familiaris) impacted the spatiotemporal behavior of reintroduced Chinese water deer (Hydropotes inermis). Results indicate that the deer exhibited an uncommon unimodal diurnal activity pattern and temporally avoided sympatric mammals. Chinese water deer tended to avoid areas frequently used by both dogs and hares. Deer adopted fine-scale spatial-temporal segregation to avoid direct encounters with pack-hunting dogs during the day, prompting deer to increase their daytime activity. Consequently, a notable decrease in dusk activity was observed, which may represent an adaptive strategy to further separate from hares temporally, ultimately facilitating coexistence between these species. Evaluating the trade-offs between spatial and temporal responses is crucial for developing management practices and ensuring the long-term sustainability of urban biodiversity.