Bark stripping and browsing behaviors of deer on trees and vegetation affect forest species composition and overall biodiversity. In recent years, the population of Formosan sambar deer (Rusa unicolor swinhoei) in Taiwan has continued to increase, affecting not only the normal functioning of high-mountain forest ecosystems but also potentially posing risks to traffic safety. Therefore, managing the population size has become an important future task. This project aims to estimate the population size of Formosan sambar deer in the Tataka area of Yushan National Park from March 2024 to December 2025 by deploying a network of 100 camera traps. The estimation will be assisted by calculating movement speed, identifying individual males, assessing relative abundance indices, and setting up bait stations, with four estimation sessions planned in total. In addition, exclusion fences will be established to compare browsing pressure between fenced and unfenced areas, in order to evaluate the impact of sambar deer on vegetation.
The results showed that the average movement speed of Formosan sambar deer was 20 m/min, with significant differences between males and females, as well as between males and subadults. The deer showed a preference for salt and mixed (salt + oyster shell powder) baits, but not for scent attractants. The differing attractiveness of baits to males and females may potentially influence relative abundance values, suggesting that the use of bait is not essential. A camera density of 25 units per km² was found to be insufficient to capture all individuals within a short period and is therefore unsuitable for Total count estimation of population size. In the Capture-mark-recapture analysis, a 5-day sampling period most likely met the closed-population assumption. The estimated population sizes were 166 individuals in June–July 2024, 183 in November–December 2024, 128 in February–March 2025, and 286 in June–July 2025, showing clear seasonal variation, with an average population size of 191 individuals. Based on the maximum movement distance of males (531 m), the effective sampling area was calculated as 9.61 km², resulting in an average density of approximately 20 individuals per km². The relative abundance of sambar deer was significantly negatively correlated with that of the Mikado pheasant (Syrmaticus mikado) (rs = –0.215), suggesting that sambar deer may have an impact on ground-dwelling bird species..
The deer exclusion fence was completed in December 2024. As of October 2025, no significant differences were found between the inside and outside of the fence in terms of bamboo height, bamboo cover, number of herbaceous species, number of woody seedlings, Shannon diversity index, or Simpson diversity index. Since July 2025, subadult sambar deer have been observed entering the fenced area, indicating that the bottom gap of the fence should be reduced to below 40 cm. Currently, the density of Formosan sambar deer in the Tataka area has far exceeded the threshold reported in the literature(5.5-15 individuals per km²) for deer-induced vegetation damage, suggesting that population control measures should be implemented as soon as possible. It is recommended that future population estimations of sambar deer adopt a high-density camera trapping network (over 25 cameras per km²) combined with the mark–recapture method, conducted in June–July when antler conditions are most diverse to facilitate individual identification. The exclosure experiment should be continued to quantify the impact of sambar deer on vegetation and to serve as an educational site for environmental awareness.