Zoological Studies

Vol. 61, 2022

(update: 2022.5.26)

Bark-stripping Behavior of Formosan Sambar (Rusa unicolor swinhoii) at Tataka, Yushan National Park in Taiwan

Guo-Jing Weng1,*, Shu-Mei Chen2, Li-Min Yin2, I-Chen Wu2, and Ting-An Chou1

11, Shuefu Road, Neipu, Pingtung 91201, Taiwan. Institute of Wildlife Conservation, College of Veterinary Medicine, National Pingtung University of Science and Technology, Taiwan. *Correspondence: E-mail: gjw@mail.npust.edu.tw (Weng).
E-mail: m10817012@g4e.npust.edu.tw (Chou)
2515, Sec. 1, Jhongshan Rd., Shueili, Nantou 553203, Taiwan. Yushan National Park Headquarters, Taiwan. E-mail: shumeic@ysnp.gov.tw (Chen); limi@ysnp.gov.tw (Yin); windwardkw@ysnp.gov.tw (Wu)

Received 31 October 2021 / Accepted 2 March 2022
Communicated by Teng-Chiu Lin

The bark-stripping behavior of Formosan sambar, Rusa unicolor swinhoii, has become conspicuous in recent years in the Tataka area, Yushan National Park in Taiwan and caused concerns of visitors and ecologists. We conducted a monthly survey on 537 tagged trees of 21 species and monitored abundance of sambar using camera traps from October 2018 to January 2021, aiming to interpret possible causes of the bark-stripping behavior at Tataka. We also used a generalized linear model to evaluate potential factors that may affect the probability of a tree being bark stripped. Both our observations and the model predictions showed that sambar had a strong preference for bark of Pinus armandii, Photinia niitakayamensis, and Salix fulvopubeseens and for trees with diameter at breast height around 14 cm. Bark stripping mainly occurred between July and October when major forage was most abundant. However, sambar’s need for bark surged in May when sambar abundance was moderate and decreased in October when sambar abundance was high. The seasonality of bark stripping was synchronized with peak period of antler development, fawn nursing, and spread of gastrointestinal parasites, suggesting that sambar likely strip bark to ingest minerals for their physiological needs and/or to acquire plant secondary metabolites to repel gastrointestinal parasites. Sambar abundance alone was not sufficient to predict the overall intensity of bark stripping. Rather, the product of sambar abundance and the necessity index (average wound size) strongly correlated with the overall bark-stripping intensity. Therefore, controlling sambar abundance is essential but it alone may not be the optimal strategy for the control of bark stripping. A combination of population control and relaxing of sambar’s parasite loading and/or physiological needs for minerals is an important strategy to control the overall bark stripping. Future research could use the necessity index to investigate the synchronicity of the bark-stripping behavior, deer’s physiological state, environmental factors and phenology to better understand the cause of this behavior.

Key words: Deer, Plant secondary metabolites, Gastrointestinal parasites, Forest, Necessity index.

Citation: Weng GJ, Chen SM, Yin LM, Wu IC, and Chou TA. 2022. Bark-stripping behavior of Formosan sambar (Rusa unicolor swinhoii) at Tataka, Yushan National Park in Taiwan. Zool Stud 61:19. doi:10.6620/ZS.2022.61-19