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

The bark-stripping behavior of Formosan sambar, Rusa unicolor swinhoii, has become conspicuous in recent years in the Tataka area of Yushan National Park in Taiwan and a cause for concern to visitors and ecologists. We conducted a monthly survey of 537 tagged trees of 21 species and monitored the abundance of sambar using camera traps from October 2018 to January 2021, aiming to interpret possible causes of the bark-stripping behavior in Tataka. We also used a generalized linear model to evaluate factors that may affect the probability of a tree having its bark stripped. Both our observations and the model predictions showed that sambar has 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 the peak periods of antler development, fawn nursing, and spread of gastrointestinal parasites, suggesting that sambar strips 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) were strongly correlated with the overall bark-stripping intensity. Therefore, controlling sambar abundance is essential but it alone may not be the optimal strategy for controlling 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.

Stop and Smell the Pollen: The Role of Olfaction and Vision of the Oriental Honey Buzzard in Identifying Food.

The importance of olfaction for various avian behaviors has become increasingly evident. So far, the use of olfaction for food detection among raptors has only been demonstrated for Cathartes vultures. The Oriental honey buzzard (Pernis orientalis) is a resident and migrant in Taiwan and regularly forages in apiaries. One of its foods in apiaries is yellow pollen dough, a softball-sized mixture of pollen, soybeans, and sugar that beekeepers provide as a supplementary food for bees. Given that pollen dough is not similar to any naturally occurring food, we hypothesized that buzzards identify the dough's nutritious contents using olfaction, perhaps in combination with vision. Using a series of choice experiments in which individuals could choose between two doughs, we showed that (1) buzzards almost unerringly chose pollen-containing over pollen lacking doughs when otherwise the doughs were identical in size, shape, and yellow color; (2) buzzards always preferred yellow over black or green doughs if both doughs contained pollen; (3) buzzards still preferred pollen-containing over pollen-lacking doughs when both doughs were black, but at a lower rate than in (1). We statistically excluded the possible influences of the doughs' relative brightness or of repeat visits by the same individuals. Our experiments thus suggest the use of a 'multi-modal foraging strategy' among buzzards whereby olfaction and vision are likely to be both used in identifying food at close distances. We also estimated the olfactory receptor gene repertoire size in the buzzard's genome which is almost five times as large as that of three other raptor species. Therefore, olfaction is likely of far greater ecological importance to this species than to other raptor species. We suggest that olfaction should be considered in the design of behavioral and genetic studies to better understand the use of multiple senses in avian behaviors.

Isolation and characterization of 10 microsatellite DNA markers in the oriental honey buzzard (Pernis ptilorhyncus).

We designed 10 new microsatellite markers for the oriental honey buzzard (Pernis ptilorhyncus) and tested them on 44 individuals. The number of alleles ranged from two to 12 with an average of five, while the observed heterozygosity ranged from 0.273 to 1.0. Linkage disequilibrium was not found. These markers are being used in a study of the ecology of this species in Taiwan. We also tested their utility on eight other raptor species.