台灣黑熊（Ursus thibetanus formosanus）是雜食性的食肉動物，且植物果實為重要的主食，加上攝食量大且活動範圍廣泛，故為潛在的種子播遷者。本研究旨藉由了觀察台灣黑熊取食野外季節性的果實，以瞭解對其種子萌芽率與萌芽時間之影響。野外季節性採集的果實共七種，包括青剛櫟（Quercus glauca）、山櫻花（Prunus campanulata）、香楠（Machilus zuihoensis）、呂宋莢蒾（Viburnum luzonicum）、台灣蘋果（Malus doumeri）、山枇杷（Eriobotrya deflexa）及山柿（Diospyros japonica），依次餵食圈養的台灣黑熊四隻，紀錄攝食方式，以及收集內含試驗種子的排遺，並檢視種子受損程度，再分別置於生長箱及苗圃觀察種子萌芽數量及時間。
Formosan black bears (Ursus thibetanus formosanus) are omnivorous carnivores, and fruit is comprised of their primary diet. Besides, because of their enormous intake volume and extensive home range, bears are believed to be potential seed dispersers. The objective was to observe the consumption of various fruits by bears to understand the effects on seed germination percentage and germination time. I fed 4 captive Formosan black bears with seven hand-picked fruits, including Quercus glauca, Prunus campanulata, Machilus zuihoensis, Viburnum luzonicum, Malus doumeri, Eriobotrya deflexa and Diospyros japonica, which wild bears used seasonally. Bear feces with ingested seeds were collected. After classifying the abrasion level of 100 seeds out of each feces, I planted seeds separately in growth chambers and green houses.
Formosan black bears consumed fruits differently. They often swallowed fleshy-fruits directly (63-100%). However, they often crashed the Q. glauca acorn (73%) or spited out (27%), and no intact seeds were found from feces except 2 seeds. The abrasion level of ingested seeds varied by species. Except for E. deflexa, most seeds of the fleshy -fruits collected from bear feces were intact (40%-99%), followed by slightly-damaged or pulp-wrapped seeds, and <10% were partially-damaged or severely-damaged seeds. However, higher percentages of slightly-damaged and intact seeds were found in E. deflexa (48% and 23%), along with partially-damaged seeds (24%).
No matter seeds were ingested by bears or not, seeds with pericarps removed (i.e., intact seeds) germinated more than pulp-wrapped seeds. For seeds with dormancy behavior such as P. campanulata, M. zuihoensis, V. luzonicum and M. doumeri, the germination percentages of ingested seeds were significantly higher than the control groups. It indicated pulps would inhibit seed germination. Bear consumption could help to remove pulps and enhance germination.
Seeds with diverse ingestion-caused abrasion geminated differently. Pulp-wrapped and severely-damaged seeds often germinated less than other groups. Wrapped seeds of all 3 drupes (P. campanulata, M. zuihoensis and V. luzonicum) in control groups did not germinate, but for those collected from bear feces, the germination percentages were 21-70%, with an average germination time of 1-8 months. Pome seeds of E. deflexa and M. doumeri ingested by bears had the highest germination percentages (88% and 96%) among all species, which was 1.5 and 1.8 times of the control groups, and their average germination time was only half of the control seeds. Ingested seeds of D. japonica also geminated 1.5 months earlier than the control seeds.
Compared with the naturally fallen fleshy-fruit under parent trees (i.e., pulp-wrapped seed in control group), Formosan black bears enhanced the seed germination percentage and shortened the average germination time. This may further decrease the possibility of seed predation or fungal infection, and improve the ultimate germination success. But for acorns like Q. glauca, bears may work as seed predators. Therefore, my study suggested that Formosan black bears are an legitimate long-distance seed disperser for fleshy-fruits.