Question: To what extent do bison serve as seed dispersers via epizoochory and endozoochory in tallgrass prairie, and does this differ by age-sex class of bison and by month?

Location: Tallgrass Prairie Preserve, Osage County, Oklahoma, USA.

Methods: We collected bison hair from 19 bulls, 45 cows, and 47 juveniles in fall and we collected bison dung monthly for a year. We recovered and identified seeds from hair and dung samples, and classified seeds by size and diaspore characteristics.

Results: Bison hair samples contained 2768 seeds from at least 76 plant species. Several species found in hair did not feature specialized appendages for adhesive dispersal. Seed species composition differed in hair collected from bulls, cows and juveniles, possibly due to differential habitat use. Dung samples contained 7418 seeds from at least 70 species, from which graminoids accounted for 3936 seeds from 27 species. Species composition of seeds contained in dung samples differed among months, corresponding to availability. Grasses constituted about half the seeds in both dung and hair samples, but Asteraceae were more strongly represented in hair, while Scrophulariaceae and Solanaceae were more strongly represented in dung.

Conclusions: We conclude that bison are potentially important dispersers of forbs as well as graminoids. A high abundance and wide diversity of seeds were found in both bison hair and dung. The great majority of seeds found undamaged in bison dung were small seeds, which agrees with the ‘foliage is the fruit’ hypothesis. Dispersal by both epizoochory and endozoochory may play an important role in life history of many species in tallgrass prairie landscapes.

Nomenclature: Kartesz & Kartesz (1980).