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1 April 2002 Are American Black Bears (Ursus americanus) Legitimate Seed Dispersers for Fleshy-fruited Shrubs?
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Seeds of seven fleshy-fruited shrubs used by American black bears (Ursus americanus) were extracted from fresh fruit (controls) and from scats of free-ranging and captive bears (ingestion treatments). Effects of the digestive process on viability, germinability and germination rate were measured against controls. Results were species specific. Filled control seeds of all species were highly viable (>74%). Digestion by bears had no significant effect on initial viability, except for serviceberry (Amelanchier alnifolia) for which viability of seeds passed through captive bears decreased 14%. Percent germination of control seeds summed over five chilling durations at 1 C was significantly different from that of at least one bear ingestion treatment for five of the seven species. For chokecherry (Prunus virginiana), Oregon grape (Mahonia repens) and skunkbush sumac (Rhus trilobata), seeds ingested by wild black bears germinated to a significantly higher percentage than controls, but for snowberry (Symphoricarpos oreophilus) control seeds germinated significantly better. For serviceberry all viable seeds germinated after sufficient chilling, but germination of controls was higher than ingested seeds after shorter chilling durations. When seeds were prewarmed for 5 wk before chilling, percent germination of Oregon grape, skunkbush sumac and snowberry significantly increased. For serviceberry, prewarming lengthened the minimum chilling requirement from 7 to 14 wk. Results from ingestion treatments suggest that the digestive process of black bears may simulate prewarming of seeds. Future work clarifying the role of bears as seed dispersers should involve characterization of: (1) scat deposition sites, (2) activities of seed predators and secondary dispersers at the scats and (3) the relative importance of bears in communities containing other dispersal agents.

JANENE AUGER, SUSAN E. MEYER, and HAL L. BLACK "Are American Black Bears (Ursus americanus) Legitimate Seed Dispersers for Fleshy-fruited Shrubs?," The American Midland Naturalist 147(2), 352-367, (1 April 2002).[0352:AABBUA]2.0.CO;2
Accepted: 1 December 2001; Published: 1 April 2002
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