The dispersal of fruits and seeds of Poison-ivy, Toxicodendron radicans, by Ruffed Grouse, Bonasa umbellus, and squirrels, Tamiasciurus hudsonicus and Sciurus carolinensis

Abstract

A study was conducted to determine the dispersal potential of seeds and fruits of Poison-ivy (Toxicodendron radicans (L) Rydb.) by mammals and birds in a study plot near Stonewall, Manitoba, Canada. Ruffed Grouse (Bonasa umbellus) and Red Squirrels (Tamiasciurus hudsonicus) and Grey Squirrels (Sciurus carolinensis) were the most common visitors to feeders containing fruits and to fruit-bearing plants. Squirrels acted as seed predators by removing the exocarps and mesocarps from fruits and eating the seeds. However, they often dropped individual fruits or entire infructescences that they had been carrying to dining or caching sites and because of this they were effective dispersal agents for the seeds. Ruffed Grouse behaved as frugivores by eating the fruits and excreting intact seeds. Germination in seeds extracted from grouse faeces was not significantly different from seeds from fruits taken directly from the plants. Germination of seeds from within intact fruit was higher but, not significantly, than that from seeds from which the exocarps and mesocarps had been removed. These results show that the fruit and seeds of Poison-ivy are food resources for Ruffed Grouse and squirrels, respectively. Both kinds of animals are effective seed dispersal agents for seeds of this species.