Date Awarded


Document Type


Degree Name

Master of Science (M.Sc.)




Harmony J Dalgleish

Committee Member

Martha A Case

Committee Member

Matthias Leu


Animal-mediated dispersal of seeds is a crucial step for many trees to relocate propagules to favorable locations for establishment. Scatter-hoarding rodents, such as the Eastern grey squirrel (Sciurus carolinensis), choose cache locations in such a way as to balance the value of the seed and effort taken to cache it against the risk of pilferage from conspecifics. Pilferage avoidance strategies observed in squirrels and other rodents have been described by the optimal density model and the habitat structure hypothesis. These mutually non-exclusive models suggest, respectively, that rodents increase the dispersion of seeds proportional to the value of the seeds and utilize the landscape of fear to reduce pilferage. These caching outcomes often increase the likelihood of establishment for the seedling as well. If seeds of higher value, which are placed in more open locations, are also of lower shade tolerance than it would be an example of directed dispersal. We performed two experiments to better understand these dynamics. The first was a field experiment which found support for both the optimal density model and the habitat structure hypothesis in a typical Eastern mixed forest. The second, agreenhouse experiment, established a quantitative measure of shade tolerance and found an inverse relationship between caching value and shade tolerance which suggests directed dispersal in rodent-dispersed hardwoods.




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