Acorn Contribution to Mammalian Energetics
Acorns are a highly nutritious food source for many mammal species including white-tailed deer (Odocoileus virginianus), white-footed mice (Peromyscus leucopus), eastern gray squirrels (Sciurus carolinenis), and fox squirrels (S. niger). Oak trees (genus (Quercus) produce variable amounts of acorn mast each autumn. Variation in acorn crop yields has been shown to affect reproductive success, population size, body condition, and survival of deer and granivorous rodents. Conversely, the seed dispersal action of these mammalian predators is vital to the reproductive success of the oak trees. The objective of this study was to determine the significance of acorns as a food source for mammals at the Missouri State University (MSU) Bull Shoals Field Station in Taney County, Missouri. Acorns of the white oak subgenus were used because of differences in palatability between the oak subgenera. Different feeding stations were constructed to distinguish between acorns eaten by three mammal taxa (mice, squirrels, and deer). The numbers of acorns removed from feeding stations (September 2004 – February 2005) were used as a measure of acorn consumption. The presence of squirrels and deer at study sites, as well as the populations of mice, were monitored using infrared motion sensitive cameras and live-trapping. Squirrels consumed the most acorns (P<0.005). The number of acorns removed by each group of mammals changed temporally (P<0.005), with the most consumed from November 2004 through January 2005. The impact of mice and deer on the acorn crop was minimal. Using metabolic rate data and the caloric content of acorns, I calculated the amount of acorns necessary for each of three mammal taxa. Knowledge about these interactions is useful in conservation and management. Specifically, when oaks, deer, squirrels, or mice are species of concern, this knowledge can be used to determine the impact of mammal predation non oak recruitment, and estimate the effect that a decline in oaks would have on these mammals.
acorn, mast, Sciurus, Quercus, Peromyscus leucopus, seed dispersal, field metabolic rate, Odocoileus virginianus, Biology
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