Field Observation Summary
by Peter Leitheiser
Regarding the Diet of Sciurus niger rufiventer
Location: McCrory Garden, Brookings, South Dakota
Date: 2008NOV11 to 2011JUL23
Introduction
The fox squirrel's diet is highly variable, making use of a wide range of food sources from trees, ground plants, fungi, insects, and occasional carrion. The ability to digest cellulose plant material is less than that of ground squirrels who feed primarily on grasses, but the fox squirrel has still been observed eating buds, young leaves, and some ground plants.
Studies by Nixon et al., (1968) and Nixon and Hansen (1987) reported that the important foods of the fox squirrel and gray squirrels in Ohio and Illinois were hickory nuts, chestnuts, acorns, black walnuts, osage orange seeds, maple seeds, hackberry seeds, elm buds, hop hornbeam nuts, ironwood nuts, yellow-buckeye nuts, corn, soybeans, mulberry, grape, green vegetation including yellow-poplar samaras, flowering dogwood drupes, oak buds and flower, elm buds, hickory flowers, maple buds and flowers.
Procedure and Results
Fox squirrels (Sciurus niger rufiventer) of McCrory Garden, a 25 hectare display garden and arboretum in Brookings, South Dakota, were observed during eighty-nine periods of a few hours in length between 2008NOV11 and 2010OCT07, and herbivory was observed and recorded.
Foods were grouped into fifteen categories.
Figure 1 : Major Foods Consumed by the Fox Squirrel over Time
Figure 2 : Minor Foods Consumed by the Fox Squirrel over Time
Figure 1 : Major Foods Consumed by the Fox Squirrel over Time and Figure 2 : Minor Foods Consumed by the Fox Squirrel over Time is the result of diving time over which these observations were made into thirty-two day bins. During each thirty-two day period, the number of days the squirrels were observed eating the foods in the categories was divided by the number of days observations were made for the y-axis. During the summer of 2009, no observations were made, so the graph shows no data. Most observations were made in the southernmost six hectares of the garden.
Figure 3 : Major Foods Consumed by the Fox Squirrel
Figure 3 graphs an average of the data graphed in Figure 1 and 2.
Discussion
McCrory Garden represents a wider variety of flora than is generally present in South Dakota because the area is extensively landscaped. Even so, the squirrels make use of nearly every major type of tree in the garden. In this sense, the graph is more an indication of the availability of food sources than an indication of the squirrels' preference.
The diet differed from that reported by Nixon et al., (1968) and Nixon and Hansen (1987) from observations in Ohio and Illinois, respectively. In South Dakota the squirrels did not eat Beech, Hickory, and other mast trees since these are not found in this area. The squirrels in South Dakota also consumed pine nuts frequently, however they were not mentioned in the other two studies.
The ultimate goal of this sort of analysis would be to report on what constitutes the diet, by mass, of the fox squirrel population. Little quantitative data of this type has been collected. The method of cataloging sighting of herbavivory can only establish that the diet consists of at least some of a particular food, but can not say with confidence the amount, so as to establish habitat requirements or dietary requirements of the animals.
If the time the squirrels foraged foods could be found and multiplied by foraging efficiency (grams consumed per hour), a quantitative diet could be established. But there are many challenges to this approach. The squirrel would have to permit several mass measurements, or close observation of the number of food items consumed (eg. the squirrel ate 15 apples), so to establish foraging efficiency functions. The analysis of the data would be considerably more complicated.
Works Cited
Nixon, C. M., Worley, D. M., and McClain, M. W. (1968). Food habits of the squirrels in southeast Ohio. Journal of Wildlife Management 32:294-305.
Nixon, C. M. and Hansen, L. P. (1987). Managing forests to maintain populations of gray and fox squirrels. Illinois Department of Conservation.
by Peter Leitheiser
Regarding the Diet of Sciurus niger rufiventer
Location: McCrory Garden, Brookings, South Dakota
Date: 2008NOV11 to 2011JUL23
Introduction
The fox squirrel's diet is highly variable, making use of a wide range of food sources from trees, ground plants, fungi, insects, and occasional carrion. The ability to digest cellulose plant material is less than that of ground squirrels who feed primarily on grasses, but the fox squirrel has still been observed eating buds, young leaves, and some ground plants.
Studies by Nixon et al., (1968) and Nixon and Hansen (1987) reported that the important foods of the fox squirrel and gray squirrels in Ohio and Illinois were hickory nuts, chestnuts, acorns, black walnuts, osage orange seeds, maple seeds, hackberry seeds, elm buds, hop hornbeam nuts, ironwood nuts, yellow-buckeye nuts, corn, soybeans, mulberry, grape, green vegetation including yellow-poplar samaras, flowering dogwood drupes, oak buds and flower, elm buds, hickory flowers, maple buds and flowers.
Procedure and Results
Fox squirrels (Sciurus niger rufiventer) of McCrory Garden, a 25 hectare display garden and arboretum in Brookings, South Dakota, were observed during eighty-nine periods of a few hours in length between 2008NOV11 and 2010OCT07, and herbivory was observed and recorded.
Foods were grouped into fifteen categories.
- Black Walnut (Walnuts of Juglans nigra)
- Oak (Acorns of Quercus macrocarpa)
- Buckeye (Nuts of Aesculus x 'Homestead')
- Pine nuts (Pinus ponderosa scopulorum, Pinus sylvestris Picea pungens )
- Elm (Seeds of Ulmus americana )
- Apple (Full sized and crab-apples of various species)
- Pear
- Mulberry (Berries of Morus rubra)
- Hawthorn
- Honey Locust (Seeds of Gleditsia triacanthos)
- Aborial Leaves Catins and Flowers (young leaves and buds of various trees including willow, cottonwood, hawthorn, and oak, catkins of willow and oak, flowers of Buckeye)
- Winterberry (seeds of Ilex verticillata but not fruit)
- Maple Seeds (Seeds from Acer saccharum, Acer rubrum, Acer ginnala, Acer x freemanii, Acer saccharinum)
- Roots and Ground Vegetation (Echinacea and other flowers, Ginko roots, other roots)
- Maple Sap (mostly from Acer saccharum)
Figure 1 : Major Foods Consumed by the Fox Squirrel over Time
Figure 2 : Minor Foods Consumed by the Fox Squirrel over Time
Figure 1 : Major Foods Consumed by the Fox Squirrel over Time and Figure 2 : Minor Foods Consumed by the Fox Squirrel over Time is the result of diving time over which these observations were made into thirty-two day bins. During each thirty-two day period, the number of days the squirrels were observed eating the foods in the categories was divided by the number of days observations were made for the y-axis. During the summer of 2009, no observations were made, so the graph shows no data. Most observations were made in the southernmost six hectares of the garden.
Figure 3 : Major Foods Consumed by the Fox Squirrel
Figure 3 graphs an average of the data graphed in Figure 1 and 2.
Discussion
McCrory Garden represents a wider variety of flora than is generally present in South Dakota because the area is extensively landscaped. Even so, the squirrels make use of nearly every major type of tree in the garden. In this sense, the graph is more an indication of the availability of food sources than an indication of the squirrels' preference.
The diet differed from that reported by Nixon et al., (1968) and Nixon and Hansen (1987) from observations in Ohio and Illinois, respectively. In South Dakota the squirrels did not eat Beech, Hickory, and other mast trees since these are not found in this area. The squirrels in South Dakota also consumed pine nuts frequently, however they were not mentioned in the other two studies.
The ultimate goal of this sort of analysis would be to report on what constitutes the diet, by mass, of the fox squirrel population. Little quantitative data of this type has been collected. The method of cataloging sighting of herbavivory can only establish that the diet consists of at least some of a particular food, but can not say with confidence the amount, so as to establish habitat requirements or dietary requirements of the animals.
If the time the squirrels foraged foods could be found and multiplied by foraging efficiency (grams consumed per hour), a quantitative diet could be established. But there are many challenges to this approach. The squirrel would have to permit several mass measurements, or close observation of the number of food items consumed (eg. the squirrel ate 15 apples), so to establish foraging efficiency functions. The analysis of the data would be considerably more complicated.
Works Cited
Nixon, C. M., Worley, D. M., and McClain, M. W. (1968). Food habits of the squirrels in southeast Ohio. Journal of Wildlife Management 32:294-305.
Nixon, C. M. and Hansen, L. P. (1987). Managing forests to maintain populations of gray and fox squirrels. Illinois Department of Conservation.