Draft 1: Do Squirrels have a feeding pattern?

This topic submitted by Christine Miller, Shiree Campbell, Ray Devine, Nick Riedel, and Meagan Dickerman ( mille121@miamioh.edu ) on 10/6/04 .
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Natural Systems 1 Syllabus---Western Program---Miami University


Christine Miller 10-6-04
Nick Riedel
Ray Devine Lab Proposal
Shiree Campbell
Meagan Dickerman Chris Myers


Introduction:
Testable Hypothesis:

We will be testing how squirrels, specifically gray squirrels, feed and search for food. We will test whether squirrels prefer to eat or hunt in certain times of the day, whether their feeding behavior is affected by the location or the weather or temperature. The experiment will take place in Oxford, Ohio, where the gray squirrel is the dominant species of squirrel, but the red squirrel and fox squirrel also inhabit the area, so they will be tested as well.

Our prediction is that there will be some sort of pattern to the squirrel behavior. It would almost be illogical to believe that any animal's behavior is not affected by location, darkness or weather. We predict that the squirrels in this area will do most of their hunting between the
hours of 7 am and 10 am, and between 3 pm and 6 pm. The times will fluctuate, as the weather gets colder. The squirrels will spend more time hunting the closer it gets to winter. The gap between the times of forging will become smaller and smaller until it is non-existent. The location of the hunting should have to effect of the feeding behavior of the squirrels. The area in which we are testing lacks sufficient landscape variation to affect their behavior. It has been proven that in the summer season squirrels will consistently takes naps in the middle of the day. The naps differ in length and time
due to the different climates and the changing of season. The naps become shorter the colder the weather gets and the closer the season is moving into winter. In the winter the squirrels will take no naps, but will sleep the most, bundled together in their nests. The rest of the time they will spend foraging for food (Halle & Stenseth 2002).

Squirrels eat a variety of foods including acorns, various nuts, and pinecones. We have based our predictions of a scheduled feeding day based on many known facts, one being the availability of these foods. Acorns, which are the main source of food for the gray squirrel, fall at certain time of the year, somewhere between late September and early October. It has been proven that squirrels must be competitive in order to gather enough food to survive the winter. This leads us to the
assumption that squirrels must then hunt the most when the acorns first fall. This would then show that the squirrels already have a scheduled hunting time due to the acorns falling ( Merritt 1998). When winter arrives the squirrels will spend most of their time sleeping, and the rest will be foraging for energy rich foods; specifically pinecones. It is this fact that leads us to believe that the squirrels in this area will have more centralized foraging times as the season moves toward winter
(Halle & Stenseth 2002).

Visibility is another aspect in which we have based our hypothesis on. Squirrels are diurnal, which means they would most likely do must of their hunting during the day.

Alternate Hypothesis:

Besides discovering how the feeding behavior of squirrels is affected by the time of day, location and weather, we should be able to discover other scheduled behaviors of the squirrel. We have predicted that not only do squirrels have a schedule time and place for hunting, but for
playing, sleeping, and nesting as well. It is obvious that squirrels have an active social life; they can be seen interacting with each other on a daily basis. In order to be successful in gathering food, they must find the most efficient times to hunt, leaving inefficient times for either playing, sleeping or nesting.

We predict that the squirrels spend most of their social time later in the afternoon, around dusk. It would be at this time that there would not be enough sunlight to efficiently look for food, but not late enough to sleep. We predict that these results will not be as consistent as the hunting times due to the fact that playing can sometimes, if not all the time, be an action of spontaneity. As the weather gets colder and its gets closer to winter, the squirrels will spend more time sleeping, and
less time playing because of their need to gather food for the winter. Once again we predict that the location will have little affect on the squirrels' behavior due to the lack of variation.

Seeing fewer squirrels, as the weather gets colder leads us to assuming that the squirrels are sleeping. We will need to use this assumption in order to prove our hypothesis. Even though it has been proven that squirrels sleep more in colder weather, we will still study the specific sleeping hours due to specific weather conditions.

Background Information:

Squirrels are classified within the order of Rodentia and the family Sciuridae. They are small tree dwelling rodent-like mammals who are usually active from sunrise to sunset. These diurnal animals typically have large bushy tails. The tails serve as balancing devices while the animals are passing limb to limb through the tree tops. Squirrels are less active during the winter time and are unimodal; spending one chunk of time being active throughout the day. They become more and more active as the days get longer and warmer until eventually they become bimodal. During summer days they are active in the morning, take a rest around noon to avoid overheating, and then finish out with an active evening. This pattern, therefore, indicates that squirrel activity is closely related with daylight and temperature.

"Squirrels have a great awareness of their environment. Their feeding strategy is one of moving about sampling various items and in the process locating the best of a variety of foods as they become available" (Whitaker and Hamilton, 1998). Squirrels are foraging animals. Foraging
is an action that "consists of walking with the nose close to the ground, moving the head slightly up and down, forward and backward" (Horwich,1972). Some of the many items that they choose to consume include: nuts, seeds, budding leaves, catkins, spring flowers, weevil larvae, fungi, tree sap, conifer cones, nestlings, insects, insect eggs, birds eggs, lick road salt, and "calcium and other minerals are obtained by chewing on bones including antlers and turtle shells" (Whitaker and
Hamilton, 1998). However, the most commonly understood nutrition source for these rodents are nuts, and even more specifically: acorns.

The small animals are almost always seen with a nut in their mouth either eating it or preparing to bury it. Watching a squirrel "digging with the forepaws, nudging of the nut with the nose, and the final covering motion of the forepaws" (Horwich, 1972) has been fascinating, it seems, since
the beginning of time. Equally intriguing is watching a squirrel retrieve a nut. Squirrels use their olfactory sense to recover their nuts, and they have been known to find them buried beneath over a foot of snow, but as one would guess many nuts are not found. The burying of nuts is known as caching and this "caching behavior makes squirrels an important dispenser of plant seeds, as buried seeds are often not found and may germinate" (S. Jansa and P. Myers, 2000).

Some squirrels travel to different patches of food. The density of food within these patches determines how long the squirrel will stay. The patch must also have a certain density to make the travel to the patch worth while to the squirrel. Similarly, squirrels look for cones in trees with higher numbers of cones, and also for cones with a higher quality. Usually, the larger trees provide more food and also even provide for better nesting options. Squirrels' nests are either made in the hollows of such large trees or in the crooks of the branches. These nests are made up of leaves and bark. While they eat, squirrels usually sit up on their haunches, however, some of the younger squirrels are "unable to balance themselves on their haunches", and without "support may fall over and rest on their forearms" (Horwich, 1972).

During the autumn all the squirrels gain weight and are at their maximum body mass. This is due to the food being so abundant, and they have no need to travel as much. Maximum body mass is also beneficial for warmth and the coming shortage of food in winter. It is interesting to find out
that "with the fragmentation of forests, food hoarding behavior has changed. Most squirrels hoard rather than consume food on the spot" (Goheen and Swihart, 2003). It is also interesting to find out that different types of squirrels have separate ways to hoard/cache their nuts.

There are three different squirrels that appear around the area of Oxford, Ohio. The Red Squirrel (Tamiasciurus Hudsonicus), the Eastern Grey Squirrel (Sciurus Carolinensis), and the Fox Squirrel (Sciurus Niger) not only slightly differ in appearances but there are many more differences that appear between the species. Their hoarding habits and eating habits are two of the more major variations.

The Red Squirrel (Tamiasciurus Hudsonicus) is the smallest tree squirrel. This squirrel has a red-grey color of fur and also a white ring around their eye. The Red Squirrel prefers coniferous forests but also lives in hardwood forests as well. They are even known for tunneling underneath
the snow. Red Squirrels have what are called middens, they are favorite feeding posts, and pine cones, pine cone fragments, and nutshells accumulate underneath/around them. Red Squirrels have a special way of hoarding their nuts. They bury their nuts in one central cache. This is called larder hoarding. It tends to make them more territorial because there is an increased risk of their food being taken. Red Squirrels set up circular territories and defend them from outsiders. "Red Squirrels can do considerable damage to forest plantation by eating conifer shoots" (S. Jansa and P. Myers, 2000), and their larder hoarding does not give acorns very good seed dispersal. They have recently expanded their territory to Indiana, and whether this is because of another species of squirrels' population (Eastern Grey Squirrel) going down or their moving in has actually caused this decline
in population is unclear (Goheen and Swihart, 2003).

The Eastern Grey Squirrel is "generally grey but is suffused with light brown in the summertime" and has a "large tail with white bands of hairs" (nearctica website2004). They primarily live in hardwood forests and suburban areas as well. The Eastern Grey is the most common species of squirrels east of the Mississippi River, and is sometimes recognized by the short barks it utters when excited. Unlike Red Squirrels, Grey Squirrels scatter hoard their nuts. They bury each nut close to the surface and close to where the nut was found. Such hoarding discourages pilferage and is extremely important to reforestation. In a study by Goheen and Swihart (2003) they "recorded the caching behavior of twelve Red Squirrels and thirteen Grey Squirrels. Of these, one individual of these species only consumed and did not hoard the mass items offered." Grey Squirrels also have the ability to coexist with Fox Squirrels.

Fox Squirrels are the largest tree squirrels and are almost identical to Grey Squirrels except that their bellies are more of a yellow-tan color than white. They live in hardwood forests but prefer small areas of hardwoods and open spaces. Being tree squirrels "Fox and Grey Squirrels neither hibernate nor store a lot of body fat; the extra weight would be a handicap when climbing trees" (Line, 1999). Fox and Grey Squirrels share another piece of common ground. Fox Squirrels are also scatter hoarders, burying their nuts close to the surface, and even close to where they were found. Both Species eat their buried nuts during the winter when provisions are low.

The last piece of background information that was collected regarding squirrels and their eating habits is regarding the type of acorns they eat. Two types of acorns are to be distinguished from one another: the white oak and the red oak. White oak leaves have more rounded lobes;
examples include the white and chestnut oaks. Their acorns mature in one growing season (Line, 1999), sprout as soon as they are on the ground, and are sweeter to the taste. Red oaks (e.g. red and scarlet oaks) on the other hand have leaves that have pointed spine tipped lobes. Their acorns
take two years to mature, have "three times more fat" (Line, 1999), and are bitter to taste. This bitterness is from a substance called tannin within the nut. The tannin may even inhibit digestive enzymes as well. Red oak acorns "lie dormant through the winter and sprout in spring"
(Line, 1999). Due to the bitterness of the red oak's acorns, the white oak's acorns are the more coveted nut among squirrels.

Methods:

Five students are involved in finding if there is a daily pattern in the squirrels on Miami University campus. The first step taken in order to discover this pattern is to write out a table in which the data collected while observing the squirrels' behavior is to be written. Each student involved in this experiment will create a table in which to record their observations. These data tables are the only material necessary in this lab since only visual observations will be made and no interaction with the squirrel should occur.

The observations that are to be recorded are: what the activity of the squirrel is, (ex. eating, foraging, interacting with other squirrels, sleeping), what kind of food the squirrel is eating if it is eating, what time and day the observation is made, the location where the observation is made on the Miami campus, and what the average temperature is for the day. Sleeping squirrels will most likely not be seen due to the diurnal nature of squirrels, and if they are sleeping, they would be hidden in the trees. Therefore, if a lack of squirrels at any time during observation is recorded, then one explanation may be that the squirrels are sleeping. A squirrel will be recorded as foraging if they are seen moving about on the ground, sniffing with their head moving up and down through the grass. Eating will be recorded if a squirrel is seen holding a nuts and gnawing on it. A squirrel will be recorded as interacting with other squirrels if they are chasing one another.

Observations such as the temperature of the day and the location where the observation is made is recorded in order to see if other factors such as weather and location affect the activity of squirrels. Temperature may affect the squirrels behavior because an unusually cold day may influence the squirrels to stay in their drey to keep warm. Squirrels sleep a great deal more in the winter than in the summer so as the weather becomes colder, they sleep for longer hours of the day. Also the location of the squirrels may affect the observations made. In areas on campus that receive a great deal of traffic by humans, squirrels may be more scarce than in more isolated aresas. Also, areas with less trees, specifically trees that harvest nuts, squirrels will probably be less abundant because squirrels have no reason to forage there.

During the times of observation, the activity of every squirrel in sight is to be recorded in order to gain a large, accurate sample of squirrels to study. In order to gather accurate data of the squirrels' activity pattern, observations must be made throughout the day because squirrels are active during the daylight hours. If observations were made at night, no squirrels would be seen because they all would be asleep. Although it is impossible to record the activity of all of the squirrels on Miami Campus, all hours of the day, we hope to record a large enough sample of times and squirrels to discover the average daily pattern of activity in squirrels.

Observations are made at various locations around campus from 9 in the morning until 7 at night on Mondays, and 10 in the morning until 8 at night on Fridays. These ten hours of observation should cover the majority of squirrel activity since squirrels are diurnal. Since each student is responsible for two hours of a day, and there are five students conducting this experiment, observations on squirrels are made continuously throughout the day, with no single slot of time not being used for squirrel observation. Shiree observes squirrel activity on Mondays from 2pm until 3pm, and from 6pm until 7pm, and on Fridays from 2-3pm and 7-8pm; Ray makes observations from 9am until 10am and from 3-4pm on Mondays, and from 10am until 12pm on Fridays; Nick makes observations from 12-2pm on Mondays and from 12-1pm and 6-7pm am on Fridays; Christine makes observations from 4-6pm on Mondays and 3-5pm on Fridays; and Meagan makes observations from 10am until 12 pm on Mondays and on Fridays from 1pm until 2pm, and from 5pm until 6pm. Monday and Friday are chosen as days of observation because two nonconsecutive days a week will hopefully display an accurate sample pattern of activity in squirrels since the squirrels cannot be observed everyday due to time restrictions. These observations will last for two weeks so that 60 hours of observations on squirrels on four full days of observations are made.

After all of the data on squirrel activity is collected after two full weeks, the information is combined into one large table. The data is analyzed to see if any activity such as eating occurs more at certain times of the day as opposed to others. The activity of the squirrels will hopefully display a pattern in the times throughout the day that they eat food. If any pattern in the activity of the squirrels emerges, either only on one of the days of observation or throughout both of the weeks of observation, then outside sources such as temperature and location will be examined to see if there is any other explanation of the pattern in squirrels behavior besides a daily routine.

Results

Since our student generated lab is only beginning, we have very little results and data to show. However, I will overview the tests and variables we will study, and also relay the preliminary data we do have. Every Monday and Friday, each individual member of our lab group observes squirrels for two hours. This adds up to ten hours per day and twenty hours per week that we will be spent observing squirrels. When observing them, for every squirrel we see we will write down the time, place, weather, and if it is eating or not. Therefore, we have four variables we will be working with in this experiment. We hope to recognize a significant pattern in squirrel eating behavior.

Squirrel Sightings/Observations:
Observer Date Number of Squirrels Time Location Nut? Weather
Christine 10/4/04 1 4:06p Pbdy. lawn no sunny
Christine 10/4/04 1 4:37p Front of Tmson. yes sunny
Christine 10/4/04 1 4:38p by Boyd no sunny
Shiree 10/4/04 2 2-3p Pbdy. lawn no sunny
Shiree 10/4/04 1 6-7p Pbdy. lawn no sunny
Shiree 10/4/04 4 6-7p by McKee yes, all with sunny
Shiree 10/4/04 2 6-7p McKee beach no sunny







As you can, see it is still too early to discern any pattern from this preliminary data. However, when we thoroughly conduct our experiment, we hope a more concrete pattern will appear to us.

Conclusions:

Based on our research and projected results in our hypothesis, the product of our observations should yield positive proof of regular squirrel behavior. Consistent observations of squirrel activity in the early and mid morning, along with a lack of activity during midday followed by resurgence would support the statements of our research and our hypothesis. The slow digression of activity focusing during the midday as the weather approaches full winter status also would support our hypothesis. Energy conservation as well as personal health should also affect squirrel behavior in relation to adverse weather conditions. During a violent storm or snowfall should produce less observations of squirrel activity, unless the personal schedules of a squirrel override such commonsense. The expected regular observations should also support the assumption that location is not a factor in Oxford, as we believe the terrain is uniform enough to be irrelevant. The appearance of more obvious behavior should become more discernable as the weather changes to a colder climate, such as the increased focus towards food stores. Should the observations be more erratic and spontaneous then we will know that squirrel behavior is just that and our hypothesis is completely wrong and squirrels either know something we do not or are just crazy little critters.


Bibliography

Burt, William Henry, (1975). Mammals of the Great Lake Region. Ann Arbor, MI: The University of Michigan Press.
Burt, William Henry, (1980). A Field Guide to the Mammals North America North of Mexico. 3rd ed. New York, NY: Houghton Mifflin Company.
Goheen, Jacob R., Swihart, Robert K., (Eds.). (2003). Foodhoarding Behavior of Grey Squirrels and North American Red Squirrels in Central Hardwoods Region: Implications of Forest Regeneration. Canadian Journal of Zoology: Vol. 31, Issue 9 (1636-1640).
Halle, S., Stenseth, N.C., (Eds.). (2000). Activity Patterns in Small Mammals. Berlin.
Halloran, Peg, (1999). Fox Squirrels. http://spot.colorado.edu/~halloran/sq_fox.html
Horwich, Dr. Robert H., (1972). The Ontogeny of Social Behavior in the Grey Squirrel (Sciurus Carolinensis). Brookfield, Illinois: Chicago Zoological Park.
http://pubs.nrc-chrc.gc.ca/cgi-bin/rp/rpz_abst_f?cjz_z03-143_81_ns_nf_cjz
http://www.nearctica.com/biomes/edf/mamonal/squirrel.htm
Jansa,S., Myers, P., (2000). Sciuridae.
http://animaldiversity.umm2.umich.edu/site/accounts/information/sciuridae.html
Kays, Roland W., Wilson, Don E., (1971). Kays and Wilson The Mamals of North America. 3 Market Place Woodstock Oxfordshire: Princeton University Press.
Knox Jr., J., Armstrong, David M, Hoffman, Robert S., Jones, Clyde (Eds.). (1983). Mammals of the northern great plains. Lincoln, NB: University of Nebraska Press.
Knox Jr., J., Birner, Elmer C., (Eds.). (1988). Handbook of the north central states. Minneapolis, MN: University of Minnesota Press.
Koprowski, John L., Steele, Michael A., (2001). North American Tree Squirrels. Washington D.C.: Smithsonian Institution Press.
Merritt, Joseph F., Steele, Michael A., Zegers, David A. (Eds.). (1998) Ecology and Evolutionary Biology of Tree Squirrels. VA: Virginia Museum Natural History Press.
Line, Les, (1999). When Nature Goes Nuts. National Wildlife: Vol. 37, Issue 6 (48).
Whitaker Jr., J., Hmilton, William J. Jr., (Eds.). (1998). Mammals of the eastern united states. 3rd ed. Ithaca: Comstock Publishing Associates Cornell University Press.
Wilson, Don E., Ruff, Sue, (Eds.). (1999). The Smithsonian Book of North American Mammals. Smithsonian Institute Press.
Yahner, Richard H., (2001). Fascinating Mammals Conservation and Ecology in the Mid-Eastern States. Pittsburgh, PA: University of Pittsburgh

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