Home Range Size Indicators for the Eastern Chipmunk (Tamias striatus)

Joneve M Murphy

The eastern chipmunk is an animal that is seen throughout the Adirondack Park, located in northern New York State, as well as throughout the East Coast. There is currently a study being performed where in the diversity of small mammals is being looked at through out the Adirondacks. This study is being conducted on various human impact levels fromold growth to managed forests and finally in developed areas. In conjunction with this study I looked at small mammal trapping data from the years 1999, 2000, and 2001 for an old growth plot, and a managed stand, in Huntington Wildlife Forest located in Newcomb, NY. I wanted to determine an estimate for the home range size of the eastern chipmunk, and compare the homerange sizes for the two areas as well as comparing males against females. I predicted that since the trapping was done during a mating period for this species that there would not only be a difference in size between the sexes but that the male's homerange would be much larger. I also predicted that there was a difference in size of home range between the two habitat sites.

The eastern chipmunk (Tamias striatus) is found in most of eastern North America. In the Adirondacks it is generally found around elevations of 1220m. It is found mostly in mixed forests with an abundance of older hardwoods such as sugar maple (Acer saccharum) and American beech (Fagus grandifolia) and an open understory. A chipmunk home is composed mainly of interweaving connecting tunnels that range is length of four to ten meters (Saunders 1998).
The homerange of any animal is defined as the space used during the acquisition of all life cycle necessities. This space may be determined by the location of food supply, and cover. The size is also affected by such factors as population density and, territoriality. (Stickel 1954) Therefore the size of an animals home range is ultimately determined by the habitat not the individual.

STUDY AREA
This study was conducted in the Huntington Wildlife Forest, located in Newcomb New York. The property is approximately 6000 ha. belonging to the State University of New York College of Environmental Science and Forestry, the area is primarily used for research purposes. It is a forest comprised mainly of hardwood (72%) stands with mixed wood (18%), and conifer stands (10%) (Philips 1992). There are five sites on Huntington Wildlife Forest where small mammal live trapping is conducted. The two used for this analysis were the called the Natural Area and the Maple Sale.
The Maple Sale was given its name by way of a shelter cut conducted in 1979-1980, during which a large portion of the sugar maple and red maple was harvested. The area is now comprised of a young, even aged yellow birch and sugar maple stand (Steblein et al 1988). The undergrowth is quite dense with beech saplings, and there is a moderate amount of little leaf litter and coarse woody debris.
The Natural Area is a characteristic old growth northern hardwood stand. There has been no harvesting in this area except for a small amount of white pine and spruce taken out in the early 1800's (Adirondack Ecological Center, unpublished data). The area has a well-developed and dense canopy of sugar maple, yellow birch, and eastern hemlock (Baumflek 1999). The understory is made up of an immense amount of witch hobble as well as numerous hardwood saplings. The leaf litter is deep and the forest floor has an abundant amount of coarse woody debris.

TRAPPING TECHNIQUE
At each site trapping was conducted on a seven by seven box grid wherein each of the forty-nine traps were set twenty meters apart, therefore the entire grid encompassed approximately 1.96 ha. These grids are used annually for live trapping in a mark recapture program (ALTEMP #24) performed in Huntington Forest. The live trapping was conducted using alternating Tomahawk (25) and Sherman (24) traps, over a period of five days where-in the traps were set and checked in the morning and the evening, for a total of eight trapping intervals. All traps were baited with a mixture of peanut butter, paraffin wax and oatmeal.

METHODS
Live trapping data was taken from the years 1999, 2000, and 2001. Each set of data contained the identification, weight, sex and areas of entrapment for each individual. This information was compiled and used to create a collection of polygons each representing one individual. These polygons were analyzed according to the following method. Each straight line in between two traps either horizontally or vertically was counted as one, each straight line between two traps that was diagonal was counted as radical two. The figures derived from these methods were used as home range indicators and compared against one another. Forty- one individuals were analyzed. All individuals were treated equally when analyzed, no matter where on the grid they were captured. This was under the assumption that the grid would have the same influence on all individuals despite any differences in the individual's physiology.
Once all of the individuals were analyzed, they were lumped unto categories and compared using t tests with and alpha of 0.05.

RESULTS
It was found that there was no significant difference between the average value of home range indicator for both males and females in either area. The natural area when males were compared to females in a t test the P value was equal to 0.7894. In the maple sale a comparison of males and females, by way of a t test, resulted in a P value of 0.9749. Neither of these numbers is significant.
It was also found that an overall comparison, by way of a t test, of males and females for both areas resulted in a P value of 0.8329. this number is also not significant; there fore there is no recognizable difference between males and females in terms of home range size.
Finally it was also found that there was no significant difference in the averages of the natural area and the maple sale with both sexes included. The P value was 0.1233 This last figure however did show a trend depicted in figure 4.

DISCUSSION
The results of this study suggest that there is not a difference in the size of homerange between males and females. It was expected that since the trapping was done during mating season, that the male, being the more promiscuous of the species, would cover more area while looking for a mate. However it was found in a prior study that an increase in activity among females was found and attributed to a need for more nutrition for energy stores to be used in lactation (Lacki, Gregory, Williams 1884). There fore with this increase in female activity during this season it is reasonable to believe that lack of difference in home range size between the two sexes is feasible.
It is also suggested that there is a difference in the size of homerange between the Natural Area and the Maple Sale. Although the t test result determined the difference to be insignificant, there is definitely a trend and this insignificance can be attributed to a small sample size. So this trend depicts that chipmunks in the Maple Sale have a smaller homerange than those in the Natural Area. It is theorized that organisms in general will adjust their use of an area in terms of size in order to maximize the benefits relative to the costs of occupancy in a certain habitat. (Bowers 1995) There fore the Maple sale is a better habitat where in the individual can attain all needed resources close to their den and does not need a large home rage. As opposed to the Natural area where the individual needs to take more risk and go to a further extent in order to attain necessities.

ABOUT THE AUTHOR: Joneve M Murphy

I am currently working on my Bachelors Degree at the State of New York College of Environmental Science and Forestry. I am majoring in Environmental and Forest Biology. I am interested in conservation biology, although I also have interest in Animal Behavior. I will graduate in May of 2002, and plan to further my education eventually. I would like to take some time off and try to involve myself in several different types of jobs in order to broaden my experience before attending graduate school.


LITERATURE CITED

~ Baumflek, M1999. Techniques for Assesing Small Mammal Diversity. Special Report Number 146, Adirondack Ecological Center, Newcomb NY, USA

~ Bowers, Michael A. 1995 Use of Space and Habitats by the Eastern Chipmunk. Journal of Mammology 76 (1) 12-10

~ Drennan, EJ., Beir, P., and Dodd, LN. 1998 Use of Track Stations to Index Abundance of Sciurids. Journal of Mammology, 79 (1): 352 - 359

~ Hayne, Don W 1949 Calculation of Size of Home Range. Journal of Mammology, 30 (1) 1-16

~ Lakci, Michael J., Gregory, Michael J., Williams, Kelly P. 1984 Summer Activity of Tamias Striatus in Response to Suplemented Food. Journal of Mammology, 65 (3): 521-523

~ Philips, ME., T Donovan 1992. Nest predation and the Coexistance of Bird Species, Revisitedd. Special Report Number 141, Adirondack Ecological Center Newcomb New York, USA

~ Saunders, Andrew 1998 Adirondack Mammals, State Univ. of New York College of Environmantal Science and Forestry

~ Stebien, P., R Prachar, W.F. Porter 1988. Long Term Dynamics of Small Mammal Populations in Northern Hardwood Forests of the Adirondack Mountains, NY. ALTEMP # 10, Adirondack Ecological Center, Newcomb New York, USA.

~ Stickel, Lucille F., 1954 A Comparison of Certain Methods of Measuring Ranges of Small Mammals. Journal of Mammology 35 (1): 1-15