THE COMPARISON OF SMALL MAMMAL COMMUNITIES IN TWO FORESTED SITES

By

Elizabeth Adeoye

Peyton Allison

Mikal Blocker

Carmen Carroll

J. Grams

Annetta Hartman

Alex Johnson

Shanae Jones

Josh Mason

Ildi Moreno

Ben Perkins

Kaya Shelley

Robert Smith

Taylor Swails

Lili Tha

Deanna Turner

July 25, 2012

Science Teacher: Christina Fairbanks

TCs:

Daveon McMullen

Jasmine Meade

Caroline Prendergast

1

INTRODUCTION

Small mammals, members of the class Mammalia, are warm-blooded animals that give

live birth, provide milk to their young (Mitchell, Rinehart, Pagels, Buhlmann, & Pague, 1997),

and often need complex and diverse habitat components for shelter and protection from

predators, and also need a variety of food resources such as vegetation or other animals. Within

complex habitats, like forests, are microhabitats which are small areas that support a specific

species or community (Mitchell, Rinehart, Pagels, Buhlmann, & Pague, 1997). Examples of

microhabitats can include rocks that chipmunks can burrow under, dead trees that squirrels can

nest in, leaf litter that voles can burrow in and eat, and herbaceous plants that provide rabbits

with cover and food (Mitchell, Rinehart, Pagels, Buhlmann, & Pague, 1997).

A mature, or old-aged, forest is often more beneficial to small mammals than a young or

previously disturbed forest due to an increase in microhabitats and diversity of food resources

(Buehler, & Percy, 2012). Older forests often have higher biodiversity, that is the overall

abundance and diversity of living and nonliving things in an area, because they have a variety of

components such as leaf litter and various aged trees. Younger forests often lack these

components, and therefore are often less biodiverse. The biodiversity and complex structure of a

forest affects a small mammal’s ability to survive, so the presence of small mammals in an area

may indicate the health of the ecosystem, as well as how a forest may be able to recover from a

disturbance.

One way a forest can be disturbed is through clear-cutting. When clear-cutting occurs,

the forest is cut down and the area is cleared of all vegetation and dead trees. The clear-cutting of

a forest initially changes the forest’s structure by decreasing the microhabitats and vegetation,

which reduces shelter and food resources for mammals (Mitchell, Rinehart, Pagels, Buhlmann, &

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Pague, 1997). If the area is allowed to regrow naturally, there may still be an absence of

biodiversity in vegetation because faster growing plants may out-compete other types of

vegetation (Mitchell, Rinehart, Pagels, Buhlmann, & Pague, 1997). The changes clear-cutting

causes in the habitat and forest structure may negatively affect small mammal communities.

Another type of disturbance is forest reclamation which occurs after some surface coal

mining jobs. The process of surface mining often involves clear-cutting of an area followed by

mountain-top removal in order to extract the coal underneath. After the coal is mined, the forest

reclamation process begins. The area is first re-contoured, then the topsoil is replaced and the

area is re-vegetated. Some of the effects from clear-cutting may already influence the forest, but

due to the re-contouring and replacing of the topsoil, there may also be soil compaction along

with the loss of buried and emergent rocks (Buehler, & Percy, 2012). This could affect small

mammals’ ability to burrow or hide which may cause an increase in predation (Buehler, & Percy,

2012). When re-vegetation occurs, the area may not be replanted with the original species or

even a variety of trees. Often, only pine trees are planted during reclamation because they are

inexpensive and they grow quickly. In addition, invasive species, which are not planted, may

out-compete the re-planted trees. The lack of variety of trees planted and invasive species may

contribute to a lower biodiversity of the forest (Buehler, & Percy, 2012). A lack of biodiversity

of tree types may cause mammals that are specialized or adapted to the trees in the original forest

to relocate and may ultimately lead to low biodiversity of animals (Buehler, & Percy, 2012).

Researchers have found that small mammal communities in clear-cut, white pine, and oak-

hickory forests were different from mixed hardwood and climax hardwood forests (Mitchell,

Rinehart, Pagels, Buhlmann, &Pague, 1997). This may be due to the lower tree biodiversity in

clear-cut, white pine and oak-hickory forests. It is possible that as a forest ages after a

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disturbance, small mammal communities can change based on the forest’s ability to support

them. Therefore, small mammals can be used to indicate how a forest is recovering from a

disturbance as well as its health (Glennon, Porter, & Demers, 2002 and Wiewel, Clark, &

Sovada, 2007).

Small mammals can be used to determine the health of an ecosystem because of their

habitat selection, their community interactions, and their low place in the food web. Different

species of small mammals choose different habitats based on the specific resources available, so

the availability of resources may affect the presence of certain species (Glennon, Porter, &

Demers, 2002 and Wiewel, Clark, & Sovada, 2007). Small mammals depend on prey and

producers to eat, while also supporting animals that depend on them as prey. Therefore, if the

small mammal populations are low, we can sometimes assume that their food resources are also

low (Glennon, Porter, & Demers, 2002 and Wiewel, Clark, & Sovada, 2007). Low small

mammal populations may also indicate that there are no large predators in the area that depend

on them as a food source. This means that the composition of different mammal communities

may change based on the forest’s ability to support small mammals’ requirements. Thus, if the

area can support more communities, there may be a high biodiversity, which may indicate a

healthy ecosystem. A healthy ecosystem with a high biodiversity may be more resilient to

disturbances because of the multiple prey and predator roles in an ecosystem (Glennon, Porter, &

Demers, 2002 and Wiewel, Clark, & Sovada, 2007). For example, if a disturbance kills one

species of prey, predators will still have food resources in a biodiverse area. Ultimately, the

diversity of small mammals can be used to indicate the presence of specific habitat requirements,

such as microhabitats and food sources, and in turn can indicate the health of an ecosystem

(Glennon, Porter, & Demers, 2002, and Wiewel, Clark, & Sovada, 2007).

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There are two main techniques used for studying small mammal populations, live-

trapping and track plates. The live-trapping method involves the capturing of live animals and

the collection of data regarding the species, sex, age, and weight of each animal (Wiewel, Clark,

& Sovada, 2007). Each of the captured animals may be marked with a serial numbered tag which

allows for the identification and tracking of the animals if they are re-captured. Due to the

identification and tracking of specific animals, live-trapping has been supported as an accurate

method for estimating abundance and diversity of small mammal populations. There are,

however, several disadvantages to live-trapping including expense, consuming large amounts of

time, and potentially exposing humans to wildlife diseases (Glennon, Porter & Demers, 2002;

Wiewel, Clark, & Sovada, 2007). The track-plate method involves the recording of animal tracks

on a piece of paper after the animal crosses a sooted or inked pad. This allows for the detection

of the presence of a species without actually capturing the animal (Glennon, Porter, & Demers,

2002). A disadvantage to the track-plate technique is that the track-plates are left out for at least

48 hours before being checked. During this time, multiple animals may enter the station and each

leave prints on the paper. Smaller prints could then be destroyed by larger prints, meaning results

could underrepresent the populations and diversity (Wiewel, Clark, & Sovada, 2007). Also the

presence of a species can only be counted once per track-plate which may reduce the sample size

(Wiewel, Clark, & Sovada, 2007). It is also unknown if the same individual visits more than one

track-plate. If the same small mammal visits more than one track-plate, the collected data may

over represent the abundance and diversity of mammal communities (Wiewel, Clark, & Sovada,

2007). One of the advantages to the track-plate technique is that the abundance data is similar to

that of live-trapping (Glennon, Porter, & Demers, 2002). Other advantages include less effort,

time, and exposure to diseases (Glennon, Porter, & Demers, 2002 and Wiewel, Clark, & Sovada,

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2007). The most important advantage to our study is that it allows sampling over multiple areas

simultaneously (Glennon, Porter, & Demers, 2002 and Wiewel, Clark, & Sovada, 2007).

We are performing this study to learn about small mammal communities in two different

forested sites, one mature mixed hardwood forest and one disturbed forest that was reclaimed

approximately 50 years ago. We chose these sites because they were once the same forest, and

therefore, they would have been expected to age and change the same if there had been no

disturbance. The differences in forests’ ages and compositions allow us to examine if the

reclaimed forest can support similar mammal communities to that of the mature mixed hardwood

forest. A previous study on forest composition and small mammal communities found that the

highest species diversity occurred in the mixed hardwood forest and lowest in a recently clear-

cut and replanted forest (Mitchell, Rinehart, Pagels, Buhlmann, & Pague, 1997). We will be

studying a forest cleared and replanted 50 years ago. As a result of the 50 years of re-growth

after reclamation, it is possible that the area has developed microhabitats and attracted specific

species of small mammals. Although live-trapping provides an more accurate representation of

mammal populations, our study used the track-plate technique because it allowed us to collect

data from both sites at the same time within one week.

Our null hypothesis is that both forested sites will have the same abundance and diversity

of small mammals. Our alternative hypothesis is that there will be a greater abundance and

diversity of small mammals in the mixed hardwood forest as compared to the previously clear-

cut and reclaimed forest.

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METHODS

We studied small mammal communities using 10 track-plate stations at each of two

forested sites. Our sites, one mature mixed hardwood forest and one reclaimed forest, are located

in Frostburg, Maryland, and are one half of a mile apart. The mature mixed hardwood forest has

woody understory, various aged trees, and emergent rocks. The reclaimed forest is a

monoculture of red and white pine trees that were planted in rows about 50 years ago. Unlike the

mixed hardwood forest, the reclaimed forest has little understory and few emergent rocks.

Data was collected using track-plates, in which small mammals cross a sooted plate and

move onto contact paper where they leave their footprints. To assemble a track-plate station, two

sheets of flexible black plastic were bent into a semi-circle and inserted into slits in a plywood

base and duct taped together. This created a cover over the plywood, making a tunnel with

openings at each end of the track-plate. An aluminum plate was two thirds covered in soot, and a

piece of contact paper, sticky side up, was put on the remaining one third of the aluminum plate.

Bait was then put on the contact paper and the aluminum plate was placed on the plywood.

To bait the station, we placed a can of wet cat food (Liver and Chicken), approximately a

tablespoon of smooth peanut butter, and about a teaspoon of rolled oats on the far edge of the

aluminum plate covered with contact paper. We placed the baited aluminum plate in the track-

plate station with the contact paper end closest to the tree. We placed the station against a tree

trunk and placed branches and debris on the opening of the station closest to the tree to prevent

the small mammals from entering through the rear. When small mammals entered the station,

their feet picked up carbon soot and their footprints were transferred onto the contact paper as

they approached the bait. Footprints left on the contact paper were later collected and identified.

7

The track-plate stations were first assembled and placed at the sites on June 19, 2012,

two weeks prior to collecting the data to allow the wildlife to get used to the stations. At each

site, we placed 10 stations at the bases of trees 15 meters apart from one another. We collected

the data from July 2 to July 6, 2012. We first baited the stations on July 2. On July 4, we re-

baited the stations and removed the first set of contact paper. We then replaced the contact paper

with new sheets. When collecting the contact paper, it was covered with transparency paper to

preserve the prints. The final collection of marked contact paper was on July 6.

In order to identify the small mammal tracks, we used a classification key and analyzed

the tracks from the two sites separately. If multiple prints of the same species were found on a

track plate, only one individual of the species was counted and recorded. Each track-plate station

over the two days when the data was collected was counted independently. This gave our study

an overall sample size of 20 track-plate stations per site.

The Track-Tube Index (TTI), or detection rate for each species, is the total number of

track-plates per site that contained a print of a species within the two data collection days divided

by the total number of track-plates analyzed per site (20). For example, if we detected chipmunk

prints on 7 track-plates over the two days we collected data at Site 1, we would divide 7 by 20.

This gives a chipmunk TTI of 0.35 at Site 1. Using the chi-square test statistic we compared the

TTI values between the two sites. To determine whether the chi-square value was significant, we

used a p-value of 0.05. We used Excel to calculate p-value associated with chi-square. A p-value

of less than 0.05 would mean that the small mammal communities of the two sites are

significantly different. However, a p-value of greater than 0.05 would mean that the differences

in communities were most likely due to chance and there is no significant difference in the

communities.

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To determine the diversity of each site, we used the Shannon-Weiner Index. We used a

website to calculate the Shannon-Weiner Index. This calculation takes into account the species

richness and abundance of mammals in each of our sites. The species richness is the total number

of species and the abundance is the total number of organisms detected per site.

RESULTS

Fig.1. –This figure shows the Track Tube Index (TTI) values for each of the small mammals detected at our two

sites in Frostburg, MD. There is no significant difference in TTI between the two sites.

As shown in Figure 1, the four species detected were the raccoon, vole, skunk, and long-

tailed weasel. Although the Track-Tube Index (TTI) values appear to be different, the chi-square

test statistic indicated that there was not a significant difference in values between the two sites.

Table 2 displays the total abundance and diversity data. The total abundance of mammals

1

0.7

0.2

0

0.95

0.6

0.45

0.1

0

0.2

0.4

0.6

0.8

1

1.2

Raccoon Vole Skunk Long TailedWeasel

TTI

Val

ue

Mammal

Track-Tube Index (TTI) Data Per Site

Mixed Hardwood Site Reclaimed Site

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detected was only slightly higher in the reclaimed forest. The reclaimed site had a species

richness of four, compared to the species richness of three in the mixed hardwood forest, because

the long-tailed weasel was only detected in the reclaimed site. We can conclude that there is no

significant difference in the abundance and Shannon-Wiener Index values between the two sites

because the Shannon-Weiner Index value depends upon the same data as the TTI (which was not

significantly different).

Table 2. –This table shows the total mammal abundance, species richness, and diversity values in our two sites in

Frostburg, MD.

As shown in Table 1, the animals detected varied in diet and activity patterns. In the

mixed hardwood forest, omnivores and herbivores visited the stations. In the reclaimed forest,

omnivores, herbivores, and carnivores were detected. Nocturnal (active at night) and crepuscular

(active at dusk and dawn) animals visited stations in the mixed hardwood forest, while nocturnal,

crepuscular, and animals that were both diurnal (active in day) and nocturnal were detected in the

reclaimed forest.

Table 1. –This table shows the diet, activity patterns, and the forests the mammals were detected in.

Mammal Diet Activity Patterns Detected in:

Reclaimed

Forest

Mixed Hardwood

Forest

Raccoon Omnivore Nocturnal X X

Vole Herbivore Nocturnal X X

Skunk Omnivore Crepuscular X X

Long-Tailed

Weasel

Carnivore Diurnal and

Nocturnal

X

Total Number of

Organisms Detected

Species Richness Shannon-Weiner

Diversity Index

Value

Undisturbed Forest 38 3 1.36

Reclaimed Forest 42 4 1.719

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CONCLUSIONS AND DISCUSSION

Based on our results, we cannot reject our null hypothesis that both sites will have the

same abundance and diversity of small mammals. In turn, we can reject our alternative

hypothesis that there will be a greater abundance and diversity of small mammals in the mixed

hardwood forest compared to the reclaimed forest. We failed to reject our null hypothesis and

rejected our alternative hypothesis because the abundance, TTI, and diversity of mammals

detected were not significantly different between the two sites.

The purpose of our study was to see if there was a significant difference of small

mammal populations between mixed hardwood and previously disturbed and then reclaimed

forests. We found that there was no significant difference in the abundance and diversity

between the mixed hardwood forest and the reclaimed forest. These results contrast the findings

of a study that found that a mixed hardwood forest had the highest diversity of small mammals

when compared to other forest types (Mitchell, Rinehart, Pagels, Buhlmann, & Pague, 1997).

However, the previous study used a clear-cut forest that was two years old; therefore, it had no

time to age or allow small mammals to return like our reclaimed forest. The reclaimed site we

studied is a pine forest that has had fifty years to grow, mature, and develop microhabitats that

small mammals need to survive. The accumulation of pine needles allows certain small

mammals, such as the vole, to burrow despite the compacted soil. Pine needles also provide food

for voles. In addition dead trees, which can be found in the reclaimed forest, provide an area for

small to hide as well as seek shelter and cover. Because both forests have microhabitats, they

can both provide adequate shelter and cover which could explain why they had similar small

mammal abundances.

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In our study, we found that the diet types of the mammals found in both sites were similar

and generalists were found in both sites. Generalist species have a broad diet while specialist

species eat a narrow range of food resources. Both sites support generalist species, but we do not

know if both sites can support specialist species. The only specialist found was in the reclaimed

site and not in the mixed hardwood forest, indicating that the mixed hardwood site may not be

healthier than the reclaimed site. Also, we found both sites are bordered by an active coal mine

and Frostburg State University, which may be disturbing the sites. Generalist species, such as the

raccoon, which were what we found the most of in both sites, are more adapted to human

presence which could explain why there was no difference between the sites and why we

detected mostly generalists.

Our study had several limitations that may have influenced our results. One limitation to

our study was time, as we only had a week to collect data. With more time, we could have

obtained a larger sample size and a better representation of the population. Our study was

conducted during the summer which only represents mammals that are active during the summer

season. To acquire a better representation of the small mammal communities, we could have

sampled throughout the year. Weather conditions during data collection were another limitation

to our study. The rain storms experienced during our study had damaged some of the track-plate

stations. This could have impacted our data because the mammals would have been less likely to

enter a damaged track-plate station. To avoid damaged stations, it would be beneficial to make

the stations stormproof by constructing them out of stronger materials.

Other limitations to our study involved the track-plate technique. There may be an over-

or underrepresentation of species because of destroyed or misidentified of tracks. It is also

unknown if the same individual visits multiple track-plates or visits the same track-plate more

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than once. We could have increased the distance between the stations to reduce the possibility of

the same individual visiting multiple track plate stations. Animals may also have entered through

the back of the station and eaten the bait without leaving tracks, which could have caused

underrepresentation of the species. This could have been avoided by closing of the back of the

station permanently so that animals had to enter through the front. Also, the soot on the track-

plates was not replenished each time; therefore, it was harder to identify the tracks from the

second day of data collection. This could be improved by replacing the soot each time the

stations were re-baited. Additionally, the bait used in our study is not naturally found in a forest

which may have made it un-attractive to the small mammals. The bait may have been removed

or eaten by previous animals, which could reduce incentive for other animals to enter the station.

The baiting technique could be improved by supplying a steady amount of more natural bait.

Future studies could collect additional data. For example, future researchers could

determine whether mammals move between the two sites. This could be done through the mark

and recapture technique or using motion-sensor cameras to identify individual mammals.

Therefore, we could determine if one individual visited more than one track-plate and whether

small mammals traveled between both sites. Future researchers could also conduct a habitat

assessment, such as examining the microhabitats, plants or available water in an area. If these

resources are available but small mammal populations are low then there may be outside

influences or disturbances affecting the area. For example the active coal mine nearby has

decreased the size of both forests. Also the nearby university may disturb the forest with its

sound pollution and construction. Lastly, researchers could determine whether small mammal

communities change between seasons by conducting a year-round study. A year round study

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would give us a more accurate representation of the mammal populations rather than just the

summer population.

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REFERENCES CITED

Buehler, D.A. and Percy, K. (2012). Coal Mining and Wildlife in the Eastern United States: A

Literature Review.

“Coal Mining and the Environment.” (n.d.). Retrieved from www.worldcoal.org.

Fairbanks, Christina. Class lecture. Frostburg State University, 2012.

Glennon, M.J., Porter, W.F., and Demers, C.L. (2002). An Alternative Field Technique for

Estimating Diversity of Small-Mammal Populations. Journal of Mammology, Vol. 83(3),

734-742.

Mitchell, J.C., Rinehart, S.C., Pagels, J.F., Buhlmann, K.A., and Pague, C.A. (1997). Factors

Influencing Amphibian and Small Mammal Assemblages in Central Appalachian Forests.

Forest Ecology and Management. Vol.96, 65-76.

Wiewel, A.S., Clark, W.R., Sovada, M.A. (2007). Assessing Small Mammal Abundance with

Track-Tube Indices and Mark-Recapture Population Estimates. Journal of Mammology.

Vol.88(1), 250-260.