Using line transects to determine interrelationships between vegetation type and small mammal activity.

John Olson, New Ulm High School, New Ulm, MN 56073
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Initial Publication Date: August 24, 2007


Students will use quadrats located every 50 feet along line transects in two different habitats to determine the vegetation types present in each habitat. Habitats may include but are not limited to, prairie, upland grassland, early stage forests, mature (climax) forests, and coniferous forests. Vegetation types will be described as percent coverage of, grass, herbs, shrubs, and mature trees. Specific species of shrubs and trees found in each quadrat will be noted whenever possible. When the vegetation analysis is completed, live traps will be placed at each point along the transect for two consecutive nights. The number and species of small mammals (mice, moles, voles) caught and released will be recorded. Florescent dyes placed on the small mammals will determine their home range. Data analysis will attempt to determine if a correlation exists between vegetation type/abundance in each habitat and small mammal activity.

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Learning Goals

This activity is designed for students to
1) Design proper field techniques used in determining variation in plant distribution within a habitat
2) question the validity and reliability of the data collected in a field study
3) interpret data, write logical conclusions while understanding the limitations of field data

Main concepts that students will understand after completion of the activity are that
1) the plant types and species present in various habitats are controlled by both biotic and abiotic factors
2) small mammal species are dependent on various plant species for food and cover
3) plant and animal populations change in an area over time
4) Evolution selects plants and animals with specific adaptations to survive specific environmental conditions

Context for Use

This field exercise would work best, as written, for advanced classes in ecology, field biology, or enviromental studies but could be adapted for life science classes. If specific plant species are to be identified, the activity could take 5-7 class periods depending on the prior knowledge of the students and the habitat(s) chosen to investigate. The equipment required consists of a rope and live traps, and optional florescent dyes and a portable black light. No prior student knowledge would be required.

Description and Teaching Materials

Materials required
12 small mammal live traps
2 ropes/lines 300 feet long marked at 50 foot intervals
12 ropes 10 feet long
florescent dyes
portable black light

1) The teacher will introduce the study by posing questions. Which of the two available habitats has more small mammal activity, (your choice of habitats)? What would make one habitat more suitable to small mammals? What small mammals might live in these habitats? Background information on the expected small mammals can either be presented by the teacher or by students

2) Have students produce a testable hypothesis.
3) Discuss field investigation techniques. How can we control the study so the results are as reliable as possible? What are the difficulties with setting up a field study? Help students understand how to plan a transect study.

4) 24 students will be divided into two groups of 12 students. One group will investigate habitat #1 while the second group of 12 students will investigate habitat #2. The 300 foot rope will be laid out in a straight line in each of the two habitats. A set of two students will go to one of the six points marked along the transect. Here the two students will define a circular quadrat around their designated point by using a 10 foot section of rope. Students will record approximate percent of transect covered by bare ground, grass and herbs. The number and species of shrubs and trees found within the circular quadrat will be recorded as accurately as possible.
After vegetation analysis, each set of two students will set out a small mammal live trap baited with peanut butter and oatmeal. The number and species of small mammals caught and released for two nights will be recorded for each point along both transects. The optional part of the activity will be to put the small mammal in a zip lock bag with a florescent dye and shake the bag. Mark where the mammal was released and return at night with a portable black light. Use the black light to track the movement of the mammal to get an idea of the size of the home range used by the mammal.
5) Share data
6) Discuss succession and the biotic and abiotic factors that influence the change in vegetation over time; parent soils, moisture, light availability, shade tolerant / shade intolerant plants.
7) Using scientific method, write field report

Teaching Notes and Tips

I expect data to be overwhelming and difficult to draw specific conclusions from. Can one really determine what habitat supplies the needs of a small mammal in such a short study? This can be a major point of the activity, that is, it will show students how complex ecosystems are, how difficult it may be to control field studies, and to help students recognize the limitations of the collected data.
The major safety guidelines to focus on include the handling of rodents. This should not be done with bare hands and traps should be disinfected with 10% chlorine bleach.
In order to be consistent in determining the percent coverage of grass, herbs, etc in a quadrat, this method may have to be modeled for the entire class in one of the habitats before each set of two students collect data on their own.
This activity varies from previous studies in that I have had students set out only small mammal traps to see what species of mammal would be caught as well as how many of each species. I haven't specifically tried to correlate the presence of the small mammal and the percent coverage of various plant species. I also have not tried using the florescent dyes to trace the path of the small mammal.
Students, depending on their background, may need help using the scientific method in writing a field report.


Students will turn in a field study report based on the scientific method. This will include title, purpose of study, hypothesis, methods used, data collected, results, conclusions. Students will show proper use of ecological terms, show that they recognize the limitations of the data, and develop a new experimental question.


Strand IV Sub-strand E Benchmark 1. Understanding that species change over time
4. Use biological evolution to explain diversity
Strand IV Sub-strand F. Benchmark 1. Explain relationship between abiotic and biotic components of an ecosystem

References and Resources