Spotted Salamander Population Estimation: Capture, Mark, and Recapture Method
OverviewStudents will learn how to estimate an animal population and evaluate the results when an unnatural event affects that population. Discuss the necessity for researchers to know how many animals are in a population, and various events that might affect an animal population. They will start with a “spotted salamander population” represented by white beans. They will then “mark” salamanders by replacing spotted beans with white beans. They will estimate the number of individuals in their population
Enduring Understanding: Populations should be monitored in order to determine if conservation efforts are needed to help support the population.
Essential Question: When is the Capture Mark Recapture method most useful?
The student will:
1) understand how the capture, mark and recapture method is used to estimate wildlife populations.
2) estimate an imaginary population of the spotted salamander by a pseudo mark and recapture method.
3) analyze and list factors that can affect the accuracy and precision of a population estimate.
4) observe the effects of a disastrous event on the salamander population.
5) predict results, observe and record data, summarize and report results.
(see attached Fact Sheet) The spotted salamander is indigenous to the areas surrounding the Natchez Trace Parkway. When the salamanders breed, they usually return to the same vernal pond from which they hatched. Unfortunately for some populations, this presents a hazard as the Natchez Trace Parkway is in between their forest habitat and the vernal breeding ponds. In the spring during the first few warm rains, the salamanders migrate en masse to the vernal pools. This means that many of them are crossing the road at the same time. Unfortunately, many are killed during this reproductive migration. As time passes, the salamander population may be affected. Population estimates will be necessary.
To get the most accurate population estimations, a variety of methods must be employed when attempting to estimate a population. The capture, mark and recapture method (CMR) is used by wildlife biologists. The CMR method is a sampling method that is particularly useful with animals where the researcher cannot see or find all of the animals in a particular area.
Ear tags, tattoos, clipped ears, bird bands and other methods mark the animals more or less permanently. In the case of salamanders, one of their toes is removed.
In field biology on the recapture, animals may be harvested (taken out of the population) or they may be returned to the population. The Petersen CMR formula is one method for estimating population size:
N1 x N2
P = ----------------
N1 = number of individuals initially capture and marked
N2 = number of individuals in second or recapture sample
M = number of marked individuals in second or recapture sample
P = population estimate
1.) Fact Sheet
2.) Capture Mark Recapture Instructions
3.) Report Sheet
4.) Natural Population Data Sheet
5.) Salamander Slaughter Data Sheet
6.) 2 cups uncooked dry pinto beans
7.) 1 cup uncooked dry white beans
8.) A paper bag and 2 plastic cups, plates or similar containers.
Provides information on the spotted salamander. Download
Provides the instructions for the activity. Download
To be filled out by each student at the end of the activity. Download
To be filled out by each student regarding the first population. Download
To be filled out by each student regarding the second population. Download
Student Task: Complete the worksheet assignment.
1.) The students will be learning one method that wildlife biologists use to estimate the population of an animal species.
2.) Hand out the worksheets and explain to the students the elements of the CMR formula.
3.) Next have the students get a paper bag and put two cups of dry pinto beans in the bag.
4.) They will also need about 1 cup of white beans in a separate container (plastic cups work well). The second plastic cup will be for "trash" beans.
Teacher Closure: Discuss possible weaknesses and strengths of this population estimator. Brain storm about how spotted salamanders could be saved from destruction.
AssessmentParticipation in the activity.
Park ConnectionsSpotted Salamanders are found along the Trace and their populations can be estimated using the Petersen method.
1.) As the opportunity occurs, relate the problem with the spotted salamander to other environmental problems.
2.) Have the students further research and write reports about the spotted salamander.
3.) Have the students research how others are attempting to help the spotted salamander.
4.) Organize a debate comparing two different viewpoints as to what should be done about the salamanders getting run over.
5.) Have the students draft a management plan for the spotted salamander.