Lesson Plan

Spotted Salamander Population Estimation: Capture, Mark, and Recapture Method

Three juvenile Spotted Salamnders (Ambystoma maculatum), and one adult Webster's Salamander (Plethodon websteri), captures along Natchez Trace Parkway, Milepost 86.1

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Grade Level:
Ninth Grade-Twelfth Grade
Biology: Animals, Community, Ecology, Environment, Mathematics, Science and Technology
50 minutes or more
Group Size:
Up to 36
National/State Standards:
MS Objectives:
Intro to Biology: 3d
Biology 1: 3c
Environmental Science: 3a, 3b, 3c
salamander, metamorphosis, Amphibian, spotted salamander, adaptations, animal population, ecology, population dynamics, wildlife, wildlife biology


Students 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.



Participation in the activity.

Park Connections

Spotted 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.


Population, Capture-Mark-Recapture

Last updated: April 14, 2015