SEE-UAtlantic Forest

Exercise 4: Population Size in Habitats of Different Area
Module 4: Growth and Competition: Population and Metapopulation Dynamics


Your Questions

  1. Does population size change in response to changes in habitat?

Background

The study of the population size, structure and dynamics is fundamental for understanding how to conserve and manage any species. In many tropical ecosystems populations are relatively small, especially for insects, except under special conditions. There are several problems associated with small populations and a discussion of these can be found in your text (Wilson and Perlman).

Estimating population size requires counting the number of individuals present in a certain area, or population density. The method of obtaining this data will of course vary with the particular species being studied. For plant species, the usual method is through placement of quadrats and measuring and counting all the individuals inside the quadrats. For sessile animals, this method also works well. However, for many animals the usual technique for estimating population size is by capture and recapturing individuals.

To study population dynamics, aside from collection of data on the number of individuals, other data required are the population structure, rates of population growth, mortality and recruitment. With these data it is possible to construct models, using matrixes, to predict future trends in population density.

In this lab we will look at population size of species in relation to the size of their local habitat and build a simple model of population growth.

Your Assignment

  1. Estimate population size for species in habitat patches of different sizes
  2. Build a simple population growth model

Methodology

  1. Task A—Select sampling areas
  2. Task B—Estimate population size
  3. Task C—Data analysis
  4. Task D—Study population growth

Objectives

  1. Estimate the population size of several species
  2. Introduce basic concepts of population structure and dynamics
  3. Introduce population sampling techniques
  4. Introduce a modeling technique (Stella)

Key Skills

  1. Learn methods for estimation of population size
  2. Become familiar with population dynamics models
  3. Use of a modeling program (Stella)

Timetable

Total time—2 days

  1. Morning—Day 1
  2. Morning—Day 2
  3. Afternoon—Day 2

Materials Needed

  1. Local maps
  2. Field notebook and writing equipment
  3. Tape measures (50 m)
  4. Compass and GPS
  5. Material for establishing quadrats (stakes, string, flagging)
  6. Collection or observation equipment for studied species
  7. Equipment for marking captured individuals