-- BrianMendonca - 14 Sep 2010

Case Study: Involving Endangered Species

Jane Doe walks into a bio-statistics drop-in workshop with questions about her endangered species study. She wants to find the possible severity of various different factors on the population of an endangered species. Unfortunately, her sample size is limited in both the number of places to draw her sample from but yet the number of factors which could be influencing the species of interest population is high. How can she deal with this?

When analyzing the endangered species, it may be difficult to generate data. The first step in collecting information would to first see what information is already publicly available. When data on the species you want has already been collected, then significant amounts of money can be saved during the duration of your study. If you are beginning a totally new study and looking at the endangered species in a way that has not been done before, then actually finding the species will be necessary, but this can be terribly difficult. Many of the endangered species are supposed to be left undisturbed, very difficult to find in the wild, or are already under careful watch of a third party in a man-made habitat. So what happens when you cannot find many of them? Is it time to give up and abandon your study? Not quite!

One possible cure for a small sample of your endangered species is to look into the realm of phylogeny. For those who are not familiar with this term, phylogeny is the study of how lineages of different species have developed over time from a common ancestry. What this means in the context of an endangered species study is that every species presently on Earth has or had in the past, a sister species. The amount of genetic, physical appearance, and behavioral aspects among sister species varies depending on the lineage, but some are only separated by a few different traits. Additionally, many sister species live or lived in similar habitats. Depending on the goal and design of your study and the factors influencing the endangered species and its sister(s), it may be possible to integrate those sister species into your study as well. Ideally, a valid study utilizing this approach would include very little difference between the sister species AND the environment that they exist. If you do not have this, then phylogeny is a dead end for your study.

Let us assume that you have gotten over that sample size roadblock and can now conduct your study. Now that you have enough endangered species to make your statistical N give your study enough power, it is time to consider all of the possible factors that could be influencing your study. In the wild, there are countless influences to consider, but here is a concise list of the most important factors you might want to include in your study (or watch out for!):

Animal Behavior

Natural Environment

Human Interference

Mating Season


Chemical Pollution

Rate of Attempted Mating

Plant Levels (can be measured by chloroplast levels via satellite)

Direct Human Interference (such as poachers, feeding or consumption

Success Rate of Birth

Water Depth (for aquatic species)

Light Pollution

% Chance of Living to Adulthood

Predator/Prey Evolution (are species that eat or are eaten by the species of interest changing?)

Introduction of non-native plant/animal species to habitat

Migration or loss of migration pattern

Environment Temperature Difference

Acid Rain

Diet change

Salinity of Water


Inability/Change in Courting

Competition for Resources by neighboring species

Agriculture (including herbicides/pesticides)

Changes in Ocean Current