Suggestions for Analyzing the Right Whale Population Data

Scientists and researchers are concerned about the plight of the endangered right whale. Although protected since 1935, this large aquatic mammal is struggling on the brink of extinction. In 2001, a large increase in recorded births provides hope for this small group of whales. This simplified population graphing exercize serves as a springboard for discussions of the factors that are involved in studying population dynamics.

The population figures below represent the number of recorded births of right whale calves for the past six years. These numbers represent calves sighted by researchers from many research groups studying the right whale. Using the population data from 1996 to the present, and the facts we have listed below, make the following graphs to look at the population patterns.

Graph:
Assuming the right whale population is 300 in 1996, create the following graphs to look at some of the population trends the whale births affect.

1. The number of recorded births each year.
2. Assuming that the population in 1996 was 300, graph the percentage of increase in the right whale population that the births represent each year.

Recorded Right Whale Births
 Year Recorded Births 1996 22 1997 18 1998 5 1999 4 2000 1 2001 26

How would the following variables affect the population size?

• A female right whale reaches reproductive maturity between seven and ten years old.
• The right whale population total is 300 whales, with an estimated 70 breeding females.
• Juveniles and calves constitute 26 to 31% of the population.
• Females reproduce every one to three years.
• Females carry and give birth to only one calf at a time.
• Although it is difficult to determine right whale longevity, researchers estimate life spans at around 30 years, however there are known cases of 65 years.

Discussion:

• Describe the different visual picture each graph gives you. Was it helpful to graph the data in these different ways?
• Why is it important to know the death rate? How much information is available about death rate in the population? Where could we find information?
• Scientists refer year after year to the number 300 when describing the population. Why is it difficult to be more accurate each year?
• Think about what each graph means. What different information does each show you?
• What questions did the graphs give you about the population size? What reasons do you suppose are behind these changes?
• List all the factors that affect the right whale population growth which might have caused the population to rise (or fall) as the data show.