Summary
This activity will have students practice their measuring and data analysis skills as well as reading and understanding graphs. The first case study has students look at the body measurements of gray seals and look for patterns in relation to sexual dimorphism (differences between males and females). The second case study compares the body sizes of three different polar animals over a span of 25 years (polar bears, harbor seals, and gray seals). Students will use this data set to find patterns and draw conclusions about the environments that those species live in to explain the population trends.
Materials and Preparation
- Writing utensil
- Three different colors of markers, colored pencils, or crayons
- Student worksheet
- Teacher guide
Learning Objectives
Opening Activity
Ask students how they think scientists weigh large animals such as polar bears or seals. Have a discussion about the potential challenges of researching large mammals and what we can gain from collecting that information.
Activity Overview
Case Study #1 Estimating Body Size in Grey Seals
- Students will learn how scientists measure gray seals in the wild
- Students will learn how gray seals are sexually dimorphic and scientists can determine the sex of a seal through estimating their weight using their body length
- Students will practice measuring body length (using seal images on the worksheet and a ruler/measuring tape) to estimate the weight of their seals through graphing
- Students will then turn identify whether the seals are male or female based on their results
Case Study #2 Polar Mammal Body Size Over Time
- Students will examine a data set containing the weights of a polar bear, harbor seal, and grey seal over 25 years.
- Students will create a line graph (digitally or on paper) graphing the changes in weight over time for each species.
- Students will use the graph to analyze the data and answer reflection questions
Reflection
Students will answer a few questions analyzing data trends after completing the graphing section
- How does body size change through time for female polar bears? Female harbor seals? Female gray seals?
- For each of the species, provide a possible explanation for an increase, decrease, or no change in weight over time.
- How do scientists determine body size in large animals when they can’t measure their mass?
References:
- “How Do Scientists Weigh Wild Polar Bears?”
- “Drones Are Helping Scientists Weigh Seals in Antarctica”
- Durner and Amstrup (1996) Mass and body dimension relationship of polar bears in Northern Alaska. Wildlife Society Bulletin
- Kolenosky, G. B., Lunn, N. J., Greenwood, C. J., & Abraham, K. F. (1989). Estimating the weight of polar bears from body measurements. The Journal of wildlife management, 188-190
- Malenfant, R. M., Davis, C. S., Richardson, E. S., Lunn, N. J., & Coltman, D. W. (2018). Heritability of body size in the polar bears of Western Hudson Bay. Molecular Ecology Resources, 18(4), 854-866
- Lidgard, D. C., Boness, D. J., Bowen, W. D., & McMillan, J. I. (2005). State-dependent male mating tactics in the grey seal: the importance of body size. Behavioral Ecology, 16(3), 541-549
Standards:
Polar Literacy Principles:
Made possible with funding by the U.S. National Science Foundation Award #2221990. The information contained here is those of the author(s) and does not necessarily reflect the views of the U.S. National Science Foundation.