by Mark MacAllister
As part of our elephant research in Cameroon, we collect morphology data about the animals we find. Morphology is the term we use to describe the study of an animal's physical body or its "structure": its height and weight, the size of its feet or limbs, and so on.
Some morphological data is easy to gather—see Measurement and Data Collection in the Field for an example of one process. Some data, however, is very difficult to obtain.
Perhaps the most difficult data to gather on an elephant is its weight. Obviously, we cannot carry a big scale with us into the rainforest, so we can't just weigh the animal. On the other hand, our experience has shown us that we can estimate an elephant's weight by measuring three body features and then entering those numbers into a simple formula.
Here's what we have to measure:
- the girth of the elephant at her heart; in other words, how big around is she?
- the length of the elephant;
- the circumference of one of her footpads (that is, how big around is the footpad?).
All of these measures are taken in centimeters. Next, we enter those numbers into the following formula:
(11.5 * heart girth) + (7.55 * length) + (12.5 * pad circumference) - 4016 = elephant weight
The total we get from the formula above gives us a good approximation of the elephant's weight in kilograms.
In the media gallery of this article is a dataset of elephant measurements. (One version of the dataset is in Microsoft Excel format; the other is a tab-delimited text file that can be imported into any spreadsheet or database program.) The dataset includes age, heart girth, length, and pad circumference data for more than fifty elephants. Use this data, and the formula above, to estimate the weight of some or all of these animals. Once you've done that, ask yourself the following questions:
- do male or female elephants tend to weigh more; which tends to have a larger girth? which tends to be longer? which tends to have larger footpads?
- what is the relationship between age and weight? do elephants ever appear to "stop growing"? is it possible that older elephants get smaller as they age?
- what are the differences between the oldest and youngest males? what about between the largest and smallest females?
- can you create a formula that would help you approximate your weight based on two or more of your morphological measurements?
Be sure to use graphs and other visual tools to help you better analyze the data.
About the author:
Mark MacAllister is the Project Coordinator for Field Trip Earth.
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