The Great Crab Race

by Carmelina Livingston & Robin Rutherford

• Question: Does size affect velocity of a land hermit crab?

• Hypothesis: The velocity of the large hermit crab will be greater than the velocity of the small hermit crab.

• Materials: One large land hermit crab, one small land hermit crab, ruler, stopwatch.

• Procedures: We obtain two land hermit crabs on Hoffman Cay. The shell of crab one was approximately 3/4 of an inch. The shell of crab two was approximately 2 inches. We timed the crabs for specific time trials. Trial one was set for five minutes with both crabs having the same obstructions. Trial two and three were set for approximately two minutes with various obstructions for the small crab. Trial four was set for a specific displacement with no obstructions for either crab.

• Results: When environmental conditions are controlled as in trials one and four, both the small crab and the large crab have the same velocity. When environmental conditions are not controlled, such as in trials two and three, the crab with more obstacles to overcome is slower. In this experiment, the smaller crab had more obstacles to overcome.

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This formula was used to calculate velocity:

velocity - displacement / time (v - d/t)

 Crab One Crab Two

  Trials

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