Hobbies And Interests
Observing Shell Changes
One simple science project for elementary-age students to conduct with hermit crabs is to observe how they change their shells. Place a few crabs in a tank with an assortment of shells, and observe how frequently crabs change shells. Observe factors such as whether larger or smaller crabs change shells more often, whether crabs outgrow shells before changing, or what time of day crabs are more likely to change shells.
Types of Shells
Determine what types of materials a hermit crab will use as a shell. Keep just one hermit crab in a tank so that it will not be threatened by predators, including other crabs. Provide it with a number of options to use as a shell, and see which type of seashell the crab prefers. Note if it is a round or spiral-shaped shell, or whether it sports a smooth or rough interior.
Re-using Shells
Determine if a hermit crab will use a shell more than once. Keep a hermit crab in a tank with a number of shell options. Carefully observe a hermit crab molting its shell and moving into a new one; then, remove all other possible shells other than its original shell and one that is obviously too small. Record whether the hermit crab re-use an old shell, take one that is not the right size, or simply keep the current shell indefinitely.
Man-made Shells
Hermit crabs have appeared on beaches wearing man-made materials, such as bottle caps, in place of shells. Provide a hermit crab with a few natural seashells, and a number of man-made alternatives. Observe whether the hermit crab will seek out a natural shell or perhaps try something new and not-so-natural. In determining why the crab has chosen one over the other, consider the size, scent and shape.