Habitat Selection in Hermit Crabs Erika McLellan Erin Henderson Michelle Johnson Meghan Keddy

Background Hermit crabs prefer dark, moist environments They choose discarded shells Shell size may affect habitat preference Sediment texture influences habitat selection They will bury themselves into the sand before they molt and for protection

Hypothesis We predicted the hermit crabs would show preference for a different substrate than sand

Methods 10 crabs were taken out of holding tank and placed in a tank with small amount of warm water Bin filled with leaves, rocks, and sand: 6 trials Dark room (red light) Each crab was placed in center substrate one at a time Stopwatch was started: time was recorded when movement began, and crabs were observed for 5 minutes ANOVA and Tukey Test used to determine if there was a significant difference in the average percent time the crabs spent in each substrate

Crab Details Largest crab: 5.5 cm Smallest crab: 2.5 cm Varying shell types

Results Testing time of 15275 seconds Total time (s) spent in each substrate Percent time: Rocks 32%, Leave 52%, Sand 16 %

Average percent time spent in each substrate Rocks: 33.6% , Leaves: 46.5%, 18.34%

Rocks vs. Leaves vs. Sand ANOVA test determined that there was a significant difference in the average % time spent between substrates (p = 0.0001) Tukey Test determined: Rocks vs. Sand: not significant Rocks vs. Leave: not significant Sand vs. Leaves: significant

What does it all mean… Overall assumption Prediction Sand is the preferred habitat Prediction Rocks and leaves will be preferred over sand

Rocks Rocks not statistically different than the leaves or sand Observed behaviour Along vs. on top of rocks Reasons Camouflage? Size related?

Leaves The hermit crabs spent half their time in the leaves. Observed behaviour Moved underneath the leaves Reasons Moist and humid Shelter?

Sand The hermit crabs spent the least amount of time in the sand. Observed behaviour Burrowing Reasons Protection Molting

Conclusion Crabs will pick leaves over sand Cannot say if they would pick rocks over sand Cannot say if they would pick leaves over rocks Their preference for leaves may be because leaves offer the same coverage and protection as sand, but it takes less energy to hide in.

Limitations Used an bottom layer of sand across the entire bin Should have created barriers The smell of the leaves Could have used fake leaves Including time in shell in 5 min Should have started 5 min trial when they began to move