Shell fighting and competition between two hermit crab species in Panama

Area of Science:

• Marine Biology
• Ecology
• Behavioral Ecology

Background:

• Hermit crabs rely on gastropod shells for protection.
• Shell availability is a critical resource, driving interspecific and intraspecific competition.
• Shell fighting is a key interaction influencing hermit crab population dynamics.

Purpose of the Study:

• To investigate shell fighting dynamics between Calcinus obscurus and Clibanarius albidigitus in Panama.
• To compare laboratory and field estimates of shell exchange frequencies.
• To assess the impact of shell fighting on relative shell size use between species.

Main Methods:

• Laboratory experiments simulating shell fighting scenarios.
• Field observations and experiments to estimate shell exchange rates.
• Analysis of shell size occupancy in sympatric and allopatric populations.

Main Results:

• High shell exchange frequencies observed when Calcinus obscurus occupied poor-quality shells.
• Exchange frequencies differed significantly across collection sites, notably low from Venado Beach.
• Field and laboratory exchange frequency estimates were comparable.
• No clear evidence of one species altering the other's shell size use was found.

Conclusions:

• Shell fighting is a component of hermit crab interaction, but intraspecific competition is dominant (approx. 90%).
• Findings contrast with previous studies, highlighting the importance of local conditions and shell quality.
• Resource competition dynamics in intertidal ecosystems are complex and species-specific.