Nature Field Guide
Calcinus Hermit Crab
- Spanish name
- Cangrejo ermitaño Calcinus
- Scientific name
- Calcinus obscurus
What Do Pico & Tati Think?
Pico thinks a shell has moved. Tati waits until a small leg appears before writing down what she has seen.
Species overview
About the Calcinus Hermit Crab
Calcinus obscurus is a marine hermit crab. It uses a gastropod shell to protect its soft abdomen and lives in lower intertidal habitat. The shell belongs to a different animal species, so the shell’s shape cannot identify the crab by itself. Observe the visible crab rather than turning the shell over.
Identification
Key Features of the Calcinus Hermit Crab
A marine hermit crab in a borrowed shell
Visible legs and claws at the shell opening
The shell species and crab species are separate identifications
Habitat & range
Rocky shore and naturally visible tidal habitat. Choose a permitted observation point with an adult; do not turn rocks or reach into holes.
Local observations
Documented in Guanacaste. Museum specimens document Gulf of Nicoya/peninsula sites, Central Pacific sites and the Osa Peninsula. Region tags represent documented locations, not an exhaustive range or a promise of occurrence at every beach. Additional regional assignments require locality evidence.
When to observe
Visibility depends on the site, conditions and the animal. Ask a local guide about an appropriate visit; no fixed encounter season is promised.
Conservation & care
Give claws and burrow entrances space. Do not handle, feed, chase or collect crabs. Leave rocks and shells where they are, and follow your adult’s route and local signs.
Observation activity
Draw the shell and the part of the crab you can see. Give each a separate label.
Explore by location
Central Pacific · Guanacaste · Puntarenas & the Gulf Islands · South Pacific